| 摘要 |
The residual current device is provided with a transformer through whose primary windings load current flows in both directions and whose secondary winding is connected to a tripping device. Means for selective premagnetisation of the transformer (1) are provided, the premagnetisation current being derived from mains voltage. The residual current device has a test circuit in which a simulated fault current, which causes the tripping device of the switch to respond, can be connected with the aid of a test button. A resistor (13) can be connected in parallel with the test button contact (10) in order to produce the premagnetisation current which can be switched on selectively. <IMAGE>
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