As commonly used components in circuits, relays and contactors are electromagnetic switching devices, but they are different in principle or function. Relays convert physical quantities into electrical signals, or control lines in a control loop. Carry out automatic switching, or convert the weak signal into a strong signal to control the contactor to drive the electrical components that perform the system work. In a broad sense, a contactor refers to an electrical appliance that uses a coil to flow a current to generate a magnetic field and close the contact to control the load. Let's understand the difference between the two:
Relays and contactors are electrical appliances with contacts. The same thing is that they both rely on controlling the small current or low voltage in the coil to make the electromagnet magnetic to attract or release the armature to drive the contact switch. The on-off of electrical components to control the on-off of circuits with larger current or higher voltage.
The main difference:
Contact setting. Relay contacts are generally not divided into main and auxiliary, and are mostly set in pairs. Normally open contacts and normally closed contacts are combined; contactor contacts are not set in pairs.
The magnitude of controlled current. Some of the maximum current allowed by the relay contacts is less than 1A, and most are 1~2A, and the maximum current is not more than 5A; the maximum current allowed by the contactor contacts is not less than 9A.
Use occasions. Relays are generally used in control circuits where controlled signals or currents are not too strong, and have the functions of signal detection, transmission, conversion, and processing; contactors are generally used for on-off control of the main (power supply) circuit.
Whether there is an arc extinguisher. The relay has a small on-off current, and although it may generate electric sparks, it will not form an arc, so there is no arc extinguishing cover; contactors, especially contactors with larger control currents, generally have an arc extinguishing cover.
Additional functions. Relays can be connected to logical operation functions according to needs, or combined with other equipment or components and parts to form time relays, pressure relays, sound relays, light and brightness relays, counters, etc.; contactors generally do not have these additional functions.
Self-locking function. Since the contactor is used for the load with large on-off power, in order to prevent the main circuit from being automatically disconnected due to vibration, the main contact sometimes needs to be connected to the auxiliary excitation coil with self-locking function by the way; the relay does not need to have This self-locking function.
The above is the introduction of the difference between relay and contactor. At present, there are many types of relays. According to the input quantity, they can be divided into voltage relays, current relays, time relays, speed relays, etc. According to the working principle, they can be divided into electromagnetic relays, inductive relays, electric relays, etc., and can be divided into control according to their purposes. Relays, protection relays, etc., can be divided into presence or absence relays and measuring relays according to the form of input changes. Therefore, everyone should choose the appropriate relay when using it.
Summarized by Easybom （https://www.easybom.com/）