An intermediate relay is a part of an electronic device used in electrical and electronic circuits to convert and amplify electrical signals, open and close circuits. The apparatus coordinates the work of equipment units, individual elements, powerful devices. Used in almost all industries and household appliances.
Intermediate relay assignment
This is an auxiliary device that is designed to control the operation of various machines and complexes. Provides the operation of several electrical circuits at once, when it is necessary to simultaneously switch different contacts.
For example, one of the contacts should give an alarm on the relay screen, and the other should shut down. Or, with the help of one connection, the machine is started, the other turns off another part of the device.
And also an intermediate relay (RP) is used to slow down the reaction at the necessary high loads. For monitoring a main relay that commutes high currents in high voltage conditions.
An intermediate relay is called because in the control circuit it is located between the source of the impulse that it controls and the power executive circuits.
RP device
The design of the device depends on the manufacturer and can be changed in accordance with the purpose. A standard device consists of the following components:
- an electromagnetic coil with a core;
- magnetic circuit;
- spring mechanism;
- contact group.
The coil winding contains a large number of turns of insulated copper wire. Inside there is a metal core, which is fixed with an L-shaped plate (yoke). A plate or anchor is installed above the coil. It is made of metal and is held in place by a return spring. The movable contacts are fixed to the anchor. A pair of fixed contacts is located opposite. The core and coil together form an electromagnet. Parts such as yoke, core, and armature are integral parts of the magnetic circuit.
RP can be designed for both direct and alternating current, with voltage from 12 to 220 volts. Outwardly, the devices are no different. The DC device has a one-piece magnetic circuit. If it is assembled from separate plates, the device is designed to operate with an alternating current not exceeding 10 amperes.
For the convenience of installation, the device uses a kind of pads, which allows you to install an intermediate relay for 220V on a din rail. The fixture has holes for relay contacts, as well as contact screws to connect external conductors. Both the input and output pins are numbered the same.
Types of intermediate relays
By design, they are divided into electromagnetic intermediate relays or mechanical and electronic devices. Mechanical relays can operate in a variety of conditions. These are durable and reliable instruments, but not accurate enough. Therefore, more often their analogs are mounted in the circuit - electronic relays on a din-rail. Also, the relay can be installed on a flat surface. To do this, the locks must be pushed apart.
By purpose, the devices are divided into the following categories.
- Combined interdependent devices operating in a group.
- Logic devices that operate on microprocessors in a circuit with digital relays.
- Measuring, with an adjustment mechanism, triggered by a certain signal level.
According to the method of operation of the RP, there are direct ones, which directly open or close the circuit, and indirect ones, working together with other devices. They do not open the circuit immediately after a signal is received.
There are devices of the maximum type of switching, when the actuation occurs at the moment of increasing the threshold value of the circuit parameter. The minimum type is triggered during derating.
According to the method of connection to the circuit, there are primary ones that can be connected directly to the circuit. The secondary ones are installed through inductors or capacitors.
There is a group of protection relays, similar in principle to intermediate ones. Distinguish between semiconductor devices, induction, polarizing and electromagnetic. For example, a phase monitor is a kv relay.
Principle of operation
The basis of functioning is the coordinated interaction of the magnetic flux of the coil and the moving armature, which is magnetized by this flux. The armature is held by a spring and does not touch the core until voltage is applied to the winding.
When current begins to flow, the magnetic field magnetizes the core. It attracts the armature, forcing the spring tension. Moving contacts on the armature move, closing or opening with fixed contacts. After disconnecting the voltage, the current disappears, the core is demagnetized, the return spring returns the armature and contacts to their original position.
With regard to the purpose of the relay, contacts can be normally open, normally closed and changeover. One device can have several contact groups at once. This design allows you to control several electrical circuits at the same time.
There are special requirements for contacts. They must have good electrical conductivity, low contact resistance, no tendency to be welded, and also have great wear resistance and a long service life.
Contacts are made of an alloy of hard and refractory metals, cermet compositions. Most often they are made of silver. The material has low resistance, high electrical conductivity, good technological properties, besides, it is relatively inexpensive.
In the diagrams, the relay coil is designated as a rectangle with the letter "K" and a serial number. Contacts are written with the same letter, but with two numbers. Of these, the first means the serial number of the relay, and the second - the number of the contact group to which it belongs. The numbers are written through a dot. Contacts are connected by a straight dashed line if they are adjacent.
Contacts in the diagram are shown provided that no voltage is applied to the relay. The diagram and designation of the contact output is usually indicated by the manufacturer on the cover that covers the working part of the device.
Application area
RP is found in almost all power supply, control and protection circuits. Switching devices are used in substations, control rooms, boiler rooms. On the production line, the device can perform both simultaneously and sequentially several switchings in the control or power circuits. RP is widely used for computers, telecommunications, control facilities and other electronic devices.
In water supply and heating systems, when the submersible pump is turned on, power is supplied to the coil. When the contacts are closed, the monitoring system starts working. The display shows voltage parameters, phase load currents, temperature, if necessary, and other data depending on the complexity of the circuit.
In the heating system, the relay acts as a control signal amplifier. The heat sensor gives a signal that turns on the RP.The contacts of the latter apply voltage to the winding, after which the contacts are closed. Thus, the power is connected to a heating element, a boiler, a boiler and other powerful heating devices.
Product parameters
- sensitivity;
- current (voltage) of operation, release, holding;
- safety factor;
- working current;
- winding resistance;
- switching capacity;
- dimensions;
- electrical insulation.
You need to know at what temperature and humidity the device can be used, the explosiveness of the working environment, the permissible concentration of dust. These parameters are stated in the technical specifications or the manual for use. The type of current and operating voltage are indicated on the winding of the device.
RP is an important and integral part of most energy chains. The variety of models indicates that such a switching device is capable of fully performing many functions in any circuit.
