Miniature Circuit Breakers (mcb) Multi 9 Definition Protect cables against overloads and short circuits

Miniature Circuit Breakers (MCB) Multi 9

Definition

• 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)

Definition

• A mechanical system to open and close the circuit

• A bimetal strip to act against overloads

• A magnetic trip to act against short circuits

Definition

• It has standardized modular dimensions

•  125A   50 kA   440 V CA

Definition

• The modular design meets 2 criteria:

•  mounting on a 35 mm symmetrical rail

• dimensions - modules in widths of 17.5 mm + 0.5 - 0 - external part = 45 mm - depth between 55 and 70 mm

The technology

Overload protection

• A bimetal strip is used:  to protect the cable against overloads symbol:

• principle of the bimetal: in a Multi 9 circuit breaker 

Overload protection

• Thermal tripping curve

• the "thermal" part of the tripping curve must be in accordance with the standard

Overload protection

• Temperature derating  our circuit breakers do not have temperature compensation  if the calibration temperature is different from the ambient temperature: derating is required

Short-circuit protection

Short-circuit protection

Short-circuit protection

The magnetic tripping levels with high inrush current: like LV/LV transformers

• B curve

•  3 and 5 In protection low short-circuit current generators

Marking

• Side panel marking:

Choosing a circuit breaker

Auxiliaries: C60

• SD: alarm switch

• MX + OF: shunt trip  MN: undervoltage release

Auxiliaries: NC100 - NC125

• SD: alarm switch  MX + OF: shunt trip  MN: undervoltage release

End presentation