This section provides overview, applications, and principles of control relays. Also, please take a look at the list of 46 control relay manufacturers and their company rankings.
A control relay is an electrical component for control that turns its contacts on or off according to a certain current or voltage signal given to the coil. It consists of an electromagnet and a switch.
The name "control relay" is derived from the image of a baton relay, in which one input starts a relay and affects the output of another.
There are two types of electromagnetic relays: mechanical relays with contacts and solid-state relays (SSR) without contacts.
They are mainly used in controls where an input signal emitted from a sensor or pushbutton causes another device to move.
Since they are used in places where control is being performed, they are used not only in plants but also in electrical appliances.
A similar application is the programmable logic controller (PLC), which uses relays configured in a program to perform control. If control is to be performed using several hundred relays, a PLC will occupy less space. Conversely, if only a few relays are used, an electromagnetic relay is a cheaper and easier way to introduce control.
First, let's discuss contact relays. When a current or voltage signal is input to the coil, it becomes an electromagnet. The switch is mechanically moved by the magnetic force. The switch on the input side is connected to the switch on the output side, and the switch on the output side is switched by the switch on the input side that is moved. Hinged relays are mainly used. An electromagnet rotates around a fulcrum, which opens and closes the switch. When current flows, the relay rotates toward the electromagnet, and when current ceases to flow, it is pushed back by the force of the return spring, thereby separating from the electromagnet.
Next, we will discuss non-contact relays. The signal is transmitted through an electronic circuit using semiconductors. When current flows on the input side, a photocoupler (a switch using light) operates, allowing current to flow on the output side. Since there are no mechanical contacts, the relay has the advantage of good insulation performance and high-speed opening/closing. On the other hand, it is slightly larger than a contact relay.
*Including some distributors, etc.
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