Testing of Induction Motor
As energy costs rise, more emphasis is being placed on determining the health of large inductive motors. By using different technique of Testing of Induction Motor along with standard vibration analysis, voltage monitoring, and temperature monitoring provides a complete diagnostic perspective of motor health and condition, power consumption, and overall efficiency.
Now a day lots of techniques and tests are available which gives the complete health card of the induction motors. By monitoring some parameters like voltage, current, temperature, and vibration problem could be diagnosed and by correcting these faults the overall efficiency of the machine can be improved. This will reduce the energy consumption and operational costs.
Why Test Motors?
- Winding defects can occur due to insulation age, contamination, power surges, thermal overload, damaged wire/materials, vibration, and other causes.
- They begin as energy crossing an insulation fault (such as moisture or contamination), which isolates at least one turn. This generates additional stress and heat across the defect, which progresses until an arc is drawn and the winding fails.
All induction motors are tested before shipment from the factory. This testing can be subdivided in two groups:
- Routine tests
- Performance tests
The primary purpose of the routine test is to insure freedom from electrical and mechanical defects, and to demonstrate by means of key tests the similarity of the motor to a “standard” motor of the same design. The “standard” motor is an imaginary motor whose performance characteristics would agree exactly with the expected performance predictions.
Depending on the size of the motor, some or all of the following tests could constitute routine tests:
- No-load running current and power
- High-Voltage test
- Magnetic center at no-load
- Blocked-rotor test
- Winding resistance measurement
- Air-gap measurement (Ag)
- Direction of rotation and phase sequence
- Current balance
- Insulation resistance measurement test
- Temperature rise test
- Shaft voltages
The purpose of a Performance test is to evaluate all the performance characteristics of the induction motor. This test consists of the following tests in addition to the routine tests:
- Loss measurement including stray load loss
- Blocked rotor saturation characteristic
- Blocked rotor torque and current
- Surge withstand test
- Determination of efficiency
- Temperature rise determination
- No-load saturation characteristic
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