Electric Motor Windings Resistance

This magnetic field causes a metal bar inside the coil to rotate and power the motor.

Electric motor windings resistance.

Set the voltage setting of the insulation resistance tester to 500v and check motor windings to earth. Studies conducted by ieee and the electric power research institute epri on electric rotating machinery failures show that 48 of motor failures are due to electrical failures. 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. Consult the motor schematic or a diagram of the motor s windings and use the meter to measure the resistance of the windings.

An electrical induction motor contains windings or wire wrapped around a cylindrical shaft. Values greater than this indicate a potential problem and values significantly greater than this indicate the winding has failed opened. 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.

As with transformers a motor or generator is broken down into two main components. The meter should not show an open or a short when a winding leg is measured. All values obtained from winding dc resistance test should be below 1 megohm and similar in value. Insulation resistance is usually measured between motor windings and earth using an insulation tester or megometer.

When an electric current flows though the wire a magnetic field is induced inside the coil of wire. During the measurement and immediately afterwards some of the terminals carry dangerous voltages and must not be touched. Set the voltage setting of the insulation. Winding dc resistance test follow usace procedure three sets of results total a to b phase b to c phase c to a phase correct values to 40 c using the formula in step 8.

Insulation resistance failure of an electric motor is one of the first signs that the motor is about to fail. Insulation resistance failure of an electric motor is one of the first signs that the motor is about to fail. 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. Record initial and corrected values on motor testing record sheet.

A if the insulation resistance of a new cleaned or repaired motor that has been stored for some time is less then 10 mω the reason might be that the windings are humid and. For a three phase motor insulation resistance is usually measured between each motor winding or phase and between each motor phase and motor frame earth using an insulation tester or megger. The most common failure mode of a 3 phase ac motor is burnt winding or shorted winding leading to the damage of the motor.