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Miniature Circuit Breakers (MCB) for Residential and Commercial Distribution | 6A-63A | 6kA-10kA
Electrical Circuit Protection-MCB
KRIPAL manufactures miniature circuit breakers (MCBs) in the UKB5, UKB7, UKNT50 and UKBH series for final circuit overcurrent and short-circuit protection in residential, commercial and light industrial distribution boards. Rated from 1A to 63A with a breaking capacity of 6kA or 10kA per IEC/EN 60898-1, these MCBs provide protection for lighting circuits, socket outlets, appliance circuits and motor feeders. The thermal-magnetic trip unit combines a bimetallic strip for overload protection (thermal, with an inverse time-current characteristic) and a magnetic coil for instantaneous short-circuit tripping (within 0.1 second at 3-5 In for B-curve, 5-10 In for C-curve and 10-20 In for D-curve). Available in 1P, 1P+N, 2P, 3P, 3P+N and 4P configurations, KRIPAL MCBs occupy a standard 18mm modular width per pole on a DIN-rail, with busbar-compatible terminals that accept both pin-type and fork-type busbars for rapid multi-pole installation. Certified to IEC/EN 60898-1 with CE and UKCA marking, KRIPAL MCBs are shipped factory-direct to distribution board manufacturers, electrical wholesalers and OEM panel builders worldwide.
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UKB5 MCB 6-63A 2Pole 6kA Semko CE Certified
The UKB5-63 series Miniature Circuit Breaker (MCB) is a core protection device designed for modern residential and commercial electrical installations.
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UKB5 MCB 6-63A 1Pole 6kA Semko CE Certified
The UKB5-63 series Miniature Circuit Breaker (MCB) is a core protection device designed for modern residential and commercial electrical installations.
Ask a QuoteMCB Technical Guide: Protecting Final Circuits from Overload and Short Circuit
A miniature circuit breaker provides automatic overcurrent protection for final circuits in low-voltage electrical installations up to 440V AC. The MCB detects two types of fault: sustained overload (current slightly above the circuit rating for minutes to hours, caused by too many appliances on one circuit) and short-circuit (current hundreds of times the circuit rating for milliseconds, caused by a direct phase-to-neutral or phase-to-earth fault). The thermal element responds to overloads with a time delay that mimics the heating characteristic of the circuit cable, while the magnetic element responds to short-circuits with no intentional delay to minimize the let-through energy. This selection guide covers current rating, trip curve, pole count and breaking capacity to match your distribution board circuit requirements.
MCB Series Technical Specifications
Trip Curve Selection: B, C or D
The trip curve determines the instantaneous magnetic trip threshold. B-curve (3-5 In) is for resistive circuits with low inrush current: lighting, electric heating, cookers. C-curve (5-10 In) is the general-purpose choice for socket outlet circuits, small motors up to 3 kW and most commercial applications where moderate inrush from electronic power supplies is expected. D-curve (10-20 In) is for circuits with high inrush current: transformers, large fluorescent lighting banks with magnetic ballasts, X-ray machines and industrial motors above 3 kW. Selecting the wrong curve leads to nuisance tripping (curve too low for the inrush) or inadequate protection (curve too high, circuit cable overheats before the magnetic trip activates).
Breaking Capacity and Supply Impedance
The MCB breaking capacity (Icn) must exceed the maximum prospective short-circuit current at the point of installation. KRIPAL MCBs are available in 6kA (standard for domestic and most commercial installations) and 10kA (for installations close to the distribution transformer where the supply impedance is lower and fault currents are higher). The 10kA UKNT50 series uses a reinforced arc chamber with additional splitter plates to handle the higher arc energy. For installations where the prospective fault current exceeds 10kA, back-up protection by an upstream HRC fuse or MCCB with a higher breaking capacity is required, and the MCB and fuse must be from the same manufacturer (or tested together) to ensure coordinated operation per IEC 60898-1 Annex E.
Pole Configuration for Single and Three-Phase Circuits
The pole count is determined by the circuit type. Single-phase circuits (230V) use 1P (switched line, solid neutral) or 1P+N (switched line and neutral, with the neutral pole switching simultaneously). Three-phase circuits (400V) use 3P for balanced loads without neutral or 3P+N for loads requiring a switched neutral. The 2P configuration is used for single-phase circuits where both poles must be switched for safety (caravan park supplies, medical IT systems) or for 400V phase-to-phase single-phase loads. All multi-pole KRIPAL MCBs use an internal toggle linkage that mechanically couples the poles, ensuring that an overload or short-circuit on any single pole trips all poles simultaneously, preventing single-phasing of three-phase motors.
