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Which device used for excess current protection?
Rewirable fuse
Cut out fuse
Miniature Circuit Breaker (MCB)
ICDP main switch
Miniature Circuit Breaker (MCB)
A Miniature Circuit Breaker (MCB) is a modern electromechanical device used for the automatic protection of electrical circuits against overcurrent, which may result from an overload or a short circuit.
A Miniature Circuit Breaker (MCB) is a modern electromechanical device used for the automatic protection of electrical circuits against overcurrent, which may result from an overload or a short circuit.
ItrippingтАЛ=IthermalтАЛ+ImagneticтАЛ тАФ Total trip current logic
Q=I2Rt тАФ Heat generated in bimetallic strip leading to thermal trip
MCBs utilize two distinct mechanisms: thermal tripping and magnetic tripping. The thermal mechanism uses a bimetallic strip that bends upon overheating from sustained overcurrent (overload), while the magnetic mechanism uses a solenoid with a plunger that reacts instantaneously to high current spikes (short circuit) to trip the mechanism.
MCBs are safer and more convenient than rewirable fuses because they do not require replacement after operation.
They are categorized by tripping curves (e.g., Type B, C, D) based on their sensitivity to inrush currents.
Operating current usually ranges from 0.5A to 125A in standard domestic applications.
They provide both overload and short-circuit protection in a single compact housing.
Reusable without replacement
Visible trip indication
Faster response time compared to traditional fuses
Safe handling for the end-user
Higher initial cost compared to simple fuse wires
Requires precise calibration during manufacturing
Sensitive to high ambient temperatures if not de-rated
Domestic lighting and power circuits
Industrial distribution boards
Commercial building electrification
| Feature | Rewirable Fuse | MCB |
|---|---|---|
Reusability | No (Destroyed) | Yes (Resetable) |
IE Rule 32 focuses on the installation of cut-outs or circuit breakers at the point of commencement of supply.
Rewirable fuses (Option A) are obsolete in modern installations due to lack of discrimination and slow response times.
ICDP (Iron Clad Double Pole) switches are primarily for isolation and do not typically offer sensitive overcurrent protection.
C is correct тАФ Miniature Circuit Breaker (MCB) is the industry-standard protective device that automatically switches off the circuit during overcurrent or short-circuit faults.
Always remember that MCBs are current-sensitive devices, while RCDs (Residual Current Devices) are leakage-current sensitive; don't confuse them.