WSB1-63 MCB Miniature Circuit Breaker

An MCB is a reusable electromechanical switch that automatically protects an electrical circuit from damage caused by overload or short circuit. Unlike a fuse, it does not have to be replaced after it trips — you simply identify and clear the fault, then flip the lever back to ON. It is the most common overcurrent protection device in residential and commercial distribution boards.

Inside the MCB are two independent trip mechanisms. A bimetallic strip heats up under sustained overcurrent and bends to release the latch, giving inverse-time overload protection (longer time for small overloads, shorter for large). A solenoid coil generates a strong magnetic field under very high current and snaps the mechanism instantly, clearing a short circuit in a matter of milliseconds.

The curve defines the instantaneous (magnetic) trip band relative to rated current (In). Curve B trips at 3–5× In and suits resistive loads such as lighting. Curve C trips at 5–10× In and is the standard choice for sockets, small motors, fans and general commercial circuits. Curve D trips at 10–20× In and is for high-inrush loads such as large motors, transformers and welding equipment.

The WSB1-63 series covers 6A through 63A in standard values: 6, 10, 16, 20, 25, 32, 40, 50 and 63 A. The "63" in the model name refers to the maximum frame rating. Choose the smallest standard rating that exceeds your calculated design current but does not exceed the ampacity of the cable it protects.

Breaking capacity (Icn) is the maximum prospective short-circuit current the breaker can safely interrupt. A 6kA breaker clears up to 6,000 A, which is sufficient for most residential boards where cable length limits fault level. A 10kA breaker is required for commercial or industrial panels close to a large transformer, where fault currents can reach 10,000 A; using a 6kA device in that situation risks destruction under fault.

It is rated for AC 230V (phase-to-neutral) / 400V (three-phase) at 50/60 Hz, matching standard low-voltage distribution worldwide. The exact rated voltage is printed on the front of the breaker; do not apply DC or higher voltages, as the arc-quenching design is optimised for AC sinusoidal current zero-crossings.

1P protects a single phase and is used for most single-phase final circuits. 2P switches phase and neutral together for single-phase isolation. 3P switches the three phases of a three-phase circuit without breaking neutral. 4P switches phases plus neutral, used when neutral isolation is required for safety, metering or specific code requirements.

It clips onto a standard 35 mm DIN rail inside a distribution board. The supply conductor goes to the top terminal (marked LINE/IN) and the load conductor to the bottom terminal (LOAD/OUT), with correct polarity observed for single-phase units. Strip only the length recommended by the datasheet, insert the conductor fully into the terminal, and tighten to the specified torque to avoid loose connections that cause overheating.

First, note the timing: a trip after minutes of use suggests overload or overheating, while an instant trip on start-up suggests inrush entering the magnetic band or a hard short circuit. Unplug all loads, reset once, then reconnect appliances one at a time to identify the faulty device. If the breaker trips immediately with all loads disconnected, suspect a fault in the fixed wiring and call a qualified electrician — do not repeatedly reset an MCB that trips under no load.

It is designed and type-tested to IEC 60898-1, the international standard for miniature circuit breakers for household and similar low-voltage overcurrent protection, and carries CE marking for the EU/EEA market. Type tests cover overload and short-circuit performance, temperature rise, mechanical endurance and breaking capacity. Always confirm the certificate number on the product label matches the exact model, rating and curve you are installing.