I'm still working on a driver for this motor. When I have it working I'll post a short video showing the motor running at speed. Edit: the motor now runs, here's a link to the video: ruclips.net/video/TAhF45AtsgA/видео.htmlsi=qABbtBXH8Mqic1_W
@@candas1 I was planning to code something from scratch. I didn't know about simplefoc, looks like very solid stuff, I'll definitely keep it in mind. Not sure if it supports this kind of motor/my driver electronics, so I'll have to look into that. Thanks for the suggestion!
Why not use a brushless motor speed controller, typically used for drones. Most of the time they are 'sensorless' using the collapsing magnetic field of the un-energized coils to figure out the position. It may not work in your case as drone motors use magnets on the rotor, which would amplify the 'sensor' signal.
@@moddaudioA SRM and BLDC motor are very, very different. FOC does not apply to this motor type. Timing is much much more tricky to achieve. The maths differs.
I got the 1980s Open University vibe (if you are in the UK and over 40 you'll know what I mean). He's got the right voice/presentation and excellent way of explaining everything. I enjoyed this video and am looking forward to more of them.
Excellent presentation. You explain the concepts and the problems without tedious math, just simple graphs. I am hoping for more info on the controller. 👍🏻
I have seen a switched reluctance motor, my Rainbow vacuum cleaner has one in it. Inside is an asterisk shaped laminated steel rotor and what appears to be either two or four coils of wire in the stator. It's a neat sounding machine starting up as well. There's also a microcontroller board on top of it to start and run it.
Thanks I'm going to be looking for one in our markets and second hand stores. I used to have a Rainbow, when they first came out. I loved it because it got rid of the dust issue that conventional vacs at the time did. Thanks again.
Pointing out a concept by starting with a constant voltage supply where one switches a coil off when a rotor pole is in position over the coil. The current flowing in the coil is related to the load (because of time for current to build) as well as the inductance. Besides the energy in the magnetic field converted work done in movibg the load, there will be some energy still left in the magnetic field at the point of maximum inductance and maximum current. But because inductance in coils opposes changes in current then switching the current off would create an inductive voltage spike across the coil. While many coils like those used in relays use a flyback diode to and sometimes a capacitor to snub the inductive kick back, that remaining energy in the collapsing magnetic field can instead be dumped in the next set of coils that are swiched in. And this can be repeated over and over. The high voltage output spike can drive the next set of stator coils. This is not perpetual motion motor but just minimizing energy loss and proposing a way to get get more torque at the beginning of the next coil's cycle and minimize torque ripple. Lastly, the coils are now nolonger constant voltage driven, but ratherly approximating constant current driven. 😊
Reminds me of when I was playing with multi-stage rail guns but rotary rather than propelling a projectile in a straight line. Lots of incredible use cases for this type of motor - I wasn't aware of it. Great vid - thanks, subscribed.
It’s interesting because torque ripple in motorcycle engines can have a significant impact on maintaining traction between the tire and road. The phase of the power pulses can help prevent slip and maintain grip in certain situations. So in some applications torque ripple can be a good thing.
Nice review. Although switched reluctance motors may be rare, they have a much more prevalent cousin in the form of the variable reluctance sensor. These are found in wheel speed sensors and propeller shaft sensors of older cars built around 2000 and before. They are self powered little generators that produce a voltage and current sine wave that correlates frequency with angular velocity. The pulsating output is easily converted into a signal that accurately shows wheel speed, with the only weakness being a difficulty quantifying very slow speeds. For that reason newer vehicles largely switched to hall effect sensors.
VERY well done! Excellent video. Very clear and understandable descriptions of, like everything. That's so cool that you hand built your own motor. I'm an inventor, and I think I want to develop my own electric motor that is pre-configuered to compensate for reluctance variences.
You've got a good presence on the tube and do a great job of explaining the operation of the SRM. One other thing you may want to point out is the torque on the rotor with respect to the angle as it approaches the stator. It too is complicated because the percentage of the pull forces are greater when the angle is greatest, but the fringing magnetic field is weak. There is an optimal point as the rotor nears the stator winding where the vector force due to the angle and the fringing magnetic field is stronger such that the torque is maximum.
Yep... you can slow down the saturation time by introducing air gaps into the rotor, and increase efficiency by moving away from any solid metals... a metal powder mixed into an insulator bind (like iron powder mixed into epoxy as a simple example) stops eddy currents from being able to form, so it runs cooler, losing less energy to heat. You can also deal with some of the switching issues by adding a few windings from one magnet to the neighbouring magnet. Big advantage is that you don't need the rare earth minerals to make the magnets that can survive higher temperatures that you can get making high power motors... there's a lot of human exploitation found in those supply chains, making their use difficult to justify in any kind of "future for humanity" project, and somewhat self defeating.
It would be interesting to get the difference between "Switched Reluctance" motors and the old stepping motors that have been around for 50 years or so, used in hard drives, floppy disc drives, video players~recorders etc
Depends, some have magnets in the rotor and are more like a pmdc, others are basically a small switched reluctance motor. All have a lot more teeth on the rotor.
I used to work at for a well known vacuum cleaner company (probably better known now for expensive hair straighteners). They were very secretive but I did manage to find out that they were using these motors in their line of handheld vacs. Ebay might be a cheap way of getting hold of a small low voltage motor/controller to play with.
Yes, I recall seeing some teardown videos of those products. I can see why they'd use it: it's cheap, robust and can spin fast. Torque ripple is not much of a concern for a tiny, high speed fan that makes 10x more noise than the motor anyway.
Thank you very much! A clear and concise explanation of this motor was very helpful to me with my own designs. Keep on making them, please. I do not have any benefit of higher ed that is not autodidactic, and things like this are a big help.
While an SRM is arguably a type of stepper motor, most stepper motors use permanent magnets unlike SRMs. The driver needed is also different. A different type of bridge configuration is used, but perhaps most importantly the control scheme is different, because the motor is designed for an entirely different purpose: stepper motors are used for accurate positioning systems, whereas an SRM is used for driving machinery and so more dc motor-like characteristics are wanted. You can also see this in the physical design, the "steps" of most SRMs are far too big to make a usable stepper motor. So yeah technically you can see it as a type of stepper motor, but it differs quite a bit from most other steppers people are used to.
Thanks for publishing a video like this, I thoroughly enjoyed your whiteboard explanations. I explored SRM's several years ago, prototyped a driver and modified a universal AC motor into a 1-phase 2-pole radial SRM after a lot of rotor stripping and shaping. I have a short video briefly discussing my driver's principle of operation, some active scope waveforms, and deliberately forcing the SRM into a poor firing angle. You might find it interesting as you work on your SRM driver. My intent is more spirited towards Peter Lindemann's "rotary attraction motor" drive principles over traditional designs that may simply use a snubber circuit, or the primary link capacitors as the closed-circuit to dump the stored energy from the coil's magnetic field. I was focused on creating a driver that managed a mechanical output, and a secondary regulated electrical output. My drive used transistor logic with hall sensors rather than an MCU, and it worked great for a universal motor turned into an SRM. For a given input power of 165W, I was able to recover 60% of the stored magnetic energy simply as a consequence of running the motor. The recovery was actually essential for maintaining a tight firing angle like you mentioned in the video. My setup could benefit from a higher resolution to achieve the perfect firing angle, but beyond that I would need a dedicated rotor and stator design and more poles to increase efficiency and reduce vibrations above 8000 RPM. I tried purchasing a ~$800 SRM from a company called Striatech in 2018 so I had a proper motor to use as a dev platform to work towards a more intelligent driver with firing angle phase adjustment, torque control, and a few other control and feedback features, but Striatech was dragging their feet and giving supplychain excuses. It went from a "a shipment is arriving in a couple days" to 1-2 months, and then they stopped replying to me alltogether. I got my money but it took the wind out of my sails and I just moved on without there really being any good companies selling small SRM's for development in that period in North America. I've been focused on other subjects since then, but I'd like to start putting time into motor design again with renewed interest. Hey if you ever feel like bouncing some motor related questions or thoughts off of while you engineer the motor and driver for your project, feel free to throw me an email!
