Protective circuit for intrinsically safe electromagnetic actuators and protective circuit for intrinsically safe power supply systems

摘要

The invention relates to a protective circuit 30 for intrinsically safe, with the voltage of an approved for underground mining power supply operable electromagnetic actuators for switching electro-hydraulic valves in underground mining, with a connected to a first potential 2 and a second potential 3 of the power supply coil 11, at least two separately executed, parallel to the coil 11 of the solenoid actuator connected short-circuit means 12 are assigned for short-circuiting the coil at a potential reversal of the coil voltage. According to the invention, the protective circuit comprises a semiconductor switch T3 interposed between the coil 11 and the second potential 3, which disconnects the coil 11 from the second potential at a voltage reduction or potential reversal, so that the discharge of the coil 11 has no effect on the power supply system and intrinsic safety endangered.