Question: There is an electrical problem in our plant: An auxiliary lube oil pump trips frequently due to high current. So, could you please show me how I can start the troubleshooting? Actually, I have no experience in electrical. I am a new engineer. Your help is highly appreciated.
Motor Doc: Thank you for your question. If possible, could you supply the nameplate information and also, when does it trip on high current? On startup or when it is operating normally?
There is a thermal overload frequently tripping the “Lube Oil Pump for Wash Oil Pump Motor” 3P-2875-OPM. As per the motor solo-run test with a no-load current, the result was 1.3 amperes (motor-rated current in accordance to the LV MCC is 3.26 amperes).
Pump was checked by mechanic and found no problem at all. On the other hand, the mechanic ran a test with a load current result of 4.8 amperes. So, that high load current causes a thermal overload; then it will trip the pump motor. The load current is more than the motor rated current. According to the operation personnel, the lube oil pump will be running for a minimum of 30 seconds and maximum of 3 minutes to lubricate the main pump (3P-2875) and then stops after building-up pressure.
So, what we can do to avoid the thermal overload tripping of the pump motor. Please help us to solve this problem. See the specification of the motor below.
MOTOR, ABB 90, 1.5KW, 3/60/400
EEX NA, T3, TEFC, 1P55
IM B35 MOUNTING
Motor Doc: In fact, the motor is operating at 160% load, well over the load rating of a standard motor, so the fact that it is tripping is not surprising.
The motor rating, per your attachment, is actually 3amps. The motor seems to be performing within it’s operating specifications with the no load current being 1.3amps per the attachment.
If this problem has been with the system since it’s installation, then the motor may not have been selected correctly, or there may be a problem in the pump system. Otherwise, it is a problem in the pump system.
Check filters and strainers, valves or other restrictions in the pumping system.