# VFD as main power supply for chiller



## santisiah (Apr 6, 2014)

Hello,

I recently started at a new company and they purchased Chillers direct from China. The chillers run on 380VAC 50Hz. We have a VFD (Schneider ATV312 to be exact) and are intending to use the VFD to step down the 480VAC 60Hz feed to the 380VAC 50Hz needed. 

I am no expert at VFDs and have run them with motors and pumps, but have never used them as a direct supply. The Chillers have their own controls internally so we would basically be using the VFD as a step down transformer. Like I said, I am no expert with VFDs, but I would assume that the VFD will not work with what I am explaining due to the fact that the VFD will not see the same load on all 3 phases.

Can somebody please explain if this will or will not work and why? My superiors seem to think it will work and I'm afraid of damaging the chillers as soon as they are powered up. 

Thanks for all the help.


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## JRaef (Mar 23, 2009)

santisiah said:


> Hello,
> 
> I recently started at a new company and they purchased Chillers direct from China. The chillers run on 380VAC 50Hz. We have a VFD (Schneider ATV312 to be exact) and are intending to use the VFD to step down the 480VAC 60Hz feed to the 380VAC 50Hz needed.
> 
> ...


Without being able to know all of the equipment inside of the system, the safe bet is to say no, it is not a good idea. VFDs are not designed to handle inruch current of a motor starting directly (Across-the-Line). Usually, a VFD is controlling the motor alone, so it is controlling the inrush (magnetizing) and starting current. But as a supply source for the entire machine, your controls for it will not work until AFTER the VFD is already fully on, which means the motor will be started AFTER the VFD is done ramping. The magnetizing inrush current can be as high as 2000X the nameplate FLC, followed by the starting current surge of 600%. Either or both of those current levels will damage the transistors of the VFD, they are NOT designed to handle that.

Secondly, you will not know if the low voltage control system inside of the chiller controller is capable of being fed from a PWM source, which is the output of a VFD. That PWM out is not really AC, it is a string of DC pulses that is fed to an AC induction motor, which the motor REACTS TO AS IF it is AC. Without the motor, it is not AC and some control systems will be adversely affected. Only the designer of the control system would be able to answer that question, and being something from China, good luck with that. Most likely it is cheaper, and it is cheaper because nobody really engineered it, they just copied it from someone else.

Lastly, the internal controls, since it was NOT designed to be used here, is most likely designed around using 220V as a single phase control power source, because in countries that use 380V 50Hz, they are always a grounded Wye system, so they are 380Y220, and the control power is derived from connecting one phase to a grounded neutral. With the VFD as a power source, you CANNOT set it up as a grounded Wye output to create that neutral.

The closes you may be able to get to would be to disassemble the control system, investigate all aspects of it, separate out the motor power and use the VFD for ONLY the motor, then deal with the control power issues separately depending on what you find.

Or buy products designed to be used in our country... I know it's not your decision here, that statement is meant for future readers who might be thinking the same thing when looking at cheap Chinese imports.


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## Southeast Power (Jan 18, 2009)

Seems to be a very small chiller using that VFD. What kinda BTU or HP are you dealing with?
Can you split out the controls from the motor? Does it just start the motor with a contactor or does it use a DC motor or a drive inside?


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## oliquir (Jan 13, 2011)

you will fry all electronics controls on the chiller. get a step down xfmr, chiller may run ok at 60 hz, if it has internals vfds they wont care about input frequency


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## micromind (Aug 11, 2007)

Using a VFD to power a single 380 volt 50 HZ motor from a 480 volt 60 HZ source is perfectly fine; I've done it myself. Simply program the VFD for the the motor data and it'll work just fine.

As noted above, using a VFD to power any type of controls will almost certainly be trouble. Also, a VFD cannot be powered from another VFD. 

VFDs are designed to power motors and only motors. Preferable only one motor. Using them for anything else might work for a while, but in the end it'll be trouble.


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## varmit (Apr 19, 2009)

Since your company has already bought this equipment, I guess that they want you to make it work? 

As JRaef stated, The short answer to your question is NO. Is the chiller motor controlled by a starter or a VFD? If the chiller motor already has a VFD, you could use a 480 to 380/220Y transformer to power the machine. You should be able to change the VFD frequency input parameter to 60 HZ. If the controls are 220 VAC, 50 HZ, They will PROBABLY work OK on 60 HZ, but will have a shorter life due to the increased heating effect of the higher frequency.

