Circuit Breakers

Miniature circuit breakers (MCB) for electrical panels

Miniature circuit breakers (MCB) provide automatic disconnection in case of overload (thermal trip) or short circuit (magnetic trip). They are used in electrical distribution boards to protect circuits, outlets and loads in residential, commercial and industrial environments.

How they work

Thermal protection: trips on sustained overloads linked to conductor heating.
Magnetic protection: trips quickly on high fault currents typical of short circuits.

Typical use cases

Distribution in residential panels and small sub-boards.
Commercial/industrial panels for auxiliary lines, control circuits and dedicated loads.
Circuit protection for lighting, sockets, HVAC and small motors (depending on the selected curve).

Selection checklist (technical)

Correct selection requires consistency between the circuit, cable sizing and the prospective short-circuit current at the installation point. Follow applicable standards and project requirements.

Rated current (In): must match conductor cross-section and expected load.
Trip curve: typically B, C, D (and others depending on manufacturer) according to inrush currents:
- B: resistive loads and low inrush (traditional lighting, standard outlets).
- C: general use with moderate inrush (power supplies, small motors, mixed loads).
- D: high inrush (motors, transformers, significant inductive loads), where applicable.
Breaking capacity (Icn/Icu): must be suitable for the prospective fault current at the installation point.
Number of poles: 1P, 1P+N, 2P, 3P, 3P+N, 4P depending on the network and isolation requirements.
Rated voltage and frequency: ensure compatibility with the supply (e.g., 230/400V, 50/60Hz depending on model).
Mounting: typically on DIN rail; check module width and accessory options (auxiliary contacts, shunt trips, etc. where available).

Installation notes and coordination

Selectivity and coordination: in multi-level protection schemes, evaluate coordination with upstream devices (selectivity, back-up protection).
RCD protection: for protection against indirect contact, an RCD may be required, or an RCBO where applicable.
Ambient conditions: temperature, panel ventilation and grouping can affect tripping behaviour and current carrying capacity.

FAQ

What is the difference between B and C curves?
The curve defines the magnetic trip threshold (inrush). B is more sensitive (lower inrush), while C tolerates higher inrush and is common for mixed loads and power supplies.

Does breaking capacity really matter?
Yes. It must match the prospective short-circuit current at the installation point. An insufficient rating can compromise safety.

Do I always need an RCD?
It depends on the installation and circuit type. In many cases it is required for personal protection; follow local standards and the electrical design.

Chint NBH8-40 Compact Circuit Breaker 1P+N 6A 4.5kA Curve C 1 DIN Module

SKU: 305190234

In Stock

Interruttori magnetotermici compatti serie NBH8-40 progettati per occupare lo spazio di un solo modulo DIN, 230Vac 6A.

Codici Prodotto: 190234, 073827, 6925808308490