| 摘要 |
<p>A residual current detector capable of detecting an earth leakage current, e.g. for use in a circuit breaker, includes a toroidal core (2) through which passes the live and neutral wires (3, 4) of an electrical installation, to form the primary windings of a differential transformer. At least one secondary winding (5, 6) is wound on to the core (2) and driven with an alternating voltage by a generator (7). A phase sensitive detector (11) identifies a residual current by detecting the change in phase of the voltage across the at least one secondary winding (5, 6).</p><p>The secondary winding may comprise two coils, a first coil (5) driven by the generator (7) and a second coil (6) adapted to pick up an induced voltage from the toroidal core (2). The phase sensitive detector (11), which may form part of a phase locked loop (30), compares the phase of the signal from the second coil (6) with that of the alternating voltage of the generator (7).</p> |