If the chiller motor is now controlled by a starter, your best option would be to use an add on VFD to control the chiller motor only and add a transformer for the controls. 

A 380 volt 50 HZ motor will run on 480 volt 60 hz, BUT the motor will run faster than nameplate and draw more current. This would be a real problem on a compressor, pump or fan.


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## santisiah (Apr 6, 2014)

JRaef said:


> Without being able to know all of the equipment inside of the system, the safe bet is to say no, it is not a good idea. VFDs are not designed to handle inruch current of a motor starting directly (Across-the-Line). Usually, a VFD is controlling the motor alone, so it is controlling the inrush (magnetizing) and starting current. But as a supply source for the entire machine, your controls for it will not work until AFTER the VFD is already fully on, which means the motor will be started AFTER the VFD is done ramping. The magnetizing inrush current can be as high as 2000X the nameplate FLC, followed by the starting current surge of 600%. Either or both of those current levels will damage the transistors of the VFD, they are NOT designed to handle that.
> 
> Secondly, you will not know if the low voltage control system inside of the chiller controller is capable of being fed from a PWM source, which is the output of a VFD. That PWM out is not really AC, it is a string of DC pulses that is fed to an AC induction motor, which the motor REACTS TO AS IF it is AC. Without the motor, it is not AC and some control systems will be adversely affected. Only the designer of the control system would be able to answer that question, and being something from China, good luck with that. Most likely it is cheaper, and it is cheaper because nobody really engineered it, they just copied it from someone else.
> 
> ...


JRaef,

I completely agree with your last paragraph and unfortunately I wasn't here in time to help with that decision. Now we have about 10 pieces of equipment that are from China and have probably spent well over $100,000 in Electrician fees to get us VFDs and so forth to try to make it all work. 

We do have pumps and motors that are running on 380VAC 50Hz from the VFDs and those are working just fine after I programmed them. 

Also, you are correct in that they do have a grounded neutral and controls are running on 220VAC (something I have not seen before). The electrician contractor has an engineering degree and seems to think that the VFD will and should work with the chiller in its current configuration. We will see if he shows up today so we can go over it.

Varmit- You are exactly right with your statement as well. They expect me to make it work. I did mention to them that we can get the motor running straight off the VFD and we would have to make the compressor somehow work also. I was just afraid of using the 60Hz on the electronic equipment. The problem with all of this is, we need to be up and running within 2 weeks and now we have a bigger issue than they thought. 

The craftsmanship of the Chiller looks very nice though 

Thanks again for all your help and I will try to update after today.


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## Ultrafault (Dec 16, 2012)

santisiah said:


> JRaef,
> 
> I completely agree with your last paragraph and unfortunately I wasn't here in time to help with that decision. Now we have about 10 pieces of equipment that are from China and have probably spent well over $100,000 in Electrician fees to get us VFDs and so forth to try to make it all work.
> 
> ...


If you read this forum regularly you would know after seeing the people who responded to you and what they said your "engineer" contractor is taking you for a ride. Do what they say exactly and you will be the hero.


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## santisiah (Apr 6, 2014)

Ultrafault said:


> If you read this forum regularly you would know after seeing the people who responded to you and what they said your "engineer" contractor is taking you for a ride. Do what they say exactly and you will be the hero.


That is my intention


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## JRaef (Mar 23, 2009)

If it were me, I would go into the control system and separate out the tap-off point for the controls from the incoming line (hopefully there is only one). Then feed ONLY the motor(s) with the VFD, using the VFD to turn it on and off, not the contactor (assuming here). Then get a small frequency converting UPS for the controls. Good UPS systems will include filtering that your controls will need to run reliably, and in general, UPS units that can convert the output frequency will be better quality versions, often marketed as "true sine wave" type, or words to that effect. You will have to separate the controls no matter what, because you CANNOT use the VFD to feed into a grounded Wye system. That would be an unmitigated disaster all around.

Or, do exactly what your "consultant" is suggesting, but insist that he stand behind his design idea by providing a 5 year parts and labor warranty for it, because the failure of the VFD and/or control systems will not happen immediately, it will be incremental damage that will take time to show up. If he is so confident that it will work, RELIABLY OVER TIME, then he should back up his words.


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