For low voltage distribution projects, electrical engineers, panel builders and procurement teams constantly evaluate whether to adopt MCB (Miniature Circuit Breaker) or MCCB (Moulded Case Circuit Breaker). Total project cost, cabinet installation space, rated current and short circuit withstand capability are core factors influencing component selection.

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. Even so, MCBs are constrained by upper current limits and short circuit breaking performance. For high current main incoming feeders, heavy load motor circuits and industrial distribution systems, MCCB remains the necessary protective device. Zhejiang C&J Electrical co., ltd. (shortened as C&J Electrical) developed the CJMM9 series moulded case circuit breaker, catering to diverse requirements for global commercial and industrial power distribution projects.

CJMM9 Series Product Overview

CJMM9 moulded case circuit breakers are engineered to satisfy both domestic and international market requirements. Rated insulation voltage reaches up to 1000V, with the 125 frame version rated at 690V. Designed for AC 50Hz networks with rated operational voltage 400V, the series covers rated operational current ranging from 32A to 1600A.

The product portfolio is divided into M type (standard breaking capacity) and H type (high breaking capacity) according to ultimate shortcircuit breaking capacity. Both vertical upright mounting and horizontal sideways mounting are supported for flexible cabinet layout. CJMM9 complies with IEC 60947-2 and GB/T 14048.2 standards. Available frame sizes include 125, 160, 250, 400, 630, 800, 1600; pole options contain 1 pole, 2 pole, 3 pole and 4 pole. Trip units cover single magnetic trip and thermal magnetic trip. A broad selection of internal and external accessories can be configured, such as auxiliary contacts, alarm contacts, shunt trip, undervoltage trip, electric operating mechanisms and rotary handle operators.

Core Technical Specifications

Note: Ultimate short circuit breaking capacity Icu ranges from 12kA up to 75kA depending on frame size and M/H grade. Two sets of trip characteristics are built in: distribution protection curve and motor protection curve for different load types.

Core Product Functions

CJMM9 moulded case circuit breakers perform power distribution duties while delivering multi layer circuit protection. It safeguards circuits and electrical equipment from overload, shortcircuit and undervoltage faults. It can also act as an infrequent starter for AC motors, delivering dedicated motor overload and short circuit protection.

For overload conditions, inverse time delay tripping activates; for sudden short circuit faults, instantaneous tripping quickly isolates the faulty circuit to prevent cascading equipment damage. Users can select different wiring methods based on cabinet design requirements. External accessories such as electric operating devices enable remote switching on / switching off; rotary manual handles support local manual operation. A full set of auxiliary and alarm contacts provides real time status feedback for monitoring systems.

Typical Application Scenarios

Thanks to wide ranging current grades and flexible accessory combinations, CJMM9 MCCB adapts to various working environments:

1. Industrial power distribution: Used as main incoming breaker or branch feeder protection inside factory control cabinets for transformers, distribution panels and production machinery.
2. Commercial building projects: Shopping malls, office towers and hotels for main power distribution and high power load protection.
3. Motor control applications: Infrequent start stop for heavy duty motors, providing integrated overload and short circuit protection for motor loops.
4. Other low voltage sites: Auxiliary power supply for data centres, logistics warehouses and new energy distribution cabinets.

When deployed outside standard working conditions such as high altitude or extreme ambient temperature, current derating must be implemented to guarantee reliable operation.

Customization & Supply Services from C&J Electrical

C&J Electrical maintains a complete low voltage circuit breaker product portfolio. Besides CJMM9 moulded case circuit breakers, we also supply fullrange MCB miniature circuit breakers for terminal circuit protection.

We support OEM / ODM brand customization services. Multiple specifications of CJMM9 are available for selection. Customers can customize brand logos, marking labels, packaging solutions and accessory combinations to match regional market or project specific demands. Apart from finished unit delivery, we provide SKD semi knocked down component shipment, allowing partners to complete local assembly for better cost control and local inventory management.

All products undergo standardized performance testing to maintain stable safety performance throughout service life. If you have technical enquiries, sample requests, quotation requirements or questions around custom cooperation, please feel free to contact our sales team.