Motors are susceptible to the gradual failure of their insulation resistance.
Insulation resistance test 3 phase motor pdf.
We ll learn how to identify windings check windings.
In an industrial facility the recommended procedure is to perform periodic tests and record the results so damaging trends can be detected and corrected to prevent an outage.
Introduction the induction motor is one of the most important motors used in industrial applications.
During the measurement and immediately afterwards some of the terminals carry dangerous voltages and must not be touched.
Three phase dual voltage motor insulation resistance testing three phase dual voltage motors are used for most day to day operations in today s industrial plants.
The primary causes of insulation.
Figure 4 typical record of insulation resistance of a mill motor.
Curve a shows test values as measured.
The insulation resistance tester or megohmmeter generally known by its trade name megger can provide critical information regarding the condition of motor insulation.
Unlike an ohmmeter a megger can measure high voltage resistance values which are generally the kinds of values you will encounter with three phase motors.
Dc voltage of 500 or 1000 v is applied between the windings and the ground of the motor.
Figure 3 typical scale on the megger insulation tester.
Insulation resistance test insulation resistance failure of an electric motor is one of the first signs that the motor is about to fail.
These motors run conveyor belts pumps fans and many other applications.
Induction motor no load test blocked rotor test vibration test temperature test phase sequence test insulation resistance test.
Ground insulation test of a motor.
The measurement of insulation resistance is carried out by means of a megohmmeter high resistance range ohmmeter this is how the test works.
Loss of insulation resistance of an electric motor is one of the first signs of motor failure.
Regular checks of motor insulation resistance the key to prolonging the life of any electrical device is periodic checks maintenance the insulation resistance of stored and active motors should be checked regularly.
For tests we ll use megger mit 310.
Reverse side of card at right is used to record the test data.
It is used to convert electrical energy into mechanical energy.
To measure the resistance in a three phase motor you will need a megohmmeter otherwise known as a megger.
Curve b shows same values corrected to 20 c see page 22 giving a definite downward trend toward an unsafe condition.
For a three phase motor the isolation resistance can usually be measured between each motor winding or phase and between each motor stage and motor frame earth by an insulation tester or megger 4.
