# Derating VFD for use with single phase input



## Doubleeboy (Jan 29, 2015)

I am looking at buying a new lathe either new or used.  Most have motors 4 to 5 hp, frequently 2 speed motors.  I read somewhere that you could derate a 3ph input VFD so that you could use single phase.  I was wondering if anyone has experience with this and  specifically if the Hitachi WJ200 110LF would work with 4 or 5 hp motors if I used single phase input instead of 3?

Any other suggestions would be appreciated.

Michael


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## JimDawson (Jan 29, 2015)

It may work, I have never tried anything like that. The 110L is rated for 20 HP, so it should be be OK.  I don't think it will hurt the output section.  The problem might be if it has input phase monitoring it might shut it's self down because it has a phase loss.  If it has it, I'm not sure if it can be turned off, but maybe thee is a workaround.  Dunno.


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## cjtoombs (Jan 29, 2015)

I read a white paper, I think by Hitachi, that explained the reason for derating three phase VFDs for use on single phase power.  It came down to the input filtering and capability of the drive.  Basicaly, you will be cramming as much power through two of the inputs as you would normally put through three.  There was also additional derating due to needing additional filtering for the single phase vs three phase.  There was a caution that some drives sense the input voltage on all three phases and will throw an error if one is disconnected (this would be remedied by hooking up one leg to two of the inputs).  Since the principle of the VFD is that they convert the input AC to DC, then chop it up back into AC using a computer, then filter It again and send it to the motor, once it gets past the input stage and converted to DC, the VFD doesn't care what the input was.  I did find a white paper, on a site called Dartcontrols, not the original one (I looked for it) that gives a formula, but little explanation. Here's the link:


http://www.dartcontrols.com/wp-content/uploads/2012/01/De-Rating-VFD-for-Single-Phase-Power.pdf


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## LEEQ (Jan 29, 2015)

The one I saw running was a vfd the size of a computer tower. It was a 15hp vfd to run 1/3 less motor, or close to it. I understand that to use single phase that this is necessary. I can't imagine it being cheaper than outfitting one with a three phase motor and vfd, and running a 220v line.  You might look for dealers electric and check out their very affordable vfd/motor combos. I got a spare motor for my mill with the vfd I needed for little more than I could buy that vfd alone. Also, if it is a small enough motor there are  units made to take single phase and make three, Teco has one I saw.   I'm very interested to see the how to and benefits if you go the route of feeding your drive off single phase.)


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## cjtoombs (Jan 29, 2015)

LEEQ said:


> The one I saw running was a vfd the size of a computer tower. It was a 15hp vfd to run 1/3 less motor, or close to it. I understand that to use single phase that this is necessary. I can't imagine it being cheaper than outfitting one with a three phase motor and vfd, and running a 220v line.  You might look for dealers electric and check out their very affordable vfd/motor combos. I got a spare motor for my mill with the vfd I needed for little more than I could buy that vfd alone. Also, if it is a small enough motor there are  units made to take single phase and make three, Teco has one I saw.   I'm very interested to see the how to and benefits if you go the route of feeding your drive off single phase.)



What I was talking about, and what I thought the OP was asking was the use of single phase input to run a three phase motor.  As far as I know, you can't run a single phase motor using a three phase VFD.  They do make some small (<2hp) VFDs that are designed for single phase input and single phase output.  I've bought a few of them used on ebay for reasonable prices, but new they are very expensive.


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## Doubleeboy (Jan 29, 2015)

Leeq, I have 220 volts, the problem is all the lathes I am looking at have 3 phase 4-5 hp motors.  No inverters that I can find from a name brand company say that you can use single phase input for anything over 3 hp.  I have seen folks talk about derating a 3ph input VFD and running it on single ph input.  I hope I am being clear.  I have no interest in taking a 3 phase motor out of a lathe and putting in a single phase motor.

Cj, I will look over that white paper.  I hope some one will come along who has done this.

Thanks to all for your input!
michael


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## LEEQ (Jan 29, 2015)

Try dealerselectric.com.  Look for teco ma 7200-2005-n1. It goes for $360 and says it takes 230v single OR 3phase in with 3 phase output. It's a 5hp model. They get bigger.  I was surprised to see them. To be clear, the 15hp vfd I was talking about earlier was fed with single phase and If I understood him right, the reason it was so big compared to the motor had something to do with feeding it single phase required a way bigger vfd than the motor you want to run. I think this is the single phase into a three phase input vfd set up you're talking about. He was a electrical genius explaining it quickly to the slow kid (me) nodding along, so I can't do much better than tell you it's been done. I hope the vfd I found helps you find what you are needing without much trouble. If I found one, I'm sure there has to be more out there.


