Understanding the Core Differences: ACB vs. MCCB
When designing a low-voltage power distribution system, one of the most critical decisions is selecting the right circuit protection device. Two of the most common options are Air Circuit Breakers (ACBs) and Moulded Case Circuit Breakers (MCCBs) . While both serve the fundamental purpose of protecting electrical circuits from overloads and short circuits, they are designed for different applications, current ranges, and operational environments.
What is an MCCB?
A Moulded Case Circuit Breaker (MCCB) is a type of electrical protection device that features a robust, insulated casing manufactured using a molding process. This structural design provides excellent mechanical strength and electrical insulation, making MCCBs suitable for a wide range of environments, from industrial plants to commercial buildings and residential complexes.
MCCBs are designed to protect electrical circuits from damage caused by overcurrents, short circuits, and other faults. Their key distinguishing feature is the molded housing that contains all internal components, including the operating mechanism, contacts, arc extinguishing chamber, and trip units. This enclosed design enhances safety and durability while maintaining a relatively compact footprint.
The CJMM6 Series MCCB: A Comprehensive Solution
At Zhejiang C&J Electrical Co., Ltd. , we have developed the CJMM6 Series Moulded Case Circuit Breaker to deliver outstanding protection performance across diverse applications. This series represents the perfect balance of versatility, reliability, and advanced technology.
Product Overview
The CJMM6 Series offers an extensive current range from 10A to 2000A, with multiple pole configurations available including 1P, 2P, 3P, and 4P options. This wide selection ensures compatibility with virtually any circuit layout and load requirement. The product family includes various models:
l Fixed type – Standard installation configuration
l Residual current (leakage) type – Enhanced protection against earth faults
l Single-adjustable type – Flexible trip setting adjustments
l Double-adjustable type (CJMM6RT) – Independent thermal and magnetic adjustment
l Electronic type (CJMM6E) – Advanced electronic protection with high integration
l Electronic type with LCD display (CJMM6EY) – Real-time monitoring and remote control capabilities
l Key Technical Parameters
The CJMM6 Series is engineered with impressive technical specifications that ensure reliable performance under demanding conditions:
Rated Voltage & Insulation:
l Rated working voltage (Ue): AC230V/AC400V/AC690V
l Rated insulation voltage (Ui): 1000V
l Rated impulse withstand voltage (Uimp): 8kV
l Breaking Capacity (Icu): The CJMM6 Series offers multiple short-circuit breaking capacity levels depending on the model and frame size:
| Model | AC 230V (Icu) | AC 400V (Icu) | AC 690V (Icu) |
| CJMM6-125 (H) | up to 50kA | up to 50kA | up to 15kA |
| CJMM6-160 (H) | up to 50kA | up to 50kA | up to 15kA |
| CJMM6-250 (H) | up to 70kA | up to 65kA | up to 20kA |
| CJMM6-400 (H) | up to 70kA | up to 65kA | up to 25kA |
| CJMM6-630 (H) | up to 50kA | up to 65kA | up to 20kA |
| CJMM6-800 (H) | up to 85kA | up to 85kA | up to 35kA |
Service Breaking Capacity (Ics): Expressed as a percentage of Icu, typically ranging from 25% to 100% depending on the model and voltage.
Selective Category: Class A
Overcurrent Release Type: Thermomagnetic
Product Features and Advantages
The CJMM6 Series stands out with several compelling features:
Compact Design: Despite their robust construction, CJMM6 breakers feature a compact footprint with low temperature rise and an elegant appearance.
Wide Current Coverage: From 10A to 2000A, covering virtually all low-voltage distribution needs.
Multiple Breaking Capacity Options: Available in C, S, M, and H breaking capacity codes to match specific application requirements.
Versatile Pole Configurations: 1P, 2P, 3P, and 4P options available across different models.
Advanced Protection Functions: The electronic models (CJMM6E and CJMM6EY) provide comprehensive protection against overcurrent, short circuit, overvoltage, undervoltage, and phase failure.
Real-Time Monitoring: The LCD-equipped CJMM6EY model offers three-phase voltage and load current monitoring with 0.5-class high-precision measurement, supporting four remote control functions (remote measurement, remote signaling, remote control, remote adjustment).
Rich Accessory Options: The CJMM6 Series supports a wide range of internal and external accessories including shunt releases, undervoltage releases, auxiliary contacts, alarm contacts, electric operation, mechanical interlocking, and plug-in/draw-out options.
CJMM6 Series Dimensions (Reference)
| Model | Poles | Width (mm) | Length (mm) | Height (mm) |
| CJMM6-125 | 1P/2P/3P/4P | 25/50/75/100 | 130 | 68 (cover)/94.5 (handle) |
| CJMM6-160 | 2P/3P/4P | 60/90/120 | 155 | 68-82 (cover)/94-108 (handle) |
| CJMM6-250 | 3P/4P | 105/140 | 165 | 68-88 (cover)/96-116 (handle) |
| CJMM6-400/630 | 3P/4P | 140/184 | 257 | 68-88 (cover)/116 (handle) |
| CJMM6-800/1250 | 3P/4P | 210/280 | 275.5 | 103 (cover)/152 (handle) |
Application Scenarios for MCCBs
MCCBs like the CJMM6 Series are ideal for:
Industrial Facilities: Protection of motors, control panels, and distribution boards in factories and manufacturing plants.
Commercial Buildings: Power distribution in office complexes, shopping centers, and hotels.
Residential Complexes: Main distribution panels for large residential buildings.
Infrastructure Projects: Power systems for transportation hubs, hospitals, and data centers.
Equipment Protection: Serving as main circuit protection for various electrical equipment with rated currents below 630A.
Working Environment Conditions
The CJMM6 Series is designed to operate reliably in demanding conditions:
l Temperature: -5°C to +40°C (with 24-hour average not exceeding +35°C)
l Relative Humidity: Up to 50% at 40°C, with higher humidity allowed at lower temperatures (up to 90% at 20°C)
l Installation: Vertical mounting
l Altitude: Suitable for operation below 2000 meters above sea level
l Pollution Level: Level 3
l Suitable for environments without explosive hazards, corrosive gases, or conductive dust
Why Choose C&J Electrical?
Zhejiang C&J Electrical Co., Ltd. has established itself as a trusted manufacturer in the electrical protection industry. Our CJMM6 Series MCCBs are engineered to deliver consistent performance with long service life, reducing maintenance frequency and costs for our customers.
We understand that every project has unique requirements, which is why we offer:
l OEM Brand Customization Services – We can manufacture products with your brand specifications
l Multiple Specification Options – Extensive range of models, current ratings, and accessories
l Broad Application Suitability – From general industrial to critical infrastructure
l High Safety Performance – Rigorously tested to meet international standards
l SKD (Semi-Knocked Down) Parts Shipment – Convenient shipping options for assembly at your location
l If you have any questions about product selection, technical parameters, or customization requirements, please do not hesitate to contact us. Our professional team is ready to provide timely and comprehensive support.
Post time: Sep-04-2026