Phase converter gone bad

ulav8r · Jul 21, 2008

A friend has a phase converter that is having problems. We need help to figure out the problem. It is hooked to a Mori Seiki manual lathe. It has recently started chattering when starting and then rumbling. He checked the forward run cont actor on the lathe for sticking contacts. They are just starting to look rough. He then checked the voltage coming out of the converter. One leg is at 198V, the other two are at 103-106V.

Could a bad cap cause the two legs to drop like that? How do you check a cap, other than visually? I sure don't know what could drop the voltage on two legs. If it were only one leg out, I could understand that.

ben80 · Jul 21, 2008

third leg

Hi,
I'm not a elect. but I think in three phase one leg is going to be higher. I don't know if the voltage levels are right or not( seem to be a little low), but then I have not worked with converters YET but its coming......I am sure others with more knowledge will jump in , am I am interested in your outcome.

good luck

toolnut · Jul 21, 2008

You provided the voltages from phase to ground. Please also provide the phase to phase voltages. You can locate the generated leg as it is the one with the 198 volts you have already listed.
A-C
A-B
B-C

Bruce Norton

gpkull · Jul 22, 2008

#1 if you want to check caps get a supco cap checker.
#2 if this is an rpc one cap should not be pulling down the volts on two legs.
#3 your volt measure should be leg to leg. keep all single phase controls and devises off the man. leg.

2Slow · Jul 22, 2008

Your voltages do not seem that far off from hot to ground.

The most useful information would be voltage from leg to leg.

-Joe

ulav8r · Jul 22, 2008

He got some other help last night. They changed the leads around, ended up getting 200-230 leg to leg without doing anything to the caps, etc. None of the legs were closer than 8 volts to the others.

Thanks for your input.

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Phase converter gone bad

ulav8r

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ben80

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toolnut

Stainless

gpkull

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2Slow

Hot Rolled

ulav8r

Cast Iron

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