Instantly subscribed. Very clear presentation. I designed a similar motor that drives a ceiling fan in my welding shop. It is always ready, meaning it is battery driven and operates by SELF-switching its circuitry on and off. I just reach up and give it a push and away it goes. I also have one that operates on compressed air and it too is always ready and starts & stops by hand.
I was just about to break out in a cold sweat in anticipation of a sensorless field oriented control, Clarke & Park transform lecture coming on 😅😂 Nice job. Well explained and kept simple.
I had the privilege of learning under a man called Dr Jasmine Corda who did a massive amount of work on switched reluctance motors during my degree. absolute powerhouse of a intellect. been a while but i believe switched reluctance motors have a very strong use case in precision speed controlled motors, like in places like fab houses where they need consistent flowrates in pumps/fans with little variation. I think they are also great at very high speeds. But one of his favourite anecdotes was that in like the 80's they had a small van like thing full of batteries with a powerful switched reluctance motor which would out accelerate most cars of the time, similar to how teslas do now, albeit with horrendously bad batteries of the time.
In the 40s or 50s, the company General Models made a simple model of a self-propelled railroad inspection car and a Birney streetcar using a motor that operates on the same principal- the design had a single winding that energized two poles, and one of the axles of the cars was a metal bar that would align itself with the poles when energized. The wheels on the axle acted as a sort of commutator, making contact with the track to complete a circuit with the coil. As the axle rotated to align with the poles, the wheels broke contact, and it would coast until making contact again- there were two power strokes per revolution of the axle. Due to the design, they needed a push to start, and weren't suited for operating up inclines. I own one of the inspection cars, and never knew what the type of motor was called, it was unlike anything I'd seen before on a piece of model railroad equipment. They called their system "Elec-Traction". I don't think it was around for more than a few years.
We need to put you and that contraption in a museum for education purposes.... Please repeat how it worked...in a detailed manner in a video then send it to AKIO TV to post for us.
I bought a chineese fan motor, it has no magnets and only one coil and some funny metal rotor design made of steel plates. You put AC into it and it spins. Its almost like a shaded pole but its not. Its a very strange design and the coil being AC swaps the poles at the frequency of the AC supply which in turn drives the motor almost like a switched reluctance/shaded pole combined. It also generates electricity but to do that it needs a tiny bit of help. I just put a single magnet near it and its enough to excite it into generating electricity. Good explanation of how it works. Thank you.
@cslim3881 I looked but can't find it. It's a really old motor. Imagine a single coil with a sprocket on each side of it. The sprocket has fingers like triangles. They are bent towards each other. So when the coil is energized one sprocket is all north poles, and the other is all south poles. So the fingers are like the magnets because they are connected to the core of the coil one on each side. But because the coil is AC, they are constantly flipping poles. I hope that makes sense. It's actually quite simple design.
@newmonengineering hi, is there a brand name on the fan? I play with vacuum motors. The closest is a two coils motor. Never seen a one coil motor before. THANKS.
Excellent description. I hope you go far. What control scheme are you considering? Remember the saying "A grinder and paint makes you the welder you ain't."
At the moment I'm working on the electronics, which will use a microcontroller. I can then program this mcu with whatever control scheme I want, try out a bunch of different things and see what works best.
You could just use a set of mechanical points, set slightly ahead of the rotor, to activate and deactivate the coils. No fancy controller needed. Points could be actuated off a lobed cam, similar to point ignition in a car.
Three hall sensors and a microcontroller and some mosFETs is super cheap, that's what they use for BLDC motors and this is basically just that with a passive iron rotor instead of a rotor with magnets on it. Electronics have gotten so cheap they are actually less expensive than a mechanical solution now. Plus there's no contact so there's nothing to wear out. Electronically commutated motors can approach 98% efficient because the commutation can be adaptive. If the RPM will be high and fairly constant you can use a "sensorless" controller design that determines the rotor position via back EMF from the motor. BLDC motors used in drones and model aircraft use sensorless motors for that reason.
@@atomicskull6405microcontrollers are a great option if you like working with them. I don’t. Personally I prefer dead nuts, simple, mechanical solutions over using micro controllers and such. Partially because I’m ass at coding, partially because I feel like they’re cheating on certain projects. But I also design and engineer totally different than most people.
I had designing an electric drive based on this type of motor. I`m even built my own dynamometer equipment for this purpose. It's pretty interesting but you have to know exactly the position of the rotor (rotary encoder or too many online calculations by measuring currents and voltages in all phases at the same time) to control this motor in proper way. Or you just can use it simple - in stepper mode (without feedback).
Only advantage if these motors over brushless DC motors with magnets isbthat they dint use permanent magnets. But for any tyoe of these motors adding magnets should make it more efficient right ? Like if you replace the iron cores with magnets the motor will have greater torque and speed right?
A crude way of controlling the motor would be a commutator and brushes. Build it inside out, deliver DC to the iron rotor via slip rings, then have brushes facing outward from the iron rotor to fixed contacts on the stator part, connecting the coils in sequence. Another way would be to install a magnet disk on the rotor with hall sensors on the stator part. When a magnet comes by, the hall sensor triggers a transistor to supply current to a particular coil.
These motors don’t need a fancy controller. Closed loop is great, but just to spin it, open loop is fine. You need a 3-phase square wave source and low side drivers. Arduino will do it, or a couple gates. IIRC Lancaster’s CMOS cookbook has a 3-phase generator schematics that uses a single chip or two.
A proper controller like what is used on BLDC motors (which are basically the same as this only with magnets on the rotor) will be much more efficient though. If you use an off the shelf BLDC ESC that supports open source and modified AM32 it'd probably work for this. You can get these for $20 or less.
Really enjoyed your presentation. I'm just leaving your comment to make sure you get extra points as a way of saying thank you. Motor design is close to my heart. I'm not an engineer, just a wannabe.
The simplest switched reluctance moter I seen was commutated and used only one coil. Its construction was like this. The rotor had 6 nails driven into a circle and the stator had one coil that was switched on by two brushes that make concurent contact radially with a nail when a nail was close, and was switched off when momentum moved that nail over the coil. The magnetic circuit could be be improved with a second coil 180 degrees out from the first coil. Self starting could be had by two more pairs of coils. The three sets of brushes need be placed radially 120 degrees apart, and sweep at least 60 degrees.
Best boom mic ever. 1. Dimensionsal lumber✅ 2. Duct tape✅ 3. Zip ties✅ Extra points would have been awarded for: Bubblegum Baling Wire Twine Vice Grips
Another sensor for monitoring compliance would be a microphone. An advantage would be optimising energy efficiency at any load. A disadvantage would be circuit complexity, perhaps even involving a DSP.
