Sunday, November 8, 2015

Signs/Causes/Reasons for Overload trip - Motor troubleshooting


- blown fuse
- improperly sized fuse
- tripped/open circuit breaker
- failed capacitor
- overheating
- poor ventilation/lack of cooling
- high ambient temperature
- broken motor fan
- low voltage
- overvoltage
- voltage fluctuation, transient voltages
- power imbalance to the phases (not same power to each phase)
- insufficient torque
- belts too tight
- one phase drawing excessive amps
- one phase is open (single phasing)
- phase imbalance (voltage on one phase lesser than others)
- one phase drawing no (zero) amps
- open contactor contacts
- open motor winding
- low insulation resistance
- low resistances causing high currents
- vibration
- damaged stator
- loose wiring
- improper wiring combinations
- loose contactor contacts
- grounded motor
- shorted motor
- defective overload heater
- malfunctioning overload block
- overload relay failure
- overload protection not properly sized/not properly set
- motor sitting for long period of time (e.g. not operated during winter)
- seized motor
- rotor not turning
- shaft not turning freely
- shaft misalignment
- shaft too loose
- rotating parts contact stationary parts
- soft footing/foundation
- pipe strain
- moisture
- rust, contamination, dirt, accumulated dust
- bearing failure
- overlubrication
- inadequate or incorrect lubrication
- jam/obstruction inside/outside motor
- inadequate wiring/undersize wires
- undersized motor
- tripping of thermal protection/overload trip
- system alteration (e.g load increase, power supply changes, etc)
- new component added
- flowrate increase (airflow, water flow, heat load increase)
- operating a motor at 10% to 15% above rated speed
- harmonic distortion causing high frequency voltages or high current
- wear, incorrect fit
- shaft voltages/currents while rotating
- variable frequency drive (VFD) has improper pulses generated