Power transformer installation

[larry t]

I have a 43 amp 230Volt motor that needs wiring in and and the only power source is a 277/480 panel.

I was told by a mfg that I needed a 10KVA transformer, but that calculates to 42 amps one amp short so I believe that I need a 15KVA transformer single phase 480/240 for this application.

I know the formulas for figuring amps on each side of the transformer, but unsure about disconnects and panel circuit breaker size.

The machine is within sight of the panel about 30 feet away so I don't think I need a disconnect there.

I do believe that I need a disconnect on the load side of the transformer, and plan to wire in a fused disconnect with dual element fuses.

Talked to the manufacturer about the overloads and they say they are built into the units control system.

Do I just take two legs of the 480 and wire them into H1 H2 then secondary off X1 and X2?

Also grounding.... Do I just run a ground to the transformer cabnet and then on to the load?

Would appreciate any advice I could get thanks
Larry

 

[dbuckley]

Also grounding.... Do I just run a ground to the transformer cabnet and then on to the load?

Using the tranny gives you a SDS, so you need to ground the neutral of the secondary; search the forum for any of the million topics on SDS, they pretty much all say the same thing...

 

[jim dungar]

Transformers need to be sized larger than the FLA of a motor to allow for reasonable voltage regulation during starting. One rule of thumb is to provide 1kVA of tranformer for each 1HP output of motor.

 

[George Stolz]

Note: I removed my last post, it contributed nothing of value. My apologies to Larry, I did not mean to poke you in the eye for asking questions, and that's just what I did.

Do I just take two legs of the 480 and wire them into H1 H2 then secondary off X1 and X2?

I believe what you would use is a tranformer specifically for that purpose (480 - 240), and that sounds right - but I am no transformer expert.

Also grounding.... Do I just run a ground to the transformer cabnet and then on to the load?

See 250.30.

 

[larry t]

That would pu me at 17kva do you think 15 kva is close enough?
Larry t