You can control the switching of the coils without a controller, just add a disc to the shaft that has parts that are conduction and parts that are not and a set of brushes that energize the coils. At the end you get a motor with 2 leads that can be run from a battery or power source. But is way cooler to use a controller :D, For the disc encoder i propose something using the grey code
It would be interesting to go through the differences between driving this and a permanent magnet motor- they seem strikingly similar but with very important differences.
I had a idea quite a while ago, that I've never been able to either confirm or debunk, but I think perhaps, having watched this brilliant video, that you are the right one to to do so. Basically, and I did not know this beforehand, the idea is based on exactly this motor design, at least I think so, with the twist that you wind coils on the rotor. They will not be powered as such, rather the inducted, thingy magik, magnetism or what not (suffice to say that both my memory and my expertise leaves something to be desired) result in a power spike in the rotor, though only some of the coils, which then in turn are connected up with the other coils, in such a way the their magnetic field are appropriately usefull, considering that the stator coils are not in fact swtiched, but static, only the intensity of their magnetig field being adjustable. Effectively you have half a generator and half a motor, and the energy generated byt the generator powers the elektromagnets, replacing what would've been permanent magnets, only these magnet can change and vary their magnetic field. The idea furthermre is that this motor should be power direktly by DC, with no swtching or conversion, the speed controlled by adjusting the voltage, or the available power in some other way. I hope my explanaion is good enough, as it is pretty much the best I can do I think, and the questions are simply, could it potentially work, and if so, could it eliminate the complexity added by active and regulated switching? Also, you got yourself a new sub.
The principle you describe, (I think) is essentially what an induction motor does. Although it doesn't use coils on the rotor per se, but instead has a rotor containing some thick copper/aluminium bars to form single-turn induction windings. The stator field induces a current in these windings, which then effectively turns the rotor into a magnet and so it starts spinning. This is a very common industrial motor that is used a lot. However, where it differs from what you explained, is that the stator coils do have to be driven using an AC power supply, otherwise no current can be induced in the rotor windings, since induced voltage (or current) is proportional to the rate of change of the magnetic field. So if the magnetic field doesn't change (aka, the stator is purely DC powered) there won't be a voltage induced in your rotor windings. So you do need to drive the stator with AC or use some kind of switching supply. The good thing about an induction machine though, is that it runs on a regular AC sinewave, which can be easily created using a simple inverter, or even taken directly from a power outlet, so these motors are very easy to drive. Position measurement of the rotor is also not required. However they are slightly less efficient than SRMs, since these currents in the rotor windings produce some (minor) losses.
@@AKIOTV Thank you for the very thurough reply.I think perhaps that there's something I've not been able to explain properly, as what I have in my mind, does run pn AC, really, only the rotor is responcible for dc to ac conversion so to speak. Then againk if it could actually work, no doubt someone had come up with the idea a long time ago. at any rate, thanks again.
@@edeaglehouse2221 I have found a few different design, some with permanent magnets and some with coils. I cannot say that they function the same, but it certainly seems so. Thanks for the tip.
I thought it was time I tried to understand the motor inside my BMW i3, about time after 7yrs and my second one. In fact it's not a true SRM but a hybrid synchronous motor with a little bit of permanent magnet and some use of reluctance. In August 2013, Green Car Congress had an article on the BMW patent. When Sandy Munro was interviewed in 2014 on Autoline Daily about his teardown of the i3, he was quite impressed with the motor. However I'm not sure BMW have developed the idea further, it's certainly not in the iX M60 whose motor even has brushes!! Also ref. to David Bricknell's book: "Electric Vehicles and the BMW i3".
it is kind of magical how awfully difficult it is to make a "normal looking" motor (I mean the kind of electricity + motor = movement) using reluctance, while the reluctance part of stepper motors is absolutely trivial.
That axial flux design would be very suitable for a PCB based design. For small motors could use standard inductive coils even. And of course the PCB could easily hold the sendors, power and control electronics as well. Microcontrollers are now very cheap. Could make for a nice open source computer fan design?
you could try making the motor bigger with lots more little coils and maybe changing the shape of the rotor. rarely do you see any straight, perfect lines in nature, the greatest machine ever made.
Now is the time to look into & understand the SYNCHRONOUS RELUCTANCE MOTOR (also a doubly salient design like SRM).... a new entry into the game promising to have simpler electronics , more efficiency , than SRM or any other conventional type motor
I have a suggestion for a method to switch the coils on and off. It is quite magical and doesn't involve technologies so advanced that a solid state physics laboratory is required to build them: Connect the each pair of coils to a series of contacts positioned on opposite sides of the rotor's shaft. Arrange pairs of contacts fixed to the motor's frame to touch the rotor's contact pairs. Position the fixed contacts such that they are rotated slightly in advance of the pair of coils to which they are connected so that the motor is self-starting. Sound familiar?
Putting brushes on this motor renders the whole reluctance based design pointless, since at that point you might as well use a wound rotor, (a rotor with coils) aka make it a regular dc motor. The SRM only makes sense as a brushless design.
You could use reluctance to get a buf in while it had some teoricaly to 2x aplying the oposite voltage in the same coil like in permanent ones im not sure but it would be a diferent output and the motor need to be design it for it, the buf in weight/power ratio
Reminds me of steppers and what powers the 3 phases of a electric unicycle motor and the early modles at low speed had that grinding effects of phase ripple at low speed. Controller advancements and tech improvement smooth it out.
You have to do something with that horizontal stripe in the bottom part of the picture as it might confuse some people:))) That made me watch the video twice on two different devices as firstly I thought my screen is dying due to bad pixels:)))) But the video itself and your presentation style is great! Here I will echo to many of the comments blw - very clear explanation and it is really interesting watching and listening you! Now subscribed to your channel, thumbs up! Keep going!
Haha yes the bad pixels are on my camera sensor not your screen. This must be the first time someone notices it. I've been thinking about potential fixes for a while, I'll try and implement one in my next video.
If im not mistaken, the modern day switched reluctance motor is not really anything more than a multiphase version of the lindemann attraction motor, which is has only one single coil and a two or four "pole" rotor from what i've seen.
The shape you need to power the coils should be exactly the same that is coming out of the coil when used as a generator. One of the more complicated things will be that the shape is dependent on the speed of the motor. This means every speed the motor is running the power curve has to change to create the optimal power output. I played around with the concept of recording and playback 25 years ago in a summer vacation. I was playing around with a big audio amp where the one of the amps where broken. I recorded the generator phase on to an audio cassette and playing it back through the amplifier to get the same speed out. My first tests where nice, but i blew out the audio amplifier, because i didn't thought of the feed back into the amp. I didn't had a replacement, so everything went into the trash. 🙂
@@jaro6985 The residual magnetism was enough to create enough voltage for the recording. I had to use a voltage divider to dampen the signal with higher speeds.
Nice explanation...I now understand a bit more, thank you. I also understand that the stepper motors that are everywhere are also switched reluctance but with more poles ?
Good job on your tube. You can make an old school cam switcher, or a solid state switcher with a freq drive .also the many other ways such a optical switcher. Show the world the diffrent ways to skin the cat. Have fun with it and your tube will grow. Best Regards Jack.
Switching on the current is not such a problem, as the inductance is low. But as the inductance MUST rise as the pols overlap, inductance will be 5-10 times higher, so the current decay is much slower. There are different ways to optimize the overlapping scheme. On the other hand: a useful SRM must be magnetized to 1.7+ Tesla, so the inductance is no longer linear with the current.
