Demand of energy is growing day by day and along with it cost of energy rising abruptly, so now it is necessary that the health of large motors which consumes maximum power should be taken care off. Tests are required to check the condition of the induction motor and to get the basic idea of malfunctioning of the motor. 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.
Basic Parameters to be Checked
Current
As line current in all the phases are not equal so the arithmetic mean of the phase currents should be used for evaluating machine performance.
Voltage
voltage is measured at the motor terminals and at the time of test, it should be approximately balanced. Machine performance can be calculated by using average of the phase voltages.
Power
power input to three phase motor can be calculated by a single watt meters as they are connected in two watt meter method.
Resistance
It is necessary to check the ground resistance between the motor body and terminals of the machine.
Tests for Induction Motor
Number of test is done on induction motor to check its different parameters. All the tests are divided into two parts:
Preliminary Tests
These tests are performed to check the electrical or mechanical defects of the induction motor.
1.Firstly check the components of motor like
1a.Broken rotor bars
1b.High resistance joints
1c.Cracked end rings
2.No-load running current test
3.High potential test
4.Air-gap measurement
5.Balancing of current
6.Temperature rise in bearing
7.Voltages in shaft
8.Direction of rotation
9.Level of noise
10.Strength of vibration
11.Air gap eccentricity
Performance Tests
The purpose of these tests is to estimate the performance characteristics of the induction motor. Along with preliminary tests, these tests are also done on motor.
1.No load test
2.Locked rotor test
3.Breakdown torque load performance test
4.Temperature test
5.Stray load loss test
6.Determination of efficiency test
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