Brad and Michelle have been on trouble call overload all week. An unexpected shutdown and restart failure brought them to a critical line. They determined a motor needed replacement, partly because Michelle smelled the burned windings almost as soon as she got there.
After replacing the motor, they found voltage imbalance and power factor within limits. So, they figured the motor had just gone bad, maybe the winding insulation had been damaged during manufacture. They aligned the new motor, attached the vibration sensors, and put it back in service.
Shortly after they arrived at the next trouble call, the operator they’d just left approached them. The new motor was turning, but something wasn’t right so he shut it off.
Back at that motor, the operator explained that he’d put his hand on the drive gearbox on the load side of the motor to feel for vibration and had nearly burned himself. Further investigation revealed the gearbox bearings had been improperly packed. This extra load had caused the previous motor to burn itself up because its thermal overloads were one size oversized. Lesson? When a motor burns up, check the whole system.