| 摘要 |
<p>An electric through-flow heater consists of a set of tubes hydraulically in series and heated electrically by resistances connected directly or via switches onto a three phase supply. The series switching of the resistances is so formed that the locally neighbouring ends of the resistances are coupled at connection points (12,15). These connection points as far as they limit a load stage are coupled directly with the output conductors of the three phase network (L1,L2,L3). One load stage (9) is for a large step, and one (8) for a small step. Local neighbouring resistances are attached to the load stages, which are made of directly interconnected resistances. A further constant stage (10) is provided, and phase controlled switches (T13-T17) couple in the mains supply.</p> |
