What is an intermediate relay and what is it for?
Appointment
In automation and control systems, intermediate relays are widely used (see photo below). These devices commute control signals, control powerful devices, separate control circuits from power ones and play an equally important role as power relays.
The intermediate relay got its name because of the situation in the automation and control circuits. They are located between the source of the job and the actuator, such as a contactor, so it becomes clear why the relay was called so.
You can get additional information about the purpose and types of products by watching this video:
Device
These devices come in all kinds of types and sizes. From miniature relays to two contacts, up to several dozen in the repeater relay.In all their constructive principle is the same. The intermediate relay device is represented byelectromagnetic control coil, magnetic circuit, spring mechanism and group of contacts. You can learn more about the design of the device by looking at the picture below:
The industry produces a wide range of devices for a variety of control voltages from 5 volts to 220. They can be designed for alternating "AC" voltage and constant "DC".
Outwardly, they are practically no different. The difference is only in the design of the magnetic circuit. For alternating current, it is drawn from a group of plates, and direct current is solid. This is done to reduce heating losses in the magnetic circuit during the passage of alternating current.
As for the technical characteristics of the devices, for each type they are different. For example, for the RE series, they will look like:
For industrial purposes, blocks for intermediate relays are manufactured with installation on DIN rail. Relays and pads for them are also available with a wide range of types of connectors. This is done for ease of operation within the same device, when there are models of different voltages, and inattention did not replace one type with another.
Principle of operation
It is equally important to know how the intermediate relay works. The principle of operation is as follows: when voltage is applied to the control coil, the magnetic flux that appears in the core draws in the contact mechanism. The latter, in turn, change position, and switch, while opening or closing the contacts.
You can learn more about the principle of operation by watching this video:
Application area
Intermediate relays are used in control circuits for switching power circuits from a low current source.They are also needed to assemble a circuit for holding contacts, repeating a signal and outputting to indicators, duplication to remote control panels, etc.
Very often, these devices are used in emergency systems, industrial equipment, relay protection devices and electric power facilities.
For example, take the control circuit of an induction motor, with phase presence control. This circuit is assembled on intermediate relays of the type 1РН, 2РН, 3РН, 1РП, 2РП, and also with repetition of the phase status to the light indicators. By the way, immediately pay attention to the symbol of this element in the diagram.
That's all I wanted to tell you about the device, the principle of operation and the purpose of the intermediate relay. As you can see, in the control circuits this device performs an important function, therefore it is often used in production.
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