| 摘要 |
The present invention relates to a protection circuit for intrinsically safe electromagnetic actuators operating on the voltage from a power unit ( 1 ) approved for underground mining, for switching electrohydraulic valves ( 5 ) in underground mining, comprising at least two spaced-apart short-circuit means ( 14, 16 or 16 A) connected in parallel with the electromagnetic actuator coil ( 11 ) for short-circuiting the coil in the event of a reversal of the coil voltage. According to the invention, at least one of the short-circuit means comprises a short-circuit semi-conductor switch ( 16 or 16 A) and a voltage-reversal detecting circuit ( 30 ) for activating the short-circuit semiconductor switch ( 16 ).
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