What is a Variable Frequency Drive?

Posted by Craig Hartman 20/03/2014 142 Comment(s) Variable Frequency Drives,

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142 Comment(s)

NAGULA MEERA:
27/09/2016, 02:41:08 AM
Reply

Your comment is 100 % correct but our problem is drive running up to 10.5 Amps(5.5kw) more than 10.5 Amps its immediately tripping ACS550-01-12A-04 we have to go how much drive capable FLA setting with safe running condition. can i know your contact no.

Yin (Admin):
27/09/2016, 08:16:53 AM

Hi Nagula,

Did you by chance see the response I sent to your email yesterday? I don't quite understand your question. You are welcome to call us at 800-800-2261.

nagulmeera:
22/09/2016, 03:05:03 AM
Reply

we are having acs550-01-12a-04 for application is fine coal discharge serew conveyor 5.5kw problem is immediately tripping with overload alarm limited seting is 12.5a replacing vfd to motor and arrange to dol starter running with 10-12.5a why it is not running with vfd.

Yin (Admin):
22/09/2016, 03:16:26 PM

Nagulmeera,
If your VFD does not ramp up at all but trips immediately; you should check your FLA (amps) parameter. You need to set the FLA to match your motor's FLA. If that is correct, check all of your wiring of the VFD. If that is also correct, I would pull the leads and check your motor with a meter. You are having some sort of ground fault or line to line short circuit. Hope that helps!

Chip:
21/09/2016, 10:31:45 AM
Reply

Can two motors be controlled by one VFD controller. Have have both running a the same time??
We have this situation at our water plant. THE VFD of course run warm to hot?

Yin (Admin):
21/09/2016, 10:48:22 AM

Chip,

Yes, you can with a couple of conditions. You will need a VFD with an FLA (amps) higher than the two motors combined, plus possible derating based on altitude and ambient temperature. The limitation is that you have to start and stop the two motors at the same time with the same setting. If you need help choosing one for your pumps, feel free to contact us at bdt@emcsolutions.com or call us at 800-800-2261.

Ali bedaiwe:
21/09/2016, 09:00:29 AM
Reply

appreciate your attention
so if I want to control frequency in an induction heating system (without motor) what can I use

Yin (Admin):
21/09/2016, 11:15:08 AM

Ali, we have no expertise in induction heating system, so we cannot make any recommendations. I would suggest contacting the manufacturer of your system to see what they advice. Sorry we cannot be more helpful.

Ali bedaiwe:
21/09/2016, 08:18:38 AM
Reply

very helpful article
can I use VFD for induction heating system ?
If so, is it suitable for for to regulate volt and frequency in the sane time in stead of solid state power controller?

Yin (Admin):
21/09/2016, 08:52:59 AM

Ali,
If there is not an electric motor in the system, you cannot use a VFD. VFDs are designed for 3 phase electric motors.

balramsingh:
20/09/2016, 12:15:32 PM
Reply

Very nice

Roly Agbayani:
18/09/2016, 08:46:13 PM
Reply

What is the problem if the fuses before the transformer gets busted? it always happen in the Plant on the VFD's for Cooling Tower fans. your advise would be highly appreciated.

Ashutosh singh:
18/09/2016, 03:20:41 AM
Reply

very good

mukesh:
08/09/2016, 02:48:20 AM
Reply

Very nice

John Saunders:
07/09/2016, 04:59:11 PM
Reply

Hello - would a VFD be useful when the power supply is single phase 240V 50Hz ... but the motor is a 110V 60Hz one ?

VFDs.com Admin:
08/09/2016, 06:59:18 AM

Hello John,

VFDs output three phase power, therefore, cannot be used on single-phase motors. A VFD rated for 240V input can accept an input voltage of 200-240V at a one frequency, single- or three-phase power, and output the same or different voltage at a different frequency. For example, if you had single-phase, 200V @ 50Hz power, you could use a VFD to supply power to a three-phase, 240V @ 60 HZ motor.

Asim Jan:
03/09/2016, 12:18:33 PM
Reply

I have a question what will be the voltage at motor terminals when RPM of motor is zero?
Motor is 37 KW and is connected with VFD made by ABB.

Yin (Admin):
07/09/2016, 08:55:48 AM

Asim,

When the motor is not running, you should have minimal voltage readings (close to nothing) at the terminals. Be careful when you check the readings, you should always wear proper protective clothing and equipment. Hope that helps.

M.P.Mathew.:
01/09/2016, 10:50:11 PM
Reply

Extremely useful information.

Balikuddembe Ibrahim:
11/08/2016, 03:12:02 AM
Reply

Comment
Am pleased with this technological innovations. The explanation about VFD system triggers every industrialist to run, purchase and install. In reality, the benefits are tangible. Even a lay man can understand this. Infinity Thks. Ibra - Production Supervisor.

arun:
22/07/2016, 12:17:33 AM
Reply

Operation of capacitor in the circuit??
How it will remove.a c ripples??

Alind:
19/07/2016, 08:50:12 PM
Reply

What is expected life of VFD?
Is its costs worth over its useful life?

Yin (Admin):
20/07/2016, 04:39:41 PM

Hello Alind,

What is the expected life of a VFD?
If a VFD chassis is simply mounted on the wall, with no protection from dust and particulates, many manufacturers are prediction a lifespan of 5-7 years. The secret to VFD longevity is to keep it cool, clean, and free from dust, particulates, and other environmental hazards. In most instances, this is done by putting the VFD in a positive pressure ventilated cabinet with air filters. The air filters should be accessible from the outside of the cabinet and easily changeable. The filters should also be readily visible. Otherwise, the maintenance staff tends not to change them as they get dirty. We have many VFDs in cabinets of this type that have been in operation 25 years and longer.

Is a VFD worth the cost?
In most applications, a VFD will pay for itself within 1 to 3 years. Of course, this is only a general rule of thumb. In some cases VFDs can pay for themselves in only a few months. In other cases there is little or no savings. But, in the wide majority of applications, there is a significant energy savings.