I would suggest to use Hall switches, that one can integrate into your coils, switched off at 3 degrees before top dead center as your rotor turns. And, yes one would need to attach a very small Nib on each pair of rotor poles. Subbed, and looking forward to your next vid. Nice job...
Intuition tells me the optimal angle would change with the speed. As the speed increases, you would want to remove power from the coil earlier because of the momentum of the rotor. Made sense in my head, anyway.
@@edeaglehouse2221Correct because the pulse width length which would be represented as a unit of time would decreses inverse to the speed of the rotor. So as the cycle rate of the rotor increases the impulse that's generated in your stator windings decreases in terms of duration. An increase in the angular momentum is effectively converted to a higher voltage output in the stator windings. However if you can manipulate the reluctance of you stator windings with a modulating circuit you could probably mitigate much of the drag created by the stator windings. I've often wondered if you switch the coil from open to closed only when you've passed 51% of the pulse duration. I'm curious to see how this would effect the motors natural acceleration and deceleration rates. Also what running it inside of a vaccum chamber would do to eliminate overall resistance. Air alone is exerting alot drag on the rotor alone. Also friction due metal in metal contact inside the bearings could be mitigated by using magnetic levitation bearings. If anyone has tried this I'm curious to see it and the results. Lol
This is a synchronous reluctance motor A switched reluctance motor is an asynchronous induction motor with switchable resistors in the middle of the induction coils, usually through brushes
Watched the video til the end. The video explains the physics behind this motor properly. To the point. Switching the polarity at predefined intervals can be a solution, but altering the speed will be difficult, and the motor will not generate its maximum possible torque by doing so. It's a good proposition, yet, another never-ending exploration for cheaper propulsion like pulsejet (at least at the moment). I'd have to look at the history of this motor.
I just saw your video, and I am now a subscriber! I never heard of a reluctance motor. But I like to play with big bars of copper and silver, it's neat to see how Strong magnets and silver and copper interact. How would your motor work with a copper rotor??? Would it just need to adjust the timing to deal with eddy currents? How about it? Are you willing to replace the rotor with a copper rotor? I for one would love to see THAT!
When the rotor blade aligns with the center of coil, then the coil should turn off, and when coil turns off, the magnetic field of coil collapses, can we capture that collapsing field energy into a capacitor and reuse the charge stored in capacitor?
What happens if your reverse the current in the second half of the cycle you described? I ask because it looks like you would drive each pole pair with a full sine wave. Looking forward to your next instalment on this reluctance motor.
So with a brushless DC motors like we use in the RC world, it seems the only difference from an SRM is permanent magnets are placed on the rotor of the BLDC. No? Or am I missing something here? Everything you described is how BLDC motors work down to the motor controller. We call them the ESC (Electronic Speed Controller.) We have both sensored (Using a hall sensor) and sensorless that relies on back EMF. Sensorless can cog at low speeds, but once going, they work smooth and flawless. One more question...LOL Do SRM's need, or benefit from a startup capacitor? I would imagine there is a heavy current draw to get moving.
The absence of magnets is a small physical difference, but makes the motor very different to drive. The details are too much to write in this comment, but if you compare the output sequence of a normal esc to what you saw in the video, you'll notice it's not the same. Another difference is the ideal drive waveform; the best shape for current in a bldc motor is a (pure) sinusoid, which is not the case for an srm.
The most perfect motors, I swear are direct drive BLDC, out of washing machine. You can take the motor and connect any two of the wires and spin the motor by hand say 60 rpm get 120 v at 60 htz, hook 2 together and spin one to drive the other, variable speed motor, generat at 1500 rpm ,1000 volts ,snap!!!😊
These motors sound very similar in some ways to BLDC motors. I think it would be possible to just reprogram a BLDC motor driver to drive one of these too. BLDC motors also need position sensing (physical sensors or measuring the unpowered coil) and they need precise timing/positioning for when it switches the coils on, just like these motors. Would it be possible to connect these motors coils up in a star configuration too, similar to how BLDC motors already work? Another thing to look at is stepper motors and their drivers, they also require energising coils in a certain order and precisely.
Since Electronic Speed Controllers (3 phase ESC) is used to drive most brushless DC motors, would you be attempting to modify one of those to get it to be able work as a controller here?
sounds like the controls would be very similar for a BLDC motor. should be a software modification for an ESC There are a few that have open source firmware (look for ones that are simonk ), they are setup to PWM the signals as well. with Field Oriented Control, the system can measure the shaft angle and can apply the exact power needed across multiple coils, it should be able to pretty much eliminate the torque ripple
Why not just use a commutator with an adjustable brush cage? I know brushless is frowned upon these days but there are advances that can be made in that direction too. Could be fun?
I'm still working on a driver for this motor. When I have it working I'll post a short video showing the motor running at speed.
Edit: the motor now runs, here's a link to the video: ruclips.net/video/TAhF45AtsgA/видео.htmlsi=qABbtBXH8Mqic1_W
What will you use as software? Do you know SimpleFOC?
@@candas1 I was planning to code something from scratch. I didn't know about simplefoc, looks like very solid stuff, I'll definitely keep it in mind. Not sure if it supports this kind of motor/my driver electronics, so I'll have to look into that. Thanks for the suggestion!
@@AKIOTVprobably not out of the box, but it will get you started faster. There are a lot of knowledgeable guys on the forum
Why not use a brushless motor speed controller, typically used for drones. Most of the time they are 'sensorless' using the collapsing magnetic field of the un-energized coils to figure out the position. It may not work in your case as drone motors use magnets on the rotor, which would amplify the 'sensor' signal.
@@moddaudioA SRM and BLDC motor are very, very different. FOC does not apply to this motor type. Timing is much much more tricky to achieve. The maths differs.
I heard people were reluctant to use these motors but then something just switched.
Very good / bad. It depends however on how frequently they switch between the two, problems get induced.
Quite genius 😂
I'm reluctant to approve of the switched meanings of these puns..
@@Dr_Wrong being reluctant just means that there's an opportunity for your opinion to switch 😂
I feel like this was a very good dad joke
Very well explained. Feels like a seminar in university back in the days. Thumps up!
I got the 1980s Open University vibe (if you are in the UK and over 40 you'll know what I mean). He's got the right voice/presentation and excellent way of explaining everything. I enjoyed this video and am looking forward to more of them.
Stepper motors are effectively switched reluctance motors as well. They get around control problems by just letting them "cog" to wherever.
Exactly, this is just an axial flux stepper motor.
Excellent presentation. You explain the concepts and the problems without tedious math, just simple graphs. I am hoping for more info on the controller. 👍🏻
I say! Retired lecturer here, it seems the future is in good hands!
I have seen a switched reluctance motor, my Rainbow vacuum cleaner has one in it. Inside is an asterisk shaped laminated steel rotor and what appears to be either two or four coils of wire in the stator. It's a neat sounding machine starting up as well. There's also a microcontroller board on top of it to start and run it.
Thanks I'm going to be looking for one in our markets and second hand stores. I used to have a Rainbow, when they first came out. I loved it because it got rid of the dust issue that conventional vacs at the time did. Thanks again.
What is the failure rate of that vacuum cleaner with such a motor? Do you know?
