The main drive motor for Line 3 has been replaced three times in as many years. The CFO knows your reputation as a crack troubleshooter, and she’s told the plant manager that unless he wants to keep buying replacement motors, to have you solve the failure cause.
After the second failure, a power analyzer was installed on the feeder. It shows a (corrected) PF of 96% at the motor, but the history doesn’t show any power event that could have caused the latest failure.
To live up to the expectations set by the CFO, what should you do next?
First, look more closely at what the power analyzer can tell you. Does it show chronic undervoltage, voltage imbalance, or excessive voltage distortion?
Next, look closely at the gearbox this motor drives.
- Thermography can tell you if it needs attention from the mechanics. If it runs hot, it could be overloading the motor.
- Check the coupling (alignment, smooth action, etc.).
- Replace the gear oil (use synthetic).
- Measure deflection of the gearbox mounting while under load.
- Perform vibration analysis.
While the motor is running, conduct thermographic inspection and vibration analysis.
Obtain forensic data on the replaced motors. If those weren’t sent out to the motor shop and have already been disposed of, prepare a forensic exam checklist for the motor that’s now in service. You must know the failure mode to be sure you’ve correctly solved for the failure cause. A motor shop can provide that information.
