Motor & VFD Online testing

Motor & VFD Online testing


– Identify the abnormalities in the operation of electric motors and the VFD (if any);
– Identify the causes related to the electrical parts affecting the condition of electric motors;
– Measure actual motor efficiency and identify influencing causes such as: power quality, stator failure, power circuit;
– Identify VFD’s failures in rectifiers, DC bus, inverters …


– Eletric motors, VFDs with high criticality in factory


The condition assessment of electric motors & VFDs during operating is a very important task in predictive maintenance (PdM) program of whole plant. The difficulties in data collection and analysis will disappear as diagnostic technologies is developed and experience accumulates over the years. With nearly 10 years of experience and analysis equipments (such as Fluke 438-II, MDA 550), RCMI is capable to provide online condition assessment services for electric motors and VFDs to help customers identifying potential problems in the operation of critical electric motors and drives.

Electric motor online testing
– Power quality analysis
– Current, voltage; Imbalance current, voltage
– Harmonics of current, voltage according to IEEE 519
– Current, voltage time domain
Evaluate power and efficiency of electric motor
– Electrical power, power factor of 3 phases
– Mechanical power, torque
– Operating efficiency of motor
NEMA derating factor: evaluate the working efficiency of motor compared to the design
– NEMA derating factor relating to harmonics
– NEMA derating factor relating to imbalance voltage
– NEMA derating chart
Evaluate the condition of stator winding and power circuit

VFD online testing
– Analyze the condition of rectifier circuit
– Analyze the condition of DC bus
– Analyze the condition of inverter circuit
– Checking carrier frequency, V/f ratio of VFD
– Evaluate voltage spike at motor terminations box
– Evaluate bearing discharge and check shaft voltage

Fluke MDA 550


Fluke 438-II



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