| 摘要 |
<p>An earth leakage unit (10) includes a core (12); a live input terminal (26) for connection to a live supply cable; a neutral input terminal (28) for connection to a neutral supply cable; a live wire (14) connected to the live input terminal at one end and connectable to a load at its other end; a neutral wire (16) connected to the neutral input terminal at one end and connectable to the load at its other end, the live and neutral wires passing through the core; a primary coil (44) on the core for detecting a current imbalance between the live and neutral wires; an auxiliary coil (18) on the core; a current blocking device (20) in series with the auxiliary coil for permitting a current flow through the auxiliary coil when a voltage is applied across the auxiliary coil and the current blocking device that is greater than a predetermined value; a DC supply arrangement (30) connected between the live and neutral wires; and a test button (54) connected between the DC supply arrangement and the auxiliary coil. The unit is characterised in that the serially connected auxiliary coil and current blocking device are connected between the live and neutral wires such that current flows through the auxiliary coil only when the voltage between the live and neutral wires exceeds the predetermined value; a first end of the auxiliary coil is connected via the current blocking device to the live wire and a second opposite end is connected directly to the neutral wire; and the test button is connected to the first end of the auxiliary coil. <IMAGE></p> |
