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    Using a Multimeter to Measure the Motor Insulated Resistance

    An AC motor is a device that converts electrical energy from alternating current into mechanical energy. Its main components include a stator and a rotor. The principle of operation of an AC motor is based on the interaction of the magnetic field produced by electromagnetic induction with the magnetic field of the stator. When an AC current is passed through the stator windings, the resulting magnetic field passes through the coils on the rotor, whereupon an induced current is generated within the coils. This induced current generates another magnetic field, which produces a continuous current and rotating torque.

    Unlike DC motors with a DC power supply, their advantages are their simple structure, ease of manufacture, comparative robustness, and large power coverage, which makes them widely used in a variety of industrial and household appliances. Insulation check is very important for AC motors, and it is also a very important technical index in the operation and maintenance of electric motors. In practice, it not only protects against current leakage or short-circuiting but also ensures the safety of the operator. In this article, ATO will show you how to carry out insulation inspection.


    This process is very simple, you need to prepare a screwdriver and multimeter, here we use an induction motor, use a screwdriver to remove the wiring housing of the motor, and then turn the dial in the dial to four megohms, the next step is to test.


    Inspection Method

    First of all, use two pens to contact the winding and shell respectively, measure their resistance value, then read the value of the multimeter to see whether it is beyond the measurement range of the multimeter, such as the dial shows 'OL', which means that the resistance being measured is very high and exceeds the limit of the range, then there may be a short circuit between these components. Based on the test results, you can determine whether the condition of the insulation function of this AC induction motor is good or not, and draw a safe conclusion.

    Insulation check on an ac motor


    Make sure that the motor is completely de-energized before checking, and confirm that the surrounding environment is safe to avoid danger during the test. The resistance setting of the multimeter usually measures only a few thousand ohms at the highest, and for higher resistance measurements, it may be necessary to use a specialized insulation resistance tester for a more accurate test. In addition, due to the low test voltage of the resistance gear of the multimeter, it may not be able to detect some subtle insulation defects, so in practice, it is necessary to combine with other testing methods and experience to make a comprehensive judgment. If you want to know more, please watch the detailed video below.

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