ABB 3HAC7344-1

可控硅(Silicon Controlled Rectifier) 简称SCR,是一种大功率电器元件，也称晶闸管。它具有体积小、效率高、寿命长等优点。在自动控制系统中，可作为大功率驱动器件，实现用小功率控件控制大功率设备。它在交直流电机调速系统、调功系统及随动系统中得到了广泛的应用。

可控硅分单向可控硅和双向可控硅两种。双向可控硅也叫三端双向可控硅，简称TRIAC。双向可控硅在结构上相当于两个单向可控硅反向连接，这种可控硅具有双向导通功能。其通断状态由控制极G决定。在控制极G上加正脉冲(或负脉冲)可使其正向(或反向)导通。这种装置的优点是控制电路简单，没有反向耐压问题，因此特别适合做交流无触点开关使用。

Silicon Controlled Rectifier (SCR), also known as thyristor, is a high-power electrical component. It has the advantages of small size, high efficiency, and long service life. In automatic control systems, it can be used as a high-power driver to control high-power devices with low-power controls. It has been widely used in AC and DC motor speed control systems, power regulation systems, and servo systems.

There are two types of thyristor: unidirectional thyristor and bidirectional thyristor. Bidirectional thyristor, also known as three-terminal bidirectional thyristor, abbreviated as TRIAC. Bidirectional thyristor is structurally equivalent to two unidirectional thyristors connected in reverse, and this type of thyristor has bidirectional conduction function. Its on/off state is determined by the control pole G. Adding a positive (or negative) pulse to the control pole G can make it conduct in the forward (or reverse) direction. The advantage of this device is that the control circuit is simple and there is no reverse voltage withstand problem, so it is particularly suitable for use as an AC contactless switch.