Variable Frequency Drives Explained | VFD Basics - Part 1
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- Опубликовано: 25 июн 2024
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⌚Timestamps:
00:00 - Intro
00:15 - AC motor rotational speed
00:54 - Speed reduction
01:45 - VFD
02:23 - VFD applications
03:05 - VFD working
03:45 - Six-pulse rectifier or converter
05:18 - DC bus or DC filter and buffer
06:57 - IGBT
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In this video, we will learn about VFD and its applications. We will also cover in detail the converter and the DC link.
Induction or alternating current electric motors rotate at a rate that is set by the number of poles inside the motor itself, and the power supplied.
The frequency is directly related to the RPM of a motor. The higher the frequency, the faster the RPM or the higher the engine rotation speed.
In the United States, electric power utilities provide alternating energy with a frequency of 60Hz. A standard two-pole AC motor operating at this frequency provides a nominal rotation of 3600 RPM.
If an application does not require an electric motor running at full speed of 3600 RPM, which is very common, a few solutions exist:
- Using a mechanical speed reducer decreases the output speed by increasing torque - the output gear has more teeth than the input gear. They require lubrication, provide no flexibility, are subtle to vibration and noise, and are not suitable when shafts are distant.
- Adding more sets of poles reduces the speed without altering it electrically. Currently, there are transistor systems that allow for poles inside motors to be turned on and off. However, those systems can be complex and don’t provide fine control.
- Using a Variable Frequency Drive (VFD) can be configured and fine-tuned to generate a ramp, frequency, and voltage so that the motor operates according to the load requirements (desired speed and voltage).
An important feature of the variable frequency drive is that as the motor speed requirements in a given application change, the drive can simply raise or lower the motor’s speed in order to meet new operating requirements.
The use of VFDs is widespread in numerous industrial and commercial applications.
- In industrial applications, VFDs are used to control from extruders, and electric cranes, to roller coasters, and mechanical bulls, with so much in between!
- In commercial applications, VFDs are widely used in pumps to control flow and even volume in a tank, as well as in the HVAC industry, being considered green technology.
Ultimately, a VFD varies the supplied frequency to an AC motor in order to control its speed; allowing a smooth startup, and adjusting motor speed as the application requires.
Let’s dive into the How does a VFD work?
1) A six-pulse rectifier or converter is where the three-phase alternating current gets converted into direct current by the use of diodes.
When we connect a three-phase alternating current to the converter:
- When phase A is greater than phase B or C voltages, this diode opens, allowing current to flow,
- When phase B becomes greater than phase A, then it is phase B diode that opens while phase A diode is closed,
- The same is true for C, as well as for the three diodes on the negative side of the bus.
That results in six pulses of currents as each diode opens and closes. The resultant waveform will look like this:
2) The DC bus is represented by only one capacitor and resistor on the diagram, but in reality, there are various capacitors and resistors associated in series and in parallel.
Since the capacitors are not charged, their impedance is very low. If we were to charge them, the initial inrush could damage the input power devices, or the rectifier/converter, in case the entry fuses didn’t interrupt the circuit.
So instead, we have a pre-charge circuit. Pre-charge is a current limiting circuit that slows the charge rate of the bus capacitors during power-up.
3) IGBT is the last step of the drive output: the DC to AC converter and our PWM output.
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This is why RUclips is becoming a good source of knowledge.... Especially with creators like you. Please discuss the difference between a VFD and a IGBT-VVVF electric drive in a future video....and whether EVs with asynchronous traction motors use VFD....or IGBT VVVF drives....
Bbebhhksh
Excellent Video and Explanation as always! I think these VFD series are going to be amazing to get acquainted. Thanks Real Pars!
Glad you like them!
Can't wait for the second part
So helpful. I was wondering this last 2 days ago and forgot to search it up. Then it appeared on my feed.🎉
Glad to hear that it has been helpful, Fernandez! Happy learning
Really very useful for beginners… thank you for your team work…
Glad to hear that! Our pleasure
Thank you , I could wish your videos were better known by the people in the field .
This is awesome. Look forward to part 2
Glad to hear that, Matthew!
Thanks guys. Very informative!
Glad it was helpful!
Great work RealPars..!! The Whole team is doing excellent work. !
Thank you very much!
VFDs are the unsung hereos of todays industrial triumph. Love your content and infographics. Always a treat to watch.
Thank you, Farhan!
@@realparsHi sir, i have one question.
When the input ( ac 220v) rectifier with dioda bride it become to 310v DC right. But my pmsm motor only aceptable of 200v max. So how to step down the voltage sir?? Iam still confiusd on this hardware. Thank u.@mata
@@realparsHi sir, i have one question.
