Modern electronic devices cannot do without protection against unacceptably low or high voltage supply. A variety of threshold schemes have been developed to implement these functions. The principle of their operation is based on a device called a voltage relay. In addition to protective functions, such circuits are used in the automation of production processes, they can be found in household appliances, they are successfully used in the automotive industry, etc. The use of a voltage relay has long been a sign of good design in electrical and electronic circuit design.
Let's look at a few examples of the use of such devices. Overvoltage or voltage loss is a serious problem, and if the power fails, all electronics will fail with various consequences. When powerful engines are turned on in production, a short-term power supply drawdown may occur, which will negatively affect the operation of all devices. Failure of the electronic circuits involved in the control will lead to the creation of emergencysituations and stop the entire production line. Overvoltage will also lead to negative consequences. To minimize losses in this case, voltage relays are used. They are compact, reliable in operation and differ only in basic elements.
They work according to the following principle. If the actual voltage exceeds the setting, then the voltage relay is activated, which protects the circuit. Protection schemes work according to the same principle in case of an unacceptable power supply drawdown.
Separately, we can consider the use of such devices in the automotive industry. They monitor the state of the on-board network and prevent the voltage from rising above a predetermined level. This is usually done by limiting the alternator stator winding current, which feeds the battery when the engine is running.
Currently, serial production of such devices has been launched. For example, the single-phase voltage relay RN-111 is designed to turn off consumers in case of unacceptable fluctuations in the supply network. After restoring all parameters, it will automatically turn on.
The relay has an indication of the presence of power, which simplifies troubleshooting. In addition, potentiometers are installed on the front side to set the minimum and maximum response voltage. It also provides visual control over relay parameters and simplifies initial setup. A delay is also provided for operation during short-term fluctuations in the network. Exceptovervoltage protection, it acts as an undervoltage relay. A large number of changeover contacts allows them to be used both for protective shutdown and in control and automation circuits.
Besides relay protection, there are various electronic circuits that perform the same function. The advantages of such schemes include high sensitivity and speed. The disadvantages are the complexity in manufacturing and low reliability.
