Air Circuit Breaker Distribution Box

Choosing Shangming, a Chinese company, as your air circuit breaker distribution box supplier will grant you access to technical support and competitive pricing. This distribution box supports intelligent monitoring and remote control.

Main Functions

Main Power Control: As the main incoming switch for the low-voltage system, the air circuit breaker distribution box is responsible for controlling the main power switch for the entire building or production line, controlling the on/off state of the entire power distribution system.

Multiple Protections: The equipment provides precise three-stage protection: long-delay overload, short-circuit short-delay, short-circuit instantaneous, and ground fault protection.

Power Monitoring: The air circuit breaker can integrate an intelligent controller to display real-time data such as voltage, current, frequency, and power factor.

Hierarchical Interlocking: The air circuit breaker distribution box can be logically interlocked with upstream transformers or downstream branch cabinets to prevent cascading tripping from causing large-scale power outages, protecting cables, equipment, and personnel safety.

Product Comparison: Air Circuit Breaker Distribution Box vs. Standard Distribution Box

How to Choose the Right Air Circuit Breaker Distribution Box Specifications?

Correct selection will improve subsequent installation, maintenance, performance, and lifespan. Shangming, as a manufacturer of air circuit breaker distribution boxes, provides advice based on a standard selection process: Application → Voltage → Current → Short-circuit capacity → Structural form → Cabinet specifications → Outgoing line scheme → Intelligent configuration → Environmental verification.

I. Clarify the Application

Before selecting specifications, first determine the function of the air circuit breaker distribution box in your system.

Low-voltage main incoming line distribution box: Serves as the main switch for the entire low-voltage system, corresponding to the maximum load and maximum short-circuit current.

Bus tie distribution box: Used for connection between two busbar sections; key considerations are tie capacity and operating frequency.

Important load feeder distribution box: Powers critical equipment, requiring high reliability and selective protection.

Different applications require significantly different specifications; this is the first step.

II. Determine Rated Voltage and System Type

Common rated voltages: AC 380V / 400V / 690V, must be consistent with the on-site power supply system.

System type: Three-phase three-wire / Three-phase four-wire. Please confirm whether a neutral (N) line and a protective earth (PE) line are required.

Incorrect voltage and system type will directly render the equipment unusable.

III. Calculate and Select Rated Current

Calculate the actual load current and summarize the design current of all downstream circuits, based on the maximum simultaneous operating conditions.

When selecting, we recommend reserving a reasonable margin, generally 10%–30% for future expansion.

Common ACB rated current ratings: 630A, 800A, 1000A, 1250A, 1600A, 2000A, 2500A, 3200A, 4000A–6300A.

In principle, the long-term operating current should be ≤ 80%–90% of the ACB rated current.

IV. Checking Short-Circuit Breaking Capacity

Many customers overlook this point when selecting circuit breakers, but it's crucial. Insufficient breaking capacity can cause serious safety hazards.

The short-circuit current at the installation point needs to be determined, calculated from transformer capacity, impedance, and cable length.

Select a matching breaking capacity: Icu / Ics ≥ the system's maximum short-circuit current.

Common ratings: 50kA, 65kA, 80kA, 100kA.

V. Selecting Circuit Breaker Structure

Fixed ACB: Low cost, maintenance requires power outage.

Drawer-type ACB: Convenient maintenance, supports uninterrupted maintenance, more commonly used in industrial projects.

VI. Determining Distribution Box Cabinet Specifications and Structure

Cabinet dimensions depend on ACB specifications, busbar capacity, and the number of outgoing circuits. The main types are wall-mounted and floor-standing.

Protection rating: Indoor: IP30 / IP40; Outdoor: IP54 / IP65.

VII. Busbar and Outgoing Line Configuration Selection

Busbar specifications should be selected based on the rated current and copper busbar cross-section, taking into account temperature rise and long-term operation.

Outgoing line circuit types: MCCB outgoing line, MCB outgoing line, direct cable outgoing line.

Is a backup circuit required? If so, reserve space for future capacity expansion.

VIII. Intelligent Features and Accessory Configuration

Optional functions include: current, voltage, and energy monitoring; communication interface; remote opening and closing; fault alarm and status feedback.

Intelligent type is recommended for factory, data center, and public building projects.

IX. Environmental and Usage Condition Verification

Please confirm the following environmental factors:

Ambient temperature (derating required for high temperatures)

Installation altitude

Presence of dust, humidity, or corrosive gases

Is seismic design required?