If your evaluation of the winding temperature points to a problem, take steps to solve it. If the motor is getting close to or exceeding its class temperature limit, you may indeed have a problem. For electric motors, the class is usually B, F, or H (see table). Once you know the winding temperature, compare it to the motor’s nameplate temperature, i.e., allowable temperature.įrequently, only the insulation class will be listed. (Ask your service center for assistance with this if needed.) While this approach requires shutting down and opening the motor terminations, depending on the unit, it may be worth it.
#3 phase motor winding series#
If temperature detectors are not installed or operable, winding temperature can be extrapolated using a time series of winding-resistance measurements taken after shutdown. In such cases, the winding temperature is usually around 5 to 10 C above the back-iron temperature. A thermocouple or RTD can be affixed to the stator core back iron, using proper electrical-safety precautions.
Thermistors may require a controller, but thermocouples and resistance temperature detectors (RTDs) can be easily read with common, handheld meters and reference tables. If the motor is equipped with temperature detectors that are capable of providing readings, use them.Ī controller isn’t always necessary. Winding temperatures can’t be properly evaluated based on outside frame temperatures. Don’t conclude the winding is too hot by simply touching the motor’s frame.