Circuit arrangement for controlling the electromagnetic drive of a switching device

摘要

A reduction in contact bounce in an electromagnetic switch is accomplished by optimizing armature speed over its travel path with a circuit arrangement for controlling a drive current in the coil of the electromagnetic switch. A superposed speed loop including a speed sensor produces a measured voltage in response to speed of the armature. A converter coupled to the speed sensor converts the measured voltage into a value corresponding to an actual speed of the armature. A first summer receives a constant reference value corresponding to a desired speed for the armature and the value corresponding to the actual speed of the armature, and produces a difference voltage corresponding to a difference between the desired speed and the actual speed of the armature. A proportional element amplifies the difference voltage and produces a desired current value corresponding to the amplified difference voltage. An underlying current control loop including a current sensor produces a measured current value corresponding to a current in the coil. A second summer receiving the measured current value and the desired current value produces an output current corresponding to a difference between the desired current value and the measured current value. A chopper coupled to the output current of the second summer operates with hysteresis for conducting a pulsed control voltage to the coil and is interrupted from doing so when the measured current value is greater than the desired current value plus an hysteresis value.