Patent ID: 7122984

Claim:
A method to detect sluggishness or blocking of an electric drive ( 3 ) which is triggered via a first power semiconductor component ( 7 ) and can be operated in a partial load range (PWM<100%) and in a full load range (PWM=100%) as a function of the timing of a PWM signal ( 29 , 31 ) and having an evaluation circuit ( 37 ) connected with a micro-controller ( 25 ), wherein pulses generated within a time interval are detected in the evaluation circuit ( 37 ) from current I flowing over the first power semiconductor component ( 7 ) and detected pulses are compared with normal operation number of pulses, and wherein the triggering of the electrical drive ( 3 ), having a free-wheeling circuit ( 6 ) containing a second power semiconductor component ( 32 ), takes place via the PWM signal ( 29 , 31 ), which is output to a first PWM triggering branch ( 32 ) and a second PWM triggering branch ( 34 ) for alternating triggering of the power semiconductor components ( 7 , 32 ).