| 摘要 |
<p>1,134,590. Protective arrangements. HARVEY HUBBELL Inc. 19 July, 1967 [14 April, 1967], No. 33108/67. Heading H2K. In an earth leakage protective arrangement having a differential transformer 20 with primary windings 22, 24 in series in the line and earthed neutral conductors 10, 12 to a load 18, an impedance 28 is connected in series in the neutral conductor to prevent incorrect operation due to an earth fault 36 on the neutral conductor. Such an earth fault would otherwise cause the short-circuiting of the primary winding 24 which would then act as a short-circuited secondary winding and prevent adequate power being supplied from the secondary winding 30 to the trip coil 32 of a circuit interrupter 26 should earth leakage occur, as at 34, from the line conductor. The impedance 28 may be resistive, capacitative or inductive. In the last case, it may be a transformer secondary winding wound so as to produce a potential opposing that across the secondary winding 24. The primary winding of the further transformer may be connected in series in the line conductor, Fig. 2 (not shown) or between the line and neutral conductors, Fig. 3 (not shown).</p> |
