| 摘要 |
<p>This system is used on supply and return pipes which carry a heat medium, e.g. hot water or steam, around a neighbourhood central heating system. When the system has been out of operation for some time, electrical heating is used to prepare the pipes to carry the medium, and thus to reduce the time needed to get the system working normally. The supply from a generator (11) is fed via a thyristor control circuit (10) to the primary of a transformer (7). The transformer sec. (6) delivers a very high current, e.g. several thousand amps, at a low voltage e.g. 1 volt. One end of the sec. is clamped (5) to the middle of the supply pipe (1), and one to the middle of the return pipe (2). At the supply and destination ends of the pipes, clamps (4) and heavy current braided cables areused to connect the supply and return pipes together.</p> |
