METHOD OF THERMAL PROTECTION OF ELECTRIC MOTOR AND ARRANGEMENT FOR ITS REALIZATION Russian patent published in 2004 - IPC

FIELD: electrical devices utilized in thermal protection of electric motors. SUBSTANCE: method refers to thermal protection of electric motors against emergency conditions accompanied by inadmissible rise of temperature of their windings. In compliance with given method of thermal protection of electric motor current consumed by electric motor and temperature of windings of electric motor are measured by means of controller and electric motor is switched off when temperature of winding of electric motor reaches or exceeds upper limit. Ohmic resistance of its winding is measured in addition before switching on of electric motor and after its switching off and initial and final temperatures of its winding re computed. Data on initial temperature is used to compute changes of its temperature in process of operation of electric motor. Data on final temperature are compared with data computed on basis of measured current, if these data show discrepancy then parameters of thermal model of electric motor are corrected thanks to insertion of unit measuring resistance, intermediate relays into arrangement for thermal protection of electric motor which includes contactor with contacts sand winding, current pickups in supply circuits of electric motor, unit controlling controls and controller. EFFECT: increased accuracy of computation of temperature of winding of protected electric motor that excludes false operation and failure of thermal protection to operate. 2 cl, 1 dwg