可控硅在电动机控制中的应用

Application of SCR in Motor Control

可控硅也称晶闸管,在自动控制中可控硅比机械式继电器更适用于负载需要频繁接通、断开操作的电路。在三相电动机控制电路中,通常机械式继电器作为主要控制器件。但在类如管道电伴加热、电动阀门这样需要频繁启停的负载,机械式继电器由于反复操作故障率明显提高;同时电气触点操作中会产生电弧,多次操作后将引起触头烧毁或短路故障。三相可控硅电源接通、断开时不产生电弧,适用于防爆场所;可控硅没有机械式行程动作,寿命长不易损坏;因此性能优于机械式继电器,在现今电动机控制电路中得到广泛应用。本文对比2种控制方式阐述了可控硅控制的低压三相380V交流异步电动机电路设计的特点。为保证可控硅在电动机控制回路可靠运行,介绍了几种在实际工程中保护的应用。通过设置完善的保护电路,确保可控硅元件在电动机控制中安全可靠运行。

SCR is also called thyristor.In automatic control,SCR is more suitable for circuits where the load needs to be switched on and off frequently than mechanical relays.In the three-phase motor control circuit,usually mechanical relays are used as the main control device.However,for loads that require frequent start and stop,such as pipeline electric heating and electric valves,the failure rate of mechanical relays is significantly increased due to repeated operations;at the same time,electrical contact operations will produce arcs,which will cause contacts to burn or burn after multiple operations.Short circuit fault.Three-phase thyristor power supply does not produce arcs when it is switched on and off,and it is suitable for explosion-proof places;thyristors have no mechanical stroke action and have a long life and are not easily damaged;therefore,their performance is better than mechanical relays,which are obtained in current motor control circuits widely used.This article compares the two control methods and expounds the characteristics of the circuit design of low-voltage three-phase 380V AC asynchronous motor controlled by thyristor.In order to ensure the reliable operation of the SCR in the motor control loop,several protection applications in actual engineering are introduced.A complete protection circuit is provided to ensure the safe and reliable operation of SCR components in motor control.