What is the difference between a relay and a contactor
Posted by Admin | 24 Jun
Has anyone confused relay and contactor knowledge, you will find it difficult to learn before you know these two knowledge. But it does not matter Xiaobian to explain the difference between relays and contactors. After reading it, you may have a clearer understanding of relays and contactors.
It is an electronic control device, which has a control system (also known as an input loop) and a controlled system (also known as an output loop). It is usually used in automatic control circuits. It actually uses a smaller current to control a larger current. A kind of "automatic switch". Therefore, it plays the role of automatic adjustment, safety protection, and conversion circuit in the circuit. The relay coil is represented by a long box symbol in the circuit. If the relay has two coils, draw two parallel long boxes. At the same time, mark the relay's text symbol "J" in or beside the long box.
The working principle of the contactor is to control the on-off of the main contact connected to the main circuit by controlling the on-off of the auxiliary contact connected to the control circuit to meet the requirements of the control circuit. Because it can quickly cut off AC and DC main circuits and can frequently connect and control high-current (up to 800 amps for some types) circuits, it is often used in motors as control objects, and can also be used to control factory equipment. ﹑ Electric heaters, working mother machines and various power units and other electrical loads, the contactor can not only connect and cut off the circuit, but also has the function of low voltage release protection. The contactor has a large control capacity and is suitable for frequent operation and long-distance control. It is one of the important components in the automatic control system.
Third, the difference between relays and contactors
The main function of the relay is for signal detection, transmission, transformation or processing. The circuit current of its on and off is usually small, that is, it is generally used in the control circuit (compared with the "main circuit").
The main function of the contactor is to connect or disconnect the main circuit. The so-called main circuit refers to whether a circuit works or not is marked by whether the circuit is turned on. The main circuit concept corresponds to the control circuit. Generally, the current passing through the main circuit is larger than that of the control circuit. Therefore, as a friend on the first floor said, a contactor with a large capacity generally has an arc extinguishing cover (because a large current is disconnected, an arc will occur, and the arc extinguishing cover is not used to extinguish the arc, which will burn the contacts).
If the working current of a certain main circuit is small, then the electrical appliances usually used as relays can be used as the device for switching the main circuit. The relay will be used as a contactor. However, if the working current of a certain main circuit is so large that the capacity of the contactor for switching the main circuit is very large, the current to make such a contactor work is also very large, that is to say, the current flowing in its control circuit is very large. It is very large, and it is difficult to turn on and off its control circuit with ordinary relays. At this time, an electrical appliance originally used as a contactor can be selected as the on-off of the control circuit. The function of the contactor in this case is a relay.