Electric Motor Winding Resistance Test

With a multimeter set to low ohms usually 200 test between each winding terminal and the metal casing of the motor.

Electric motor winding resistance test.

Insulation resistance is usually measured between motor windings and earth using an insulation tester or megometer. A number of standards provide maximum deviation percentages but typical limits are 1 to 3 between the mean average for the three windings. The meter should not show an open or a short when a winding leg is measured. An electrical induction motor contains windings or wire wrapped around a cylindrical shaft.

You may find that when it runs ungrounded that the casing becomes live at up to supply voltage. When an electric motor is broken one suspect is the fiel coild of the motor stator. When an electric current flows though the wire a magnetic field is induced inside the coil of wire. Loss of insulation resistance of an electric motor is one of the first signs of motor failure.

Consult the motor schematic or a diagram of the motor s windings and use the meter to measure the resistance of the windings. An overview of two basic winding resistance tests one can perform in the shop. The most common failure mode of a 3 phase ac motor is burnt winding or shorted winding leading to the damage of the motor. For expert repair guidance or more information call 800 551 4420 or http www.

How to check the motor winding resistance by william hirsch updated march 16 2018. Winding resistance test results are compared between the three phases on a 3 phase motor. 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. Insulation resistance test insulation resistance failure of an electric motor is one of the first signs that the motor is about to fail.

Set the voltage setting of the insulation resistance tester to 500v and check motor windings. Minimum test value of the electric motor is 1 meg ohm 1 mω. With the motor running check the running amps of the motor using. If there is any reading on any of these then the motor is bad do not use it.

Each winding leg should have some small resistance reading. In this video we show different tests balancing test continuity coil.