Low-voltage miniature circuit breakers · B, C and D tripping curves, 1.13/1.45 In thermal limits, breaking capacity, endurance, ratings
A miniature circuit breaker (MCB) is a DIN-rail switch that opens a low-voltage circuit automatically, with a time delay on overload and instantaneously on short circuit. Ask three things first: which tripping curve suits the load's inrush current, what breaking capacity the board's fault level needs, and the rated current, poles and voltage.
Low-voltage miniature circuit breakers for AC distribution boards, consumer units and control panels, with notes on DC and moulded-case types. Medium- and high-voltage vacuum and SF6 breakers, residual-current devices on their own, and fuses are outside this page.
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01
VIOX's VOB3-63 MCB, built to IEC 60898-1, lists instantaneous tripping bands of B (3–5 In), C (5–10 In) and D (10–20 In) for resistive, general-purpose and high-inrush loads respectively. Its thermal limits are a non-trip time of 1 h at 1.13 In from cold and a trip within 1 h at 1.45 In from hot for ratings up to 63 A (2 h above 63 A), at a 30 °C reference temperature. [1]
Fuji Electric's BC63 MCB, also to IEC 60898-1, offers Curve C at 5–10 In for illumination distribution and Curve D at 10–14 In for industrial distribution. The D band therefore differs between makers' datasheets, so check the band printed for the exact model. [2] CNC Electric lists its MCB ranges with B, C and D curve options, for example YCB9-125 at 10–125 A with B/C/D and YCB7-125N with C/D only. [3]
Editorial calculation: for a 16 A breaker, the instantaneous release trips between 48 and 80 A on curve B, 80 and 160 A on curve C, and from 160 A up to 320 A on VIOX's D band or 224 A on Fuji's; the thermal release must not trip at 1.13 × 16 ≈ 18.1 A within 1 h and must trip at 1.45 × 16 = 23.2 A within 1 h. [1] [2]
Give the supplier the circuit's rated current, load type and inrush (lighting, sockets, motors, transformers), the prospective short-circuit current at the board, number of poles, supply voltage and frequency, ambient temperature in the enclosure, and any accessories (auxiliary, alarm or shunt trip).
02
Fuji rates its BC63 Curve C breakers at 6 kA for 1–40 A and 4.5 kA for 50 and 63 A, and Curve D at 4.5 kA for 1–40 A, all at 230/400 V AC. It specifies 10,000 mechanical operations, operation from −35 °C to +70 °C up to 2,000 m, 25 mm² wiring capacity and 35 mm DIN-rail mounting. [2] VIOX rates the VOB3-63 at 6 kA with 500 V insulation voltage, 4 kV impulse withstand, 20,000 mechanical and 4,000 electrical operations, IP20 and 18 mm per pole. [1]
CNC Electric's ranges show how breaking capacity varies within one maker: YCB6-63 at 3 kA (4.5 kA H version), YCB9-80M/H at 6 or 10 kA, and YCB9-63R at 15 kA for 1–63 A and 25 kA for 1–40 A. [3]
Beyond the MCB range, Andeli lists its AM9 moulded-case circuit breakers for up to AC 600 V/DC 250 V and 630 A, and an ADB3-63DC miniature breaker for DC up to 1,000 V and 63 A, citing IEC 60898-2. [4]
03
The suppliers linked to this page list miniature circuit breakers; their cards link to the pages reviewed.
Ask any supplier for the standard and certificates, tripping curve bands as printed for the model, breaking capacity at your voltage, rated currents and poles, endurance, temperature derating, terminal capacity, accessories and the test reports behind the ratings.
04
This is a functional reference built from the sources cited; it is not one maker's specification.
| Part | Role | Fix in the order |
|---|---|---|
| Overload (time-delay) release | Trip on overload (1.13/1.45 In). [1] | Rated current. |
| Instantaneous release | Trip instantly on short circuit. [1] [2] | Curve B, C or D. |
| Contacts and arc quenching | Break the fault current. | Breaking capacity. |
| Operating mechanism and handle | Switch and show position. [1] | Indicator; lock-off. |
| Terminals | Connect conductors. [2] [1] | Capacity, e.g. 25 mm². |
| DIN-rail clip | Mount on 35 mm rail. [2] | Rail type. |
05
An MCB quotation needs values for your circuits. The table explains each field, gives published values where a reviewed source states them, and says what to obtain from the supplier.
| Field | What it means and published values | Ask the supplier for |
|---|---|---|
| Rated Current (A) | e.g. 1–63 A; 10–125 A. [1] [3] | Ratings needed. |
| Rated Voltage (V AC) | e.g. 230/400 V; 240/400 V. [2] [1] | Voltage per pole count. |
| Breaking Capacity (kA) | e.g. 4.5 kA, 6 kA; up to 25 kA. [2] [1] [3] | Rating at your voltage. |
| Tripping Curve | B 3–5, C 5–10, D 10–20 In (D 10–14 In at Fuji). [1] [2] | Band for the model. |
| Number of Poles (P) | 1P to 4P; 1P+N. [1] [3] | Poles. |
| Rated Frequency (Hz) | 50/60 Hz. [1] [2] | Frequency. |
| Mechanical Endurance (cycles) | e.g. 10,000; 20,000. [2] [1] | Operations. |
| Electrical Endurance (cycles) | e.g. 4,000. [1] | Operations at rated load. |
| Operating Temperature (°C) | e.g. −35 to +70 °C; reference 30 °C. [2] [1] | Range and derating. |
| Degree of Protection | e.g. IP20. [1] | IP code. |
| Terminal Capacity (mm²) | e.g. 25 mm². [2] [1] | Conductor range. |
| Mounting Type (mm DIN rail) | 35 mm DIN rail. [2] | Rail. |
| Weight (kg) | Per pole. | Mass. |
06
Paste it into your enquiry below or into an email to a maker, then replace every bracket.
Circuits: [rated current; load type; inrush] Fault level: [prospective short-circuit current] Breaker: [curve; poles; voltage; frequency] Environment: [enclosure temperature; altitude] Accessories: [auxiliary; alarm; shunt trip] Documents: [standard; certificates; test reports]
These companies list miniature circuit breakers.
Lists YCB-series miniature circuit breakers from 3 kA to 25 kA with B, C and D curves.
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Explore company information and manufacturing capabilities, then discuss the scope of your project with a relevant supplier.
They trip instantly at different multiples of rated current: VIOX lists B at 3–5 In, C at 5–10 In and D at 10–20 In, for resistive, general and high-inrush loads; Fuji gives D at 10–14 In. [1] [2]
VIOX states no trip within 1 h at 1.13 In from cold and a trip within 1 h at 1.45 In from hot, for ratings up to 63 A. [1]
Sources checked 2026-10-11. Fuji Electric and VIOX publish MCB datasheets; CNC Electric and Andeli are suppliers linked to this page.
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