3 phase motor test.
3 phase motor test.
(OP)
I am a self employed residential and light industrial repairman. I don't get many calls on 3 phase stuff but have recently with the addition of a new customer. He is a propane dealer and has several 3phase applications for his pump motors. I am about to check on a job this morning and was wondering what would be the best route in diagnosing his problem.
PROBLEM: 1 to 1.5 hp seald elctric motor.240 three phase. The pump is tripping the reset switch. ( this what I was told I haven't gotten to the site yet to determine if "reset" switch means motor temp overload switch or breaker switch.)I was wanying to know the steps I should take in determining if the motor is bad or ineffecient voltage or faulty "reset" switch.
I am about to leave to go check on it so I doubt I will get a reply before I leave But I would like to see if I checked everything right, when I get back. I will also have alot more details on the specifics of the situation.
P.S. I did ask him if this was a new install and he replied that it was a fairly new customer but he did reuse a pump and motor from another account and that the pump did have some age on it.
Love the site and really appreciate the replies that I have read on other posts. Thanks for your help.
Sincerely Rockytee.
PROBLEM: 1 to 1.5 hp seald elctric motor.240 three phase. The pump is tripping the reset switch. ( this what I was told I haven't gotten to the site yet to determine if "reset" switch means motor temp overload switch or breaker switch.)I was wanying to know the steps I should take in determining if the motor is bad or ineffecient voltage or faulty "reset" switch.
I am about to leave to go check on it so I doubt I will get a reply before I leave But I would like to see if I checked everything right, when I get back. I will also have alot more details on the specifics of the situation.
P.S. I did ask him if this was a new install and he replied that it was a fairly new customer but he did reuse a pump and motor from another account and that the pump did have some age on it.
Love the site and really appreciate the replies that I have read on other posts. Thanks for your help.
Sincerely Rockytee.





RE: 3 phase motor test.
Confirm the motor rated voltage (on the name-plate) matches the supply voltage (through a voltmeter/multimeter). If it doesn't, then the motor is unfit to run at that supply voltage.
Check the running current against the rated motor current. If it is high, probably, motor and pump are mismatched.
*Why make the same mistake twice when there so many new ones available*
RE: 3 phase motor test.
Megohms is good. Over 50,000 to 100,000 ohms is acceptable.
Less than that, use ohms law to determine the leakage current and use some common sense to decide if this is enough currrent to cause your problems.
Use voltage to ground, 120 volts on 120/208 volt systems.
No megger, use a light bulb and 120 volts to ring to ground. It's better than nothing and better than a multi meter for insulation resistance.
respectfully
RE: 3 phase motor test.
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Sometimes I only open my mouth to swap feet...
RE: 3 phase motor test.
The connection box on the side of the motor was very rusty and the wires were coroded very badly. I wire brushed and cleaned them as well as I could and put new wire nuts on to help continuity. No change.I don't have a megger really not sure what that is. Well I'll check back tomorrow and let you guys know what else I've found out and see what new advice yall have. Thanks again hope yall had a great weekend.
RE: 3 phase motor test.
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Sometimes I only open my mouth to swap feet...
RE: 3 phase motor test.
respectfully
RE: 3 phase motor test.
1. Check direction of rotation
2. Check the set-point of the trip (is it an mcb ?)
*Why make the same mistake twice when there so many new ones available*
RE: 3 phase motor test.
1st
Do you have a mechanical problem? How would you determine this with a pump?
If it is a pump, the pressure has to build for it to be a mechanical issue therefore the pump motor will trip some time after in most cases. Check all the valves for proper settings.
2nd
99% of the time when I have a 3 phase motor fault, the motor is usually single phasing. Check the 3 phase connection, motor contactor, overload, and at the pecker head at the pump. Is it a VFD? If so, check the parameters that have been changed and do they match the motor nameplate data? Any instantanous trip is usually loose wiring.
RE: 3 phase motor test.
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RE: 3 phase motor test.
RE: 3 phase motor test.
I suggested plumbing in a guage to see how and how much pressure was building. Once I told him My estimate of time of trouble shooting and parts to do so, then actually replacing it with a new one or repairing the relief vavle he decided to have it rebuilt.
When it comes back if the problem was windings then all will be well if not then it will be overload protection or vave problems
I would like to thank everyone for your help. Thanks, Rocky
RE: 3 phase motor test.
RE: 3 phase motor test.
Then, i later ask some experts of how OEM performed bench test of newly built machine. One said; "since plenty of machine were manufactured in a row, a random testing were made. Thus, there would be a chance of having a defective products on a certaing population or batch." Quite real??
Make a consideration about the machine itself.
"Whenever you are asked if you can do a job, tell them, certainly I can! Then get busy and find out how to do it." Theodore Roosevelt.
RE: 3 phase motor test.
Having current readings over the FLA is a sure sign of overloading. All your readings being consistent sounds good. In most of these cases I almost always find the system to be the problem, not the motor or pump.
Your inprompto test was an excellent idea. It further points to the system as having some restriction. Possibly a filter or if no filter, debris in a line, or valve, or orifice, or seat. I would pursue that angle. A gauge is a 'must' as it is one of the few windows into the system.
Once you have a gauge in you can hopefully load the system down with your bypass valve until the FLA is reached. Mark this point and everywhere further upscale with a RED sharpie so the customer knows when their filter or, methods are going to toast the motor.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: 3 phase motor test.
I would like to thoroughly thank everybody for your valuable in-put. I hope I sent the thank-you to everbody. If not, I appologize. I stay soo busy I don't get much time on the computer to keep up on a regular basis. Again I thank you. I'm sure glad to be a member of Eng. Tips.
Greatfully, Rockytee
RE: 3 phase motor test.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: 3 phase motor test.
Dan
RE: 3 phase motor test.
RE: 3 phase motor test.