Overload relay keeps tripping.

Ok, it's drawing 10.8a 11.2a and 0 on the third leg while it's running. Way out of the 6.6 breaker's limit. The motor tag says it's supposed to be drawing 8.8... :dunno:
 
Ok, it's drawing 10.8a 11.2a and 0 on the third leg while it's running. Way out of the 6.6 breaker's limit. The motor tag says it's supposed to be drawing 8.8... :dunno:
We need to understand why you're seeing 0A on the third leg. Are you running off or a rotary phase converter (RPC), static converter, or what? Some "static converters" are nothing more than a set of motor starting caps and let the motor run on two phases once it's running.

Your overload relay is not going to work in this application. I would expect the machine to draw about 4.4A at 480, so the overload would have worked fine there. You should consider getting a correctly sized unit.

Cal
 
Since you reported 170 volts on the third phase, that suggests to me that there may be an open winding, but I fail to understand how it would start. Might be worth taking to a motor shop to ensure the motor is not the source of the problem. But most assuredly, that heater is going to be wrong for an 8.8 amp nominal draw. The reasons the other two legs are drawing more may be related to a problem with the third winding.
 
I'm running a static phase converter 220v. For what I paid for it, most likely nothing more than starting caps. I'm looking for a motor for a RPC. I thought this static phase converter get me by for a little bit. I was also worried that I would have to buy 2 motors instead of one.
 
Tony,

The 170 may be because the motor is providing the voltage, along the lines of an RPC idler motor. I suspect that his static converter is only connecting the third phase during startup.

Brandon,

You can check for an open winding with your Ohmmeter. With the motor leads disconnected you should see about the same resistance between any two of the three wires going to the motor itself. While you're at it, check to make sure you have infinite resistance between any of the 3 wires and the motor's case.

You can also swap T3 with T1 or T2, start her up and check the current again. The motor will probably run backwards, but it will tell you if the third set of windings are OK. (T1, T2 and T3 are the designations for the three phases on the load side of the contactor.)

Cal
 
I'm not an electrician, but I stayed at a Holiday Inn last night....

I don't think there is any problem with the motor or the wiring. I think that it's the result of trying to run that motor on a static phase converter and nothing else.
There are a 1,350,000 (according to Google) explanations of static vs rotary vs VFD on the net, and after reading 1,299,000 of them the symptoms being shown are just what I'd expect to see.

This site has a rather clear explanation of what it is: http://www.phaseconverter.com/what-is-static.html#faq

And the same site says this could be one of the effects:
Static phase converters are designed to start three phase electric motors to run on single phase power. The machinery they are setup to run must be able to operate on two thirds to one half of their rated motor horsepower. If this is not the case then when the machinery is put under its full rated load the motor or machinery will most commonly stall-out or overheat and even burn out.

That's my guess. It's just a guess. Perhaps a call-out on Craigslist would find someone nearby with a rotary phase converter of the correct size that would let you test it out to confirm before swapping out parts/wires.

good luck
Joe
 
It depends on the design of the static converter. Some have a potential relay that connects one or two starting capacitors to the third phase to get the motor started, then disconnect the starting caps, leaving the third phase without power. Others add two run capacitors that stay connected to the motor to power the third phase. It just depends on what he's got. There's not a whole lot of difference between a low end static converter and the motor starter part of a typical rotary phase converter. Something like a PhasePerfect, the provides true 3-phase, is another animal altogether.

Brandon,

This might be a good time to consider going with a variable frequency drive (VFD). This one has built in overload protection, so you can ditch the static converter, the undersized starting relay and add variable speed control for under $200:
http://www.factorymation.com/FM50_230V/FM50-202-C.html

Cal
 
A VFD is an alternative that I haven't given much thought. I would figure I would have to wire the VFD directly to the forward and reverse contactors... Hmmm....
Thanks to everyone that took the time to help me out.
 
If you go with a VFD, you can bypass the forward and reverse contactors. The VFD will handle reversing and give you very nice speed control.
 
I have limited experience with a static converter, but 2 incidents similar to your description turned out to be the converter was the problem - 1hp rated converter would do this trying to drive a 1hp motor. I ended up using a VFD.

But I think I would want to confirm the the motor is OK -- I have a small elec shop near and 2-3 times I have had an unknown motor that I would drop by there and have him 'check' it out. One was a suspected 440v and he confirmed this and suggested he could "pick" (I think that was the term?) the wires and change it to 220v - I said OK and for $60 he did it and every thing was OK. Another was a scrap yard find and he just plugged it into 3ph and it was fine - charged me $10.
 
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