Scientific Selection, Safe Foundation: The Industry Focuses On The Core Factors Of Circuit Breaker Selection

A circuit breaker is a mechanical switch capable of connecting, carrying, and disconnecting current under normal circuit conditions, and automatically connecting, carrying, and disconnecting current under specified abnormal circuit conditions (such as short circuits and overloads). It automatically disconnects faulty circuits, protecting subsequent circuits from overheating and fire, preventing damage to connected electrical equipment, and ensuring personal safety and preventing electric shock accidents.

 

 

The selection of circuit breakers is directly related to the safety, stability, and reliability of electrical systems. Improper selection may result in failure to effectively protect circuits and equipment, and may even cause serious accidents such as fires.

The core factors that need to be considered in circuit breaker selection can be divided into main (determining) factors, application and environmental factors.

 

一,Main (determining) factors:

The basic parameters that must be determined first when selecting a circuit breaker determine whether the circuit breaker can be connected to the system and provide basic protection.

1. Rated voltage:

This is the system voltage at which the circuit breaker can operate normally over a long period of time. The circuit breaker's rated voltage must be greater than or equal to the rated voltage of the circuit at its installation point. (For example, for a 380V system, a circuit breaker with a rated voltage of 380V or 400V should be selected.)

 

2. Rated current:

This is the maximum current that a circuit breaker can pass for a long period of time without causing a trip. The rated current of the circuit breaker must be greater than the calculated load current of the line and less than or equal to the safe current carrying capacity of the conductor.

Consideration: A certain margin needs to be reserved to accommodate slight increases in future loads, but it should not be too large, otherwise the overload protection function will be lost.

 

3. Number of poles:

This is the number of conductors a circuit breaker can simultaneously disconnect (protect). The selection depends on the type of power supply system (single-phase, three-phase three-wire, three-phase four-wire) and whether the neutral conductor needs to be disconnected.

Common types:

1P	Monopolar,Disconnect only the live (phase) wire.
2P	Bipolar,Disconnect two wires at the same time (such as single-phase live and neutral wires, or two-phase wires).
3P	Three-pole,For three-phase three-wire systems.
4P	quadrupole,Disconnect three phase wires and one neutral wire at the same time.

 At SDKC, we have 3P molded case circuit breakers, 4P molded case circuit breakers, 1P miniature circuit breakers, 2P miniature circuit breakers, 3P miniature circuit breakers, 3P molded case leakage circuit breakers, 4P molded case leakage circuit breakers, 2P miniature leakage circuit breakers, 4P miniature leakage circuit breakers, etc.

 

二,Application and Environmental Factors：

1. Installation method and size：

How to fix and wire.

Fixed	Direct installation, disassembly requires wire removal.
Plug-in	The main body can be inserted into the base for quick and easy replacement.
Drawer type	Commonly used in frame-type circuit breakers, it has multiple positions such as connection, testing, separation, and withdrawal, making maintenance safe and convenient.

Size: Consider the installation space (module) within the distribution box/cabinet.

At SDKC, we primarily offer frame-mounted circuit breakers and frame-drawable circuit breakers.

 

2. Attachment function：

Select based on monitoring and control needs.
Common accessories include: shunt release (remote tripping), undervoltage release (tripping when voltage is too low), auxiliary contacts (for signaling), alarm contacts (for fault indication), etc.

 

3. Operating environment conditions：

Ambient temperature	High temperatures will reduce the current-carrying capacity and breaking capacity of the circuit breaker, and you may need to reduce the capacity or select a special model.
Altitude	The air is thin in high altitude areas, which affects the heat dissipation and arc extinguishing capabilities, and capacity derating is also required.
Humidity, pollution level, corrosive environment	Affects the life and performance of the circuit breaker.