Automatic voltage switch: know all about principles and uses

Are you curious about what an automatic voltage switch is? It is actually an important device that can automatically monitor and regulate circuit voltage. In daily life, automatic voltage switches are widely used, especially in home applications, playing a key role. It can effectively protect various home appliances from abnormal voltage fluctuations.

What is an automatic voltage switch?

Automatic voltage switch is an electrical device that can automatically monitor and control circuit voltage. It is mainly used to protect electrical equipment from damage caused by abnormal voltage (too high or too low). From the appearance, it is generally a small device with an interface for connecting circuits and contains complex electronic components inside. Its size varies depending on power and function. The small one may be about the same size as an ordinary socket, and the large one may be like a small distribution box.

Uses of automatic voltage switches

Home applications:

Protecting home appliances

In the home environment, we have a variety of electrical appliances, such as refrigerators, televisions, computers, etc. These appliances have their rated operating voltage range. For example, the power adapter of a computer generally requires an input voltage between 100-240V to work properly. When the grid voltage fluctuates, such as when the voltage is too low during peak power consumption or when the voltage is too high during a grid failure, the automatic voltage switch can play a role. It can prevent the electronic components of the appliance from being burned out due to excessive voltage, or the appliance from being unable to start normally due to too low voltage, or even damaging components such as motors.

Extend the life of home appliances.

Long-term voltage instability will accelerate the aging of home appliances. For example, if a washing machine is often operated under high voltage, the insulation layer of the motor may be damaged prematurely, causing motor failure. Automatic voltage switches can reduce equipment aging caused by voltage problems by maintaining voltage stability, thereby extending the service life of home appliances.

How does the automatic voltage switch work?

Voltage monitoring

Internal circuit structure

The automatic voltage switch has a voltage detection circuit inside, which is usually composed of components such as voltage transformers or voltage divider resistors. These components can obtain the input voltage signal in real-time and convert it into an electrical signal that can be recognized by the control circuit. For example, when the input voltage is 220V, the voltage transformer may convert it into a lower voltage signal proportional to 220V, such as a 5V signal.

Setting thresholds

The automatic voltage switch has pre-set overvoltage and undervoltage thresholds. These thresholds are determined based on the rated voltage of the electrical equipment being protected and the allowable voltage fluctuation range. For example, for a device with a rated voltage of 220V, the overvoltage threshold may be set to 242V (allowing 10% overvoltage) and the undervoltage threshold may be set to 198V (allowing 10% undervoltage). When the monitored voltage signal exceeds the overvoltage threshold or falls below the under-voltage threshold, the subsequent control action will be triggered.

Control action

Cut off the circuit

When the voltage is abnormal, the control circuit of the automatic voltage switch will issue a command to drive the switching element (such as a relay or thyristor, etc.) to operate and cut off the circuit. For example, when the input voltage reaches 245V (exceeding the set overvoltage threshold), the control circuit will disconnect the contacts of the relay, thereby cutting off the circuit connection, isolating the subsequent electrical equipment from the abnormal voltage, and preventing the equipment from being damaged by high voltage.

Recovery circuit

When the voltage returns to the normal range, the automatic voltage switch will not immediately restore the circuit connection. It will have a delayed recovery time setting, which is generally adjustable. This is to avoid some unstable factors when the voltage has just returned to normal. For example, after the grid voltage has just returned to the normal range, there may be some short-term voltage fluctuations. Delayed recovery can ensure that the circuit is reconnected after the voltage is truly stable, ensuring the safe operation of electrical equipment. Generally speaking, the delayed recovery time can range from a few seconds to a few minutes, depending on the settings of the automatic voltage switch and the application scenario.