Ohming a motor

Multimeters and ammeters can often provide diagnostic information for all sorts of motor problems. Here are some useful diagnostic tips. A motor placed in storage may or may not work, regardless of its physical appearance.

At no time during the motor check out is power required. If it is connected - disconnect it before .

As with all testing and inspections, the motor name plate provides valuable information that will help to ascertain the true health of the motor.

Examine the name plate thoroughly and compare values of running amps test (see below) with name plate value.

Testing of single phase motors is pretty easy if certain basic steps are followed. The objective of any AC motor test is to determine the health status of the motor. Also any other recommendations for testing equipment.

If the motor is not put into operation immediately upon arrival, it is important to protect it against external factors like moisture, high temperature and impurities in order to avoid damage to the insulation.

You connect the first probe of the ohm -meter to lead and then you connect the other probe of the ohm -meter to leads A, B, C, and ground ( motor chassis). If the motor has no problem, then you must find infinite resistance between all leads and groun except from one lead. First you should put on safety glasses and shut all electrical connections to the motor. This step will also assure that . Working through the system Motor to disconnect,overloads, contactor and.

Both the ohm values depend on the rating and type of the motor.

Now, you have to go to the motor ! I feel it is always better to check . Insulation resistance of motor winding using Insulation tester meter set to the 500. Check from phase to phase (U to V, V to W, W to U) and . With the motor running, check the . They are usually permanent and will probably need replacement. Check for shorts between the power wiring and ground.

Select ohms resistance on the multi -meter and set for the 3000- ohm range.

Touch one lead to each motor power lead and the other to the metal motor casing. Fan motors are the unsung “heart” of HVAC equipment. They work unobtrusively and quietly for years, often under tough conditions. The cost of overlooking regular testing and maintenance of motors can be an .