Abstract: The invention relates to a protective circuit for a breaker gap (2), said gap being used to connect a load voltage (UL) to a load (1). The circuit is characterized in that a voltage detection circuit (3) is connected to a detection point (4) on the input side and a detection point on the output side of the breaker gap (2), via detection resistances (R1) said voltage detection circuit (3) being connected to the detection points (4) at high-resistance but in a permanently galvanized manner.

Abstract: The circuit on which the present invention is based has a control circuit in which a switching element and a measurement resistor are connected in series with the contactor coil. A pickup current control circuit picks up the voltage at measurement resistor and controls the switching element after comparison with a reference voltage. By parallel connection of an additional shunt resistor with measurement resistor, a current approximately twenty to thirty times higher can be achieved during the pickup phase than the holding phase by setting only a single reference voltage. In the holding phase the parallel circuit is disabled so that only the measurement resistor is operative.

Abstract: The magnetic residual energy stored in a coil is made to decay within a shorter and/or definite time period by the use of a free-wheeling circuit connected in parallel. The free-wheeling circuit comprises a series circuit, which includes a first diode and a first switching transistor connected in parallel to a non-linear resistor, connected in parallel to the coil. The first switching transistor is driven by a parallel circuit formed by a capacitor and a first ohmic resistor, which is connected in parallel to a second switching transistor. When a switch-off overvoltage appears in the coil, the second switching transistor becomes conductive and thus the first switching transistor is reliably blocked, so that the residual energy decays through the non-linear resistor.

Abstract: Electronic driving components sized to drive contactors of a determined power class are generally used. The object of the invention is to create a process and circuitry which allows contactors of different power classes to be driven by a single driving component. The user selects on a scale the switching position corresponding to the contactor to be driven. A reference voltage proportional to the magnitude of the starting current of the respective contactor is thus selected. An automatic regulation keeps constant the starting current during the starting time of the contactor. For that purpose, a measurement voltage proportional to the magnitude of the starting system and dropping across a measuring resistor is supplied to a first input of a comparator, a reference voltage which may be selected by a coding switch (6) being applied to the second input of the comparator. The output of the comparator co-operates with a switching element which switches the starting current.