Single coil
DC relays can have one or two coils. DC relays can be divided into the following types according to their structure and working principle:
Single coil DC electromagnetic relay: This relay has only one coil. When DC current passes through the coil, the magnetic field generated by the coil attracts the armature to close or open the contacts. Single coil DC electromagnetic relays have the advantages of simple structure, low cost, and rapid action, but there are problems such as unstable attraction and susceptibility to interference.
Dual coil DC electromagnetic relay: This relay has two coils. The magnetic fields generated by the two coils cancel each other out. Only when the currents passing through the two coils are equal and opposite in direction, the magnetic field will attract the armature. Double coil DC electromagnetic relays have the advantages of stable attraction and strong anti-interference ability, but the structure is complex and the cost is high.
Differential DC electromagnetic relay: This relay achieves the attraction or release of contacts by comparing two DC currents of different sizes. Differential DC electromagnetic relays have the characteristics of strong anti-interference ability and high precision, and are widely used in precision control systems.