Control Transformer

Okay, not being an electrician or a 3 phase expert here's my question: I'm taking a control transformer, and running it backward so I have 460VAC single phase ACROSS the primary winding.

Here's my dilema....I want to power up a VFD on the bench, not running any sort of load..I want to shake out this Modbus control in my office......So I have my 3 phase input on the drive, but I have 460 ACROSS my transformer winding....I'm not understanding how I would get my potential to 3 legs on the drive? How do I return back to the transformer?

TIA,

Greg

This VFD may be able to use 1-Ph 460V. Read the manual.
When stepping-up make sure the VA rating is sufficient enough to handle VFD requirements.

If you have to have 3-ph 460 for this VFD, you will need three contorl TXFR in Delta configuration (I am not sure about there phase relationship, and it may not even work).
In that case try to find 460V 3-ph close to workbench rather than rigging control TXFR.

The drive can handle single phase 460. And the xfmr is large enough...I just don't know how to get return back to the transformer? Getting true 3 phase 460 up to my office is not easy.


Thanks,


Greg

We do this all the time. Actually I have a fellow doing it as I write.

We put 120 Vac on the control power terminals from a wall outlet and the voltage steps up through the X-fo to 460.

We have 4 Mitsubishi FRS540- VFD Inverters on this side of the X-Fo.

Only single phase but enough juice to power up there electronics. This way we can pre-configure them parameters and fully test our program (analog control) before we make delivry.

Some drives will detect a loss of phase an give you a fault so you will not be able to see the frequency increase as you command it but not these ones beerchug

"The drive can handle single phase 460. And the xfmr is large enough...I just don't know how to get return back to the transformer? "

If the drive can take 1-ph 460, just use the two legs of drive input ie L1, and L3 and tie them to the TXFR 460V terminals.
Leave the middle leg unconnected.

What do you mean return to xfrmr? Connect the supply voltage to the xfrmr then take the 460vac 1 PH to the VFD...in most cases the VFD requries specific terminals to be used when connecting single phase, has to do with internal control power.

Once you correctly connect the 460vac 1 PH to the VFD the output is controlled by the VFD. The VFD actually converts it to DC then back to an AC like waveform which will be 3 phase.

This was the discussion in the IRC chat room last night Greg mentioned in THIS post. Greg has an ABB ACS550-U1 drive. The manual is HERE.

From what I can tell, he should be able to connect 460V single phase to two of the supply connections as others described. I doesn't look like it needs to be any specific legs. IOW, you can connect to U1 and U2, U1 and U3, or U2 and U3.

From the IRC discussion, Greg seems to be using a 3KVA transformer. I don't know what HP drive he has, so the 3KVA transformer may/may not be adequate to power the drive...

I too am confused about the "return back to the transformer" statement...

beerchug

-Eric

Eric, it works good...L1 and L3 is across the transformer. It's only a 3 HP drive. Thanks for the info...sorry about the quick departure from IRC last night...I got diconnected from the chat server, and could not reconnect. Then it was bedtime