Busbar Compatibility and Installation Efficiency
KRIPAL MCBs feature a dual-function terminal that accepts both cable (up to 25 sq mm for the 63A frame) and pin-type or fork-type busbars without an adapter. The busbar terminal is located at the bottom of the MCB, and a single continuous busbar can feed up to 36 MCBs in a distribution board row, eliminating 72 individual cable terminations (36 line plus 36 neutral connections) and reducing installation time by approximately 60 percent. The busbar is insulated for IP2X finger protection per IEC 60529, and end caps are supplied to cover the exposed busbar ends. For three-phase distribution boards, a 4-pole busbar system (L1, L2, L3, N) feeds the MCBs in sequence, with each row of MCBs connected to one phase to balance the three-phase load across the distribution board.
Specify MCBs for Your Distribution Board Production
- MCB Selection Tool: Provide your circuit schedule (load type, cable size, supply impedance) and we return the optimal MCB rating and curve for every circuit.
- Busbar Design Support: Request 3D models of our busbar-compatible MCBs for your distribution board layout, with recommended busbar lengths and phase allocation.
- OEM Volume Supply: Container-level pricing on MCB bulk packs (100 units per carton) with your choice of curve, rating and certification marking.
Final Circuit Protection in Residential, Commercial and Industrial Buildings
KRIPAL MCBs protect individual final circuits in low-voltage electrical installations across residential, commercial and industrial sectors. From a single lighting circuit in a domestic consumer unit to a motor feeder in a factory distribution board, the correct MCB selection ensures that a fault on one circuit does not disrupt the supply to healthy circuits.
Residential Consumer Unit Circuit Protection
A typical domestic consumer unit in a UK or European home contains 8-16 MCBs protecting individual circuits: 6A B-curve for lighting, 16A B-curve for immersion heater, 32A B-curve for ring-main socket outlets, 32A C-curve for electric shower, and 40A B-curve for electric cooker. The MCBs are fed from a split busbar with one or two RCCBs providing earth leakage protection for groups of circuits. The 6kA breaking capacity is adequate for domestic installations where the supply impedance at the consumer unit is typically above 0.25 ohms, limiting the prospective fault current to below 1kA for a 230V single-phase supply. The busbar system allows the electrician to install all MCBs in under 10 minutes during a consumer unit replacement, minimizing the time the household supply is disconnected.
Commercial Office Building Distribution Board
Commercial distribution boards serving office floors use KRIPAL MCBs in C-curve for the majority of circuits: 10A for general lighting, 16A for workstation socket outlets, 20A for server room UPS input, 32A for air conditioning indoor units, and 63A for the floor-level sub-main. The C-curve handles the inrush current from the numerous switch-mode power supplies in LED lighting drivers, computer power supplies and phone chargers that collectively draw 5-8 times their steady-state current for the first few milliseconds after energization. The 10kA breaking capacity option is specified for distribution boards in the building’s main switch room where the supply transformer is located in the basement, and the fault current at the main distribution board can exceed 6kA due to the short cable run from the transformer secondary terminals.
Industrial Motor Distribution Board
Factory distribution boards powering three-phase induction motors use KRIPAL D-curve MCBs: 10A D-curve for a 3 kW motor, 20A for 7.5 kW, 32A for 11 kW and 63A for 22 kW (with a star-delta starter to reduce starting current). The D-curve magnetic trip threshold of 10-20 In prevents nuisance tripping during the motor starting inrush, which can reach 6-8 times the motor full-load current for 2-3 seconds on a direct-on-line (DOL) starter. The 3P configuration simultaneously isolates all three phases on a trip, preventing single-phasing that would cause the motor to continue running on two phases, drawing 2-3 times rated current and burning out the stator windings within minutes if not protected by the motor overload relay.
Renewable Energy Inverter AC Output Protection
Grid-tied solar PV inverters (3-100 kW) use KRIPAL C-curve MCBs on the AC output circuit between the inverter and the building’s distribution board. The MCB rating is selected as 1.25 times the inverter’s maximum continuous output current per IEC 60364-7-712. For a 10 kW three-phase inverter with a rated output current of 14.5A per phase, a 3P 20A C-curve MCB provides overcurrent protection for the AC cable while allowing the inverter to export up to 110 percent of rated power (16A) during high-irradiance periods without tripping. The MCB also provides a means of isolation for inverter maintenance, complying with the requirement for a lockable AC isolator within sight of the inverter.
EV Home Charger Supply Circuit
A 7.4 kW single-phase EV home charger (32A continuous) is protected by a KRIPAL 40A B-curve MCB in the consumer unit, with the MCB sized at 125 percent of the charger’s rated current per IEC 60364-7-722 for EV charging installations. The B-curve is preferred over C-curve because the EV charger power electronics include a soft-start circuit that limits inrush current, and the lower magnetic trip threshold provides faster disconnection in the event of a short-circuit in the charging cable or the vehicle’s onboard charger. The MCB is backed up by a Type A RCCB to provide protection against DC leakage currents that can be generated by the charger’s power electronics and would desensitize a standard Type AC RCCB.