When the input ( ac 220v) rectifier with dioda bride it become to 310v DC right. But my pmsm motor only aceptable of 200v max. So how to step down the voltage sir?? Iam still confiusd on this hardware. Thank u.@mata
Amazing VFD explained...so cool
Glad it helped!
Thank you for providing this video. Greetings from Indnesia
You're very welcome, Handy! Happy learning
Real you are simply the best. I have learnt a whole lot from guys.
Thanks so much
We appreciate that!
ruclips.net/video/l7YHT0uIZ-8/видео.html
When capacitor is not fully charged the precharging circuit is presented in the picture inorder to avoid inrush currents at supply. For this purpose a current limiting circuit is made through a resistor, now dc current will flows through this resistor and yet this time capacitor starts charging. Once capacitor gets full charge then this DC current will by-pass through contact. What a lecture Sir 👍 really great work you have done thank you 😊😊
Our pleasure! Glad to hear that our lessons have been helpful. Happy learning!
Really clear explanation and easy to understand. Thanks and do a lot of videos.
You are welcome! Glad it helped
This is a great first video on drives. I'm looking forward to the second part.
Glad you enjoyed it!
Am also waiting for second part first part I s very liberal and am very easily understand the topic thankyou sir
هممممم. و و. ههه. م🐜
I am really happy to say that this is the first time I am viewing the video on this electro-machanical subject ! Thanks for making this video !
Please send some more videos on this subject
I know Diods ,Triods ,Triacs , and power amplifier transistors having safty diods cnected acriss Collector and emitter junctions ! 👍THANKS
ALL THE ABOVE INFORMATION I 👍👍 KNOW
Glad you enjoyed it!
Excellent video. Thanks.
Thanks a lot, Petru!
Excellent Video and Explanation thank you
Glad it was helpful!
Great 👍 job keeping it 💯 updated
Thanks!
Very clear explanation thank you
Glad you liked it, Joel!
Best automation channel ever existed💯
Thank you very much!
Thanks , good work !! 🌷🌷🌷
Our pleasure!
Very important lesson.Your explain iş very good.Thank you very much. (İn İstanbul)
Glad it was helpful!
Thanks for your invaluable explanation.I really like the concept of VFD but just didn't grasp the theoretical knowledge as I should... great job and I eagerly waiting for part 2.
You're very welcome! We're happy to hear that is has been helpful!
ruclips.net/video/l7YHT0uIZ-8/видео.html
Its good educate..guys.thanks
Their videos are excellent lessons with a wealth of amazing information, a lot of detail and quality standard to admire.
I'm very grateful to the entire RealPars team for this essential content.
Congrats👏👏👏👏👏
Glad you like them! Thank you very much for your support.
Well explained!
Thank you, Kevin!
Yes!!!! Finally...
Great learning video 📹 👏
Glad to hear that! Thanks for sharing
Nice work waiting for the next thanks
Thanks a lot!
Thank you so mu h for your informative videos. I remember when I was still on my apprenticeship programme when I used to watch your videos on PLC's, drives, sensors, etc. I learned a lot and people thought I was very smart😂😂
You are so welcome!
ruclips.net/video/l7YHT0uIZ-8/видео.html
Slt
Great video information ❤ thank you for sharing your knowledge ♥️🇵🇭
Our pleasure, Jayke! Happy learning
Gracias me sirvió mucho :)
Glad to hear that! De nada!
Soo useful, i hope you can make more vidéos in this topic about how to program it
Thanks for your kind ocmment, Nina!
Great job 👍
Thank you!
Excelente video, no pierdo la esperanza de que les pongan la voz y el texto en español
Hi Jorge,
Thanks for your comment! We currently only provide our course videos in English, you are always able to turn on the English subtitles as that might make it a bit easier for you.
Our apologies for any inconvenience!
Happy learning!
thank you so much
You're very welcome!
Thank you sir for your Great efforts ❤️
It's our pleasure!
@@realpars ن٠🎤📄📘📰📑
Thank you very very very Much
You are most welcome! Happy learning
Excellent Video
Thank you very much!
Very very informative
Glad you think so, Jake!
Nice video, thanks for sharing :)
You're very welcome! Happy learning
A great presentation
Glad you think so!
Thank you
You're very welcome!
Great video
Thank you very much!
More than great
Another banger 💯
Thank you!
Thanks 👍
You're more than welcome!
love it
Thankអរគុណ🙏
Good explanation
Thank you!
