《电子制作》94年第4期介绍的“简单经济的缺相保护电路”结构简单,有一定的应用和推广价值。但原文电路有错误:三相电源应接在接触器ZC触点的上方;如图1所示。否则电机无法启动。且保护电路还可进一步改进,原图中检测点在ZC触头外边不够可靠。应引至电动机的输入端头,且延时继电器SJ可用有关电路代替、如图2所示。C的容量亦减小,这样可进一 “Electronic production” introduced in 1994, No. 4, “simple economic phase loss protection circuit” structure is simple, there are certain applications and promotional value. However, the original circuit is wrong: three-phase power supply should be connected in the contactor above the ZC; as shown in Figure 1. Otherwise the motor will not start. And the protection circuit can be further improved, the original test point in the ZC contacts outside the reliable enough. Should be led to the motor input terminal, and delay relay SJ can be replaced with the relevant circuit, shown in Figure 2. C’s capacity is also reduced, so you can go one