Patent ID: 6434505
Filing Date: 2002-08-13
Classification: G01K,H02H

Abstract:
A method for determining an instantaneous winding temperature of a stator winding of a three-phase AC motor, comprising the steps of:(a) determining simultaneously at a point in time a motor current and a reference temperature at a measurement location of the three-phase AC motor, with the measurement location located on one of the stator, housing, and a portion of a housing of the three-phase AC motor; (b) determining a winding temperature at the point in time by calculating a change in the winding temperature with respect to an immediately preceding point in time and adding the change to the winding temperature, wherein the change in the winding temperature is proportional to an electrical heat dissipation power that is converted into heat in the stator winding at the point in time, with the heat dissipation power being calculated from the square of an effective value of the motor current at the point in time multiplied by a temperature-dependent electrical winding resistance of the stator winding, with the winding resistance taken for the winding temperature of the immediately preceding point in time, and wherein the change is also proportional to a temperature difference between the reference temperature at the point in time and the winding temperature at the immediately preceding point in time, wherein a proportionality factor of the change with the heat dissipation power is an inverse value of the heat capacity of the stator winding and the proportionality factor of the change with the temperature difference is an inverse value of the thermal resistance between the stator winding and the measurement location multiplied with the heat capacity; and (c) repeating steps (a) and (b) for the immediately following point in time.