| 摘要 |
PURPOSE:To improve the reliability of an electric motor driving means by employing a means for preventing a main power supply circuit and a braking circuit for the electric motor from being simultaneously closed, whereby the electric motor can be prevented from being erroneously started and stopped, so that a switch is never broken. CONSTITUTION:When an electric motor 1 is driven, a striking signal is input into a pulse transformer 6 so that a main loop circuit 19 is closed. As a result, one of main thyristors 2, 3 is turned on in accordance with the polarity of a power source to allow the electric motor 1 to be rotated. When the electric motor 1 is braked, a striking signal is input into a pulse transformer 9 so that a braking loop circuit 22 is closed. As a result, a dynamic braking power is applied to the electric motor 1. In a case where a command means is erroneously operated so that a striking command signal is applied to the pulse transistors 6, 9, a diode 21 is turned on to allow a transistor 5 to be turned off. Accordingly, the main loop circuit 19 is not closed; the braking loop circuit 22 only is closed. At this time, an electric current flowing through thyristors 2-4 is limited by a resistor 25a. |
