| 摘要 |
<p>In one embodiment, a sheathed electrical resistance heating unit is operated from a 120 volt unbalanced-to-ground household power line. The heating unit sheath is grounded. In order to interrupt a fault between the actual resistance heating element and the outer sheath of the heating unit, regardless of where along the length of the heating unit the fault occurs, a fuse is connected in series with the "hot" side of the power line, and, by means of at least one unidirectional current conducting device, the two terminals of the heating element are effectively connected, through the fuse, to the "hot" side of the power line during alternate AC half-cycles.</p> |