Thank you very Much.. Excellent video.. I think part 2 will be more interesting . I kindly request please make vedio regarding motor starting Current of different starting methods. I will hope your good response.. Thanks again. 👍
Thanks for your feedback and topic suggestion! I will happily pass this on to our course developers.
Happy learning!
Guys, you are the best
Thank you!
thanks for sharing ...
Thanks for watching!
More video to maintenance or fault repair for drive 👍👍👍👍
Thanks for your topic suggestion! Happy learning
Thanks 🙏🙏🙏🙏
Our pleasure!
Thanks
Thanks a lot, Bitebo! Much appreciated!
Hi! I love your videos and hope that you will keep up with the good work. I only have one question; isn't the symbol for the one-way valve in hydraulic system suppose to be the other way around? I am pretty sure that it works by pushing the ball. :P
Yes, this has been pointed out before by other readers. The description is correct,; only the graphic is incorrect. Thanks for your input!
B
Good Information
Thank you, Rajendra!
great video
Glad you enjoyed it!
Good job keep up
Thank you very much!
Sir great. Please need more episode.sir please explain how to programe vFD.at least need one lecture on LENZE and Mitshubishi vfd🤗
Hi Ekhlas,
Thanks for your topic suggestion, I will happily pass this on to our course developers.
Happy learning!
oh wow this was just uploaded! lol im over here trying to find part 2
Hopefully part two will be launched soon!
Good one
Thank you!
thanks
You're welcome!
Great
Thank you!
Errors: (1) Current transformer T3 (3:16) is shown monitoring current on all three incoming phases. That means it will read zero unless there is earth leakage and that would have nothing to do with T1 and T2. (2) The check valves (8:34) are upside down. They will prevent current flowing in the direction of the diode arrows in the neighbouring schematic.
The first item you pointed out is correct. The CT "donut" should be placed around a single phase only, with only 1 to all 3 phases monitored.
OK thanks
Hey there.. I bought a VFD for my home CNC Router build. The one I got is a 3 phase 380V 1.5KW VFD.. After getting it I began to realise there was a 1 phase VFD too. I'm very lost atm guys..
Cam I use this 3 phase VFD for my home build CNC? This is all new to me so plz excuse the silly moronic questions from myself,, I would very much appreciate ur help if possible, Thanks for a brilliant video. I'm 50 yrs of age now and only just beginning my learning experience with programming, CNC's Arduino's, etc.. I lovelearning all of this stuff about electronics, etc but I really need a lotta help. I'm hoping these tutorials cAN BE THAT BRIDGE FOR ME,, Thanks for the knowledge. I will be heading over to the wenbsite asap as well now..
Your home wiring is 1-phase. You will need a 1-phase VFD. These can be purchased in either 120VAC or 240VAC versions. I would go with a 240VAC VFD. If you do not have a spare 240VAC outlet, I suggest hiring an electrician to install one in the vicinity where you need it. A CNC machine will consume significant power, so a separate, properly sized circuit will be required. Unfortunately, your 3-phase VFD cannot be used. You may wish to return it or offer it for sale on eBay or another resale platform. OK, the other thing you need to consider before doing any of the above is to determine what your CNC machine requires. If it requires 3-phase power, then you will have another issue since you will not be able to connect it at home at all without special equipment. In this case, you may want to consider purchasing a gasoline powered 3-phase generator that you use specifically for the CNC machine. This will work, but be prepared to spend >$2000.
Very great explanation for me a junior engineer!
Glad it was helpful!
Waiting for the other parts
super
Thank you!
Can you please explain the DTC and scaler mode of a variable frequency drives.. thanks
Hi Souvik,
Thanks for your comment and your topic suggestion. I will pass this on to our course developers!
Thanks for sharing and happy learning!
Tesla, thank you for everything.
another question please and thank u what kind of filter we use after the rectifier low pass or high pass or tape pass and why thank u sirI really appreciate ur efforts to give the best
It would be considered a low-pass filter. The filter section of the VFD uses capacitors & an inductor to filter the voltage & current. The capacitors have a pre-charge circuit that allows the capacitors to reach full charge slowly so that they are not damaged. A set of resistors is provided to discharge the capacitors anytime power is removed. The filter allows the pulsing DC voltage to be changed to pure DC.
Good video one question can you run the motor at a speed greater than 60hz
Yes, but this is recommended only for inverter-duty motors. A 3600 RPM motor can only be run safely at up to 75Hz. An 1800 RPM motor can only be safely operated at up to 120 Hz. However, as speed increases above 60 Hz, torque will be reduced, so in some applications, overspeeding the motor will not be helpful.
I'm making such thing at the moment.
Thanks for video. But english subtitle has been slided. Can you fix ?