Specify MCBs for Your Project
- Circuit Protection Schedule: Send us your circuit schedule and we return a complete MCB bill of materials with ratings, curves and pole configurations.
- Discrimination Study: Request time-current curves for upstream/downstream MCB coordination to ensure a fault on a final circuit does not trip the distribution board incoming MCB.
- Bulk Pack Supply: Order MCBs in bulk packs of 100 per rating for your panel building operation, with individual carton labeling for your stores picking system.
KRIPAL MCB Manufacturing: Precision Protection from Automated Production Lines
KRIPAL miniature circuit breakers are manufactured on high-speed automated assembly lines in Zhejiang where bimetal strips are precision-calibrated, magnetic coils are wound on CNC coil winders, and silver-graphite contacts are resistance-welded to copper carriers. Each MCB undergoes a calibration and instantaneous trip test before shipment to global electrical wholesalers and panel builders.
Automated Bimetal Calibration System
Bimetal strips for each current rating are individually calibrated on automated test stations that apply a controlled overload current while measuring deflection against a laser displacement sensor. Calibration data is recorded per unit, with trip time tolerances held within the IEC 60898-1 time-current band. Strips outside tolerance are automatically rejected.
CNC Magnetic Coil Winding and Impregnation
Solenoid coils for the instantaneous trip mechanism are wound on computer-controlled winding machines that maintain consistent turn count and winding tension across all pole configurations. Completed coils are vacuum-impregnated with high-temperature varnish and tested for turn-to-turn insulation integrity at 2500V before assembly into the MCB mechanism.
Silver-Graphite Contact Assembly
Contact tips made from silver-graphite (AgC) are resistance-welded to copper carriers under precisely controlled current, pressure, and duration parameters. Weld quality is verified on sample assemblies from each production shift by peel-force testing, with minimum peel strength exceeding 80N to prevent contact detachment under short-circuit conditions.
Production-Line Trip Testing
Every MCB undergoes two mandatory tests: a thermal calibration test at 1.45 times rated current (must trip within 1 hour per IEC 60898-1) and an instantaneous trip test at the specified magnetic trip threshold. Test results are logged against the individual serial number or production lot code, with full traceability to calibration data and component batch records.
Distributor Stock Holding Programs for MCBs
KRIPAL supports distributor inventory programs with agreed stock levels for standard MCB models from 1A to 63A across B, C, and D curves. Shipments are planned based on demand data, with scheduled replenishment to maintain stable supply and consistent fill rates.
Private Label and OEM Branding for MCBs
Laser-marked part numbers aligned with your catalog, OEM-branded packaging, and customized multilingual instruction sheets are available. Unbranded supply with neutral packaging is provided upon request for private label production of MCBs.
Multi-Region Certification and Compliance Support
CE, UKCA, and IEC 60898-1 EN 60898-1 compliance documentation is provided according to target export markets. Technical documentation files including EU Declarations of Conformity are maintained and updated in line with evolving regulatory requirements.
Direct Technical Access to KRIPAL Production Engineers
Your technical team communicates with the engineers who designed and calibrated your MCBs, not a distributor’s sales engineer reading from a catalog. Application questions including selectivity coordination and back-up protection receive answers within 24 hours during China business hours.
Frequently Asked Questions
Explore FAQ >B-curve trips magnetically at 3-5 times rated current, ideal for resistive loads and general socket outlets. C-curve trips at 5-10 times In, suitable for motors and fluorescent lighting with moderate inrush. D-curve trips at 10-20 times In for transformers, X-ray machines and equipment with very high inrush currents.
The MCB rated current (In) must be greater than or equal to the circuit design current (Ib) and less than or equal to the cable current-carrying capacity (Iz). In must also be less than or equal to the protective device maximum rating specified for the circuit cable size.
The MCB breaking capacity (Icn) must exceed the maximum prospective short-circuit current at the point of installation. For domestic consumer units near the service entrance, 6kA is typically sufficient. For commercial installations close to the distribution transformer, 10kA may be required.
Yes. All UKB series MCBs are compatible with both pin-type and fork-type busbar systems. Pre-fabricated busbar assemblies reduce panel wiring time and eliminate individual terminal connection errors.
Auxiliary contacts (OF for on/off status, SD for trip alarm), shunt trip releases for remote tripping and undervoltage releases for safety interlock circuits are available as clip-on accessories for the UKB MCB range.
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