FIELD: electrical engineering; overcurrent and mechanical overload protection of induction motors. SUBSTANCE: protective system designed for motors carrying cyclic loads and used in agriculture, food, processing, and other industries has primary temperature transducers, disconnecting switch, and starter, as well as newly introduced comparator whose input is connected to motor windings and output, to fan; primary temperature transducers are connected to disconnecting switch and the latter is connected to starter; heater windings of both primary temperature transducers are connected to motor windings; comparator turns off the fan upon occurrence of undercurrent or overcurrent in motor windings; at intermediate current through windings comparator operates and fan starts running. System ensures fast response to rotor wedging, prevents malfunctions, and heat margin of motor is utilized to greater extent. EFFECT: improved reliability of system when motor carries cyclic or variable loads such as farming machines. 1 dwg
