3phase motor running on one phase

Hi.
I have 11kw 3 phase motor controlled by variable frequency drive ( siemens micromaster).
The drive can be powered with one phase ( with little pcb change ) and
it can give 3 phase output. So i was thinking to connect one phase to the drive to see how much power can i get on motor side.
My question would be, how to calculate maximum horsepower or KW used by 3 phase motor, if he is be connected to 220 / 50 HZ - 8KW source ?
Can he run on half of the power or maybe 6 - 7kw ?
Regards !
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h200 wrote:

No. TANSTAAFL.
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Not sure I understand what you are asking.
A three phase motor can be run on a single phase and will deliver about 2/3 the power it would have on three phase. And you can do this without any variable frequency drive. But you have to have a way to get the three phase motor to rotate.
I would not recommend using a VFD to run a three phase motor. I suspect it would ruin the VFD and maybe also the motor. Depends on how fast the circuit breaker acts.
Do some searches on " phase converter.
Dan.
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Bath salts ?
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GOTTA be. I run several machines in my shop on VFDs, because POWCO "don't deliver no three wires" to my locale (that's a quote).
Lloyd
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On Fri, 5 Oct 2012 14:23:47 -0700 (PDT), " snipped-for-privacy@krl.org"

Dan, you know better. VFD drives are almost exclusively used to run three phase motors. Perhaps responding to political posts has warped your mind. Or maybe you are just "taking the piss" as folks say on the other side of the pond. Eric
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On Oct 5, 6:04pm, snipped-for-privacy@whidbey.com wrote:

Dan.

I do know better. I am a slow typist and often get my thoughts way ahead of what I have typed. In this case, I meant " I would not recommend using a vfd to run a three phase motor on one phase." Three little words left out and the whole meaning is changed.
I have a three phase motor on my lathe and use a VFD to power the motor. Also got a 3 phase bench grinder recently and am going to use a VFD on that too.
Dan
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wrote:

Lots of VFDs out there that document using single phase in 3 phase out. I have three motors in my shop configured that way. Drives Warehouse even lists one that only has connections for single phase and its rated for a full 5HP. (About 3.7Kw) What I have not seen is a VFD rated for single to three phase for more than 3.7kw. The OP says 11Kw. That is one big honking motor.
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On Fri, 5 Oct 2012 17:10:53 -0700 (PDT), " snipped-for-privacy@krl.org"

Greetings Dan, I use a VFD on my band saw. The saw came with a single phase motor but I replaced it with a three phase motor and a VFD. So now I can cut steel and aluminum with the same blade without changing belts. Eric
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On Fri, 5 Oct 2012 14:23:47 -0700 (PDT), " snipped-for-privacy@krl.org"

Most...not all..but most VFD manufactures approve of running them on single phase, with the caveat that they do drop at least 25% of their capacity when doing so.
Gunner
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snipped-for-privacy@krl.org wrote:

I think (correct me if I'm wrong), the OP wants to run the input of the VFD on single phase.
It all depends on the design and rating of the input stage of the VFD. Some are rated explicitly for this mode of operation. They have beefier input rectifiers to allow for full power draw by a single (line to line) phase input.
Most VFDs are an AC to DC power supply (a rectifier array and some power factor regulation switching). Following this DC stage, the VFD has a three phase bridge, which 'chops' the DC to produce the variable frequency and duty cycle pulses. This output stage doesn't care where its DC input comes from. As long as the input rectifier can take it, you can put out full power.
Never run a VFD with an output phase disconnected (VFD to motor). There might be a few strange beasts that will tolerate this. But they are rare.
The beauty of a VFD is that they DO allow the use of three phase motors where only single phase is available. Better efficiency and starting characteristics, not to mention the speed control feature.
--
Paul Hovnanian mailto: snipped-for-privacy@Hovnanian.com
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Since PowCo won't install "three wires" (their quote) to my shop, that's how all my three-phase equipment runs. It's WAY cheaper than a rotary converter.
LLoyd
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h200 wrote:

Either 2/3 or full power depending on the drive. It should say what it's rating is on single phase input in the specs.
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The average VFD, on single phase... will deliver about 75-80% of the rating of it being run on 3phase
Gunner
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Gunner wrote:

Some VFDs are set up to alarm if they don't have all 3 phases. Most under 10 KVA will run on single phase input. If you load them to 100% rating on single phase it can damage the rectifier and will certainly shorten the life of the capacitor bank (unless the manufacturer has specifically over-designed these parts to permit full power on single phase.) Some people recommend a 50% derating for single phase, but I think your 75% is a good number for typical shop use, where the 75% rating is rarely needed.
I have a 1 HP rated VFD on my 1 HP Bridgeport, and it has run perfectly for over a decade. I got this before I knew about the derating issue, but I'm getting away with it in light home-shop use.
Jon
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