Electromagnetic relays and contactors, they work the same should be said. Sometimes that is the same device used in the circuit as a contact, use another circuit and as a relay. What difference does it make? Difference is to look at their specific use of.

The main role of the relay is the starting signal detection, transmission, transformation or processing, which is off the circuit current is typically small, that is generally used in the control circuit (with the "main circuit" comparison).

Contactor main role is to turn on or off the main circuit. The so-called main circuit refers to a circuit or not by the circuit is switched on as the symbol. The main circuit and control circuit corresponds to the concept. Through the main circuit current is generally larger than the control circuit. Therefore, as a friend said on the first floor, large capacity contactors are generally with the arc chute (because of the large current interrupting arcing, do not use arc chute interrupter, will burn out contacts).

If a main circuit current is small, then you can use commonly used as electrical relay used as off the main circuit devices. About to be used as a relay contact. However, if a main circuit current is very large, so that the use of off the main circuit contactor capacity is very large, to make such a contact current work is very large, which means that it controls the current flowing in the circuit is very large, with ordinary hard-off its relay control circuit. In this case, you can select a original use as electrical contacts to the control circuit as on-off use, this contact is the role of this occasion in the relay.