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VFD #172049 12/11/07 07:27 PM
Joined: Dec 2004
Posts: 78
C
Cinner Offline OP
Member
Has anyone heard of an application where you input a single phase voltage into a vfd and get 3 phase out with the loss of some HP. Has anyone tried this?

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Re: VFD [Re: Cinner] #172052 12/11/07 07:33 PM
Joined: Feb 2003
Posts: 939
F
frenchelectrican Offline
Member
yes i done that allready before and many manufacters did have a statement on running single phase input to reduce the capaicty of the VFD device to prevent overheating.

Merci, Marc


Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)

Re: VFD [Re: frenchelectrican] #172054 12/11/07 07:52 PM
Joined: Jan 2005
Posts: 5,316
renosteinke Offline
Cat Servant
Member
Sure, I've done it. As a result, I was able to control the speed of some air handler motors.

Was horsepower lost? I really don't know. The whole point of the exercise was to NOT use the motors to their fullest extent. The air handler's power requirements dropped from 28 amps to 8 amps, as a result.

Re: VFD [Re: frenchelectrican] #172055 12/11/07 08:00 PM
Joined: Mar 2007
Posts: 49
A
ausador Offline
Member
Yes, and before they came along we used "phase convertors" on single phase to do such applications as running an elevator(3-phase) in a residential neighborhood church.

They are a bit** to size properly and to get the ahj to authorize...the math is way too complicated for me...but engineers are cheap and slutty if you have cash money now and not the promise of payment on wednesday....(ok cheap shot and too obscure probably.....sigh)

Anyway yes it works fine....but you need engineering supervision.

Re: VFD [Re: ausador] #172061 12/11/07 09:04 PM
Joined: Nov 2005
Posts: 806
J
JoeTestingEngr Offline
Member
I'll answer a little differently in an attempt to seem high priced and somewhat selective. The single phase input works via a single phase input rectifier section to provide power to the DC bus. The 3 phase output works via a 3 phase inverter section with suitable drives. You're stuck with the horsepower loss because you will never achieve anywhere near 100% conversion efficiency. If you could the VFD would be very small and require no heat sinking. If you meant deliberately limiting the load's horsepower through the VFD's programming, that is fairly common these days. I'll ask around next time I'm over at the dollar store pickin' up chicks.
Joe

Re: VFD [Re: ausador] #172065 12/11/07 09:28 PM
Joined: Sep 2001
Posts: 806
N
NJwirenut Offline
Member
Smaller VFDs are often used that way by home shop machinists so that they can run surplus 3 phase machine tools on residential single phase 240V.

Re: VFD [Re: NJwirenut] #172077 12/12/07 12:16 AM
Joined: Dec 2004
Posts: 78
C
Cinner Offline OP
Member
If the 3 phase VFD has 3 input terminals, L1,L2,L3, how do you connect Single phase power? .... L1 to Hot, L2 to Neatral, and L3 nothing?

Re: VFD [Re: Cinner] #172078 12/12/07 12:22 AM
Joined: Feb 2003
Posts: 939
F
frenchelectrican Offline
Member
most small VFD's incomming voltage is typically L to L 240 line to line or 208 line to line as well genrally most VFD useally used the 208 or 240 volts system but very rare but some can take 120 v as input voltage

Merci, Marc


Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)

Re: VFD [Re: Cinner] #172091 12/12/07 10:54 PM
Joined: Sep 2001
Posts: 806
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NJwirenut Offline
Member
Originally Posted by Cinner
If the 3 phase VFD has 3 input terminals, L1,L2,L3, how do you connect Single phase power? .... L1 to Hot, L2 to Neatral, and L3 nothing?


You need to refer to the specific VFD's manual for this info. If the unit is capable of single phase input, then proper connections should be spelled out somewhere. You would want to connect the power to the 2 legs that feed the transformer that provides low voltage power to the drive electronics. On most this is L1 + L2, on others I have seen, L1 + L3. Depends on the manufacturer.

Input power would be 2 hot phases (240VAC), not a hot phase and a neutral (120VAC).

Re: VFD [Re: NJwirenut] #172101 12/13/07 12:07 PM
Joined: Mar 2005
Posts: 1,213
S
SteveFehr Offline
Member
VFDs and UPSs rectify AC into DC, and then create a new AC signal. The output and input are completely independant. Whether it can handle 1-phase at all really depends on the design- specifically, the controls. The guts are simple, they can handle it, but the controls might consider it a fault and shut down as opposed to switched into a derated mode.

If the input is wye, it really doesn't matter hardware-wise if you go L1-L2 or L2-L3, etc, they're all identical.

If you put 1-phase into a 3-phase VFD, even if it's rated for 1-phase use, you're going to introduce extra ripple current onto the DC bus which can may the output a bit dirty. You'll have to derate the VFD, probably to about 57% of its original rating.

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