Abstract: A circuit configuration for operating an electric motor is described, the circuit configuration containing a timer. As a function of a first differential signal between a setpoint signal and an actual value signal, a regulator supplies a first switch signal for feeding current to the electric motor. Simultaneously, the timer is started which limits the current feed signal to a specified maximum time. A detection system detects a change in the setpoint signal and thereupon outputs a second switch signal that also starts the timer and is able to trigger the current feed to the electric motor. The circuit configuration both protects the electric motor from a thermal overload and also makes it possible to feed current to the electric motor if a setpoint changes. The circuit configuration is suitable to be used in a variable speed drive.

Abstract: A circuit configuration for operating an electric motor (46) is described, the circuit configuration containing a timer (22). As a function of a first differential signal (15) between a setpoint signal (11) and an actual value signal (14), a regulator supplies a first switch signal (20) for feeding current to the electric motor (46). Simultaneously, the timer (22) is started which limits the current feed signal (45) to a specified maximum time (Tmax). A detection system (37) detects a change in the setpoint signal (11) and thereupon outputs a second switch signal (38) that also starts the timer (22) and is able to trigger the current feed to the electric motor (46). The circuit configuration both protects the electric motor (46) from a thermal overload and also makes it possible to feed current to the electric motor (46) if a setpoint changes.