Abstract: A protective circuit arrangement of a motor control for the starting and operation of a motor of a press with a power stage, a current-regulating element and a rotational speed regulating element. Comparator stages are connected to the inputs of the regulating elements for forming the guide magnitudes from the actual current value and the desired current value as well as from the actual rotational speed value and the desired rotational speed value. For suppressing the disconnect signal during the starting phase of the motor, the circuit additionally includes a rotational speed comparator stage, a desired current value memory and a current comparator stage. The desired current value, which stored after the starting phase in the desired current value memory, is compared with the current value in the current comparator stage to produce a motor current interrupt signal in case of an overload current that might lead to a press damage.

Abstract: In control drives for high speed blanking presses, a serious problem of excessive tool wear arises from increases in the immersion depth of a top tool into its associated bottom tool when the stroke frequency increases. To overcome this, a control drive is provided wherein the top tool is held at a substantially constant immersion depth in the opening in the bottom tool over the entire stroke frequency range of the press. A measuring instrument detects the stroke frequency. This detected frequency is fed into a control circuit programmed with a characteristic corresponding to either immersion depth or ram adjustment as a function of stroke frequency. The output of the control circuit is a control signal coupled to a drive motor to maintain the constant immersion depth.