An Air Circuit Breaker (ACB) is an electrical device that protects low voltage circuits from overcurrent and short circuits. They work by using pressurized air to eliminate arcs that are created when the contacts separate. This keeps the current steady and safe.
The Air Circuit Breaker (ACB) safeties on Ship as per SOLAS are
- Overcurrent protection: This protects the circuit from overloads, which can occur when too much current is drawn from the circuit.
- Long time delay: 105%-120% of FLC, 20-120sec
- Short time delay: 200%-600% of FLC, 0.1-1sec
- Instant trip: 1000% of FLC
- Short circuit protection: This protects the circuit from short circuits, which occur when two conductors come into contact with each other. Short circuits can cause very high currents to flow, which can damage the circuit and even cause fires.
- Earth fault protection: This protects the circuit from earth faults, which occur when a live conductor comes into contact with the earth. Earth faults can be dangerous because they can cause electric shocks.
- Under voltage protection: This protects the circuit from low voltages, which can occur when the voltage supply drops below a certain level. Low voltages can cause equipment to malfunction and can even damage it.
- Reverse power protection: This protects the generator from reverse power flow, which can occur when the generator is running but the main switchboard is not connected to it. Reverse power flow can damage the generator and can also cause blackouts.
- Arc contacts, Arc runner and Arc chutes: Designed to extinguish arcs that can occur when the ACB is opened or closed.
- Arc contacts make first and breaks after main contacts
- Preferential trip
- Differential protection