Because of the relay control system is a "parallel" way to work,and its contact on-off needs certain action time. So when the starting circuit,time relay KT delay time,KT whether can continue to ac induction motor keep the current state,"parallel" two actions need to be considered at the same time process: KT normally closed delay off contact,KA1,losing electricity KA1 normally open contacts disconnect; KT normally open delay contact closure,KA2 electricity,KA2 normally open contact wholesalemotor.blogspot.com closure. The results of the two process function,to determine the status of KT.

At the same time,the existence of the action time of the contact,makes the circuit in time sequence. So the circuit can not reliable work. If join the empty boxes in the loop,and as shown in high efficiency electric motor figure 1 the KA2 normally open contacts into KA3 normally open contacts (see figure 1) brackets. As a result,KT,the KT itself lost electricity,will not continue to maintain current state.