Low Voltage Electrical | Product: CJMM3 Series MCCB

Molded Case Circuit Breakers (MCCBs) are core switching and protective devices in low-voltage power distribution systems. They are widely used in power grids, commercial buildings, industrial plants, data centers, and OEM equipment to ensure safe, stable, and reliable power supply. As a professional manufacturer of low-voltage electrical components, C&J Electrical launches the CJMM3 series MCCB to provide stable circuit protection and flexible configuration for global users.

What is an MCCB?

An MCCB is a mechanical switching device designed to connect, carry, and break current under normal circuit conditions, and to withstand and break current under specified abnormal conditions for a defined time. It provides reliable protection against overload, short circuit, and undervoltage in distribution lines, effectively preventing equipment damage, fire risks, and power outages.

Compared with Miniature Circuit Breakers (MCBs), MCCBs feature higher rated current, stronger breaking capacity, and wider application scenarios. They are suitable for main power distribution, branch circuits, and heavy-load equipment protection.

There are applications where MCBs and MCCBs can overlap, making a MCB an alternative choice. The two main drivers are cost and space. MCBs cost considerably less and take up less space in a control panel. In projects with limited budget and panel space, MCBs can be used for small-load terminal protection. For medium and high current distribution, main circuits, and industrial equipment, MCCBs are more suitable due to their higher stability and safety.

Main Functions of MCCBs

• Overload Protection: Automatically trips when current exceeds rated value to avoid overheating and burnout of cables and equipment.
• Short-Circuit Protection: Quickly cuts off fault current within milliseconds to isolate short-circuit points and protect the entire power system.
• Undervoltage Protection: Trips when voltage drops to a dangerous level (optional accessory) to prevent abnormal operation and damage of motors and electrical devices.
• Normal Switching: Supports manual on/off operation for circuit commissioning, maintenance, and emergency shutdown.
• System Coordination: Cooperates with other protective devices to achieve graded protection, improve power supply continuity, and reduce fault impact scope.

CJMM3 Series MCCB – Structural Characteristics & Technical Data

C&J Electrical CJMM3 series MCCB is a standardized, high-performance molded case circuit breaker for global low-voltage distribution. It complies with IEC60947-1 / IEC60947-2 and supports multiple specifications to meet different working conditions.

Structural Characteristics

1. Core Function CJMM3 series MCCBs can connect, carry and break current under normal circuit conditions, and can also connect, carry and break current under specified abnormal circuits for a certain period of time. It provides reliable protection for lines and equipment against overload, short circuit, and undervoltage (accessory function). It is widely used in low-voltage power consumption places such as electric power, construction, industry, and OEM.
2. Frame Rating: 125A, 160A, 250A, 400A, 630A
3. Rated Working Voltage Ue: 400/415V, 690V
4. Breaking Capacity: 20kA, 36kA, 50kA, 70kA, 75kA (detailed values for each frame refer to the parameter table)
5. Number of Poles: 3-pole
6. Release Type: single magnetic type, thermal magnetic type
7. Installation Method: fixed, plug-in, drawer

Working And Installation Conditions

• Normal working temperature: -5~40°C; available for -40°C ~-5°C and 40°C ~70°C with proper derating.
• When ambient temperature exceeds 40°C, please use according to the temperature derating coefficient table.
• Storage temperature: -40~70°C. If stored below normal working temperature, return to working conditions and stand for at least 24 hours before use.
• Normal operating humidity: ≤50%RH at 40°C; higher humidity allowed at lower temperature (e.g. 90%RH at 20°C).
• Type：CJMM3-125~630A
• No. of Poles：3P
• Rated Current：16-630A
• Impulse Withstand Voltage：8kV/10kV
• Rated Operational Voltage：400V/415V/690V
• Rated Insulation Voltage：800/1000V
• Operational Frequency (Hz)：50/60Hz
• Utilisation Category：A
• Reference Temperature：-5~+40°C
• Operating Temperature：-5~+40°C
• Standard：IEC60947-1/IEC60947-2
• Electrical Life：5000/3000
• IP Protection (front side)：IP40
• Pollution Degree：III
• Release Type：Single magnetic trip / thermal magnetic trip

Complete Technical Data

Application Scenarios of CJMM3 MCCB

CJMM3 series MCCB is designed for versatility and reliability, suitable for almost all low-voltage power distribution scenarios:

• Power Industry: distribution stations, grid substations, power transformation and distribution systems.
• Construction Industry: commercial buildings, office buildings, shopping malls, hotels, residential power distribution cabinets.
• Industrial Field: factories, machinery, assembly lines, water treatment, metallurgy, textile, chemical industry.
• OEM Equipment: control panels, power cabinets, electrical equipment, new energy supporting systems.
• Infrastructure: data centers, communication base stations, transportation, lighting systems.

With its wide current range, strong breaking capacity and stable performance, CJMM3 becomes the preferred protective device for main incoming lines, branch circuits and equipment power supply.

Why Choose CJMM3 MCCB from C&J Electrical?

1. Complete Specifications Frame current from 125A to 630A, breaking capacity up to 75kA, 3-pole structure, dual release options, covering most distribution requirements.
2. Multiple Installation Methods Fixed, plug-in and drawer types are available, convenient for installation, replacement and maintenance, suitable for different cabinet designs.
3. High Safety Performance Strictly tested for overload, short circuit and undervoltage protection; high impulse withstand voltage and insulation voltage; IP40 front protection, stable under Pollution Degree III environment.
4. Wide Adaptability Works in -5~40°C environment, storage temperature -40~70°C, adaptable to harsh indoor and outdoor working conditions.
5. Flexible Customization & Supply C&J Electrical supports OEM/ODM brand customization, accepts SKD parts shipment, and provides complete technical support. We also provide MCB products to form a one-stop solution for users.

Conclusion

MCCBs are essential for modern low-voltage distribution systems. They provide safe circuit control and reliable fault protection. C&J Electrical CJMM3 series MCCB combines stable performance, complete parameters, flexible installation and global certification standards, which can meet the needs of power, construction, industrial and OEM fields.

If you are looking for high-quality MCCB products, customized solutions or SKD supply, please feel free to contact C&J Electrical for professional support.