Hope that answers you questions!

Farouqq:
19/07/2016, 11:23:51 AM
Reply

Thnke you

amer:
17/07/2016, 06:50:54 AM
Reply

sir is there any vfd inverter stablizer for air conditions which i can save money on electicity and run my ac slilent with out tourq and

Yin (Admin):
18/07/2016, 10:47:56 AM

Amer,

I am not quite sure what you mean by VFD stabilizer.

You cannot use a VFD on household air condition units. If you are using it with an industrial chiller, VFDs will allow you to control the speed of the motor which may in turn save electricity consumption, but it will not make your chiller run any quieter.

justin:
16/07/2016, 11:01:03 AM
Reply

very easy to understant about VFD controls and good explanations

Martins:
16/07/2016, 05:08:08 AM
Reply

We want to buy VFD for our machine, to reduce the rpm of the Electric motor (10hp and 7500w)

The rpm to be 5-10 rpm. The barrel load is 800kgs and rotate for 4hrs continue.
We are based in Nigeria.
Please reply promptly
Thanks and best regards
MARTINS

NAVEEN:
14/07/2016, 11:23:51 AM
Reply

Thanks sir great information for beginners

mafwere muhozya mazigo:
13/07/2016, 10:42:18 AM
Reply

Very good information about VFD,Pls send me more information about VFD

Regards

Muhozya

Tanveer Ahmed:
13/07/2016, 02:16:02 AM
Reply

Very good information about vfds. Please keep me updated about vfds in future.

Ranjit:
08/07/2016, 04:04:25 AM
Reply

It's really a nice explanation. thank you very much

rohan:
02/07/2016, 12:22:13 PM
Reply

This session was very helpful for me.....thank you....

octavian:
11/09/2016, 09:12:14 AM

can i use VFD to control the frequency of vibratory feeder?

Shunmugam:
01/07/2016, 10:18:54 AM
Reply

Got very nice explation about vfd.

Rama:
27/06/2016, 01:00:29 PM
Reply

Thank you sir for providing very useful information
Thanks sir
Rama

Kabwe Edgar:
25/06/2016, 09:19:33 AM
Reply

This is a very helpful article,it has cleared some of my doubts.... thanks for sharing, continue with the same spirit of sharing and share more if you can.

wssultan:
14/06/2016, 07:49:25 PM
Reply

very good explanations,but i wounder kindly if you show more details in process controller related to vfd and trouble shootings

mahendran:
13/06/2016, 07:01:25 PM
Reply

It is more helpful for me

armm:
10/06/2016, 06:16:57 PM
Reply

good article.thanks for sharing

santosh Pagade:
05/06/2016, 10:08:40 AM
Reply

VFD is good part of electrical motor operating system ang easy to handle

rajan soni:
05/06/2016, 03:59:14 AM
Reply

Dear sir,

Please informed me why using any AC drive's ID run mode and Auto tuning running.

Yaser:
31/05/2016, 11:53:34 PM
Reply

how I can use VFD AC power Input 1000V ,F = 60H
I Cannot Find in the Market VFD with this input 1000V or Soft Starter for 410 KW motors.
Thanks

Yin (Admin):
01/06/2016, 12:32:20 PM

Hi Yaser,

Try looking at TMEIC or Emerson. They both have 1000V VFDs.

Gurvinder Sandhu:
26/05/2016, 07:20:29 PM
Reply

Great article - I understand how a VFD works.

Naseer Muhammad:
16/05/2016, 11:45:58 AM
Reply

Very good

sisay abera:
10/05/2016, 08:31:08 AM
Reply

very good presentation

Steve:
11/04/2016, 09:18:05 AM
Reply

Great article - I understand how a VFD works. I'm looking for more info on control of the VFD vs control valves. I have a central plant (hot water) feeding multiple air handlers, each has its own valve for the heating coils, current circulating pumps run full-bore with a by-pass loop for when control valves are closed. Boilers run as required to maintain loop temperature. If I upgrade to VFD pumps, can I drive the speed of the VFD (say 1-100% speed) based on the valve positions (say 10 @ 20% to 10 @ 80% open, or some combination) through my BAS system? The BAS system drives the actuating valves - I'd want to summarize their positions to create total current system demand, and drive the pump at that speed, and more or less eliminate the need for the by-pass loop. Any good articles on how to control the VFD?

Here's the key question - any good studies / white papers on the economics of this? The powers that be want to know... Technology is great and all, but without something simple to understand to put in front of decision makers, it's hard to 'sell' it without getting into the technical lingo. Nothing sucks more than trying to explain technical stuff to a non-technical crowd - *blank stare*, but talk $$$ and we can implement energy savings measures.

Yin (Admin):
13/04/2016, 09:14:06 AM

Hi Steve!

I have chatted with our VP of engineering Craig, who is in the video, and unfortunately he has not done any white papers about energy savings. He said he had been involved in two energy saving projects (one of which we wrote about, is the Industry Spotlight: Using VFDs with Reciprocating Compressors article posted on March 20, 2015) and he had done the calculations for each of the project, but he did not create any white papers since that was not his goal.

We understand all too well how difficult it is to explain the benefits of an equipment and trying to convince someone to spend a large sum of money for it. However, based on our experience we are not completely convinced that having white papers will change the minds of our customers more than having professionals like Craig here to talk to them. So as much as we would love to provide you with some more materials on energy savings, we cannot help you with it at the moment. On another note, we have created an energy saving video, have you seen it? Saving Energys Using Variable Frequency Drives

Steve:
13/04/2016, 09:30:44 AM

Thanks for the response Folks!

Great quick little summary, the chart showing operating curves of damper/valve control vs VFD is a great visual to illustrate the savings. I especially liked the 107% pressure requirement for flow restricted conditions. Discussion around a <1yr pay-back on the investment really sells the case.

