600 (575) Volt Rotary Phase Converter Grounding

[Industrial Toys]

It all started at an auction. I bought this great Big Lincoln Mig Welder. I looked at the electrical nameplate and it said various voltages including 230. I didn't realize it was three phase only.

So the rotary converter project was born.

I decided to make it 600 volt as I am distributing that to several buildings.

I did it a little backwards as I used a ten HP 600 motor. Made the extra phase, into a transformer, and put the motor on the 600 side. Then take my 600 off at the motor. The Transformer is wired in DELTA. Not sure about the Motor. I don't remember if that was an accident or intentional.

It worked, but didn't. The computer in the Welder never did like the manufactured phase, and did ODD things. Finally I sold the welder and bought a 230 single phase welder at auction (of course). Much nicer, not having to start and stop a converter. But I miss the ooomph of that big azzz welder!

My question is, how should I provide grounding on the 600 side for prevention of a conductor touching something without a breaker tripping? I still have the converter, in case I need it.

Thanks

 

[prichard]

Do you have a wiring diagram? Is the transformer an isolation transformer?

 

[Industrial Toys]

I would have to dig out the file. The transformer is a standard building transformer, used to go from 600 three phase to 230 three phase. Basically, the transformer is three separate transformers in one cabinet. I am using it backwards. So yes, there is total isolation between primary and secondary.

 

[prichard]

Then one method is just ground one leg.

 

[prichard]

See

Is this what you were referring to? http://static.schneider-electric.us/assets/consultingengineer/appguidedocs/section6_0307.pdf

Figure 6-2, or 6-6... Pretty cool

This covers it fairly well.

 

[Industrial Toys]

If my Transformer is wired as Delta, Does the Idler motor on the 600 volt side of the transformer need to be wired as Delta? Could I change the transformer wiring to a Y? Would I need to change the motor wiring as well if it's not that?

 

[prichard]

No, Wye can connect to delta. You likely can't change either to match.

 

[Tractor Seabee]

Terminology; are we talking physical grounding to earth, bonding a neutral to ground potential, or developing a derived neutral? I would think this requires careful analysis of: the transformer internal wiring diagram, diagram of the phase converter system, and the appropriate code requirements. Frame grounding/bonding is just that, making sure all metal parts are the same earth ground potential. That ground also needs to extend to what ever equipment is connected to the output of the system so it is bonded into the system. Each of the terms ground, bond, and neutral all have there own explicit definition; even though they may be at the same potential in the system.

Our electrical experts here can figure it out with the above information in hand.

Ron