At the other hand, electromagnet is a big inductance load, when DC contactor is on or off, electricity arc is easy to happen and burnout the contactor. So the fault rate is very high and it needs much repairing work.

• 另外电磁铁是个大电感负载,当直流接触器接通和断开的时候,电感反电势非常大,很容易产生电弧光,烧坏直流接触器,因而故障率非常高,维修工作量很大。