Problems and faults occurred in the matching of three kinds of delay time relays when the motor is out of step or oscillating in step are analysed.On this basis, the relays are improved.

• 在同步电动机失步或同步振荡的情况下,分析了3个有延时的继电器在时间上互相配合出现的问题和造成的三种不同错误状况,并在此基础上做了相应的改进。