Motor Circuit Testing

If you’re looking for a full analysis of your motor condition, infrared and vibration will not provide all the answers required to properly diagnose the condition of your motor. Over time, motor circuit testing techniques have become more and more sophisticated. Motor faults such as winding short-circuits, improper torque settings, open coils, etc. can be easily evaluated with professional motor circuit testing. Motor analysis equipment remains fairly expensive and requires a degree of skill and technique. There are two commonly used tests:

Electrical Surge Comparison

One of the primary concerns of motor condition is winding insulation. Surge comparison testing can be used to properly identify turn-to-turn and phase-to-phase insulation deterioration. Due to differences in insulation thickness, motor winding insulation tends to be more susceptible to failure from stress. Surge comparison testing allows us to quickly identify where the deterioration exists by applying a high frequency transient surge to the winding and compare the resulting voltage waveforms. When differences in waveforms exist, this indicates insulation or coil deterioration.

Motor Current Signature Analysis

Another worthwhile tool in motor circuit testing is motor current signature analysis (MCSA). The benefit of MCSA is that it uses a non-intrusive method for detecting mechanical and electrical problems. The technology is based on the idea that a conventional electric motor driving a mechanical load acts as a transducer. The motor senses the mechanical load variations and then converts them into an electrical current that moves along the motor power cables. These particular currents are reflective of a machine’s condition.

Motor Circuit Testing Applications:

Stem packing degradation
Incorrect torque switch settings
Degraded stem
Worn gear tooth wear
Restricted valve stem travel
Improper seal installation
Inaccurate shaft alignment or rotor balancing
Improper bearing or gear installation
Obstructions in the valve seat area
Disengagement of the motor pinion gear
Insulation deterioration
Turn-to-turn shorting
Phase-to-phase shorting
Reversed or open coils
Short circuit