Pointing out a concept by starting with a constant voltage supply where one switches a coil off when a rotor pole is in position over the coil. The current flowing in the coil is related to the load (because of time for current to build) as well as the inductance. Besides the energy in the magnetic field converted work done in movibg the load, there will be some energy still left in the magnetic field at the point of maximum inductance and maximum current. But because inductance in coils opposes changes in current then switching the current off would create an inductive voltage spike across the coil. While many coils like those used in relays use a flyback diode to and sometimes a capacitor to snub the inductive kick back, that remaining energy in the collapsing magnetic field can instead be dumped in the next set of coils that are swiched in. And this can be repeated over and over. The high voltage output spike can drive the next set of stator coils.
This is not perpetual motion motor but just minimizing energy loss and proposing a way to get get more torque at the beginning of the next coil's cycle and minimize torque ripple.
Lastly, the coils are now nolonger constant voltage driven, but ratherly approximating constant current driven. 😊
Reminds me of when I was playing with multi-stage rail guns but rotary rather than propelling a projectile in a straight line. Lots of incredible use cases for this type of motor - I wasn't aware of it. Great vid - thanks, subscribed.
It’s interesting because torque ripple in motorcycle engines can have a significant impact on maintaining traction between the tire and road. The phase of the power pulses can help prevent slip and maintain grip in certain situations. So in some applications torque ripple can be a good thing.
My mind went right to the HD XR-750 when he mentioned tourque ripple!
Nice review. Although switched reluctance motors may be rare, they have a much more prevalent cousin in the form of the variable reluctance sensor. These are found in wheel speed sensors and propeller shaft sensors of older cars built around 2000 and before. They are self powered little generators that produce a voltage and current sine wave that correlates frequency with angular velocity. The pulsating output is easily converted into a signal that accurately shows wheel speed, with the only weakness being a difficulty quantifying very slow speeds. For that reason newer vehicles largely switched to hall effect sensors.
Still often found as crankshaft sensors with Hall effect used on the camshaft’s due to the camshaft running at half crank speed.
VERY well done! Excellent video. Very clear and understandable descriptions of, like everything. That's so cool that you hand built your own motor. I'm an inventor, and I think I want to develop my own electric motor that is pre-configuered to compensate for reluctance variences.
You've got a good presence on the tube and do a great job of explaining the operation of the SRM. One other thing you may want to point out is the torque on the rotor with respect to the angle as it approaches the stator. It too is complicated because the percentage of the pull forces are greater when the angle is greatest, but the fringing magnetic field is weak. There is an optimal point as the rotor nears the stator winding where the vector force due to the angle and the fringing magnetic field is stronger such that the torque is maximum.
The past is always the future. I was going to say these are old tech, but you said that right away. Kudos.
Yep... you can slow down the saturation time by introducing air gaps into the rotor, and increase efficiency by moving away from any solid metals... a metal powder mixed into an insulator bind (like iron powder mixed into epoxy as a simple example) stops eddy currents from being able to form, so it runs cooler, losing less energy to heat. You can also deal with some of the switching issues by adding a few windings from one magnet to the neighbouring magnet. Big advantage is that you don't need the rare earth minerals to make the magnets that can survive higher temperatures that you can get making high power motors... there's a lot of human exploitation found in those supply chains, making their use difficult to justify in any kind of "future for humanity" project, and somewhat self defeating.
It would be interesting to get the difference between "Switched Reluctance" motors and the old stepping motors that have been around for 50 years or so, used in hard drives, floppy disc drives, video players~recorders etc
...and that still drive most 3d printers or cnc machines that aren't expensive enough to use servos.
Depends, some have magnets in the rotor and are more like a pmdc, others are basically a small switched reluctance motor. All have a lot more teeth on the rotor.
I used to work at for a well known vacuum cleaner company (probably better known now for expensive hair straighteners). They were very secretive but I did manage to find out that they were using these motors in their line of handheld vacs. Ebay might be a cheap way of getting hold of a small low voltage motor/controller to play with.
Yes, I recall seeing some teardown videos of those products. I can see why they'd use it: it's cheap, robust and can spin fast. Torque ripple is not much of a concern for a tiny, high speed fan that makes 10x more noise than the motor anyway.
Thank you very much! A clear and concise explanation of this motor was very helpful to me with my own designs. Keep on making them, please. I do not have any benefit of higher ed that is not autodidactic, and things like this are a big help.
Very nice explanation of how stepper motors work. The electronic circuits for driving stepper motors are readily available.
While an SRM is arguably a type of stepper motor, most stepper motors use permanent magnets unlike SRMs. The driver needed is also different. A different type of bridge configuration is used, but perhaps most importantly the control scheme is different, because the motor is designed for an entirely different purpose: stepper motors are used for accurate positioning systems, whereas an SRM is used for driving machinery and so more dc motor-like characteristics are wanted. You can also see this in the physical design, the "steps" of most SRMs are far too big to make a usable stepper motor.
So yeah technically you can see it as a type of stepper motor, but it differs quite a bit from most other steppers people are used to.
Magnets are used in steppers for holding torque when at a stop. This motor is simply a synchronous reluctance motor.@@AKIOTV
PS. subscribed. Love your topics, your way of deconstructing them, and your style and your very understated dry humor too. “Words!” 😂
Thanks for publishing a video like this, I thoroughly enjoyed your whiteboard explanations.
I explored SRM's several years ago, prototyped a driver and modified a universal AC motor into a 1-phase 2-pole radial SRM after a lot of rotor stripping and shaping. I have a short video briefly discussing my driver's principle of operation, some active scope waveforms, and deliberately forcing the SRM into a poor firing angle. You might find it interesting as you work on your SRM driver. My intent is more spirited towards Peter Lindemann's "rotary attraction motor" drive principles over traditional designs that may simply use a snubber circuit, or the primary link capacitors as the closed-circuit to dump the stored energy from the coil's magnetic field. I was focused on creating a driver that managed a mechanical output, and a secondary regulated electrical output. My drive used transistor logic with hall sensors rather than an MCU, and it worked great for a universal motor turned into an SRM.
For a given input power of 165W, I was able to recover 60% of the stored magnetic energy simply as a consequence of running the motor. The recovery was actually essential for maintaining a tight firing angle like you mentioned in the video. My setup could benefit from a higher resolution to achieve the perfect firing angle, but beyond that I would need a dedicated rotor and stator design and more poles to increase efficiency and reduce vibrations above 8000 RPM. I tried purchasing a ~$800 SRM from a company called Striatech in 2018 so I had a proper motor to use as a dev platform to work towards a more intelligent driver with firing angle phase adjustment, torque control, and a few other control and feedback features, but Striatech was dragging their feet and giving supplychain excuses. It went from a "a shipment is arriving in a couple days" to 1-2 months, and then they stopped replying to me alltogether. I got my money but it took the wind out of my sails and I just moved on without there really being any good companies selling small SRM's for development in that period in North America.
I've been focused on other subjects since then, but I'd like to start putting time into motor design again with renewed interest. Hey if you ever feel like bouncing some motor related questions or thoughts off of while you engineer the motor and driver for your project, feel free to throw me an email!
Instantly subscribed. Very clear presentation.
I designed a similar motor that drives a ceiling fan in my welding shop.
It is always ready, meaning it is battery driven and operates by SELF-switching its circuitry on and off.
I just reach up and give it a push and away it goes.
I also have one that operates on compressed air and it too is always ready and starts & stops by hand.
Just came across this and since I had never heard of one I thought i would give it a view. Well done covering this topic.