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## cjtoombs (Jan 30, 2015)

LEEQ said:


> Try dealerselectric.com.  Look for teco ma 7200-2005-n1. It goes for $360 and says it takes 230v single OR 3phase in with 3 phase output. It's a 5hp model. They get bigger.  I was surprised to see them. To be clear, the 15hp vfd I was talking about earlier was fed with single phase and If I understood him right, the reason it was so big compared to the motor had something to do with feeding it single phase required a way bigger vfd than the motor you want to run. I think this is the single phase into a three phase input vfd set up you're talking about. He was a electrical genius explaining it quickly to the slow kid (me) nodding along, so I can't do much better than tell you it's been done. I hope the vfd I found helps you find what you are needing without much trouble. If I found one, I'm sure there has to be more out there.




A 15 hp VFD on single phase should run a 7.5 hp motor, maybe a 10hp.  That is the de-rating.  Surprised you found a 5hp single phase input, but I'll keep it in my back pocket, I'm going to need one of those at some point.


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## Jim Nunn (Jan 30, 2015)

If the VFD is designed for single phase operation no de-rating is necessary.  However you will have difficulty finding a single phase input VFD with a rating higher than 3 HP. The reason being that Fusing/Circuit Breaker would have to be in the range 30 to 40 Amps for 3 Hp motor running on Single phase 230.

 The 3 phase drives typically used on this forum would need to be de-rated 70%.  As others have pointed out it has to do with the power conversion of 3 phase to DC and the size of capacitors used in the VFD's Buss circuit.  Drives that have a DC choke in the buss circuit only need to be de-rated 40%. 

I once did a project for a 75 HP sewage lift station in a residential area that only had 230 single phase available.  the biggest problem we had was the current inrush on drive start-up.  We were seeing a 25% voltage drop on a 300 Amp transformer. Lights would dim and the PLC would drop out. 

Jim Nunn


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## stupoty (Jan 30, 2015)

I have a couple of this brand invertor, they seem quite good value and offer high power rated units.  Build quality isn't amazing but they seem to be doing te job.

Stuart

http://www.ebay.co.uk/itm/220V-VARI...NVERTER-VFD-5-5KW-7-6HP-25A-yw2-/260995796278


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## johnnyc14 (Jan 30, 2015)

I have been looking at this one on ebay. Rated at 4HP and input can be 1 or 3 phase. I'm planning on running a milling machine with a 3HP 3 phase motor from the 220V single phase in my garage. The have Mitsubishi inverter chips so I'm willing to gamble it will be OK for the price.

John

http://www.ebay.com/itm/4HP-3KW-VFD...219?pt=LH_DefaultDomain_0&hash=item1c47bf954b


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## JimDawson (Jan 30, 2015)

johnnyc14 said:


> I have been looking at this one on ebay. Rated at 4HP and input can be 1 or 3 phase. I'm planning on running a milling machine with a 3HP 3 phase motor from the 220V single phase in my garage. The have Mitsubishi inverter chips so I'm willing to gamble it will be OK for the price.
> 
> John
> 
> http://www.ebay.com/itm/4HP-3KW-VFD...219?pt=LH_DefaultDomain_0&hash=item1c47bf954b



The price is right.  I'd be willing to take a chance on it.


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## faavs730222 (Apr 6, 2015)

johnnyc14 said:


> I have been looking at this one on ebay. Rated at 4HP and input can be 1 or 3 phase. I'm planning on running a milling machine with a 3HP 3 phase motor from the 220V single phase in my garage. The have Mitsubishi inverter chips so I'm willing to gamble it will be OK for the price.
> 
> John
> 
> http://www.ebay.com/itm/4HP-3KW-VFD...219?pt=LH_DefaultDomain_0&hash=item1c47bf954b


Hi John, I am very curious if the VFD is working for you setup. I bought a 3 phase Lathe with a 2.5kw motor, that I would like to use that inverter drive to hook it up to a single phase supply.


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