1. Projekt Anglicky v odborných předmětech, CZ.1.07/1.3.09/04.0002
Anglicky v odborných předmětech "Support of teaching technical subjects in English“
Tutorial: Mechanic - electrician
Topic: Basics of electrical engineering
the 2nd. year
Three-phase current
Circuit breaker
Prepared by: Škarka Miloš
Projekt Anglicky v odborných předmětech, CZ.1.07/1.3.09/
je spolufinancován Evropským sociálním fondem a státním rozpočtem České republiky.

2. Circuit breaker
The circuit breaker is an electric device, which during the excessive current (so called over current) (usually during overload or short-circuit) automatically disconnects electric circuit and by that protects operating personnel against possible injury caused by an electric current and protected electric device against damage.

3. Circuit breaker main functions
Circuit breaker provides in electric circuit these basic functions:
Safe automatic disconnection of the circuit in case of short-circuit
Safe automatic disconnection of the circuit in case of overcurrent
Manual disconnection of the circuit
Manual connection of the circuit

4. Main parameters of circuit breakers
Circuit breaker characteristic values are:
Nominal voltage, which it is designed for
Nominal current, which is permanently transmitted without circuit disconnection
Short-circuit current, which is able to turn off (on ordinary home appliances typically 6 to 25 kiloampers).
Disconnection characteristic determines the dependence of the disconnection time on the amount of overcurrent or short-circuit current.

5. Example of the circuit breaker design
Control lever
Locking mechanism
Contacts
Supply bolt terminal
Bimetal component for overload facilities
Regulation component for sensitivity setting (usually not on ordinary home circuit breakers)
Electromagnetic trigger for short-circuit facilities
Quenching chamber

6. One-pole circuit breaker
Three-pole circuit breaker
Connection of the pad and circuit breakers using connection battens

7. Color marking according to the nominal current
grey
20 A
blue
25 A
yellow
32 A
purple
40 A
black
50 A
white
63 A
copper
0,2 A - 1,6 A
black
2 A
pink
4 A
brown
6 A
green
8 A
Light green
10 A
red
13 A
sand

8. Disconnection characteristics
Usage: for electric circuits protection
B – with devices not causing current impacts (protection of lines)
C – with devices causing current impacts (bulb groups, lines with motors)
D – with devices causing high current impacts (transformers, two-pole motors)

9. Describe and explain:
Main components of the current breaker in picture 1
Current breaker main functions
Main parameters of current breakers
Current breaker characteristics
Picture 1

10. Literature http://www.bonega.cz http://www.google.cz