You also want the drive waveform to be mostly sinusoidal to minimize eddy current losses from harmonics.
I was just about to break out in a cold sweat in anticipation of a sensorless field oriented control, Clarke & Park transform lecture coming on 😅😂
Nice job. Well explained and kept simple.
I had the privilege of learning under a man called Dr Jasmine Corda who did a massive amount of work on switched reluctance motors during my degree. absolute powerhouse of a intellect. been a while but i believe switched reluctance motors have a very strong use case in precision speed controlled motors, like in places like fab houses where they need consistent flowrates in pumps/fans with little variation. I think they are also great at very high speeds. But one of his favourite anecdotes was that in like the 80's they had a small van like thing full of batteries with a powerful switched reluctance motor which would out accelerate most cars of the time, similar to how teslas do now, albeit with horrendously bad batteries of the time.
Haha that van does sound like one fun project. Given it used an SRM it probably also made one hell of a sound.
Finally someone on RUclips has built an axial flux one.
In the 40s or 50s, the company General Models made a simple model of a self-propelled railroad inspection car and a Birney streetcar using a motor that operates on the same principal- the design had a single winding that energized two poles, and one of the axles of the cars was a metal bar that would align itself with the poles when energized. The wheels on the axle acted as a sort of commutator, making contact with the track to complete a circuit with the coil. As the axle rotated to align with the poles, the wheels broke contact, and it would coast until making contact again- there were two power strokes per revolution of the axle. Due to the design, they needed a push to start, and weren't suited for operating up inclines.
I own one of the inspection cars, and never knew what the type of motor was called, it was unlike anything I'd seen before on a piece of model railroad equipment. They called their system "Elec-Traction". I don't think it was around for more than a few years.
That's quite clever actually
We need to put you and that contraption in a museum for education purposes.... Please repeat how it worked...in a detailed manner in a video then send it to AKIO TV to post for us.
You're an excellent presenter. Even I (pensioner) understood all your explanations. Subbed, looking for more! 👍
You do not necessarily need to monitor the position of the rotating assembly... Not at all.
Enjoyed your video and also found it very helpful. Switch-Reluctance-Motors are cool. Thx AKIO TV, it inspired me to design one. 😊
A really good tutorial. Thank you for sharing.
Do it the way gasoline engines deal with their equivalent of "torque ripple" just throw a big ol' flywheel on it.
Average mechanical engineer solution
I bought a chineese fan motor, it has no magnets and only one coil and some funny metal rotor design made of steel plates. You put AC into it and it spins. Its almost like a shaded pole but its not. Its a very strange design and the coil being AC swaps the poles at the frequency of the AC supply which in turn drives the motor almost like a switched reluctance/shaded pole combined. It also generates electricity but to do that it needs a tiny bit of help. I just put a single magnet near it and its enough to excite it into generating electricity. Good explanation of how it works. Thank you.
Hi, possible to provide a link to the motor? Thanks.
@cslim3881 I looked but can't find it. It's a really old motor. Imagine a single coil with a sprocket on each side of it. The sprocket has fingers like triangles. They are bent towards each other. So when the coil is energized one sprocket is all north poles, and the other is all south poles. So the fingers are like the magnets because they are connected to the core of the coil one on each side. But because the coil is AC, they are constantly flipping poles. I hope that makes sense. It's actually quite simple design.
@newmonengineering hi, is there a brand name on the fan? I play with vacuum motors. The closest is a two coils motor. Never seen a one coil motor before. THANKS.
Very clear ! Thnx 😁👍🏻 also liking the little mistakes/errors/ falling things 😁😂😂😂 makes it real !
Excellent description. I hope you go far. What control scheme are you considering?
Remember the saying "A grinder and paint makes you the welder you ain't."
At the moment I'm working on the electronics, which will use a microcontroller. I can then program this mcu with whatever control scheme I want, try out a bunch of different things and see what works best.
You could just use a set of mechanical points, set slightly ahead of the rotor, to activate and deactivate the coils. No fancy controller needed.
Points could be actuated off a lobed cam, similar to point ignition in a car.
Three hall sensors and a microcontroller and some mosFETs is super cheap, that's what they use for BLDC motors and this is basically just that with a passive iron rotor instead of a rotor with magnets on it. Electronics have gotten so cheap they are actually less expensive than a mechanical solution now. Plus there's no contact so there's nothing to wear out. Electronically commutated motors can approach 98% efficient because the commutation can be adaptive. If the RPM will be high and fairly constant you can use a "sensorless" controller design that determines the rotor position via back EMF from the motor. BLDC motors used in drones and model aircraft use sensorless motors for that reason.
@@atomicskull6405microcontrollers are a great option if you like working with them. I don’t. Personally I prefer dead nuts, simple, mechanical solutions over using micro controllers and such. Partially because I’m ass at coding, partially because I feel like they’re cheating on certain projects. But I also design and engineer totally different than most people.
I had designing an electric drive based on this type of motor. I`m even built my own dynamometer equipment for this purpose. It's pretty interesting but you have to know exactly the position of the rotor (rotary encoder or too many online calculations by measuring currents and voltages in all phases at the same time) to control this motor in proper way. Or you just can use it simple - in stepper mode (without feedback).
Very professional presentation and nice workshop.
Only advantage if these motors over brushless DC motors with magnets isbthat they dint use permanent magnets. But for any tyoe of these motors adding magnets should make it more efficient right ? Like if you replace the iron cores with magnets the motor will have greater torque and speed right?
A crude way of controlling the motor would be a commutator and brushes. Build it inside out, deliver DC to the iron rotor via slip rings, then have brushes facing outward from the iron rotor to fixed contacts on the stator part, connecting the coils in sequence. Another way would be to install a magnet disk on the rotor with hall sensors on the stator part. When a magnet comes by, the hall sensor triggers a transistor to supply current to a particular coil.
Yep. Hall sensors and tiny magnets work good, but not as stable as an optical-encoder.
These motors don’t need a fancy controller. Closed loop is great, but just to spin it, open loop is fine. You need a 3-phase square wave source and low side drivers. Arduino will do it, or a couple gates. IIRC Lancaster’s CMOS cookbook has a 3-phase generator schematics that uses a single chip or two.
A proper controller like what is used on BLDC motors (which are basically the same as this only with magnets on the rotor) will be much more efficient though. If you use an off the shelf BLDC ESC that supports open source and modified AM32 it'd probably work for this. You can get these for $20 or less.
Really enjoyed your presentation. I'm just leaving your comment to make sure you get extra points as a way of saying thank you. Motor design is close to my heart. I'm not an engineer, just a wannabe.
Good presentation! Nascent engineer? Very clean yet felt unscripted. Bravo Zulu!
The simplest switched reluctance moter I seen was commutated and used only one coil.
Its construction was like this. The rotor had 6 nails driven into a circle and the stator had one coil that was switched on by two brushes that make concurent contact radially with a nail when a nail was close, and was switched off when momentum moved that nail over the coil.
The magnetic circuit could be be improved with a second coil 180 degrees out from the first coil.
Self starting could be had by two more pairs of coils. The three sets of brushes need be placed radially 120 degrees apart, and sweep at least 60 degrees.
A very sensible video , well presented.Give us more in future. Thanks for sharing.
Best boom mic ever.
1. Dimensionsal lumber✅
2. Duct tape✅
3. Zip ties✅
Extra points would have been awarded for:
Bubblegum
Baling Wire
Twine
Vice Grips
noted
Wow, way better than my physics teacher . Thankyou .