When you design the system, the pumps/fans have to be sized for 100% load, however in reality 100% is rarely called for. Variable speed (VFD or otherwise) simply makes sense - why run the motor at 100% all the time? Especially for HVAC, when the operating point is typically 25%-50% of total demand load for most of the season.

Interesting that this technology has been around for a couple of decades, but not widely adopted. I've heard a lot of chatter about signal interference / stray frequencies generated by VFDs, which causes all kinds of nightmares (blown motor windings, control system interference, etc.) - especially for retrofit to existing pumps/fans. Do you recommend replacing motors or just installing the VFD control module in this case? I trust the technology has come along far enough to control these hiccups. Is there design guide, or do you offer design support to engineers looking to apply this technology (like me)?

Yin (Admin):
13/04/2016, 10:10:39 AM

Steve,

You are right about HVAC. HVAC and pumps are among the most common applications for VFD. Many modern VFDs also have a set point control function called PID (Proportional–Integral–Derivative) and it is very important to many HVAC and pump users.

We like to think that VFDs are pretty common these days, you will unlikely notice them outside because they are always in electrical boxes, or they are hidden in a basement corner of a building. But we also know there are many opportunities out there to expand this technology. Unfortunately VFD is not a cookie cutter type of equipment, if you will, and people may not be willing to invest the time to learn about it even though it provides a great deal of benefits in their operations.

Regarding to signal interference and stray frequencies, you might be referring to what we call harmonics. Here is a video of Craig explaining the gist of harmonic distortions . VFD Harmonics and Power Quality VFDs do produce harmonics and could potentially cause a problem to power quality. It is a real thing, so much so that we actually have a power quality expert in our company. The bigger the VFD, the more you need to pay attention to it. We think the most cost effective way to eliminate harmonics is using line reactors or harmonic filters. These additional equipment may also be part of the reason that turns people away from this technology. Here is a more lengthy article about harmonics written by Craig: Harmonics Mitigation .

Now about retrofitting existing motors, or any motors in general, we would always recommend pairing with a VFD if you need speed control. What kind of design support are you looking for specifically? Our company specializes in automation integration, from generators to motors to VFDs. I am sure we can help you with what you need. If you would like, you are always welcome to get in touch with us about your project. You can email us at bdt@emcsolutions.com, or call us at 800-800-2261, or continue to chat with us here!

mark:
25/04/2016, 01:21:36 AM

Steve forget the guessing using valve position. Use a differential pressure transmitter across mains, usually at a higher location in building as input to bas and let bas control speed. Transmitter could also be wired to vfd for feedback as most decent drives have built in pid controllers. bas is better so you can motor or log pressure.

Surbhi Hagavane:
06/04/2016, 10:23:11 PM
Reply

Thanks alot. Truely, excellent information is provided. Cleared all my doubts.

Durgaprasad shety:
31/03/2016, 09:37:34 PM
Reply

Thank you very much for giving useful information

Ramaswami Sundar:
29/03/2016, 03:17:33 AM
Reply

Dear Author,

If there is variation of input voltage to VFD will the output voltage also will fluctuate and will lead to tripping off the motor?

birendra:
28/03/2016, 03:49:13 AM
Reply

good jobs but I need more information about vfd .

nazmul:
22/03/2016, 11:39:20 PM
Reply

What,s the work IGBT & how does it work.plz details

Nazmul:
20/03/2016, 12:25:17 AM
Reply

I have 2kw motor.I need 3kw VFD.am I correct.

admin:
21/03/2016, 09:04:36 AM

Nazmul, you need to size your VFD based on the amps of your motor. For more details, please check out our VFD Buying Guide

Krishna V Pefnekat:
16/03/2016, 08:30:42 AM
Reply

Good information I get, but I needs more information regarding that I already fwd some messages, buy overall very good information ur giving through this media. So thanks to u n ur full team. Krishna pednekar from India presently n Egypt.

Deepak:
12/03/2016, 02:15:56 AM
Reply

Hi, Good technical forum,

can we fed single phase power to run 3 PH motor via VFD.

admin:
14/03/2016, 07:04:45 AM

Yes, you can provide single phase power to the VFD, which will output 3 phase power. It’s a actually a very common application for VFDs.

dinesh:
11/03/2016, 03:54:34 AM
Reply

dear sir please guide me . for one application I am using 3 phase 450 V 50 hz RPM 1000 motor. I want to use VFD controls for to obtain 250 rpm 500rpm . can we use vfd controls for 3phase ac motor. who is making & what is the cost?is there any limitations . lese inform
Best regards
D.R.Kulkarni
9960021517

gururaj:
10/03/2016, 08:59:55 PM
Reply

good morning. I have confusion in VFD rated motors. We are running our equipment with constant speed. We are exporting our equipment to different countries. Since power supply in different countries are different, each time we have to purchase the motor according to the country specified power supply. to overcome this issue, we are purchasing VFD rated motor. Will the VFD rated motor works in different countries?. To elaborate this, I am putting below example.

I am rotating a cooling drum with constant speed of 10rpm. I have used a VFD rated geared motor with 0.75kw & connected to power supply of 3ph,415v, 50Hz. Now can I use the same motor with power supply of 400v, 60Hz. there will not be any change in o/p speed (10rpm). Could you please reply.

omarah:
02/03/2016, 02:56:32 PM
Reply

Could you please help me in developing energy model of the cooling unit in Simulink/matlab? Edit

I would like to develop energy model for the HVAC equipment (Energy model of the variable speed fan) and energy model of of cooling unit.

