Sketch of miniature circuit breaker

Here is a simple sketch of a miniature circuit breaker (MCB):

MCB Sketch

Main Components:

1. Trip Unit: This is the heart of the MCB, responsible for detecting overcurrent and tripping the circuit. It consists of:
   • Thermal Bimetallic Strip: A metal strip that bends when heated by excessive current, triggering the trip mechanism.
   • Magnetic Coil: A coil that generates a magnetic field when current flows through it, also triggering the trip mechanism.
2. Contact Assembly: This is the part that actually breaks the circuit when the trip unit trips. It consists of:
   • Main Contacts: Two metal contacts that make and break the circuit.
   • Auxiliary Contacts: Additional contacts that can be used to trigger alarms or other devices.
3. Housing: The outer casing of the MCB, which protects the internal components and provides a mounting point for the device.

How it Works:

1. When current flows through the MCB, the thermal bimetallic strip and magnetic coil are energized.
2. If the current exceeds the rated value, the thermal bimetallic strip bends, triggering the trip mechanism.
3. The trip mechanism opens the main contacts, breaking the circuit and disconnecting the power supply.
4. The auxiliary contacts can be used to trigger alarms or other devices to indicate the trip.

Dimensions:

• Length: approximately 50-70 mm (2-3 inches)
• Width: approximately 20-30 mm (0.8-1.2 inches)
• Height: approximately 10-20 mm (0.4-0.8 inches)

Note: This is a simplified sketch and actual MCB designs may vary depending on the manufacturer and specific application.