Motor Windings Insulation Resistance Test Demo (Part 1)

Motor Windings Insulation Resistance Test Demo (Part 1)


Hello, today I would like to talk about motor insulation resistance test. Insulation resistance test has been recommended and used to evaluate the winding condition of the electric motor for many decades. The insulation test result provides visibility into the winding integrity and insulation quality of the motor. Proper recording and tracking help maintenance technicians predict or identify imminent failures early, before they result in costly unplanned downtime due to motors failure. Spot test and Polarization Index test are 2 most common tests for electric motors. Spot test is used to monitor motor insulation resistance throughout it’s life time. In this test, a test voltage is applied for a fix period, normally 60 seconds or less. The resistance value is recorded at the end of this test period. This test is performed at regular interval, for example, every 6 months to track on the changes of the resistance value over time. Slow decrease in trend line may indicate that insulation is aging or contamination has happened. If there is sharp drop in value, they may be an insulation fault. Polarization Index test is the ratio of the motor winding insulation resistance value obtained at 10 minutes test time, over the value obtained at 1 minute test time. Good insulation shows continuous increasing of resistance over a period of time. Therefore, the polarization index of good insulation is normally more than 2 depend on the insulation material class. Low PI value indicates there is excess moisture or contamination, and the motor needs to send for service. However, in the advance of the insulation materials, the modern motor has faster response to the insulation test starts with test result normally at Giga-ohm range, may yield a PI between 1 and 2. In this case, the PI calculation may be disregard. As always for effective testing and safety, the insulation test should only be performed when the motors are at standstill and in a de-energized condition. Follow the safety precaution recommended by the manufacturer. For best result, isolate the motor from other circuits or parts.

3 Replies to “Motor Windings Insulation Resistance Test Demo (Part 1)”

  1. [Former technical training developer here.]

    For a given target audience (english speakers in this video), in order to communicate effectively to the greatest number of that audience, it is imperative to use a natural speaker (not necessarily a native speaker) of that language. Any accent or impediment reduces the effeciveness of your presentation to a percentage of the audience.

    Personally, I understood about 60 percent of the audio.

    Not to take away from the presenter's professionalism. It's just the nature of public speaking.

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