The main component of cybernetics is the processes of commutation. The earliest devices capable of performing these processes in electrical circuits were magnetic relays. Due to the rapid development of technological progress, semiconductor switches have been created that perform better switching. However, electromagnetic relays are still popular today. They are still used quite often in various electrical equipment.
Content
- Operating principle
- Varieties of devices
- Main characteristics
- Application area
Operating principle
Magnetic relays have a number of advantages, the most significant of which is the special properties of the contacts.
The apparatus consists of three main parts:
- Primary element. It is needed to convert an electrical signal into magnetic force.
- An intermediate element that also consists of several components. Its task is to activate the actuator. It is a plate equipped with movable contacts and a spring.
- Executive element. It is he who is activated by means of an intermediate element. Its main task is to transmit the impact to the power circuit. Usually, several power contacts play the role of an actuating element.
The principle of operation of an electromagnetic relay is very simple, which is why the device is considered very reliable. Protection and automation circuits cannot do without it.
The relay works as follows: it uses the electromagnetic forces that are generated in the metal core when an electric current appears in the coil. All three main elements are fixed to the surface, which is then closed with a cover, while the armature must be above the core of the electromagnet. A fixed contact must be located opposite each of the moving contacts. In the initial position, the movable metal plate is held by a spring.
As soon as an electric current appears in the network, the DC relay will begin to act, and then the plate will rush to meet him under the influence of the force of gravity, overcoming the force of the spring, forcing it to return to its original point. As a result, the contacts open or close and the power is then turned off. The plate after the termination of the electromagnet will return to its initial position.
Varieties of devices
All existing magnetic relays are divided into several varieties, depending on their design features, scope, control signal power, type of electric current, speed management actions.
By the features of the device, the relays can be:
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Contact. They act on the circuit with several contacts. Closing or opening them contributes to switching - the power circuit is either connected or broken. - Contactless. Affect the chain differently. These
- devices dramatically change its characteristics.
According to the scope of use, they are signaling, protective and intended for control circuits.
By the speed of the device commutations are classified into four types:
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Adjustable. When using them, you can set any speed. - Slow motion. They work no earlier than after 0.05 s.
- Fast acting. Such relays begin to operate within a millisecond.
- Inertia-free. Devices of this type are active even before one millisecond has elapsed.
Depending on the power of the control signal, the relay can belong to one of three main varieties. The power can be:
- high if its value exceeds 10 W;
- average at a value of up to 10 W, but at the same time not less than 1 V;
- small, the value of which is measured in fractions of a watt.
The relay can be used in AC or DC networks. The latter are polarized and neutral.
Main characteristics
A magnetic device has many characteristics. Its most important parameters are as follows:
- Action speed. This is the time it takes for the device to work after the signal has been given.
- Actuation power. The minimum required to start an action.
- Controlled power. This power can be controlled by contacts during commutation.
- The magnitude of the operating current. This parameter is called the setpoint.
- Drop-out current. This is the highest current value at which the sensing plate begins to return to its starting point.
The advantage is that the contacts of the magnetic relay have a low resistance, in contrast to switches based on semiconductors. Another important advantage is that its metal contacts are capable of withstanding large network overloads. In addition, the relay can perform its basic functions normally even with static electricity. Does not affect its operation and radiation.
The main advantage of the electromagnetic device is the galvanic isolation of the control and switching power grid without secondary elements. To all of the above, it is worth adding a low price.
It also has some disadvantages. First, it doesn't work very quickly. Secondly, it often fails. Third, there may be interference when the circuit is commuted.
Application area
Electromagnetic relays are widely used in manufacturing and power distribution. The relay protection installed at the substations ensures trouble-free operation. Quite often, such devices are used in modern household appliances - refrigerators, washing machines.
Previously, these devices were used in computing systems. Here they played the role of logical elements that performed simple operations.
Despite the fact that many modern electronic devices are gradually replacing the electromagnetic relay, it is still being improved, acquiring new possibilities. It is not easy to find a replacement for it where voltage drops occur when turning on and off electrical equipment.
