Importance

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Abstract

The invention relates to a method for determining the winding temperature (TW) of the stator winding of a three-phase AC motor, in particular a pole-changeable asynchronous motor. For determining the winding temperature (TW) of the stator winding of three-phase AC motors that have an unfavorable ratio of the active power to the dissipation power and react sensitively to temperature changes and changes in a main voltage, and for readily determining the heat dissipation power (PV) from the winding temperature (TW) of the stator winding, it is proposed to determine the reference temperature (TG) and the motor current (IM) simultaneously at consecutive points in time, and to determine the winding temperature (TW) by calculating step-by-step sequentially the change in the winding temperature (TW) at a point in time (tn) and adding this change to the winding temperature (TW) of the immediately preceding point in time (tn-1). The change of the winding temperature (TW) associated with a point in time (tn) is proportional to the electrical heat dissipation power (PV) that is converted into heat in the stator winding at the point in time (tn) and to the temperature difference between the reference temperature (TG) of the housing at that point in time (tn) and the winding temperature (TW) at the immediately preceding point in time (tn-1). The winding temperature (TW) of the immediately preceding point in time (tn-1) is also used for calculating the heat dissipation power (PV).

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First Claim