Thank you

pradeesh:
26/02/2016, 11:17:09 AM
Reply

m

md akbal ashraf:
23/02/2016, 08:56:18 PM
Reply

thanx. for such a helpable article abt vfd .this made it so easy to understand ..thanks

md akbal ashraf:
23/02/2016, 08:55:06 PM
Reply

thanx. for such a helpable article abt vfd .this made it so easy to understand ..thanks

anikumar:
22/02/2016, 07:50:33 AM
Reply

Nice I need more details about vfd can u sent ur mail I'd to this id

antu moonjely:
19/02/2016, 10:24:48 AM
Reply

Very clear explanation.. Thanks

Awadhut:
13/02/2016, 12:19:43 AM
Reply

Than you

s pagare:
10/02/2016, 04:04:56 AM
Reply

very nice explaination ,demonstration of VFD theory, use , benifits

Eric Watlington:
01/02/2016, 11:28:12 AM
Reply

Can a VFD work with an A/C cooling tower pump motor using differential water pressure as feedback for the frequency control? If so what equipment is needed?

admin:
01/02/2016, 03:41:42 PM

Eric,

Absolutely! The vfd has I/O capabilities and PID control. It is common to use a pressure transducer to send a signal back to the vfd to control frequency. Give us a call if you have more questions.

Ravinder:
29/01/2016, 08:01:14 AM
Reply

Good article Sir

Can we use lower HP motor with higher HP motor? I guess we can but just want to make sure.

Ravinder

MD Ekramul Haque:
24/01/2016, 12:34:00 PM
Reply

Very most important and I like it vfd

Dhiraj:
08/01/2016, 01:50:45 AM
Reply

Thank you so much for the article.
This made it so easy to understand.
I really needed this...!!!!

sivadas:
08/01/2016, 01:13:17 AM
Reply

good morning .regarding we need run 35 kw 440v 60hz fan motor but we have 380v 50HZ supply available so please give which model vfd we can use and approximatly cost. regards sivadas

waleed:
01/02/2016, 02:28:08 AM

teri maa ki choot.. thankyou!

admin:
01/02/2016, 09:43:51 AM

Hello Sivadas,

Please give us a call at 1-800-800-2261 and we can talk you through your options.

abdulmalik:
03/01/2016, 05:30:58 AM
Reply

nice information

zain ul abdin:
30/12/2015, 02:30:34 AM
Reply

Is Static Frequency Driver(Converter) is also same as VFD....???

Aditi bhelawe:
27/12/2015, 06:54:39 AM
Reply

Very informative for learning

milind shinde:
23/12/2015, 12:31:47 AM
Reply

Great article!!! Thanks for sharing .i am in solar please guide me regarding solar pump

admin:
23/12/2015, 07:06:33 AM

Glad you liked it! Do you have any specific questions regarding your pump?

gangadhar:
16/12/2015, 02:14:45 AM
Reply

thank you

Engr.Nur Mohammed:
14/12/2015, 09:22:55 AM
Reply

Thanks a lot for for your working description of VFD.I required single line diagram and part to part description.Please send me.
Thank @ regards.
Engr.Nur Mohammed.

Raymond:
09/12/2015, 08:00:44 PM
Reply

Is it possible to variable frequency drive a brushless dc motor without using a microcontroller? Says 60Hz give 1800rpm and 50Hz give 1500rpm of a BLDC motor.

siva rao T:
07/12/2015, 10:53:10 PM
Reply

Good.Thanks for sharing.

ritesh Chakravarti:
05/12/2015, 01:51:53 AM
Reply

Very nice content

ritesh Chakravarti:
05/12/2015, 01:51:51 AM
Reply

Very nice content

Md.kafil Uddin:
04/12/2015, 09:34:03 AM
Reply

Very nice

wally:
25/11/2015, 07:24:01 PM
Reply

i am a bit lost on VFD/rotary phase converters. would they supply constant on demand power while it is on? i've got a sewing machine with a servo motor. its MAYBE 1/4hp (the motor itself is about the size of a 12oz soda can around, slightly shorter height)

the only thing i am not sure about is if VFDs would be okay for low load frequent start/stops

this machine also has electronics/small LCD display. would a VFD be okay to use with the electronics? i really want to avoid using a rotary converter if i can because of the size/noise

Presley Chilumbu:
24/11/2015, 12:40:54 AM
Reply

Good topic on VFDs, just made my understanding. Thanx

Lisa Chen:
22/11/2015, 11:24:31 PM
Reply

Nice post. If using VFD motors, better install an insulated bearing at the non-drive end.

admin:
23/11/2015, 09:28:11 AM

Insulated bearings are a great option. You can also use shaft ground rings to protect the bearings already in place: http://www.vfds.com/shaft-grounding-rings

Often, for large power motors, we recommend a combination of both insulated bearings and shaft ground rings.

raza:
20/11/2015, 03:19:40 AM
Reply

nice yr its esey to understand thanx tu u yr thnxx

Abdul Basit:
10/11/2015, 09:05:04 PM
Reply

Please share that what will happen to the motor power and torque after the installation of VFD when it is operated at the lower frequency and rpm then its designed one. Will the torque reduce after reducing the rpm?

Abdul Basit:
10/11/2015, 09:05:03 PM
Reply

Please share that what will happen to the motor power and torque after the installation of VFD when it is operated at the lower frequency and rpm then its designed one. Will the torque reduce after reducing the rpm?

Abdul Basit:
10/11/2015, 09:05:01 PM
Reply

Please share that what will happen to the motor power and torque after the installation of VFD when it is operated at the lower frequency and rpm then its designed one. Will the torque reduce after reducing the rpm?

rajendra singh:
30/11/2015, 09:33:22 PM

how to work vfd and there connection.show me by picture.

sandro:
27/10/2015, 07:42:51 AM
Reply

Great article!!! Thanks for sharing

Olando:
16/10/2015, 08:21:34 PM, none
Reply

Why is the voltage to frequency (V/Hertz) important for inverters?

Is the switching time programmeable??
And why?

