Relays and contactors perform the same task of switching a circuit. Both are electromagnetic switches and operate under similar principles. The difference comes if we see from the application perspective. Contactors are used for high voltage switching purposes whereas relays are used for low voltage switching. The function of the contactor is mainly to connect and disconnect the main circuit. The main function of the relay is suitable for signal detection, conversion and transmission. Both components are very important for the design of the circuit.
The essential difference between a relay and a contactor is that they bear different loads. Contactor carry large current, while relay’s current capacity is small. In addition, the contactor is used in the main circuit and the relay is used in the control circuit. Contactor is to switch on and off large current signals and drive power equipment such as motors. Relay is to perform signal conversion.
The interface of control signals between devices of different voltage levels. The contact carrying capacity is generally small and is used to drive electrical components such as contactors.
Relays are secondary equipment, including intermediate relays, voltage relays, current relays, time relays, etc., used for signal sampling, transfer, control, protection, etc., belong to low-voltage equipment, the contact capacity is small, generally 5A.
A relay is an electrical control device. It has the interactive relationship between the control system (also called input loop) and the controlled system (also called output loop). Usually used in automated control circuits, it is actually an “automatic switch” that uses small currents to control high current operations. Therefore, it plays the role of automatic adjustment, safety protection, and conversion circuit in the circuit.
Relays are generally used in electrical control circuits to amplify the contact capacity of miniature or small relays to drive larger loads. For example, you can use the contacts of the relay to switch on or off the contactor’s coil. Generally, the relay has more opening and closing contacts. Of course, the relay can also achieve some special functions, such as logic operations, through proper connection.
When the input quantity (such as voltage, current, temperature, etc.) reaches the specified value, the relay turns on or off the controlled output circuit. Input quantity can be divided into electrical quantity (such as current, voltage, frequency, power, etc.) and non-electrical quantity (such as temperature, pressure, speed, etc.).
The contactor is used to switch on or off the load with higher power. It is used in the (power) main circuit. The main contact may have interlocking contacts to indicate the opening and closing state of the main contact.
The contactor uses the current flowing through the coil to generate a magnetic field, so that the contacts are closed, so as to reach the electrical appliance that controls the load. The contactor consists of an electromagnetic system (iron core, static iron core, electromagnetic coil) contact system (normally open contact and normally closed contact) and arc extinguishing device. The principle is that when the contactor’s electromagnetic coil is energized, a strong magnetic field will be generated, which will cause the static iron core to generate electromagnetic attraction to attract the armature and drive the contact action: normally closed contact is opened; normally open contact is closed, both are linked. When the coil is de-energized, the electromagnetic attraction force disappears, and the armature is released under the action of the release spring to restore the contacts: normally closed contacts are closed; normally open contacts are opened.
- Isolation function. Between the input part and the output part of the relay, there is an intermediate mechanism (drive part) that couples and isolates the input quantity, performs functional processing, and drives the output part.
- Expand the scope of control. When the multi-contact relay control signal reaches a certain value, the multi-circuit can be switched, disconnected and connected at the same time according to different forms of the contact group.
- Zoom in. Sensitive relays, intermediate relays, etc. can control very high power circuits with a very small amount of control.
- Comprehensive signals. When multiple control signals are input to the multi-winding relay in a prescribed form, after a comprehensive comparison, a predetermined control effect is achieved.
- Automatic, remote control and monitoring. The relays on the automatic device together with other electrical appliances can form a program control circuit to achieve automatic operation.
The function of the contactor is to use a small current to control a large current load, which can be remotely controlled, and at the same time, it can be self-locked and interlocked to prevent accidents caused by malfunction. The small current control makes the protection circuit simple and reliable.
Difference between contactor and relay
Relays: used for control circuits, low current, no arc extinguishing device, can operate under the action of electricity or non-electricity, a relay often has several pairs of normally open / normally closed nodes, which can be used for different control loops, its nodes cannot pass high current, generally not used in power circuits.
Contactor: Similar to a circuit breaker, it is used for the main circuit, has a large current, and has an arc extinguishing device. Generally, it can only operate under the action of voltage. In fact, the principle is the same, mainly because the contact capacity is different, the relay contact capacity is small, the contact can only pass a small current, which is mainly used for control, the contactor has a large capacity, and the contact can pass a large current, which is used for more main circuits.
The principle of the contactor is the same as that of the voltage relay, except that the load power controlled by the contactor is large, so the volume is also large. AC contactors are widely used as power interruption and control circuits. The relay is a small-signal control electrical appliance, which is used for motor protection or automatic control of various production machines.
The above is the difference between contactors and relays, as well as their respective structures and functions. I believe that you already have a general understanding of contactors and relays, so that when you choose, you can choose according to actual needs. HOTSON provides you with many selections of DC contactors, rating current from 10amps to 600amps, coil voltage with 12V, 24V, 48V, and rating voltage from 12V-1500V.