WSB5 1P+N MCB 4.5kA Miniature Circuit Breaker

A Miniature Circuit Breaker is a DIN-rail overcurrent protective device that trips automatically to protect wiring against overload and short circuit. It combines a thermal bimetallic strip (which bends and trips on a slow, sustained overload) and an electromagnetic solenoid (which releases instantly on a large short-circuit current), extinguishing the arc in a compact arc chute.

A 1P+N MCB switches both the phase (live) and neutral conductors together but provides overcurrent protection only on the phase pole. Wire the incoming phase (L) to the marked line terminal and the neutral (N) to the marked N terminal, observing the line/load direction, and connect earth separately to the earth bar (never through the breaker).

The 4.5 kA (4500 A) is the rated short-circuit breaking capacity — the maximum prospective fault current the breaker can safely interrupt and clear without damage. If a fault current higher than 4.5 kA could occur at the installation point, the breaker may fail to clear and be destroyed, so its kA rating must be at least the calculated available fault current.

4.5 kA is typically adequate for older or remote installations, smaller final circuits, and locations where the supply impedance and cable length limit the prospective short-circuit current. For modern main panels close to a strong transformer, a 6 kA or higher rating is usually recommended, because fault levels rise near the source.

Tripping curves define the magnetic (instantaneous) trip threshold relative to rated current: Type B trips at 3–5× In (sensitive, resistive lighting/socket loads), Type C at 5–10× In (general commercial/industrial and moderate motor starting), and Type D at 10–20× In (high inrush loads like transformers and large motors). Choose the curve so normal inrush currents do not cause nuisance tripping while faults still clear.

Select the rated current (In) to match the cable it protects and the design current of the circuit: the breaker rating should be no greater than the ampacity of the cable (so the wire is protected), while still carrying the normal load. Derate for ambient temperature and grouping, and confirm the curve suits the load type.

It snaps onto a standard 35 mm DIN rail inside a distribution board — hook the top of the breaker onto the rail and push the bottom until it clicks. Keep the supply OFF before wiring, strip and insert conductors to the marked line and load terminals, and torque the screw terminals to the value in the datasheet.

As a 1P+N single-pole-plus-neutral MCB of this type, it is typically rated for low-voltage single-phase AC (commonly 230 V between phase and neutral, per IEC 60898-1). Always confirm the exact rated voltage on the nameplate, because connecting to a higher or DC voltage than rated is unsafe.

A nuisance or repeated trip usually points to an overload (too many devices on the circuit), a short circuit (often at a socket, appliance, or damaged cable), or an earth fault. First unplug loads to isolate an overload, then check for a failed appliance or damaged wiring; do not simply keep resetting a breaker that trips repeatedly without finding the cause.

Low-voltage MCBs of this type are designed to IEC 60898-1 (the IEC standard for overcurrent protective devices for household and similar installations) and commonly carry CE marking and related safety approvals. Verify the specific certificate and curve/kA markings on the product datasheet before use in a compliant installation.