Controller for switching the electric drive motor, in particular of an air compressor, on and off to match the demand

摘要

In the case of a controller for switching the electric drive motor, in particular of an air compressor, on and off to match the demand, the thermal load on which air compressor is determined in accordance with a load characteristic from the ratio of the switched-on time to the sum of the switched-on and the switched-off time, difference values are added in order to determine the total switched-on time which is relevant for the thermal load, said difference values being formed from the individual switched-on times minus the equivalent switched-on times which correspond to the respectively subsequent switched-off times according to the load characteristic. When the relevant total switched-on time exceeds a predetermined limit value, the drive motor is turned off for a time which can be predetermined, in order to provide protection against overloading and possible destruction.