I can sleep through any lecture, good or bad and cram for tests with a 24 hr big data memory.
I can sleep through any lecture, good or bad and cram for tests with a 24 hr big data memory.
I can sleep through any lecture, good or bad and cram for tests with a 24 hr big data memory.
I can sleep through any lecture, good or bad and cram for tests with a 24 hr big data memory.
Another sensor for monitoring compliance would be a microphone. An advantage would be optimising energy efficiency at any load. A disadvantage would be circuit complexity, perhaps even involving a DSP.
You can control the switching of the coils without a controller, just add a disc to the shaft that has parts that are conduction and parts that are not and a set of brushes that energize the coils. At the end you get a motor with 2 leads that can be run from a battery or power source. But is way cooler to use a controller :D, For the disc encoder i propose something using the grey code
The technical name for the disc is a commutator and as a result of your proposed action, you’ve just made a DC motor.
Thank you for the interesting motor video, I will try to replicate it in the future
It would be interesting to go through the differences between driving this and a permanent magnet motor- they seem strikingly similar but with very important differences.
I had a idea quite a while ago, that I've never been able to either confirm or debunk, but I think perhaps, having watched this brilliant video, that you are the right one to to do so.
Basically, and I did not know this beforehand, the idea is based on exactly this motor design, at least I think so, with the twist that you wind coils on the rotor. They will not be powered as such, rather the inducted, thingy magik, magnetism or what not (suffice to say that both my memory and my expertise leaves something to be desired) result in a power spike in the rotor, though only some of the coils, which then in turn are connected up with the other coils, in such a way the their magnetic field are appropriately usefull, considering that the stator coils are not in fact swtiched, but static, only the intensity of their magnetig field being adjustable. Effectively you have half a generator and half a motor, and the energy generated byt the generator powers the elektromagnets, replacing what would've been permanent magnets, only these magnet can change and vary their magnetic field. The idea furthermre is that this motor should be power direktly by DC, with no swtching or conversion, the speed controlled by adjusting the voltage, or the available power in some other way.
I hope my explanaion is good enough, as it is pretty much the best I can do I think, and the questions are simply, could it potentially work, and if so, could it eliminate the complexity added by active and regulated switching?
Also, you got yourself a new sub.
The principle you describe, (I think) is essentially what an induction motor does. Although it doesn't use coils on the rotor per se, but instead has a rotor containing some thick copper/aluminium bars to form single-turn induction windings. The stator field induces a current in these windings, which then effectively turns the rotor into a magnet and so it starts spinning. This is a very common industrial motor that is used a lot.
However, where it differs from what you explained, is that the stator coils do have to be driven using an AC power supply, otherwise no current can be induced in the rotor windings, since induced voltage (or current) is proportional to the rate of change of the magnetic field. So if the magnetic field doesn't change (aka, the stator is purely DC powered) there won't be a voltage induced in your rotor windings. So you do need to drive the stator with AC or use some kind of switching supply.
The good thing about an induction machine though, is that it runs on a regular AC sinewave, which can be easily created using a simple inverter, or even taken directly from a power outlet, so these motors are very easy to drive. Position measurement of the rotor is also not required. However they are slightly less efficient than SRMs, since these currents in the rotor windings produce some (minor) losses.
@@AKIOTV Thank you for the very thurough reply.I think perhaps that there's something I've not been able to explain properly, as what I have in my mind, does run pn AC, really, only the rotor is responcible for dc to ac conversion so to speak. Then againk if it could actually work, no doubt someone had come up with the idea a long time ago.
at any rate, thanks again.
Sounds a lot like the design of an alternator with its "field coils".
@@edeaglehouse2221 I have found a few different design, some with permanent magnets and some with coils. I cannot say that they function the same, but it certainly seems so. Thanks for the tip.
I thought it was time I tried to understand the motor inside my BMW i3, about time after 7yrs and my second one. In fact it's not a true SRM but a hybrid synchronous motor with a little bit of permanent magnet and some use of reluctance. In August 2013, Green Car Congress had an article on the BMW patent.
When Sandy Munro was interviewed in 2014 on Autoline Daily about his teardown of the i3, he was quite impressed with the motor. However I'm not sure BMW have developed the idea further, it's certainly not in the iX M60 whose motor even has brushes!!
Also ref. to David Bricknell's book: "Electric Vehicles and the BMW i3".
Fantastic explanation! Do we have any idea of the Torque / RPM characteristics of this motor?
Bonsoir Akio, une superbe video de plus - Bravo - j'ai une fois de plus tout compris. Merci
Great intro video to SRM. Well done! Good luck getting your motor operating, it's a great concept.
it is kind of magical how awfully difficult it is to make a "normal looking" motor (I mean the kind of electricity + motor = movement) using reluctance, while the reluctance part of stepper motors is absolutely trivial.
What an excellent explainer.
That axial flux design would be very suitable for a PCB based design. For small motors could use standard inductive coils even. And of course the PCB could easily hold the sendors, power and control electronics as well. Microcontrollers are now very cheap. Could make for a nice open source computer fan design?
you could try making the motor bigger with lots more little coils and maybe changing the shape of the rotor. rarely do you see any straight, perfect lines in nature, the greatest machine ever made.
Interesting topic, good explanation. But, I'm an old man, I fall asleep after about 8 minutes, thank you.😅
Great explanation to this beginner. Thanks.
Now is the time to look into & understand the SYNCHRONOUS RELUCTANCE MOTOR (also a doubly salient design like SRM).... a new entry into the game promising to have simpler electronics , more efficiency , than SRM or any other conventional type motor
I have a suggestion for a method to switch the coils on and off. It is quite magical and doesn't involve technologies so advanced that a solid state physics laboratory is required to build them: Connect the each pair of coils to a series of contacts positioned on opposite sides of the rotor's shaft. Arrange pairs of contacts fixed to the motor's frame to touch the rotor's contact pairs. Position the fixed contacts such that they are rotated slightly in advance of the pair of coils to which they are connected so that the motor is self-starting. Sound familiar?
Putting brushes on this motor renders the whole reluctance based design pointless, since at that point you might as well use a wound rotor, (a rotor with coils) aka make it a regular dc motor. The SRM only makes sense as a brushless design.
You could use reluctance to get a buf in while it had some teoricaly to 2x aplying the oposite voltage in the same coil like in permanent ones im not sure but it would be a diferent output and the motor need to be design it for it, the buf in weight/power ratio
Great video, we have a young JW here.
Reminds me of steppers and what powers the 3 phases of a electric unicycle motor and the early modles at low speed had that grinding effects of phase ripple at low speed. Controller advancements and tech improvement smooth it out.
You have to do something with that horizontal stripe in the bottom part of the picture as it might confuse some people:))) That made me watch the video twice on two different devices as firstly I thought my screen is dying due to bad pixels:))))
But the video itself and your presentation style is great! Here I will echo to many of the comments blw - very clear explanation and it is really interesting watching and listening you! Now subscribed to your channel, thumbs up! Keep going!
Haha yes the bad pixels are on my camera sensor not your screen. This must be the first time someone notices it. I've been thinking about potential fixes for a while, I'll try and implement one in my next video.
If im not mistaken, the modern day switched reluctance motor is not really anything more than a multiphase version of the lindemann attraction motor, which is has only one single coil and a two or four "pole" rotor from what i've seen.
The shape you need to power the coils should be exactly the same that is coming out of the coil when used as a generator.
