I. Contactors are used for load types with high voltages, high currents or both.

Generally used for equipment passing loads in excess of 15 amps or in excess of 3kW. For lower quantities, ordinary relays are used. Relays are of the electromagnetic type. There are three categories of electromagnetic relays, namely voltage relays, current relays and intermediate relays. In addition, from intermediate relays can be derived time relays, signal relays, etc.

ii. Relays and contactors are both relaying electrical components

As the name implies, they are used to interrupt and renew circuit circuits in order to control the working state of the circuit. They are characterised by their ability to control large currents with small currents, their ability to open and close circuits frequently and their high efficiency. Relay load current and coil operating current are relatively small, generally common relay contact current withstand capacity of about 5 ~ 50A, mostly used in the control circuit, as the electrical signal issued and implementation part.

iii. Extended information

Contact contact is not secure will make the dynamic and static contacts between the contact resistance increases, resulting in contact surface temperature is too high, so that the surface contact into point contact, or even non-conductivity phenomenon. Causes of this fault are: 1. oil, flower hair, foreign matter on the contact. 2. long-term use, contact surface oxidation. 3. arc ablation caused by defects, burrs or the formation of metal chip particles, etc. 4. moving part of the phenomenon of stuck resistance.

IV. Electrical capacity size

Current capacity is large contactor, small relay, there is a distinction between the use of contactors in the main circuit, the control circuit with relays. The role of the contactor is used to connect and break the larger current signal, drive motors and other power equipment; the role of the relay is used for signal conversion, with the electrical level of the interface between the control signal between the equipment, its contact bearing capacity is generally small, used to drive electrical components such as contactors.