在单闭环直流调速系统中，电流截止负反馈环节是专门用来控制电流的，但它只能在超过临界电流值 Idcr 以后，靠强烈的负反馈作用限制电流的冲击，并不能很理想地控制电流的动态波形。而采用转速、电流双闭环的调速系统可以获得良好的静、动态性能。-In a single closed loop DC system, the current cut-off negative feedback link is designed to control current, but it only exceeds the critical current value Idcr later, by a strong negative feedback limits the impact of current, and can not be perfectly Dynamic control current waveform. The use of speed, current double closed loop speed control system can obtain good static and dynamic performance.