1. Magnetic Blow-Out:
- Principle: This method utilizes the electromagnetic forces generated by the interaction of the arc current and the magnetic field produced by a coil.
- Mechanism: The magnetic field exerts a force on the arc plasma, causing it to move and elongate. As the arc length increases, its resistance also increases, leading to a reduction in current and eventual arc extinction.
2. De-Ion Grid:
- Principle: De-ion grids are used in conjunction with magnetic blow-out to enhance arc extinction.
- Mechanism: The grids consist of metal plates or bars arranged with a small gap between them. As the arc passes through the grids, it comes into contact with the metal surfaces, causing ionization of the arc plasma. The de-ionized gases are then cooled and condensed, contributing to the interruption of the arc.
3. Arc Runner:
- Principle: Arc runners are employed in some ACBs to provide a controlled path for the arc to move during interruption.
- Mechanism: The arc runner is a conductive material with a high resistance compared to the main circuit. When the arc is initiated, it is attracted towards the arc runner due to the difference in potential. As the arc moves along the arc runner, its energy is dissipated, leading to arc extinction.
4. Vacuum Interruption:
- Principle: Vacuum interrupters utilize the high dielectric strength of a vacuum to extinguish the arc.
- Mechanism: In a vacuum environment, the absence of gas molecules prevents the formation of an arc. When the contacts open in a vacuum, the current is interrupted, and the arc is effectively extinguished.
5. Gas Blast Interruption:
- Principle: Gas blast interrupters use a high-pressure gas to rapidly cool and de-ionize the arc plasma.
- Mechanism: During interruption, a high-pressure gas (such as sulfur hexafluoride or nitrogen) is forced through the arc region. The high-velocity gas flow disrupts the arc, removes heat from the plasma, and facilitates arc extinction.
The selection of a particular arc extinction method in ACBs depends on various factors, including the voltage level, current rating, interrupting capacity, and specific design considerations. These methods are engineered to provide reliable and efficient arc interruption, ensuring the safety and functionality of electrical circuits and equipment.