Thanks for any input

Appreciate your Time

Ken Salvail:
15/10/2015, 07:57:22 AM
Reply

Is it possible to utilize a VFD on a single phase system?

admin:
19/10/2015, 08:30:09 AM

Hi Ken,

If you have a single phase motor, no.

If you have a three phase motor and single phase power, yes. You can find single phase input VFDs from many manufactures. Typically they go up to 3HP. Anything above 3HP, you will have to derate the drive by getting a VFD that is twice the size (in Amps) of your motor.

If you go the route of derating the VFD, it is important to know that the VFD has to go directly to the motor and nothing else should be powered downstream by the VFD. Any lights or switches should be powered from a separate source.

Hope that makes sense. If you have other questions, feel free to send us an e-mail. Thanks.

Joe helms:
26/09/2015, 04:20:40 PM
Reply

I've noticed some inverters can be fed with single phase but output three phase. Is this true of al inverters. How does it produce the phase shift required for the third leg. Are the three legs 120 degrees apart. Unlike single phase.

admin:
28/09/2015, 04:02:35 PM

Hi Joe,

All AC Variable Frequency Drives are designed to control 3-phase motors, but not all of them will accept single phase power input. The output of the drive is not exactly a true 3-phase AC power, it is a DC generated square-wave, simulated 3-phase power.

All of the input power is inverted through diodes to create DC power so the drive is able to monitor and control the power, then the DC power is ran through IGBTs that “pulse” the DC + and – currents to create the simulated 3-phase power.

The output legs are 120 degrees apart.

AC drives are specifically designed to control 3-phase AC motors, they are not designed for any other function. For more information about how a VFD works, here is a video of our VP of engineering explaining what a VFD is: https://www.youtube.com/watch?v=wDZANW2HeJ8

Hope that helps. Let us know if you have other questions.

Tom oconnell:
25/09/2015, 11:52:30 AM
Reply

When do you know when a vfd has past it operating life . Do you have a standard to follow . A motor has a L 10 life .

admin:
01/10/2015, 09:19:22 AM

Hi Tom,

Every drive is different, but most modern drives have a 10 year expected operating life if they are kept in a cool, clean, and dry environment. Hope that helps.

mosoti D:
17/09/2015, 03:21:05 AM
Reply

thanks it is a crucial information.

Vishal:
12/09/2015, 11:48:21 AM
Reply

Thanks for your explanation. And I understood total theory of vfd.and we need more information about vfd

Sanket Naresh Bavkar:
31/08/2015, 10:48:16 AM
Reply

Dear Admin,

Many many thanks for this very useful information.
Your Diagrams and simple explanations has made this complicated topic very easy.
I feel like I understand all about VFDs now only :)
and I am excited to read and reply to all your blogs .

dinesh:
26/08/2015, 07:59:13 AM
Reply

Dear Admin,

Could you explain how a VFD really saves electrical power with the help of equations?

Regs,

Dinesh

si bolah:
24/08/2015, 12:30:09 AM
Reply

The first time I visit your kesitus this unique and interesting I really like it

fauzi:
24/08/2015, 12:29:03 AM
Reply

I am very happy to read this article because of you greatly helped and thank you very much

shad md:
11/10/2015, 08:07:53 PM

I am very happy to information

Mas bram:
24/08/2015, 12:27:43 AM
Reply

thanks for sharing dude, I was greatly assisted by the article from you this

hobimasak:
24/08/2015, 12:25:34 AM
Reply

wow this is information very important

nikan:
15/08/2015, 10:57:04 AM
Reply

Hi, thanks for nice site. Does the output of the inverter 200 V to 12 V, 12 V, 50 Hz with reduced and motor launches. Thank you. - See more at: http://www.vfds.com/blog/switching-it-up-igbt#sthash.3koTVK4B.dpuf

Luis:
11/08/2015, 03:19:11 AM
Reply

How the VFDs handle the power factor correction and the reavtive power?

HARDIK:
09/08/2015, 08:16:55 AM
Reply

That was good information regarding VFD, VFD itself the answer of speed control.My question is if my Process Reactor's RPM is set with 68 max.so is it possible with the help of VFD i can make my RPM more than 68? if no that mean VFD means always decrease the RPM not increase...am i right?

abhas singh:
07/08/2015, 07:27:03 AM
Reply

sir, by which mechanism the voltage is reduced in vfds

kishan:
07/08/2015, 04:00:44 AM
Reply

sir plz tell me how much % of total current take v.f.d. in starting.

Michael:
06/08/2015, 05:30:39 PM
Reply

What is the typical efficiency range of a VFD controller? How many watts of power are drawn for the energy consumption compared to the watts of electricity passed through to the motor?

I presume this is impacted by the size of the load (motor), but am interested in a range of efficiency at the range of controlled output speeds.

Any suggestions on where I might find some information on the controllers?

Thanks,

---Michael

venkat:
03/08/2015, 08:50:22 PM
Reply

In india some wind mill generator available at 3ph 80 volt, 120 volt series. what kind of load used for this voltage? Normally in india ac is 3ph 440volt.

sanjay:
31/07/2015, 02:47:40 AM
Reply

What is minimum frequency of vfd that my motor will start to rotat.

bharat jadav:
31/07/2015, 02:20:12 AM
Reply

Thanks for your guidance....

bharat jadav:
31/07/2015, 02:19:04 AM
Reply

Thans for your guidance.....

sivaraj palanichamy:
28/06/2015, 09:30:35 AM
Reply

Sir actually i want to run 415v 5hp motor with this drive, so what the capacitance value i want to use for dc bus?

Prabhakar v patil:
06/06/2015, 02:49:26 AM
Reply

Good diagram & spcificatio

RS YADAV:
20/05/2015, 07:52:09 PM
Reply

Please let me know with so many electronic components in series.What is the overall reliability of VFD
RS Yadav

admin:
13/07/2015, 10:03:00 AM

If you size the VFD properly, keep it cool, dry, and clean; they should run for years. In our experience, we have heard them last between 5-25 years.

sivaraj palanichamy:
04/05/2015, 11:39:11 PM
Reply

Dear admin, actually in my area only 3hours will be 3 phase current available, the remaining timetime will be 2phase current only, in this situation can i use VFD for my submersible water pumb on 2phase current?

