Electrical Motor Test
Why do we test motors? We test motors in order to evaluate their current health and to predict their safe and satisfactory operation. Because many factors affect the performance and longevity of motors, we must perform a variety of tests and perform them within routine guidelines depending on their size and importance to your operation. Critical and large motors should be monitored more closely.
A reliable diagnosis of any motor condition requires gathering as much information as possible about the motor. It is necessary to evaluate the motor’s insulation health and how it performs under load. This requires dynamic or on-line testing. We use the latest, state-of-the-art test equipment developed by Baker Instrument Company, the recognized leader in electric motor testing equipment. For dynamic testing, we use the “Motor Performance Monitor” or MPM. The MPM Explorer II from Baker Instrument Company is the latest innovation in plant management and an integral tool in an excellent predictive maintenance program. This equipment utilizes multiple tests to determine power condition, health, load and energy profiles of your motors. The following five test domains describe the functions of each test.
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- Power Condition Tests: The voltage level, voltage balance and harmonic distortion tests determine the motor’s overall power condition.
- The Voltage Level Test: Identifies the incoming voltages the motor “sees” and informs you of over and under voltage conditions.
- The Voltage Balance Test: Examines the voltages of each “leg” by calculating percentage of unbalance via NEMA derating.
Note: A non-balanced voltage condition causes negative sequence currents within the stator, resulting excessive heat. The voltage balance test determines the condition of the incoming line voltages.
- The Distortion Test: Examines the total harmonic distortion of the three phases to ground. (Harmonic distortion causes excess heat in motors, and can create problems in other electronic equipment within a plant.)
- Motor Performance Tests: The service factor test, overcurrent test and efficiency test observe your motor’s performance and helps identify money saving possibilities.
- The Service Factor Test: Identifies any thermal overloading in the motor and divides the estimated percentage load into the NEMA derating factor. This test identifies how close the motor is operating to its effective service factor.
- The Overcurrent Test: Compares each phase and totals with nameplate data. The overcurrent test determines if your motor might be drawing more than its rated current on one or more phases, causing excessive heat and decreasing the life of the insulation.
- The Efficiency Test: Determines the operating efficiency of your motor. Reduced motor efficiency costs money and wastes energy. This test compares the operating efficiency with EPAct reference, giving statistical feedback on the quality of the tested motor with respect to achievable peers.
- Motor Load Tests: The rotor bar test and operating condition test evaluate the overall condition of your motor.
- The Rotor Bar Test: Inspects the relative amplitude of the rotor bar sidebands and assesses the rotor cage signature. Broken rotor bars cause excess heat, decreased efficiency and shortened motor life.
- The Operating Point Test: Compares the torque, speed and average stator current values to previously stored data and alerts you to deviations from normal operation.
- Energy Assessment Tests: Compares the performance of the tested motor with similar motor designs in the MPM Explorer II and aids in deciding when a motor should be replaced.
- Motor Load Tests: The torque ripple test and load history test.
- The Torque Ripple Test: Warns if the motor’s load requires oscillating or varying torque. The torque ripple test identifies the ripple that the load is requesting, resulting in a percentage of a ripple to steady state operation. This test shows the load stress imposed on the motor.
- The Load History Test: Compares current load levels to previously recorded levels.
Along with the results of the above testing, we also record the exact RPM of the motor, the total horsepower the load is requiring, kilowatts of energy consumed and the percentage of nameplate load being demanded from the motor. This service is offered by Evans Enterprises, Inc. to prolong the electrical life of your motor and its operating machinery.