| 摘要 |
PURPOSE:To simplify the circuit by carrying out two functions such as speed control and braking with one set of a control element and the ignition circuit when an AC electric motor is controlled by the semiconductor control element. CONSTITUTION:When triacs TRI1-TRI3 are connected to the AC electric motor M and the electric motor M is speed-controlled by switching on and off a transistor TRI on the signal emitted by a speed generator TG, photothyristers THY1-THY3 and a phototransistor TR4 are provided between G-E of triac TRI on transistor TR1 respectively. At the same time, a circuit consisting of photodiodes D1-D4 which are photocoupled to them and transistors TR2 and TR3 are connected to the control circuit. Consequently, photodiodes D1-D4 illuminate when the TR3 is in ''ON'' position, and then THY1-THY3 are turned on, igniting TRI1-TRI3 only in one direction. Thus the electric motor M is braked, enabling one set of ignition circuit to perform the job of speed control and braking. |