Azeez Monsur:
14/07/2015, 11:22:35 AM

I doubt if this can work, as some VFDs experience undervoltage when required phase is not complete. You need a complete 3-phase input to avoid the devise from being tripping off.

Nishant Shah:
01/05/2015, 12:38:42 AM
Reply



If we have VFD does there is need of Stabilizers or Voltage Controller equipment to protect our motors, VFD's if Yes why, if no why ?/ please explain.

admin:
13/07/2015, 10:06:00 AM

No Nishant, you do not need them to protect your motor. However, you might need line reactors to reduce the harmonic distortion.

Azeez Monsur:
14/07/2015, 11:24:23 AM

You don't really need any protection appliances once you are using a VDF, it comes with many protection funtionalities.

lahiru:
29/04/2015, 06:00:44 PM
Reply

I'm running 5.5 kw motor coupled to 7.5kw inverter. The motor draws 10.7 amp when 400v and 50hz when running with inverter its frequency will drop to 28hz and how much the vo lol tage and current would be at this time will burn my motor.

admin:
13/07/2015, 10:11:00 AM

Iahiru,

We need a little bit more information. Did you set the parameter for speed to 50 Hz maximum? Does it ramp up to 28 Hz and stop?

Raj kumar singh:
24/04/2015, 10:33:04 PM
Reply

Does vfd reduce starting current.If yes than how much in percentage.

MFlynn:
26/04/2015, 10:12:03 PM

Yes it does. A VFD virtually eliminates "inrush current".

virender:
22/04/2015, 07:58:09 PM, VFDs.com
Reply

Thanks For the Information.

Tim G:
18/04/2015, 09:33:47 AM
Reply

I really over spec'd a ventilation fan/motor. 30 HP 460V. Should have been 20 HP. Does the VFD have to be rated for the existing motor or the speed/draw I want to operate at?
My guess is the VFD has to be 30 HP.

Thanks

admin:
13/07/2015, 09:06:00 AM

Tim, you are correct. You have to size the VFD based on the motor's spec. More specifically, you have to find a VFD that has a higher or equal amp rating than the motor.

sheetal :
16/04/2015, 07:15:52 AM
Reply

which power vfd can display on panel ? induction motor input power or shaft power?
thanks

Navneet Gill:
06/04/2015, 01:56:03 AM, www.yogijidigi.in
Reply

Thanks For the Information, It is very useful for us specially schematic diagrams helped a lot.

admin:
06/04/2015, 09:22:00 AM

You are welcome Navneet, we are glad that you found the article useful.

-Yin

Pardeep :
04/04/2015, 07:26:21 AM
Reply

I have Schneider altivar avt312 ac drive
My motor running load is 15 amp
I want to get load under 12 by ac drive
Is it possible
With changing frequency

admin:
07/04/2015, 09:48:00 AM

Hi Pardeep,

What application/machine are you with your motor?
What do you mean exactly when you say "running load"?
What exactly are you trying to do?

-Yin

Roberto Perez:
06/03/2015, 12:58:00 PM
Reply

How much can we load a VFD for ESP's (electro submersible pumps) applications? Its true if we under load a VFD do we have more chance to get harmonics than if we load it properly ( let's say 80-90% )

admin:
11/03/2015, 02:47:00 PM

Hello Roberto,

Sorry for the delayed response. We consulted our field engineer about your questions. The lighter you load a VFD, the higher the harmonic distortion will be. If you stay within about 15% of the full current of the VFD, it should be fine.

We are unsure what you mean exactly when you "load the VFD". If you are asking how close can you get for sizing, then it is typically within 5%; possibly closer if the pump is only moving water. Technically, you can use the full range up to the rated current rating. However, we generally like to be conservative and not be right at the top of the range of the VFD rating.

If you are asking about overload conditions, the drive will run to the preset overload values that are in the drive as it relates to the parameter set points (i.e. 110% for 60 seconds at SLD rating of hte FLA in parameter #9 [Mitsubishi], or 150% for 60 seconds at LD rating of the FLA)

Let us know if you have more questions! Thanks Roberto.

-Yin

rana noman:
04/03/2015, 06:53:54 AM
Reply

can v use single phase phase motor with single phase vfd? in other words i m going to make my course project i m going to make a prototype of my idea and in this idea i m going to design a vfd motor and initially i m going to use very low power motor with vfd

Yaseen Subahani:
05/03/2015, 09:49:07 PM

Yes u can use single phase motor with single phase vfd. And I already done this project.

admin:
11/03/2015, 02:50:00 PM

Theoretically, yes you should use a single phase vfd for your single phase motor. However, single phase VFDs are not very common. We haven't heard of that many in the market.

Mike:
26/02/2015, 10:32:09 AM
Reply

Does it make a difference between 480Y or 480-Delta, corner ground, services with regard to input wiring?

admin:
02/03/2015, 11:16:00 AM

Hi Mike,

No, it makes no difference for a VFD whether you have 480Y or 480-Delta input. Most incoming services are 480Y. Hope this helps!

Yin

raj:
22/02/2015, 11:16:46 PM
Reply

Is it possible to use 3 phase variable frequency drive for 1 phase motor to differentiate the speed of the motor?
Please give me your advice

admin:
23/02/2015, 10:02:00 AM

Thanks for the question Raj. No, it is not possible to use a 3 phase VFD to power a single phase motor.