Thanks for sharing that, Semih! I will look into that.
@@realpars Realpars, you're yet to fix it. Subtitles still out of sync with video/narration. Thank for your commitment to engineering education.
Good video. Can anyone tell please @6:17 of the video (DC link), how resistors will charge the capacitor?
Thanks.
You are correct, and the video should have said, "The capacitors begin to charge with current that passes through the resistors". This allows the capacitors to charge at a slower, controlled rate.
@@realpars Thanks for the clarification. Keep it up.
Is the 6 pulse rectifier a good way to control the phases of a three phase supply?
I'm still learning about basic circuits ATM, cheers tho🙂
Using a 6-pulse rectifier is used to rectify a 3-phase circuited (2 diodes per phase) to DC voltage. This type of rectifier is useful for this purpose in a VFD. The 6-pulse rectifier is also useful for circuits in 24VDC power supplies.
I can't make sense of the pre-charge circuit at 6:15. Disregarding resistances in wiring it looks like it's shorted so any current would just go through the bottom branch straight to the low-pass filter. K1 doesn't seem to do much. What am I missing?
R is used to pre-charge the capacitor bank. Once the capacitors are charged, K1 should close, thereby by-passing R. When K1 is closed, current will flow through K1 preferentially, since it is the path of least resistance. If the motor starts and draws current for too long through R, the thermostat will trip and stop the motor. Internal circuitry is used to determine when K1 should close. The actual circuits are much more complex than what is shown, but the diagram in the video helps illustrate these concepts.
@@realpars When K1 is open, there are 2 paths : one with R and one with nothing on it (the bottom one). So, on your drawing, the current should only go to the bottom one and not through R. I don't understand why the current can go to 2 different paths at the same time (6:18). Maybe the bottom line should not be here and instead only R or K1 ?
@@idealdonor exactly I was searching for one comment that notice this problem, basically de line under the pre-charge resistor shouldn’t be there because is a short circuit, if you remove it now you can see a utility for the K1 contact that is if the capacitor is charge to some level now we can close K1 making the other path for the current killing the R pre-charging.
Every nice video some times little details that needs to be fix but we have the comments section to discuss!
@1:21Did you mean to say gearboxes are subtle or _susceptible_ to vibration and noise?
Should be "susceptible to vibration & noise". Thanks for letting us know.
So what happens when u have 277/480 three phase system that’s running too high like at 497 . And u have voltage imbalance? Will it just only be sending a signal on the highest phase to ground voltage and therefore the vfd not work properly? Or does a vfd clean it up somehow? Just got the IQ1000 outdoor box haven’t hooked up power to it yet. We need to slow the pump down it’s pumping more gallons per minute than the well can provide
Thank you for your question. The compatibility with a high leg largely depends on the VFD itself. Typically, a VFD operates by converting incoming AC voltage to DC using a rectifier, then utilizing IGBT to produce the required AC frequency and current via PWM modulation. While some VFDs may accommodate a high leg, it's often advisable, as per the manual, to connect power through a constant voltage transformer before supplying it to the VFD. This setup generally offers a more robust engineering solution. Happy learning!
Hi, Any effect when we stop vsd motor without reduce speed to 0 before that.
When a motor stops, it slows down and the electric field in the motor collapses and causes "friction" in the magnetic field. If the motor is reversed before the motor fully stops, the starting current must be strong enough to overcome this braking force and reverse the magnetic field. This is not usually a problem, but if the motor is spinning fast enough in the original direction when the direction is reversed, you may have an overcurrent situation and trip a breaker. It is also not good to put that amount of mechanical stress on the motor shaft and bearings.
Plz explain if VFDs can be used to control DC motors... Can they work without the ac dc converter and the igbt section...to convert back dc to ac output in case of controlling dc motors....
Thanks for your comment, Habibulla. I will share your topic suggestion with our course developers!
Aren’t the hydraulic check valves drawn backwards in regards to your flow direction?
Thank you for your question. Sorry for the confusion. The check valve flow is in the downward direction for the check valve to work. The voice-over person stated that the pictures show the check valves will shut down in the direction of the arrows shown. And in the down direction of the flow is when they work. Sorry, but it was not clearly shown but explained correctly.
isn't there a mistake at 6:14 it seems to me your short circuiting your charge up resistor. (or what u wanna call it?) there for still getting a peak current that could possibly damage the input device? correct me if i'm mistaken here. greetings, thanks for the informational video btw
Hi Tom, thank you for your question.
