quick question about 3 phase motors with VFD

[mreza Salav]

Ryan, I got confused with the numbers a bit. Are you saying that if the FLA of the motor (in 3 phase) is 10 you need a VFD that is capable of providing 20amps on the output?
Or are you saying that it should be able to have 20 amps on single phase (on its input)?
I checked with the tech support of factorymation (the first link) and they confirmed that the particular model linked (which provides 10.5amp on output) is good for running a
3phase motor that needs 9amp (a 3HP motor).

[Ryan Brucks]

I find that odd, given the stats on page 3.

Look where it says power ratings (A) and there are two numbers for each. Ie, the first one says 6.3/2.9. The field above shows single/threephase. This leads me to believe these VFDs are just like the other ones I have researched, but to be honest I am no expert and they could be different.

Normally you need the model to be able to handle double the power when converting single to 3 phase. It makes sense when you think about it. A single phase 5 horse motor has an FLA of 20-22. A three phase 5 horse motor has an FLA of 12-13. Obviously some of this extra power has to be eaten by the VFD to convert to the three phase. Can't magically convert 12amps three phase from 12 amps single phase when you think about it without lots of losses.

I would question what you were told and keep researching until you are confident.

[Ryan Brucks]

Clarification: I see you never mentioned single/3 phase in the tech support reply. The double power requirement is only when converting phase.

So what they said is technically correct if you forgot to ask about phase conversion too. Or did they actually say that was true for single phase input and 3 phase output?

[Ryan Brucks]

This chart shows converting amps from single to 3phase:

http://www.engineeringtoolbox.com/am...ase-d_449.html

Looking at the 240v single/3phase part of the graph, it's pretty darn close to the 20/12 FLA figures between 5hp single and 3 phase motors. So I am now pretty confident in saying that yes you always need roughly double power when converting phase.

[Ryan Brucks]

their 3hp model GS2-23PO says its rated for 27/12.5a.

That means when converting from single to three phase it can handle 27a input. More than enough since your 9a motor will only need 18 or 20 amps input from the single phase as an estimate on the high side.

[Ryan Brucks]

oops, I got my wires crossed. I mentioned the automationdirect one instead of your first link (name too similar lol).

That first TECO one you mentioned I do not think will work. I think you need the TECO listed as 20a.

[Ryan Brucks]

for the TECO you would want this model:

http://www.tecowestinghouse.com/teco...command=detail

to buy:
http://www.factorymation.com/s.nl/it.A/id.220/.f

MA7200-2005-N1

[Van Huskey]

Either I am completely stupid <very possible or won't this one work for a lot less money:

http://www.factorymation.com/s.nl/it...=2&category=32

[Ryan Brucks]

It will only power a 5fla, 3 phase motor when converting from single phase. It will not work.

You need to double the power rating when converting phases. Otherwise we would be getting free energy.

[Ryan Brucks]

This explains derating supplies when converting phase. The factor is actually 1.73, but 2x is used for simplicity and to give room for error I guess.

http://www.precision-elec.com/derati...phase-power-2/

[mreza Salav]

Either I am completely stupid <very possible or won't this one work for a lot less money:

http://www.factorymation.com/s.nl/it...=2&category=32

Van, that's what I linked in the original post.

Ryan, either I'm not understanding you or you are confusing something (or both ).
The one I (and then Van) linked specifically says it is rated for 3HP output, see the specification here:
factorymation.info/acdrives/FM50Specs.pdf

It is rated for 10.5amp on output (3phase, 230v). The motor I have listed needs 9amp on 230V (or 220?) 3 phase.
What David was suggesting (I think) is to check that the draw on input of the VFD when supplied with single phase can provide that much output. In this
case for example, the VFD on single phase input draws close to 20amp. If this is what you mean we are in agreement.
I did talk to the tech support group at factorymation about this specific unit and specifically about a motor I want to use on (with FLA of 9 as shown in my photo)
and they confirmed that this works fine.

[Ryan Brucks]

Yes. I know it says its rated for 3hp three phase and 10.5a.

But when you are feeding it with single phase, it requires almost twice the power to generate that same amount of power in 3 phase. So you always need to "de-rate" the VFD in this application. That means you take the published specs, and cut them down by that 1.73 factor.

So those specs when used in the single to 3 phase conversion application are indeed HALF what they are advertising.

Other vendors make this clear. They are just not listing it.

[Ryan Brucks]

Van, that's what I linked in the original post.

I did talk to the tech support group at factorymation about this specific unit and specifically about a motor I want to use on (with FLA of 9 as shown in my photo)
and they confirmed that this works fine.

Unless you told them you are converting from single phase, you didn't tell them everything they needed to answer properly.

[Alan Schaffter]

It will only power a 5fla, 3 phase motor when converting from single phase. It will not work.

You need to double the power rating when converting phases. Otherwise we would be getting free energy.

Please explain. Am I missing something? The FM50 203C manual and spec sheet state; 3 ph, 230V 10.2A output with "1/3 phase, 230V input". Is there a footnote I missed that says the output current rating must be derated for single phase input?

I can understand derating the output current if the rating given was for 3 phase input only, but that is not how I would interpret the literature.

[mreza Salav]

Unless you told them you are converting from single phase, you didn't tell them everything they needed to answer properly.

Yes I did and it was confirmed.