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.
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.
Excellent presentation. You explain the concepts and the problems without tedious math, just simple graphs. I am hoping for more info on the controller. 👍🏻
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.
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.
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.
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.
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.
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.
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.
Very interesting! Way back in the day (1910's) Emerson Electric had a desktop oscillating fan called the Meston. It had a switched-reluctance motor with a commutator and brushes to switch the coils. The timing of the brushes was adjustable by sliding a lever which rotated the brush holder assembly. It was infinitely variable. Interestingly, the motor used AC to power the coils, with the AC switched by the commutator. It had a two-arm rotor and a six-pole stator switched by the commutator.
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!
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?
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.
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.
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.
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.
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.
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.
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.
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?
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 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.
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.
does that generation of power also work without magnets using only the metal bar/cross and if it isn't used as a motor(which would generate a magnetic field thus magnetizing the metal)?
The motor won't generate anything unless driven actively with the correct timing. If you wanted to use it as a standalone power generator, you'd need a small battery or something like that to get it started.
@@AKIOTV Ah I was already thinking that indeed, just wanted to know for sure anyway since it might be there was some weird effect I didn't know of similar to how you can generate electricity by changing the distance between 2 capacitor electrodes in cases where the capacitor on average is atleast partly charged(since the capacitance changes) even though technically seen that also required it to be charged just like this. still wonder however how effective such a switched reluctance motor can be when using it as a generator and driving it properly yet with a cheap driver, since if it would be possible to make a relatively efficient and relyable generator like that then it would actually allow for much cheaper generators, as well as a generator which can handle insane temperatures. if you happen to end up using or testing it as a generator that would certainly be interesting to see how well it works and such as well as perhaps even multiple ways it can work.
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.
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.
I was just wondering, could you use blocking diodes on each coil so that when the iron starts to pass the coil and inductance drops the current gets dumped into the next coil and just drive the whole thing with a variable frequency signal?
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.
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
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.
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.
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
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.
To me it seems like a normal brushless motor, but with higher weight and less torque? Like a less efficient and reliable shaded pole, while having having a more reliable startup?
Does a BLDC controller or hobby esc operate your motor? Would be interesting if it did. It may need an initial push to get the field working in the rotor
Probably not, the hobby esc would always supply power to two phases at once, with poor timing. I'm also not sure if the emf would be sufficient to detect for the esc, especially at low loads and low currents. I have some escs though, I'll hook one up and give it to go, I'm curious enough to see what happens.
@@AKIOTV I have seen car alternators work after they've spun up with ESCs and electric bike controllers. He wrote a just needs a capacitor no power to the electromagnet of the alternator after it speeds up the capacitor has enough charge to interact with the outer coils
@@gregstafford2155 That is very possible, a car alternator is basically the same as a bldc motor with the exception that it uses a wound rotor rather than permanent magnets. I've seen people using car alternators as high performance go-kart motors this way. The behavior of the SRM is quite different though, and I suspect very tricky to drive with a regular esc.
SRM 's and BLDC are two totally different types..& each other's controllers cannot be swapped wrt the other type of motor...nether can a bldc controller be modified for srm. SRM electronics is a whollly different ballgame.... an SRM with 6S-4P..TOO will have different electronics when compared to another SRM of 4S-6P..or others having 6P-8S or an 8P-6S..where.. S= no.of Stator coils P = no. of rotor (Salient) POLES.
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.
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.
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.
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.
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 ?
the wire *diameter* I used for the current version is 0.8mm. Thinner wire you can fit more turns on each coil, thicker wire will handle more current. Ultimately the maximum field you can generate is the same either way, but a certain number or turns may be better suited to a particular power supply. If your supply can handle high current but is low voltage, use thick wire/few turns, if the supply voltage is high but you can't supply much current, use many turns of thin wire.
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.
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).
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.
Is the torque ripple a major problem in the automotive space? The current technology of 4 cylinder turbo diesel engines has massive torque ripple. Would a simple solution not be a flywheel?
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".
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?
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.
No, it's not. You can't advance a fixed number of degrees and stop on a dime. I'm not a genius, but that's how I understand it from my two year associate degree, or at least what I remember of it!
You didn't mention the part that the back EMF from the coils can be recycled back into the power source without dragging down the rotor for very high power efficiency
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
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.
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?
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.
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.
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
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.
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?
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!
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.
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.
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.
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.
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.
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.
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!
The past is always the future. I was going to say these are old tech, but you said that right away. Kudos.
Very interesting! Way back in the day (1910's) Emerson Electric had a desktop oscillating fan called the Meston. It had a switched-reluctance motor with a commutator and brushes to switch the coils. The timing of the brushes was adjustable by sliding a lever which rotated the brush holder assembly. It was infinitely variable. Interestingly, the motor used AC to power the coils, with the AC switched by the commutator. It had a two-arm rotor and a six-pole stator switched by the commutator.
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.
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!
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?
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.
Finally someone on RUclips has built an axial flux one.
Did you use bearings that were recovered from another device?
I bought those new actually, the bolts are recycled though.
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!” 😂
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.
You do not necessarily need to monitor the position of the rotating assembly... Not at all.
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.
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.
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.
Fantastic explanation! Do we have any idea of the Torque / RPM characteristics of this motor?
A really good tutorial. Thank you for sharing.
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.
You're an excellent presenter. Even I (pensioner) understood all your explanations. Subbed, looking for more! 👍
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.
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?
Could a BMW "Drive Shaft Flex Coupler" help mitigate the torque ripple by absorbing/releasing some of the vibration like a "mechanical capacitor?"
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.
