Published date: September 14, 2026 Author: C&J Electrical Technical Team Category: Low Voltage Circuit Protection, AC MCCB, Product News

In the field of low-voltage power distribution, many engineers and purchasers often ask: Is an MCCB the same as an MCB? Although both are circuit breakers used for overload and short-circuit protection, they differ significantly in current rating, breaking capacity, structural design, installation size, application scenarios and cost. Today, C&J Electrical will clarify the core differences between MCB and MCCB, and focus on introducing our CJMM3 series moulded case circuit breaker (AC MCCB), helping you make accurate selection for your power distribution projects.

Core Differences Between MCB and MCCB

MCB (Miniature Circuit Breaker) is a miniature protection device, mostly used for terminal branch circuits, with small current, fixed tripping curve, compact size and low cost. MCCB (Moulded Case Circuit Breaker) is a medium–high capacity protection switch, with wider current range, higher breaking capacity, flexible tripping configuration and diversified installation methods, suitable for main circuits and feeder circuits with higher power demand.

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. However, when the project requires higher current, larger breaking capacity, undervoltage protection or complex working conditions, AC MCCB becomes the irreplaceable core component.

CJMM3 Series Moulded Case Circuit Breaker (AC MCCB) Overview

CJMM3 series is a star AC MCCB product independently developed and produced by Zhejiang C&J Electrical co., ltd. (C&J Electrical). It is a mechanical switching device that can connect, carry and break current under normal circuit conditions, and can also connect, carry and break current within a specified time under abnormal circuit conditions. It provides reliable protection for lines and electrical equipment when overload, short circuit or undervoltage occurs, and is widely used in power, construction, industry, OEM and other low-voltage power consumption scenarios.

Structural Characteristics

• Frame rating: 125A, 160A, 250A, 400A, 630A
• Rated working voltage Ue: 400/415V, 690V
• Breaking capacity: 20kA, 36kA, 50kA, 70kA, 75kA (detailed data refer to the parameter table)
• Number of poles: 3-pole
• Release type: single magnetic type, thermal magnetic type
• Installation method: fixed, plug-in, drawer
• Normal working temperature: -5~40°C; applicable for -40°C ~-5°C and 40°C ~70°C with derating reference
• Storage temperature: -40~70°C (stand for 24 hours to recover to working conditions before use if stored at extreme temperature)
• Humidity: ≤50%RH at 40°C; up to 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 Prolection (from front side)：IP40
• Pollution Degree：III
• Type of Release：Single magnetic trip/thermal magnetic trip

Working And Installation Conditions

Technical Data

Application Scenarios of CJMM3 AC MCCB

CJMM3 series AC MCCB is designed for diversified low-voltage distribution scenarios, covering almost all mainstream industrial and civil power demand:

• Power industry: substation feeder protection, power distribution room main switch
• Construction industry: commercial building, residential quarter power distribution cabinet, high-rise building fire protection circuit
• Industrial field: factory production line, mechanical equipment, motor control center
• OEM supporting: electrical complete sets of equipment, control panel, distribution box customization

With stable performance and complete specifications, CJMM3 can meet the protection needs of different working conditions, and become the preferred AC MCCB for global engineering projects.

Core Advantages of CJMM3 Series AC MCCB

1. Complete specification system: 5 frame ratings, multiple breaking capacities, covering 16-630A full current range, matching different power distribution needs.
2. Flexible installation options: fixed, plug-in and drawer three installation methods, convenient for panel layout, maintenance and replacement.
3. Stable tripping performance: single magnetic and thermal magnetic two release types, accurate action, fast breaking, effectively avoiding equipment damage and circuit accidents.
4. Wide environment adaptability: wide working temperature range, strong humidity resistance, suitable for indoor and outdoor conventional and harsh environments.
5. Strict compliance with standards: designed and produced in accordance with IEC60947-1/IEC60947-2, reliable quality, safe and durable.
6. Customized service support: provide OEM/ODM brand customization, SKD parts delivery, meet the diversified needs of global customers.

Why Choose C&J Electrical CJMM3 AC MCCB?

C&J Electrical has been focusing on the R&D and production of low-voltage circuit breakers for many years. We not only provide high-quality CJMM3 series AC MCCB, but also have a full range of MCB products to meet the overlapping selection needs of cost and space. We adhere to the customer-centric principle, provide professional technical support, flexible customization services and efficient supply chain guarantee, helping global customers solve power distribution protection problems.

If you are still confused about the selection of MCB and MCCB, or need to know more details about CJMM3 series AC MCCB, parameters, quotation and customization, please feel free to contact our sales team. C&J Electrical will provide you with professional and efficient circuit protection solutions.