METHOD FOR LOW-START PROTECTION OF THREE-PHASE SQUIRREL-CAGE INDUCTION MOTOR Russian patent published in 2002 - IPC

FIELD: electrical engineering. SUBSTANCE: method is based on recording decay of free aperiodic component of stator current, comparing stator current with desired value, discriminating periodic component of stator current caused by free aperiodic component of rotor current, comparing mentioned periodic component with threshold value, and taking actions to switch off motor in case mentioned periodic component does not rise over threshold value within preset time; in addition, it involves comparison of current frequency of stator current periodic component brought in due to free aperiodic component of rotor current with threshold value with OFF- operation signal being supplied in case current frequency of said component fails to rise above threshold value within preset time. EFFECT: enhanced speed of protective gear response. 1 dwg