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.
does that generation of power also work without magnets using only the metal bar/cross and if it isn't used as a motor(which would generate a magnetic field thus magnetizing the metal)?
The motor won't generate anything unless driven actively with the correct timing. If you wanted to use it as a standalone power generator, you'd need a small battery or something like that to get it started.
@@AKIOTV Ah I was already thinking that indeed, just wanted to know for sure anyway since it might be there was some weird effect I didn't know of similar to how you can generate electricity by changing the distance between 2 capacitor electrodes in cases where the capacitor on average is atleast partly charged(since the capacitance changes) even though technically seen that also required it to be charged just like this.
still wonder however how effective such a switched reluctance motor can be when using it as a generator and driving it properly yet with a cheap driver, since if it would be possible to make a relatively efficient and relyable generator like that then it would actually allow for much cheaper generators, as well as a generator which can handle insane temperatures.
if you happen to end up using or testing it as a generator that would certainly be interesting to see how well it works and such as well as perhaps even multiple ways it can work.
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.
Can flywheel help with torque ripple?
Very professional presentation and nice workshop.
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.
I was just wondering, could you use blocking diodes on each coil so that when the iron starts to pass the coil and inductance drops the current gets dumped into the next coil and just drive the whole thing with a variable frequency signal?
It seems that the driver is very similar to the bldc esc. Could you compare the two?
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.
What is the difference in principle with a variable reluctance motor, but with axial flux instead of radial flux ?
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.
0:50 - 17:30 you showed the motor but you havent even turned it on :)
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.
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.
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
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.
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
Why the motor has only 2 power lines? Is it the driver circuit on the motor?
this particular motor has 2 cables with 3 wires each, so 6 wires in total. 2 for each coil pair.
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.
To me it seems like a normal brushless motor, but with higher weight and less torque? Like a less efficient and reliable shaded pole, while having having a more reliable startup?
Does a BLDC controller or hobby esc operate your motor? Would be interesting if it did. It may need an initial push to get the field working in the rotor
Probably not, the hobby esc would always supply power to two phases at once, with poor timing. I'm also not sure if the emf would be sufficient to detect for the esc, especially at low loads and low currents. I have some escs though, I'll hook one up and give it to go, I'm curious enough to see what happens.
@@AKIOTV I have seen car alternators work after they've spun up with ESCs and electric bike controllers. He wrote a just needs a capacitor no power to the electromagnet of the alternator after it speeds up the capacitor has enough charge to interact with the outer coils
@@gregstafford2155 That is very possible, a car alternator is basically the same as a bldc motor with the exception that it uses a wound rotor rather than permanent magnets. I've seen people using car alternators as high performance go-kart motors this way. The behavior of the SRM is quite different though, and I suspect very tricky to drive with a regular esc.
SRM 's and BLDC are two totally different types..& each other's controllers cannot be swapped wrt the other type of motor...nether can a bldc controller be modified for srm.
SRM electronics is a whollly different ballgame....
an SRM with 6S-4P..TOO will have different electronics when compared to another SRM of 4S-6P..or others having 6P-8S or an 8P-6S..where..
S= no.of Stator coils P = no. of rotor (Salient) POLES.
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.
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.
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.
What an excellent explainer.
How much different is this motor from typical AC induction motors?
Very. The induction motor operates thanks to electric current in the rotor, whereas in an SRM rotor current is an unwanted side effect.
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.
Good presentation! Nascent engineer? Very clean yet felt unscripted. Bravo Zulu!
Enjoyed your video and also found it very helpful. Switch-Reluctance-Motors are cool. Thx AKIO TV, it inspired me to design one. 😊
Thank you for the interesting motor video, I will try to replicate it in the future
A very sensible video , well presented.Give us more in future. Thanks for sharing.
Great explanation to this beginner. Thanks.
Bonsoir Akio, une superbe video de plus - Bravo - j'ai une fois de plus tout compris. Merci
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
can you use it as an actuator ? suppose you need a circular movement of X degrees
How thick wires you use to make coils for srm?
the wire *diameter* I used for the current version is 0.8mm. Thinner wire you can fit more turns on each coil, thicker wire will handle more current. Ultimately the maximum field you can generate is the same either way, but a certain number or turns may be better suited to a particular power supply. If your supply can handle high current but is low voltage, use thick wire/few turns, if the supply voltage is high but you can't supply much current, use many turns of thin wire.
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.
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).
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.
Very clear ! Thnx 😁👍🏻 also liking the little mistakes/errors/ falling things 😁😂😂😂 makes it real !
Is the torque ripple a major problem in the automotive space? The current technology of 4 cylinder turbo diesel engines has massive torque ripple. Would a simple solution not be a flywheel?
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".
Grate video! Those radial internals seems like steper motors.
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?
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.
How is this different than stepper motor?
Isn't this a stepper motor?
No, it's not. You can't advance a fixed number of degrees and stop on a dime. I'm not a genius, but that's how I understand it from my two year associate degree, or at least what I remember of it!
You didn't mention the part that the back EMF from the coils can be recycled back into the power source without dragging down the rotor for very high power efficiency
@@tech2beez199 I think I talked about that in the video I published after this one, about the electronic controller.
Great intro video to SRM. Well done! Good luck getting your motor operating, it's a great concept.
Great video, we have a young JW here.
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
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
What is the advantage of this type of motor?
reduced cost without giving up efficiency
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.
And what kind of mechanical driver did they have back in the 1800s? this is a type of stepper 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 very impressive explanation,
Keep it up young man 👍👍😍
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?
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.
Excellently presented.
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.
Excellent presentation!
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