Technical Guide
A practical guide to the C&J Electrical CJM13-63 MCB: how it works, where it fits, and what to specify
Every final circuit ends with a decision: what protects it, and how much space that protection takes. A miniature circuit breaker answers both at once — overcurrent protection, manual switching and isolation in one modular device that clips onto a 35 mm DIN rail and occupies just 17.8 mm per pole.
This article explains how an MCB operates, what the B, C and D curves mean in practice, and where the CJM13-63 from C&J Electrical fits into modern distribution.
01 Overview: What the CJM13-63 Is
The CJM13-63 is a miniature circuit breaker built by C&J Electrical (Zhejiang C&J Electrical Co., Ltd.) to IEC/EN 60898-1, the standard governing circuit breakers for household and similar installations. It covers the range most distribution boards actually need: 1 A to 63 A in thirteen steps, 1P, 1P+N, 2P, 3P, 3P+N and 4P configurations, AC 230 V / 400 V at 50/60 Hz, B, C and D curves, and 6 kA or 10 kA breaking capacity (Icu) with Ics of 6 kA or 7.5 kA.
Three details matter beyond the headline numbers. The device protects circuits carrying current up to 63 A, so one family serves both a lighting final circuit and a small sub-main. The 10 kA version gives headroom on supplies where prospective fault current exceeds what a 6 kA device can interrupt. And because it suits main switch duty, it can also sit at the incoming position of a single-phase board and isolate the whole installation.
02 How a Miniature Circuit Breaker Operates
An MCB protects against two different faults with two different mechanisms inside the same moulded case.
Thermal protection, for overloads
A bimetal strip carries the load current. Above the rated value it heats and bends, and since deflection follows the square of the current the response is inverse-time: a 1.3 times overload is tolerated for a long period, a 2.5 times overload trips far sooner.
Magnetic protection, for short circuits
A short circuit reaches many times the rating within milliseconds, far too fast for a bimetal. A solenoid coil drives a plunger straight into the trip mechanism instead. This instantaneous element defines the tripping curve.
Arc interruption
Opening a circuit under fault current produces an arc that must be quenched before it damages contacts or case. An arc chute stretches, splits and cools it across a stack of plates until the current cannot be sustained. The mechanism is trip-free.
03 Tripping Characteristics: B, C and D Curves
The curve decides how much inrush the breaker ignores before tripping magnetically.
| Curve | Magnetic trip range | Typical loads |
|---|---|---|
| B | 3–5 In | Resistive loads, lighting, socket outlets on long cable runs, electronics |
| C | 5–10 In | General-purpose circuits, small motors, LED drivers, mixed office loads |
| D | 10–20 In | Transformers, pumps, compressors, welding equipment, large chargers |
All three curves share the same thermal behaviour; only the instantaneous threshold changes. Ics ratings on the CJM13-63 ensure the breaker can be reset and reused.
Technical Specifications
| Standard | IEC/EN 60898-1 |
| Pole configuration | 1P, 1P+N, 2P, 3P, 3P+N, 4P |
| Rated voltage | AC 230 V / 400 V |
| Rated current | 1, 2, 3, 4, 6, 10, 16, 20, 25, 32, 40, 50, 63 A |
| Tripping curve | B, C, D |
| Breaking capacity (Icu) | 6 kA / 10 kA |
| Service capacity (Ics) | 6 kA / 7.5 kA |
| Mechanical life | 20,000 cycles |
| Module width | 17.8 mm per pole |
Application Scenarios
Residential: 1P/1P+N for lighting, sockets, and air conditioning.
Commercial: C-curve for LED drivers, IT equipment and mixed office loads.
Light Industrial: D-curve for transformers and motors with high starting current.
Main Switch: 2P or 1P+N devices for single-phase board isolation.
MCB or MCCB? Where the Two Overlap
MCBs and MCCBs are often presented as different worlds: MCBs for final circuits up to 63 A, MCCBs for feeders from 100 A upwards. In practice, the boundary is less tidy.
The overlap appears in small distribution boards and machine sub-panels where cost and space are primary drivers. MCBs cost considerably less and take up less space in a control panel.
Product Advantages of the CJM13-63
- ✓ High breaking capacity: 6 kA and 10 kA versions in a compact 17.8 mm pole width.
- ✓ Complete range: 1–63 A, three curves and six pole configurations.
- ✓ Visible contact position: Supports safe isolation and lock-off routines.
- ✓ Practical terminals: Clamp-type pillar terminals for up to 50 mm² rigid conductors.
Frequently Asked Questions
What is the difference between 6 kA and 10 kA MCBs?
It is the rated short-circuit breaking capacity. Select a rating above the calculated fault level with margin for supply changes.
Should I use a B, C or D curve?
B for resistive loads, C for general-purpose, and D for high-inrush loads like pumps and compressors.
Contact C&J Electrical
If you are specifying protection for a distribution board or planning a private-label range, our team can help.
Zhejiang C&J Electrical Co., Ltd.
Miniature circuit breakers, residual current devices, and distribution accessories.
Post time: Nov-13-2026