| 摘要 |
The supply circuit is for a three phase asynchronous motor (30) with three connections (31,32,33). It is fed from a single phase source with two connections (L1,L2) via a frequency converter (34) with three output connections (35,36,37). The supply circuit has a switch (42) which in a first position, respectively connects the three output connections to the three connections of the motor. In a second position it interrupts the three connections and connects directly, by excluding the converter, one line (L1) to one connection (31) by a connection (38), the other line (L2) to another connection (32) by a conductor (39) and to a switched phase shifter circuit (43) whose output connection (40) is connected to the connection (33). The phase shifter switch (6) is a triac, a pair of transistors, or a transistor with a diode bridge phase angle controlled. The control system has, in parallel with the shifter switch, a resistance (8) and capacitor (9), whilst a discharge device (12) for the capacitor which reduces its voltage to a set level, is inserted between the switch and a mid point (10) between the capacitor and the resistor. |
