What is the working principle of breaker

A breaker, also known as a circuit breaker, is an electrical device designed to protect an electrical circuit from damage caused by overcurrent, overvoltage, or other electrical faults. The working principle of a breaker is based on the concept of thermal and magnetic tripping.

Here's a step-by-step explanation of how a breaker works:

  1. Normal Operation: When the circuit is functioning normally, the breaker is in its "off" position, and the circuit is closed.
  2. Overcurrent Detection: When an overcurrent occurs, the breaker's sensing element (e.g., a thermistor or a current transformer) detects the excessive current flowing through the circuit.
  3. Thermal Tripping: The sensing element generates heat due to the excessive current. If the heat exceeds a predetermined threshold, the breaker's thermal tripping mechanism is triggered.
  4. Magnetic Tripping: Simultaneously, the breaker's magnetic tripping mechanism is also triggered. This is achieved through the interaction between the magnetic field generated by the current and the breaker's magnetic trip coil.
  5. Tripping: When both thermal and magnetic tripping mechanisms are triggered, the breaker's contacts (e.g., the moving contacts and the fixed contacts) separate, interrupting the circuit and disconnecting the power supply.
  6. Reset: After the fault is cleared, the breaker can be reset by manually operating the reset button or by automatically resetting after a predetermined time delay (e.g., 30 seconds).

Types of Breakers:

  1. Molded Case Breakers: These are the most common type of breakers, used in residential and commercial applications.
  2. Ground Fault Circuit Interrupters (GFCIs): These breakers are designed to detect ground faults and interrupt the circuit to prevent electrical shock.
  3. Arc Fault Circuit Interrupters (AFCIs): These breakers detect and interrupt arcing faults, which can cause fires.
  4. High-Voltage Breakers: These breakers are designed for high-voltage applications, such as industrial and commercial power distribution systems.

In summary, the working principle of a breaker involves thermal and magnetic tripping mechanisms that detect overcurrent and overvoltage conditions, triggering the breaker to trip and disconnect the power supply.