The working principle of relay and contactor is the same. The main difference is that the main contact of the contactor can withstand large current, while the relay contact can only withstand small current. Both relays and contactors are electromagnetic switching appliances, but the former belongs to switching appliances working in the control loop, and the latter belongs to switching appliances working in the main loop.
Definition of relay: Relay is an automatic electrical appliance, which is suitable for remote connection and disconnection of AC and DC small-capacity control circuits, and is used for control, protection and signal conversion in electric drive systems. The input quantity of the control relay is usually the electric quantity such as current and voltage, and it can also be non-electric quantity such as temperature, pressure, speed, etc. The output quantity is the electric signal issued by the contact action or the parameter change of the output circuit. The characteristic of the relay is that when the change of its input reaches a certain program, the output will change step by step.
The definition of contactor: Contactor is divided into AC contactor (voltage AC) and DC contactor (voltage DC), which are used in electric power, power distribution and electricity use occasions. In a broad sense, a contactor refers to an electrical appliance that uses a coil to flow current to generate a magnetic field and close the contact to control the load.
The effect is different:
The primary function of a relay is for signal detection, transmission, conversion or disposal. Its on-off circuit current is generally small, and it is generally used in control circuits to control weak signals.
The primary function of the contactor is to connect or disconnect the main circuit. The main circuit refers to whether a circuit works or not is marked by whether the circuit is connected or not. The main circuit concept corresponds to the control circuit. Generally, the current through the main circuit is larger than that of the control circuit.
Contactors with large capacity are generally equipped with arc extinguishing covers. The contact capacity of a relay generally does not exceed 5A. The contact capacity of a small relay generally only needs 1A or 2A, and the smallest contact capacity of a contactor is also 9A; the contactor of a contactor generally has three pairs of main contacts (main contact The heads are always open contacts) In addition, there are several pairs of auxiliary contacts.
The contacts of the relay generally do not distinguish between main and auxiliary; the contacts of the relay are sometimes set up in pairs, that is, the normally open contacts and the normally closed contacts are combined, and the contactors are not set in pairs; the relays have specific needs. When combined with other equipment, it is planned as a time relay, counter, pressure relay, etc., which have additional functions, but contactors generally do not.
The contact opening and closing are not the same:
In addition, the contactor is used to connect or disconnect the load with higher power. It is used in the (power) main circuit. The main contact can have interlocking contacts to indicate the opening and closing of the main contact. Relays are generally used in electrical control circuits to expand the contact capacity of miniature or small relays to drive larger loads.
For example, the contact of the relay can be used to connect or disconnect the coil of the contactor. Generally, relays have more open and close contacts. Of course, relays can also perform some extra functions, such as logic operations, through proper connection.
Arc extinguishing device: In fact, looking at contactors and relays, one of the most important differences is that contactors have arc extinguishing devices, while relays do not.