Principle of overvoltage and undervoltage

13 Jan 2024

The overvoltage and undervoltage protector is installed in the distribution box. Its main function is to cut off the power supply in a timely manner when the low-voltage distribution line or electrical equipment malfunctions, causing an increase or decrease in the voltage of the distribution system, thereby avoiding losses to components or distribution systems.

This article mainly introduces the working principle, structure, and main parameters of overvoltage and undervoltage protectors. Understanding these related knowledge can help to correctly select and use overvoltage and undervoltage protectors.

1、 Abbreviation for Overvoltage and Undervoltage Protector

Just like low-voltage circuit breakers and residual current operated protectors, the abbreviation for overvoltage and undervoltage protectors is OUPA.

2、 Composition

The overvoltage and undervoltage protector mainly consists of two parts: an overvoltage and undervoltage detection unit and an automatic closing switch device. The overvoltage and undervoltagedetection unit includes electronic circuits such as a high-voltage comparator, a low-voltage comparator, a voltage regulator, and an output circuit. The automatic closing switch device is a contactor.

3、 Basic working principle

When overvoltage or undervoltage occurs in electrical appliances or distribution lines due to faults, the undervoltage protector can quickly cut off the incoming power supply of the power distribution box (or cabinet), avoiding adverse effects of abnormal voltage on the electrical appliances or lines. When the voltage returns to normal, the undervoltage protector will automatically connect the circuit within the specified time.

4、 Classification of overvoltage and undervoltage protectors

Overvoltage and undervoltage protectors can be classified into various types based on their structure, stage, current protection form, installation method, etc.

a. Classification based on structural type

Overvoltage and undervoltage protectors are divided into integral and assembled types based on their structural types.

Integrated: The detection unit of the overvoltage and undervoltage protector and the automatic closing switch device are installed in the same housing.

Assembly type: The overvoltage/undervoltage detection unit and automatic closing switch device of the overvoltage/undervoltage protector are installed in two different casings, and are mechanically assembled together in the factory or on-site.

b. Classify based on the number of poles

Overvoltage and undervoltage protectors can be divided into single pole two circuit, two pole, three-phase four pole, and four pole based on the number of poles.

c. Classification based on the type of overcurrent protection with and without

Overvoltage and undervoltage protectors can be divided into two types based on whether they have

overcurrent protection: those with overcurrent protection and those without overcurrent protection.

d. Classification based on instantaneous tripping current type

Overvoltage and undervoltage protectors with overcurrent protection can be classified into B type, C

type, and D type based on their instantaneous tripping current.

e. Classify according to installation method

Overvoltage and undervoltage protectors can be divided into flat installation, embedded, and panel type (also known as distribution board type) according to their installation methods.

f. Classification based on the presence or absence of operating handle closing and opening devices

Overvoltage and undervoltage protectors can be divided into two types based on the presence or absence of operating handle closing devices: operating handle closing devices and non operating handle closing devices.

g. Classification based on voltage protection type

Overvoltage and undervoltage protectors can be classified according to the type of voltage protection: those with only undervoltage protection function, those with only overvoltage protection, and those with all types of overvoltage and undervoltage protectio

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