| 摘要 |
The present invention relates to a protective circuit ( 30 ) for intrinsically safe electromagnetic actuators operating at the voltage of a power supply approved for underground mining, for switching electrohydraulic valves in underground mining, comprising a coil ( 11 ) connected to a first potential ( 2 ) and a second potential ( 3 ) of the power supply and associated with at least two spaced-apart short-circuit means ( 12 ) connected in parallel with the electromagnetic actuator coil ( 11 ) for short-circuiting the coil in the event of a reversal of the potential of the coil voltage. In accordance with the present invention the protective circuit comprises a semiconductor switch (T 3 ) which is inserted between the coil ( 11 ) and the second potential ( 3 ) and, in the event of a voltage reduction or potential reversal, isolates the coil ( 11 ) from the second potential, so that the discharge from the coil ( 11 ) has no adverse effect on the energy supply system or the intrinsic safety.
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