Electric Motor Winding Resistance Test

Loss of insulation resistance of an electric motor is one of the first signs of motor failure.

Electric motor winding resistance test.

The meter should not show an open or a short when a winding leg is measured. Consult the motor schematic or a diagram of the motor s windings and use the meter to measure the resistance of the windings. Each winding leg should have some small resistance reading. An electrical induction motor contains windings or wire wrapped around a cylindrical shaft.

A number of standards provide maximum deviation percentages but typical limits are 1 to 3 between the mean average for the three windings. Minimum test value of the electric motor is 1 meg ohm 1 mω. Insulation resistance test insulation resistance failure of an electric motor is one of the first signs that the motor is about to fail. With a multimeter set to low ohms usually 200 test between each winding terminal and the metal casing of the motor.

For expert repair guidance or more information call 800 551 4420 or http www. Check from phase to earthing u to e v to e w to e. Winding resistance test results are compared between the three phases on a 3 phase motor. Insulation resistance of motor winding using insulation tester meter set to the 500 volt scale 1000v dc verify from phase to phase u to v v to w w to u and.

You may find that when it runs ungrounded that the casing becomes live at up to supply voltage. An overview of two basic winding resistance tests one can perform in the shop. If there is any reading on any of these then the motor is bad do not use it. In this video we show different tests balancing test continuity coil.

Insulation resistance is usually measured between motor windings and earth using an insulation tester or megometer. 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. Often it is required to test the winding of the 3 phase windings with the aid of a multimeter or ohmmeter to determine whether the motor is still good or burnt or shorted. The most common failure mode of a 3 phase ac motor is burnt winding or shorted winding leading to the damage of the motor.

When an electric current flows though the wire a magnetic field is induced inside the coil of wire. Set the voltage setting of the insulation resistance tester to 500v and check motor windings.