This is a simplified block diagram illustrating the basic concept within this circuit. Please note that in reality, the circuit is far more intricate than what we present here. The resistor in use is of a high value and wattage, designed to limit the flow of current to a predetermined safe level. This feature prevents the resistor from overheating or burning up. Instead, the current naturally follows the path of least resistance.
We hope this explanation clarifies the information for you. Should you have any further queries, please don't hesitate to ask. We appreciate your engagement and wish you continued learning and growth with RealPars!
@@realpars I know, but even if you work with equivalent values instead of the real circuit. it still should be an open circuit. now you have a parallel short circuit drawn with no switch whatsoever. which means 0 amps will flow through the 'safety' part of your circuit at any given tim? could u please look at the screenshot at 6:14 ?
Thanke you, Where can l find PART 2
We will launch that hopefully soon!
how you are able to adjust output voltage and frequency by triggering IGBT
Think of IGBT's as power switching transistors. The VFD regulates the DC voltage at the collector of the IGBT. The switching circuit fires the gate of the IGBT to allow current to flow to the emitter. By use of a control circuit, the frequency, polarity, and duration of being in the "on" position (pulses) can be controlled. This is how the VFD inverter section is able to recreate a sine wave output at the frequency required by the application from the DC output of the rectifier.
Should we use VFD and Contactor at the same time??? I'm a beginner learning curve of VFD. Please kindly to share your experiences. Thanks. From Cambodia.
they can be used both to switch on a motor...the start external terminals of the vfd are connected to the NO of the contactor while the contactor coil is connected to the start button...so when you press the start button the contactor NO contacts closes and thus gives command to vfd to start motor
Hello. The vfd does not need a contactor, the vfd has all the necessary components for easy control. You just need to carefully read the instructions for connection
There are many applications that involve contactors and VFDs used on the same equipment. They are application specific though. Are you asking about the pre charge contactor shown in the video or are you asking about contactors in general?
Better not to use contactor between VFD and motor as there is no need and can be a lot of problems during commissioning and further operation
Very glad to see that the community has been so helpful to answer your questions already! If anything remains unclear, please let us know :)
🙏🙏👍👍
for troubleshooting purposes suppose the drive is stopped intentionally, Will i read full DC voltage across the bus capacitor when stopped????
You show a single current coil on the input to the drive, if you only have one coil wouldn't that work like a GFCI if all is proper zero net current? Or is that a totally different concept in 3 phase?
When a motor that is controlled by a VFD stops, current is not allowed to pass to the motor. However, the capacitors are still charged, but will slowly drain. It is something to know about so that you don't put yourself at risk. The current transformer is used to measure current. Many times, for a balanced circuit, a single sensor is used. the current draw through each of the three phases should be similar. The current transformer is different from a GFCI, although both measure current flow. In a GFCI, the transformer looks for an imbalance of current between Hot and Neutral, indication a potential fault condition between H and N.
👍
What's solution for single phase capacitor based induction motor?
Single-phase motors can be controlled with a single-phase VFD. A simple rheostat will also work pretty well and is much less expensive than a single-phase VFD. However, the VFD can be connected to and controlled from a PLC, whereas a rheostat must be controlled manually.
Question, does the motor maintain strong torque at lower speeds ?
That depends on the motor and the load it is controlling. Normally, the answer is yes, as VFDs are able to develop strong torque at lower speeds. However, running at low speed for long periods of time can cause motor heating and other problems.
Add video about plc And how to connect relay sensor and so on with plc thank you
Thanks for your topic suggestion! I will happily pass this on to our course developers.
Hi @Mohamed. There are a few videos we've already posted that you might be interested in. ruclips.net/video/B65detMhnoc/видео.html or ruclips.net/video/oyaItbhqoW0/видео.html
@@realpars already watched them ))
Does the 120 in the formula come from the 120 degrees out of phase of a 3 phase system ?
Yes, this is correct. The sine wave for each phase is 120-degree out of phase with the other phases. This arrangement provides greater power density than a one-phase circuit at the same amperage, keeping wiring size and costs lower.
@@realpars This is incorrect. The 120 in the formula comes from 60 Hz x 2-poles since poles are always in pairs (2, 4, 6, ...)
why there 2 current transformer to measure output current instead for 1 in the input side
Hi Arjun,
Thank you for your question! In reality, the picture we show on the input side represents current transformers. We really have one for each phase. For simplicity, we just show one current transformer. Sorry if it was confusing. On the output side, we show two again for simplicity, but most likely, we have three. One for each phase. This is done to protect the VFD in case of IGBT failure.
Here is a link to the drive application manual for your review.
support.industry.siemens.com/cs/document/5824404/siemens-standard-drives-application-handbook?dti=0&lc=en-US
Happy learning!