1. Miniature Circuit Breakers (MCB) Multi 9

2. Definition Protect cables against overloads and short circuits
Main functions
Protect cables against overloads and short circuits
Let the current flow without overheating on cables
Open and close a circuit under rated current
Protect against insulation faults (see earth leakage protection module)
Symbol
Miniature circuit = switch + trip unit breaker (MCB) 4

3. Definition A mechanical system to open and close the circuit
A Multi 9 circuit breaker has:
A mechanical system to open and close the circuit
A bimetal strip to act against overloads
A magnetic trip to act against short circuits
Miniature circuit = switch + trip unit breaker (MCB) 4

4. Definition It has standardized modular dimensions
Main performances
It has standardized modular dimensions
£ 125A o £ 50 kA o £ 440 V CA
It fits in your pocket... 4

5. Definition The modular design meets 2 criteria:
o mounting on a 35 mm symmetrical rail
dimensions - modules in widths of mm external part = 45 mm - depth between 55 and 70 mm
Multi 9 standard o Multi 9 switchgear comes in 9 mm pitch 4
44 maxi
21.3 81
width
45 maxi 35
symmetrical
rail
10 maxi 60
external
part
depth

6. The technology Active parts C60N NC100 / NC125 4 terminal terminal
bimetral strip
fixed contact
movingcontact
strip braid
moving
contact
strip braid
magnetic trip
magnetic trip
strip braid
bimetal strip
load side terminal
load side terminal 4

7. Overload protection
A bimetal strip is used: o to protect the cable against overloads o symbol:
principle of the bimetal: in a Multi 9 circuit breaker 4
NC45
NC100 / NC125
bimetal
tripping bar
tripping bar
bimetal
screw
calibration
strip
braid

8. Overload protection Thermal tripping curve
the "thermal" part of the tripping curve must be in accordance with the standard
t (s)
tripping no
tripping
destruction
of bimetal
accuracy
Legend: In = rated current Ind = no tripping current Id = tripping current 4 In
Ind Id
I/In

9. Overload protection
Temperature derating o our circuit breakers do not have temperature compensation o if the calibration temperature is different from the ambient temperature: derating is required
Simultaneous multi-pole tripping 4

10. Short-circuit protection
Short-circuit current is given as RMS or peak (Isc or Îsc) RMS = Root Mean Square in symmetrical DC (with PF = I)
Short-circuit protection must limit thermal stress in the cable in order to prevent cable damage (which may reach vaporization of the copper in some cases)
Comments slide 29

11. Short-circuit protection
The arc in Multi 9 circuit breakers
NC45
NC100 / NC125
arcing
horn
arcing
horn
"By-pass" technique for the protection of sensitive parts of the circuit breaker DC breaking is difficult
"By-pass" technique for the protection of sensitive parts of the circuit breaker (magnetic trip)
2 breaking techniques used by Multi 9 4

12. Short-circuit protection
Magnetic tripping curve
t (s)
destruction
of the solenoid
tripping no
tripping
Legend: Ind = no tripping current Id = tripping current
Ind Id
I/In
Our curves are instantaneous tripping curves 4

13. The magnetic tripping levels with high inrush current: like LV/LV transformers
C Curve o 5 and 10 In control and protection of circuits with high short-circuit current in industrial and domestic distributions
D and K curves tripping betwen o tripping: 10 to 14 In; more particulary adopted for installations with high inrush currents like LV/LV transformers
Z curve o 2.4 to 3.6 In protection against electronic circuits
MA curve o 12 In; protection only against short-circuit and high inrush currents such as motors, coil 4
B curve
o 3 and 5 In protection low short-circuit current generators M G

14. Marking Side panel marking:
Front panel marking:
Circuit breaker marking is governed by strict rules in accordance with the standards and decisions made by the manufacturer 4

15. Choosing a circuit breaker
In conclusion
A Multi 9 circuit breaker is determined by: o rating o breaking capacity
number of poles o voltage o tripping curve
standard o frequency o type of load 4

16. Auxiliaries: C60 OF SD MX+OF MN C60 SD: alarm switch
4 types of auxiliaries for our Multi 9 circuit breakers o OF: indication switch
SD: alarm switch
MX + OF: shunt trip o MN: undervoltage release OF SD
MX+OF MN
C60
44/3
53/3
54/3
52/3
51/3
54 mm maxi
The information is transmitted via a mechanical link C60/NC100 and NC125 auxiliaries are not compatible 4

17. Auxiliaries: NC100 - NC125 OF SD NC100H MN or MX+OF or Vigi
4 types of auxiliaries for our Multi 9 circuit breakers o OF: indication switch
SD: alarm switch o MX + OF: shunt trip o MN: undervoltage release OF SD
NC100H
MN or
MX+OF
or Vigi
33/3
34/3
27/3
35/3
36/3
The information is transmitted via a mechanical link C60/NC100 and NC125 auxiliaries are not compatible 4

18. End presentation