| 摘要 |
PURPOSE:To prevent occurrence of abnormally high voltage due to transient phenomenon and the like by constituting a tap switching relay in a step-down transformer to function upon receiving a low voltage, providing a switching element for controlling the relay with a forcible turn OFF circuit, connecting the relay coil with a protective circuit, and providing a short circuit therefor. CONSTITUTION:A relay 1, having a normal close side NC connected with a high voltage tap 3A and a normal open side NO connected with a low voltage tap 3B, functions when the input voltage is low. Furthermore, a circuit 2 for forcibly turning OFF a switching element 8 for controlling the relay 1 when the input voltage is high is provided or a protective circuit 7 is connected in series with the coil RL of the relay 1 and the protective circuit 7 is interrupted through a short circuit 10 when the output voltage rises abnormally high. In other words, the forcible turn OFF circuit 2 prevents erroneous function of the relay 1 and the short circuit 10 interrupts the protective circuit 7 when the output voltage is abnormally high thus preventing an abnormally high voltage from appearing on the output side. |
