For safe, long-term use of a compressor, the motor winding temperature must be kept below certain limits, in all conditions in which the appliance may operate. For example, compressors from AC Compressors, whose motors are approved according to temperature Class B, are considered safe when operating with the winding temperature at no more than 130 degrees C.
Motors are developed according to this temperature norm. As a result, in the calorimeter tests for motor overheating or overload protector tripping, the limit of 130 degrees is never exceeded. These tests are carried out under standard conditions. The actual compressor is designed within the limits these conditions represent, so the compressor will run safely.