Abstract:This design deals with the main technique parameters that are given and consults CZ0 direct current contactor to design a contactor the current is 40A.The main principle of the DC contactor：The electromagnetism coil switches on electricity the title iron to match with the iron heart on，the suction of the electromagnetism system overcomes the counterforce of the spring arouses the action of the contact, the main electric circuit connected；The electromagnetism coil cuts the power the counterforce of the spring arouses the title iron from move to open, the head contact breaks to open the output electricity arc give or get an electric shock in drive to arc-extinct-chamber and made longer，the strong cooling dissociates and put out，the main electric circuit cuts off.The design includes three parts:The design of the contact system，the design of the system of arc-extinct and the design of electromagnetism system..
Key Words: DC contactor arc-extinct-chamber contact electromagnetism system
