Difference between Contactor and Relay

A contactor is mainly used in a primary loop, which can go through a large current (several hundred to about one thousand Amps). While a relay is used in a secondary circuit to achieve various control functions, which can only go through a small current (several to decades Amps). Functions, contacts opening and closing situation of the two subject are different.

Functions
Primary function of a relay is to detect, transmit, convert or dispose the signal, it's on-off current is generally small. The relay is usually used in a control circuit to control the weak signal.
Primary function of a contactor is to connect or disconnect the main circuit. The main circuit refers to the one whose working situation is determined by the connection of this circuit. The concept of main circuit corresponds to the control circuit, generally, the current of a main circuit is larger than that of a control circuit.
In general, a contactor with large capacity is equipped with an arc chute. The contact capacity of a relay will not exceed 5A, that of a midget relay may be 1A or 2A. However, the minimum contact capacity of a contactor could be 9A. Contacts of the contactor usually have three pairs of main contacts (the main contacts are normally open contacts), it also has several pairs of auxiliary contacts.
However, contacts of a relay is generally not divided into main contacts or auxiliary contacts. Sometimes, contacts of a relay are set in pairs, namely the normally open contacts and normally closed contacts are combined, while that of a contactor are not in pairs. As for specific needs, the relay will combine with other equipment into a time relay, a counter or a pressure relay, which has the additional functions, but a contactor doesn't have.

Opening and closing of contacts
In addition, a contactor is used to connect or disconnect a large power load, it's mainly used in the (power) main circuit. The main contact can be equipped with a chain connection to show the closing and opening situation of the main contact.
The relay is usually used in the electrical control circuit, it's used to extend the contact capacity of a micro or small relay, so as to drive larger load. Contact of a relay can be used to connect or disconnect the coils of a contactor. Generally, a relay has several opening and closing contacts. Of course, the relay can also complete some special functions through proper connection, such as logic operation.

ATO offers DC contactors rated current from 30A to 600A, single phase and three phase solid state relays, electromagnetic relays are available.