The Differences between Air Circuit Breakers and Residual Current Operated Circuit Breakers
Air circuit breakers (circuit breakers) and residual current operated circuit breakers (residual current circuit breakers) are two important protective devices in electrical circuits. The core differences are as follows, with a clear comparison in terms of functions, principles, application scenarios and other dimensions:
I. Different Core Functions
| Air Circuit Breaker | Residual Current Operated Circuit Breaker |
| The object of protection is the "electrical circuit": | The object of protection is "people + equipment": |
| 1. Overload protection: When the current exceeds the rated value (such as when the total power of electrical appliances is too high), the bimetallic strip heats up and bends, triggering the tripping; | Detect the residual current (leakage current) in the electrical circuit: |
| 2. Short-circuit protection: When the current surges instantaneously (such as when the live wire and the neutral wire are in direct contact), the electromagnetic release acts quickly to cut off the circuit. | When the current in the live wire is not equal to the current in the neutral wire (such as when a person gets an electric shock or the equipment leaks electricity, causing the current to leak to the ground), the zero-sequence current transformer senses the unbalanced current and triggers the tripping. |
| The goal is to prevent the line/equipment from being damaged due to abnormal current. | The core is to prevent electric shock accidents and fires caused by electricity leakage. |
II. Essential Differences in Working Principles
- **Air Circuit Breaker (Circuit Breaker)**:
- Depends on the "thermal effect of current + electromagnetic force":
- In case of overload, the bimetallic strip (metals with different expansion coefficients are bonded together) heats up and bends due to excessive current, pushing the release mechanism;
- In case of short-circuit, the electromagnetic coil generates a strong magnetic field, directly pulling the release to cut off the circuit within 0.1 seconds.
- **Only focuses on whether the total current of the "live wire + neutral wire" exceeds the standard**, and does not distinguish whether the current "leaks" to the ground.
- **Residual Current Operated Circuit Breaker (Residual Current Operated Protective Device)**:
- Depends on the "principle of zero-sequence current balance":
- Under normal conditions, the current in the live wire is equal to the current in the neutral wire, the magnetic flux in the iron core of the zero-sequence transformer is 0, and there is no induced current on the secondary side;
- In case of electricity leakage (such as the leakage current I₀ flowing to the ground), the current in the live wire = the current in the neutral wire + I₀, the magnetic flux is unbalanced, and an electromotive force is induced on the secondary side, driving the release to trip (usually the operating current is below 30mA and the response is within 0.1 seconds).
- **The core is to detect whether there is electricity leakage based on the "current difference between the live wire and the neutral wire"**.
III. Structures and Types
- **Air Circuit Breaker**:
- Basic structure: Contact system (to switch the circuit on and off), arc extinguishing device (to extinguish the short-circuit arc), bimetallic strip (for overload protection), electromagnetic release (for short-circuit protection).
- Types: Single pole (1P, only cuts off the live wire), double pole (2P, cuts off the live wire + neutral wire), etc. 1P and 2P are common in households.
- **Residual Current Operated Circuit Breaker**:
- Core components: Zero-sequence current transformer (to detect electricity leakage), residual current release (to execute tripping), test button (to test whether the function is normal).
- **Two forms**:
1. **Pure residual current operated circuit breaker**: Only has the function of electricity leakage protection and needs to be used in conjunction with an air circuit breaker;
2. **Residual current operated circuit breaker (residual current circuit breaker)**: Integrates an air circuit breaker + a residual current operated circuit breaker, such as the DZ47LE series, which has overload/short-circuit/electricity leakage protection at the same time and is more common in households.
IV. Application Scenarios and Installation Requirements
| Scenario | Air Circuit Breaker | Residual Current Operated Circuit Breaker |
| Household distribution box | Must be installed! As the basic protection for the main switch or each circuit (such as the lighting circuit and the socket circuit) to prevent overload/short-circuit. | Not necessary for all circuits, but it must be installed in the socket circuit (especially in wet places such as the kitchen, bathroom and balcony) to prevent electric shock; the main switch can be a 2P circuit breaker with electricity leakage protection (providing overall protection). |
| Electrical equipment | The circuits of high-power electrical appliances such as air conditioners and water heaters need to be equipped with separate air circuit breakers. | Electrical appliances with metal casings such as electric water heaters, washing machines and refrigerators must be powered through residual current operated circuit breakers to prevent electric shock caused by casing leakage. |
| Industrial/Engineering scenarios | Overload/short-circuit protection for motors, production lines, etc. | Residual current operated circuit breakers must be connected to equipment in construction sites, wet environments and handheld power tools (such as electric drills) to ensure the safety of operators. |
| Operating current | Overload protection current = rated current (such as 16A, 32A); | The leakage operating current is usually 30mA (for households) and 10mA (in high-risk places such as hospitals), which is much smaller than the operating threshold of the air circuit breaker. |
| Short-circuit protection current = instantaneous release threshold (such as 10 times the rated current). |
V. Summary: Differentiation in One Sentence
- **Air circuit breaker**: "Prevent the electrical circuit from malfunctioning" - Protect the line and equipment to avoid being "burned out" due to excessive current;
- **Residual current operated circuit breaker**: "Prevent people from getting injured" - Protect human safety, avoid "electric shock" in case of electricity leakage, and at the same time prevent fires caused by electricity leakage (such as heat generated by electricity leakage due to aging insulation of the line).
**Practical application**: In households, "residual current operated circuit breakers" (integrating the two) are commonly used. For example, a "1P+N residual current circuit breaker" is used for the socket circuit, and a "2P residual current circuit breaker" is used for the main switch, which saves space and achieves comprehensive protection; while for the lighting circuit, due to the low risk of electric shock, an air circuit breaker (1P) can be used alone.