Bakare Kehinde:
21/01/2015, 05:49:32 AM
Reply

How does the VFD work in varying the frequency and voltage supplied to the electric motor.

admin:
21/01/2015, 10:45:00 AM

Bakare,

The VFD is able to vary the frequency and voltage through the use of IGBTs. It is through the fast switching of IGBTs, which creates PWM wave, that allows the VFD to alter the frequency and voltage supplied to the motor. You can read more about IGBTs in another post on our blog here at:http://www.vfds.com/blog/switching-it-up-igbt.

Mackenzie

khalique:
03/01/2015, 05:35:59 AM
Reply

what type of motors can be used with vfd?

admin:
09/01/2015, 04:25:00 PM

For the VFDs available on our site you would need to use a three phase motor. Please let us know if you have any more questions about finding the right VFD for your motor.

Mackenzie

silviu dima:
27/12/2014, 10:01:19 AM
Reply

How should we choose an appropriate VFD ? Let's say we have a X KW motor, what kind of VFD shall we consider ? I mean, the maximum and minimum limits in KW.

admin:
29/12/2014, 07:42:00 AM

Silviu,

When sizing a VFD to a motor you want to match the FLA listed on the motor nameplate to the amp rating on the VFD. You will need to consider what application you have because this will determine what overload rating you will need on the VFD. Take a look at our VFD buying guide here:

http://www.vfds.com/blog/vfd-buying-guide

This article will help you better understand everything that needs to be considered when sizing a VFD.

A.GALAL:
24/12/2014, 11:47:19 AM
Reply

pls. advise if any motor operate with fixed speed for example (1500rpm, 50HZ) CAN OPERATE WITH VSD ?

Muneeb:
22/12/2014, 12:31:00 AM
Reply

This is really informative material which you shared with us. Thank you very much... Can you help me out with this, I were working on micromaster 440, it gives fault indicates overcurrent error. I unplugged the motor termination, on the drive but still found the same error. I know the drive is faulty but I am interesting to know what were the reason.. Is it the transistor malfunction or capacitor or any other? I will be very thankful if you upload some troubleshooting case studies related with VFD repairing.

Thanks
Service engineer

Muneeb:
22/12/2014, 12:45:35 AM

I would be very thankful if you clarify me in below contents
I found at motor input from drive, we occasionally placed chock transformer. I heard the purpose of it is motor protection, but how it protects if AC square wave is appropriate for motor operation as you told in article..

Thanks in advance

admin:
22/12/2014, 12:38:00 PM

It is really hard to say the exact reason for your overcurrent error without being able to directly take a look at the drive. There could be several reasons why you are having problems. Our recommendation would be to take it somewhere for diagnostics. If your location is close enough to us, you could send the drive in to us fpr diagnostics to address the issue. If you would like to do that, we can send you a repair quote.

As for your other question about DC chokes. A choke reactor is usually used on a dc bus of a drive to help with harmonics that goes back on the line.A Dv/dt filter or sine filter will help with the square wave form, which you mentioned. If the motor is not too far away from the drive it isn’t too much of a concern if you don't have one, but if it is 100 ft from the drive you should take a look at using one.

Bryan Charlton:
17/12/2014, 07:48:53 AM
Reply

Why would the switchgear that is feeding the VFD show a different current reading to that showing on the VFD?

admin:
17/12/2014, 08:43:00 AM

Without knowing more about your application it is hard to give a definitive answer. But, typically they will be different because the VFD and switchgear are not calibrated the same. The amperage that you will see from your switchgear will include everything that is on the switchgear while the amperage from the VFD is just from the motor.

Bryan Charlton:
17/12/2014, 08:49:06 AM

Sorry that was a bit misleading by me the current reading on the MV switchgear is of the CB feeding the VFD so it is dedicated to this application only.

Bryan Charlton:
17/12/2014, 09:08:16 AM

I should add also that the VFD is reading less than the switchgear up until the rated frequency which then they are identical.

DVP:
15/12/2014, 09:29:10 AM
Reply

What would cause a DC overvoltage message on an AB 300HP VFD?

admin:
16/12/2014, 08:27:00 AM

There are several reasons that might cause a DC over voltage. It is hard to identify the reason for this with out knowing more about the application. If you would like to call in and talk with one of our engineers at 800-800-2261 we can help you figure out what is causing your over voltage.

Matthew:
05/12/2014, 08:48:35 AM
Reply

Can I use your definition in a publication?

Asmat ullah khan:
28/11/2014, 04:08:29 AM
Reply

what would be the minimum DC voltage from DC voltage source on DC bus of VFD to run the induction motor?

admin:
03/12/2014, 09:27:00 AM

The DC bus voltage is directly related to the supply voltage. There is a DC bus voltage at which the VFD will trip on under-voltage and will not run at all. This will vary depending on the drive manufacturer. For one brand of drive that we offer, the DC bus under-voltage trip is set at 430V for a 480V drive. The typical DC bus voltage for a 480V drive is about 650V. Technically speaking, there is no absolute minimum voltage that the DC bus will function at, but rather a minimum source voltage that the VFD will consider acceptable voltage to operate safely.

given:
25/10/2014, 02:50:39 AM
Reply

Does vsd help for heavy load start

admin:
11/11/2014, 04:42:00 PM

Yes, it does. Base on the overload rating of the VFD, it can give you full load torque and more at all speeds, including dead stop without the typical high current associated with across the line motor start.

Ralf Meister:
16/10/2014, 07:03:02 AM
Reply

I have seen VFDs offered with 120V single phase input and 230V output. How can you get 230V out of 120V without a transformer?

Jon Novak:
22/10/2014, 11:55:35 PM

240V output is no more than 2x 120V lines phased @ 180degrees. Likewise 208V 3phase is 3x 120V lines phased at 0, 120, and 240 degrees. If you are handy with how you capture the AC power and convert it to DC, you can get a + and - DC rail at the cost of needing more current. Which will allow you to use the VFD portion to phase the output and get you the phasing you need to get "2 phase" 240, or 3 phase 208.

