You work for a technical services firm. A client company’s plant engineer needs a chronic motor failure solved but has a sticky situation. The plant is privately owned. Ted, who is officially the “electrical maintenance engineer” is a relative of two of the owners. “I can’t fire this guy, even though he doesn’t know what he’s doing.”
This key motor has failed several times over the past 18 months. Ted replaced the VFD three times, each time with a different brand. On Ted’s last vacation, the plant engineer had electricians look for voltage imbalance and voltage drop. No problems. Now Ted is on vacation again, and the plant engineer wants you to identify the problem.
Where do you start?
With so many VFDs, how do you know the latest VFD matches the motor? Contact the motor manufacturer and the drive manufacturer for a determination. Then, look at the motor for power factor (PF) correction. If it’s there, go back to the drive manufacturer for advice.
Once you’ve determined there are no Ted-induced motor/VFD issues, you can get down to the real troubleshooting.
Did a motor shop perform post-mortem analysis? If not, see if this can be done. Is there other information about the failure mode? For example, spun bearings would probably indicate a lubrication issue while failed windings would probably indicate a heat and/or power quality issue.
