| 摘要 |
An arrangement of an on-load change-over switch of a sequence switch for uninterrupted switching of the regulating coil of a transformer. On-load change-over switching is usually effected with mechanical switch elements, which entails undesirable burn-up of the contacts and contamination with oil. In other known embodiments, on-load change-over switching is achieved using mechanical switching elements and thyristors. The main drawback of these arrangements is the high cost of the control elements, which are prone to failure. According to the invention, the load current is supplied to a common branch line (16) through a lower or upper coil tapping point (11, 12) of a regulating step (13) of a regulating coil and at least two selector contacts (14, 15) and two permanent contacts (9, 10). Change-over switching from the lower to the upper coil tapping point and vice versa is effected by a change-over switch (5) which switches the load current briefly to a discharge circuit (17), arranged between the root connection (6) of the change-over switch and the common branch line. The discharge circuit can comprise, for example, two thyristor circuits (2, 3) whose thyristors (2a, 2b, 3a, 3b) are connected in anti-parallel, one of the transistor circuits being connected in series with a transition resistance. |