One of the more complicated things will be that the shape is dependent on the speed of the motor.
This means every speed the motor is running the power curve has to change to create the optimal power output.
I played around with the concept of recording and playback 25 years ago in a summer vacation. I was playing around with a big audio amp where the one of the amps where broken. I recorded the generator phase on to an audio cassette and playing it back through the amplifier to get the same speed out. My first tests where nice, but i blew out the audio amplifier, because i didn't thought of the feed back into the amp. I didn't had a replacement, so everything went into the trash. 🙂
But you can't use it as a generator without control circuitry.
@@jaro6985 The residual magnetism was enough to create enough voltage for the recording. I had to use a voltage divider to dampen the signal with higher speeds.
Excellent presentation!
You should find a Russian ShD-5 (ШД-5Д1МУ3 or simply ШД-5) variable reluctance motor. Such an interesting example of Soviet engineering.
Grate video! Those radial internals seems like steper motors.
Nice explanation...I now understand a bit more, thank you.
I also understand that the stepper motors that are everywhere are also switched reluctance but with more poles ?
kind of, although most stepper motors contain magnets and are therefore not pure reluctance motors
Good job on your tube. You can make an old school cam switcher, or a solid state switcher with a freq drive .also the many other ways such a optical switcher. Show the world the diffrent ways to skin the cat. Have fun with it and your tube will grow. Best Regards Jack.
Switching on the current is not such a problem, as the inductance is low. But as the inductance MUST rise as the pols overlap, inductance will be 5-10 times higher, so the current decay is much slower. There are different ways to optimize the overlapping scheme. On the other hand: a useful SRM must be magnetized to 1.7+ Tesla, so the inductance is no longer linear with the current.
Excellently presented.
Very very impressive explanation,
Keep it up young man 👍👍😍
I would suggest to use Hall switches, that one can integrate into your coils, switched off at 3 degrees before top dead center as your rotor turns. And, yes one would need to attach a very small Nib on each pair of rotor poles. Subbed, and looking forward to your next vid. Nice job...
Would this be any different than a optical transistor?
a shaft encoder, might be cool for prototyping so you could easily play with different timings with the controller.
@@kayakMike1000 No.
Intuition tells me the optimal angle would change with the speed. As the speed increases, you would want to remove power from the coil earlier because of the momentum of the rotor. Made sense in my head, anyway.
@@edeaglehouse2221Correct because the pulse width length which would be represented as a unit of time would decreses inverse to the speed of the rotor. So as the cycle rate of the rotor increases the impulse that's generated in your stator windings decreases in terms of duration. An increase in the angular momentum is effectively converted to a higher voltage output in the stator windings. However if you can manipulate the reluctance of you stator windings with a modulating circuit you could probably mitigate much of the drag created by the stator windings. I've often wondered if you switch the coil from open to closed only when you've passed 51% of the pulse duration. I'm curious to see how this would effect the motors natural acceleration and deceleration rates. Also what running it inside of a vaccum chamber would do to eliminate overall resistance. Air alone is exerting alot drag on the rotor alone. Also friction due metal in metal contact inside the bearings could be mitigated by using magnetic levitation bearings. If anyone has tried this I'm curious to see it and the results. Lol
This is a synchronous reluctance motor
A switched reluctance motor is an asynchronous induction motor with switchable resistors in the middle of the induction coils, usually through brushes
Watched the video til the end. The video explains the physics behind this motor properly. To the point. Switching the polarity at predefined intervals can be a solution, but altering the speed will be difficult, and the motor will not generate its maximum possible torque by doing so. It's a good proposition, yet, another never-ending exploration for cheaper propulsion like pulsejet (at least at the moment). I'd have to look at the history of this motor.
I just saw your video, and I am now a subscriber! I never heard of a reluctance motor. But I like to play with big bars of copper and silver, it's neat to see how Strong magnets and silver and copper interact. How would your motor work with a copper rotor??? Would it just need to adjust the timing to deal with eddy currents? How about it? Are you willing to replace the rotor with a copper rotor? I for one would love to see THAT!
That would make it an induction motor. It would actually be easier to drive, but achieve lower theoretical efficiency.
love the duct taped microphone.
Big props for your non-resonant microphone arm.
When the rotor blade aligns with the center of coil, then the coil should turn off, and when coil turns off, the magnetic field of coil collapses, can we capture that collapsing field energy into a capacitor and reuse the charge stored in capacitor?
That is typically done indeed.
What happens if your reverse the current in the second half of the cycle you described? I ask because it looks like you would drive each pole pair with a full sine wave. Looking forward to your next instalment on this reluctance motor.
I would think a variable-frequency three-phase sine wave driver would take care of a lot of the issues, but I'm not an expert on reluctance.
Very interesting and well explained. Thanks
So with a brushless DC motors like we use in the RC world, it seems the only difference from an SRM is permanent magnets are placed on the rotor of the BLDC. No? Or am I missing something here? Everything you described is how BLDC motors work down to the motor controller. We call them the ESC (Electronic Speed Controller.) We have both sensored (Using a hall sensor) and sensorless that relies on back EMF. Sensorless can cog at low speeds, but once going, they work smooth and flawless. One more question...LOL Do SRM's need, or benefit from a startup capacitor? I would imagine there is a heavy current draw to get moving.
The absence of magnets is a small physical difference, but makes the motor very different to drive. The details are too much to write in this comment, but if you compare the output sequence of a normal esc to what you saw in the video, you'll notice it's not the same. Another difference is the ideal drive waveform; the best shape for current in a bldc motor is a (pure) sinusoid, which is not the case for an srm.
The most perfect motors, I swear are direct drive BLDC, out of washing machine. You can take the motor and connect any two of the wires and spin the motor by hand say 60 rpm get 120 v at 60 htz, hook 2 together and spin one to drive the other, variable speed motor, generat at 1500 rpm ,1000 volts ,snap!!!😊
Nice work AKIO, thanks for the info. Just one question though: what is the difference - Switched reluctance motor and Variable reluctance motor?
afaik it's the exact same thing
Very interesting and well presented.
New subscriber here. Awesome video. Look forward to your future uploads!
Well presented, no hype.
These motors sound very similar in some ways to BLDC motors. I think it would be possible to just reprogram a BLDC motor driver to drive one of these too. BLDC motors also need position sensing (physical sensors or measuring the unpowered coil) and they need precise timing/positioning for when it switches the coils on, just like these motors.
Would it be possible to connect these motors coils up in a star configuration too, similar to how BLDC motors already work?
Another thing to look at is stepper motors and their drivers, they also require energising coils in a certain order and precisely.
Since Electronic Speed Controllers (3 phase ESC) is used to drive most brushless DC motors, would you be attempting to modify one of those to get it to be able work as a controller here?
Excellent explanation. Thanks!
sounds like the controls would be very similar for a BLDC motor. should be a software modification for an ESC There are a few that have open source firmware (look for ones that are simonk ), they are setup to PWM the signals as well.
with Field Oriented Control, the system can measure the shaft angle and can apply the exact power needed across multiple coils, it should be able to pretty much eliminate the torque ripple
🎉Modul in care explici este elocvent , poti fi profesor
Why not just use a commutator with an adjustable brush cage?
I know brushless is frowned upon these days but there are advances that can be made in that direction too.
Could be fun?
Did you use bearings that were recovered from another device?
I bought those new actually, the bolts are recycled though.