Air air circuit breaker is a low or high voltage protective device that uses air as an arc extinguishing and insulation medium. Its core function is to protect equipment and people through a quick circuit break. The operating principle can be divided into three stages: normal switching, fault interrupting and arc extinguishing. It combines mechanical and electrical mechanisms for reliable protection. Here's a closer look:
I. Basic Structure and Core Components
The air circuit breaker consists of the following key components, which work together to provide protection:
Liaison system
Motion and static contact: guide circuit when closed, arc when disconnected.
Contact Material: Made of high temperature and arc resistant alloys such as silver tungsten to reduce wear and oxidation.
Arc Fire
Arc grille: Made of metal plates, the arc is divided into short sections, increasing heat dissipation area.
Arc axis: guide the arc into the grid to prevent it from escaping.
Vehicle Services Section (Protection Device)
Thermal Trip Unit: Trip that triggers and provides overload overload protection thermal bending of a bimetallic strip.
Electromagnetic tripping device: The magnetic effect of current is used to generate attraction and quickly interrupt short-circuit circuit current.
Electronic tripping device (optional): Integrated microprocessor for accurate overload, short circuit and ground fault protection.
Operational mechanisms
Energy storage spring: energy storage tripping to ensure a rapid actuation.
Connection mechanism: passes operational force to contacts that are closed or open.
Sleeve and insulation components
Insulating casing (as molded case circuit breakers): Isolates live parts to prevent electrocution.
Framed structure (such as a box breaker): Supports large capacity components to increase mechanical strength.
ii. How it works: From closed to open.
1. Normal closure
Closed contact: The operating mechanism releases energy through the energy storage spring, and the moving contact is in close contact with the static contact, completing the circuit.
Current flow: Current flows to the load through the junction and busbar to ensure the normal operation of the 2. Fault detection and triggering
The starter triggers the circuit faults breaker when:
Overload: When the current exceeds the rated level but does not reach the short-circuit level, the two-metal band of the heat trio bends under the heat, propelling the trip lever and tripping the circuit breaker.
Short circuit: When the current increases rapidly (e.g., several times the rated current), the electromagnetic trip coil produces a strong magnetic field that attracts the armature and directly pulls operating mechanism, causing the circuit breaker to trip.
Undervoltage/Loss of Voltage: When voltage is lower than rated, the low voltage trip is released and the circuit breaker is automatically opened.
3. Tripping Process and Arc Extinguishment
Contact separation: The operating mechanism quickly separates moving contact from stationary contact, creating an arc of electricity between them.
Arc guide: The dome guides the arc into the arc quenching grids that divides the long arc into shorter arcs.
Arc extinguished:
Arc Lengthening: arc length increases increases, the heat dissipation area increases.
Cooling Effect: Air convection removes heat and reduces arc temperature below the critical value required to maintain combustion. Deionization: the arc recombine of ions and electrons in an arc to restore insulating properties.
4. Completed Disconnection
Fully separated contacts: the arc is completely extinguished and the circuit is reliably disconnected.
Reset Preparation: manually or automatically reset the operating mechanism in preparation for the next shutdown.
III. Key technology: optimization of arc Extinguishing Mechanisms
The performance of air breaker has a direct influence on the performance its interrupting performance circuit breaker. Modern design improves arc extinguishing efficiency by:
Multi-stage Arc Extinguishing Grids
Increasing the number of grids leads to finer arc segmentation, allowing faster heat dissipation.
Optimize grid spacing, balance electric field distribution and reduce arc reignition risk.
Applications Gas-Generating Materials
The inner wall of the arc hood is coated with a gas producing material (such as an organic insulating material). The arc decomposes at high temperature to produce gas, forming a high pressure airflow, blowing the arc out, accelerating arc out.
Magnetic arc extinguished
The permanent magnetic field or electromagnetic coil is placed in the arc extinguishing chamber, and the arc is drawn into the arc extinguishing gate by magnetic field, which improves arc extinguishing speed. Current Limiting Technology
Fast contact or current-limiting resistors is used to limit the peak value of short-circuit circuit current and reduce the difficulty of arc extinguishing.
IV. INTRODUCTION Typical Application Scenarios
Air circuit breakers are widely used in the following situations. Choose different types based on volume and functionality:
Low Voltage (≤1250A)
Molded Case Circuit Breakers: used in industrial motor control, commercial distribution, residential lighting and other fields.
Miniature Circuit Breakers: Protects household circuits, such as sockets and lighting circuits.
Medium and High Voltage (630A and above)
Frame-Mounted Circuit Breakers (ACB): major switches for large industrial equipment, power plant outage protection, power supply systems for data centers.
Special Environments
Explosion-proof Air Circuit Breakers: used in chemical plants, coal mines and other flammable and explosive environment.
DC air breaker: protects the DC side of renewable energy generation (e.g. photovoltaic, wind power).
V. Selection and Maintenance Key Points
Selection Parameters
Rated: Matching circuit voltage (e.g. AC 400V, DC 1000V). Rated current: Maximum working current of ≥ circuit with residual amount.
Cutoff capacity: Expected short-circuit current ≥ 50kA, 100kA.
Tripping characteristics: Type B, C or D are selected according to the type of load (Type B is for electronic equipment and Type D is for motor start).
Maintenance Recommendations
Periodic inspection: Observe contact wear and arc quenching grid integrity, dust and foreign body removal.
Functional testing: Manual disconnection and automatic tripping tests are conducted annually to ensure reliable operation.
Environmental control: avoid humidity and corrosive gases, prevent insulation performance decline. VI. INTRODUCTION Air Circuit Breakers vs. Other circuit breakers
Comparison Dimensions: Air Circuit Breaker (ACB) Vacuum Circuit Breaker (VCB) SF6 Circuit Breaker
Arc extinguishing medium: air, vacuum, SF6 Gas
Crushing capacity: medium (medium to low pressure) high (medium to high pressure) very high (medium and ultra-high pressure)
Maintenance costs: High in low (no gas leaks risk) (regular vacuum level checks required) (High (SF6 leak detection required)
Environmental impact: Non-polluting Non-polluting SF6 is a potent greenhouse gas
Uses: Industrial, commercial and residential low-voltage distribution networks; medium-voltage systems for power plants and substations; high-voltage transmission lines
