Thermal Relationships in an Induction Motor under Normal and Abnormal Operation

Improvements in motor protection and design require knowledge of the thermal effects produced in a motor when it is operating under normal and abnormal conditions. This paper describes a series of tests that were made on a 350-hp (horsepower) 900-rpm induction motor. The tests included single-and 3-phase stall and running tests, and acceleration tests at different voltage levels and subsynchronous speeds. A comprehensive picture is obtained of steady-state and transient temperatures in the stator and the rotor. An analysis of the thermal effects in terms of possible damage to the motor is presented.