Miniature Circuit Breakers

Miniature Circuit Breakers David Pitt Product Manager – Eaton Electric Ltd

Construction, Operation, and Application of Miniature Circuit Breakers

MCB Construction 1

13 12 5 3

7

2 10 8

9

11

4 6

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.

Termination clamp Fixed contact Moving contact Instantaneous magnetic trip coil Bimetal thermal trip element Bi-connect terminal clamp Tripping lever Instantaneous trip plunger Operating handle Insulation plates Arc splitter pack Bimetal setting screw DIN rail clip

MCB Construction MOULDED CASE Insulated housing for all components Must have high mechanical and electrical strength Manufactured from high grade engineering polymers / glass reinforced polyester

MCB Construction SWITCHING MECHANISM Opens and closes the contacts Fast make / fast break Trip free MCB - PCI through flag indicator

MCB Construction CONTACTS High grade silver alloy (silver tungsten, silver carbon, silver nickel, etc.) Mechanical strength for high number of switching operations Electrical strength - must resist effects of arcing

MCB Construction TRIP MECHANISM Provides the means to trip the Circuit Breaker under overcurrent conditions: Thermal tripping for overload conditions Magnetic tripping for short circuit conditions

Type-D 10-20xIn / High Inrush Loads

Type-C 5-10xIn / Comm & Ind applications

Type-B 3-5xIn / Domestic applications

Seconds

MCB Trip Characteristics

3 5 10 20 Multiple Rated Current (x In)

Amps

Current limiting feature Serves to minimise fault energy flow and peak cut-off current

MCB Application Miniature Circuit Breakers are ideal for: Final circuit protection in residential, commercial, and industrial applications. Protection of control circuitry and load components in potential applications such as: Solenoids Relay / contactor coils Transformers PLCs Computers Medical Equipment Power Supplies

Typical MCB Specifications Compliance with IEC/BSEN60898 Standard Current ratings from 1A to 63A Short circuit breaking capacity 6kA to 10kA High performance current limiting design B, C, or D trip characteristics Ability to use a wide range of accessories Ability to convert MCB to RCBO with additional earth leakage ‘pod’.

Miniature Circuit Breakers David Pitt Product Manager – Eaton Electric Ltd