Reliability test research on auxiliary contact of 3TB40 AC contactor;

in two related standards,the differences and conformity between the auxiliary contact for household use and that for industrial use can be clarified,which can also contribute to the certification of the related products in the near future as a guider in terms of standards.

,cutting all motor power of disconnector under normal condition to prevent misoperation and ensuing accident,adding diverter switch to disconnector control circuit to ensure the uniqueness of disconnection operation,and adopting gear structure as the working structure of disconnector to solve the problem of position inconsistency between auxiliary contact and main contact.

Based on an analysis of the causes,the author pointed out that the accident is caused by incorrect switching of breaker auxiliary contacts in the process of operation,then put forward the prevention measure of time-delay switching off the tripping circuit after sending of operation pulse.

This paper analyzes the problems one by one, including why switch auxiliary contact location for a long time does not correspond to the device do not report until 18 M switching operation, if not dealt with what would have serious consequences, and proposes preventive measures that other special units of the dual-bus can cause sufficient attention.