FYI in your house, this is exactly how its done. You generally get a neutral and 2 hot legs legs of power each having 120V (to neutral). But hooking Hot/Hot will give you 240, since they will be 180 out of phase.

Jun Pascasio:
29/01/2015, 10:38:41 PM

A device called Joule thief can do that. It is a configuration of a capacitor and an inductor. The configuration causes a build-up of charge at the output terminals. The oscillations on the R-C circuit makes it possible.

Mehdi:
08/10/2014, 02:48:28 AM
Reply

What is the relation between speed and power consumed by VFD

admin:
08/10/2014, 04:40:00 PM

HP = (Torque(ft-lb) * Speed(RPM)) / 5252
KW = HP * 0.7457

The above equation shows us that there is a third element outside of speed and power that must be taken into account. Torque is determined by the load. Essentially while there are small losses in power in the VFD and the motor (both are extremely efficient) you will not be able to determine the consumption of power without knowing the torque.

nel:
12/10/2014, 02:14:11 AM

what must be the rpm value, full or sync rpm?

connor:
28/08/2014, 08:59:51 AM
Reply

What controls are out there to determine the output frequency in order to match the load? In an heat pump application is this controlled by temp sensors and programmed logic similar to a traditional technology?

Dornepsd:
25/08/2014, 02:22:10 PM
Reply

I've been told to purchase an inverter for a pump application. Is there a difference between an inverter and a VFD?

ENGINEER SAMSON:
12/08/2014, 01:23:56 PM
Reply

Is it possible to use 2-wire hard contact to remotely vary the speed of the motor between 50% and full speed when using your VSD device.

Thanks

Engineer Samson rotimi Oladipo

admin:
12/08/2014, 06:17:00 PM

Yes, the drives include preset speed inputs. The two wire contact would be wired to the preset digital inputs.

SAMSON OLADIPO:
01/09/2014, 04:51:13 PM

Thanks for the answer, the actual thing we want to achieve is, if the two-wire hard contact are bridged we want to have 100% full speed and if the wires are disconnected, the motor should be running at 50% speed. Is it possible ? and how can we achieve this with the preset digital inputs. Could you help us with a typical sketch or diagram or drawings.

Thanks for using your time to help out.

Engineer Samson Oladipo

Isaac:
04/08/2014, 06:39:22 PM
Reply

I feel am already expect in VFD's. This presentation was clearly explained from what is to why we use it.

Thanks

Jack:
31/07/2014, 08:37:14 AM
Reply

Thank you for the great information on VFDs.
When you reduce the voltage to maintain the magnetic flux ratio (V/Hz), what happens to the current?

Dan:
31/07/2014, 11:32:00 AM

If the motor is running, the current will be roughly proportional to the torque required by the load.

Jack:
31/07/2014, 12:56:13 PM

Forgive me if I am being obtuse; I'm new to this. If you reduce the frequency from 60 to 30 Hz and maintain the same load, what will the current do?

admin:
08/08/2014, 03:43:00 PM

If the V/Hz is constant, the Amps will be roughly proportional to torque, regardless of speed.

Ikhtekharul Islam:
13/07/2014, 12:59:11 AM
Reply

EXCELLENT INFORMATION ABOUT VARIABLE FREQUENCY DRIVE. THANK YOU...

Myo Kyaw:
11/07/2014, 06:11:48 AM
Reply

Thank you very much for very useful information. I wish I could also read how switching with transistors is done to achieve required frequency and about frequency modulation.

admin:
15/08/2014, 02:57:00 PM

Thank you for your comment and the idea for additional content. We have written an article about the switching of the transistors. Here is a link to it:

http://www.vfds.com/blog/switching-it-up-igbt

admin:
15/08/2014, 02:57:00 PM

Thank you for your comment and the idea for additional content. We have written an article about the switching of the transistors. Here is a link to it:

http://www.vfds.com/blog/switching-it-up-igbt

P.SUBBU:
09/07/2014, 01:11:40 AM
Reply

Very very good information

John:
01/07/2014, 09:17:18 AM
Reply

In the V/Hz discussion I can't find the reference "(see the VFD Motor Theory presentation for more on this)" . Where is it located?

This site is a great, informative discussion of VFDs.

admin:
01/07/2014, 04:56:00 PM

Thanks for the kind words and for your question! We are currently in the process of editing the motor theory post but I think I can help answer your question about the V/Hz ratio.

Motors are driven by magnetic poles. The strength of the magnet is proportional to the ratio of the voltage divided by the frequency (V/Hz). If the ratio is too low, the motor will be too weak to provide full torque on the motor shaft. On the other hand, if the ratio is too high, the iron in the motor will saturate because it is being pushed too hard. It will overheat and start to smoke, and eventually fail. Therefore the ratio must remain constant.

To illustrate this further, at 460V and 60Hz, the magnetic flux ratio (V/Hz) is 460V/60Hz = 7.66 V/Hz.

Now it’s important to remember that this V/Hz ratio must be maintained in the VFD. When you reduce the frequency you must also reduce the voltage. If you were to reduce the frequency, say to 30Hz, the new required voltage to maintain the ratio would be approximately 230V.

V/Hz Equation:
Magnetic Flux = V/Hz
Example: New Voltage (230V)/30Hz = 7.66 V/Hz

I hope that answers your question. If you have other specific questions, let us know and we would be happy to answer them for you John.

AJITH KUMAR:
01/07/2014, 04:03:09 AM
Reply

thank u .... super tutorial guys

ANKIT:
29/06/2014, 10:33:04 PM
Reply

VERY GOOD INFORMATION ABOUT VFD

Thiagarajanethirajulu:
29/06/2014, 08:09:43 PM
Reply

it is a interesting subject.attach more of the same

NAND LAL GURJAR:
26/06/2014, 02:07:59 AM
Reply

here good and knowledgeable information about vfd.
thanks

amancio tapasao jr:
09/08/2015, 09:55:20 AM

Even big motor its ok using vfd?