DC Molded Case Circuit Breaker

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The DC molded case circuit breakers (MCCBs) we manufacture are equipped with overload protection, short-circuit protection, and isolation functions, ensuring the stable operation and electrical safety of your DC power distribution system.

DC MCCB 125A ZMM1-125DC

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Application Scenarios of DC Miniature Circuit Breakers (MCCB)

Molded Case Circuit Breaker （DC MCCB） is applied in electric vehicles

The working principle of DC MCCBs in new energy vehicles centers on dynamically safeguarding the vehicle’s high-voltage and low-voltage DC circuits. By monitoring current in real time, responding quickly to faults, and cutting off the circuit, it eliminates risks such as fire and equipment damage. Essentially, it serves as the “safety guardian” of the vehicle’s high-voltage system.

Molded Case Circuit Breaker （DC MCCB） is applied in Eectroplating Equipment

The working principle of DC MCCBs in electroplating/electrolysis equipment centers on real-time monitoring of DC circuit current. When faults such as overcurrent or short circuit occur in the circuit, it quickly cuts off the circuit to protect equipment and process safety. Essentially, it provides an “overload protection barrier” for a stable DC power supply environment.

Molded Case Circuit Breaker （DC MCCB） is applied inRail Transit

The working principle of DC Molded Case Circuit Breakers (DC MCCBs) in rail transit mainly involves normal switching (closing and opening), overload and short-circuit protection, and arc extinguishing. They are used in scenarios such as the DC traction systems of subways and light rails, or the DC auxiliary power supply circuits inside vehicles, to protect the circuit safety of traction motors and on-board equipment.

Molded Case Circuit Breaker （DC MCCB） is applied in Wind Power System

DC MCCBs safeguard the current safety of critical DC-side circuits in wind power systems. By real-time monitoring current fluctuations of core components such as wind power converters and energy storage units, they can quickly disconnect circuits in the event of overloads and short-circuits. Meanwhile, they are adaptable to the intermittent energy characteristics of wind power. They serve as the “current safety sentinels” for the DC systems in wind power applications.

Molded Case Circuit Breaker （DC MCCB） is applied in Commercial Building

When it comes to power supply in commercial buildings, no margin for error is acceptable. Our DC Molded Case Circuit Breakers (DC MCCBs), equipped with the dual advantages of “robust protection and intelligent control”, accurately meet the core demands of commercial buildings for power supply reliability and intelligent management—ensuring every kilowatt-hour of electricity is “stable for the present and intelligently controlled for the future”.

Molded Case Circuit Breaker （DC MCCB） is applied in Aerospace Systems

In aerospace systems, DC MCCBs ensure the absolute reliability of DC power supplies under extreme operating conditions. By adapting to special environments such as high-altitude low pressure, intense vibration, and wide temperature fluctuations, they continuously monitor the current in on-board DC circuits, accurately and quickly disconnect circuits in the event of overloads and short-circuits, while preventing misoperations.

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Frequently Asked Questions

What is a DC Molded Case Circuit Breaker?

A DC Molded Case Circuit Breaker (referred to as DC MCCB for short; full name: DC Molded Case Circuit Breaker) is a core protective device specially designed for medium- and low-voltage DC power supply systems. Its core function is to monitor the circuit current in real time through built-in current detection components (such as electromagnetic trip units and bimetallic strips) and arc-extinguishing devices. When faults like overload or short circuit occur, it quickly cuts off the circuit to prevent safety accidents such as equipment burnout or fire.

Its key feature lies in the “molded case” structure — an insulating housing made of flame-retardant thermosetting or thermoplastic materials. This housing not only fixes internal core components (such as contacts and arc-extinguishing systems) but also isolates arcs and electric shock risks, while possessing a certain level of impact resistance and environmental corrosion resistance.

Compared with AC circuit breakers, DC MCCB has an optimized arc-extinguishing chamber design tailored to the characteristics of DC current (which has “no zero-crossing point and high difficulty in arc extinguishing”), enabling it to effectively extinguish DC arcs. Therefore, it is mainly suitable for scenarios requiring stable DC protection, such as new energy storage, rail transit, industrial DC drives, and marine power supply. Its current rating usually ranges from 10A to 1600A, making it a key device for “ensuring circuit safety” in DC power supply systems.

How MCBs work？

The core working mechanism of a DC Molded Case Circuit Breaker (DC MCCB) is a closed-loop process of “real-time monitoring – fault identification – rapid interruption”. It accurately addresses overload and short-circuit faults in DC circuits and resolves the challenge of DC arc extinguishing through the collaborative operation of three built-in key systems.

1. Core Working Logic: Three-Step Fault Protection

The working process of a DC MCCB centers on “protection triggered by abnormal current” and is specifically divided into three stages:

Step 1: Current Monitoring

When the circuit operates normally, the main circuit current flows through the current detection components (such as bimetallic strips and electromagnetic coils) inside the circuit breaker. These components “sense” the current magnitude in real time. At this point, the current remains within the rated range, the components do not act, and the circuit stays conducting.

Step 2: Fault Identification

When a fault occurs in the circuit, the detection components trigger different responses based on the fault type:

Overload Fault: When the current exceeds the rated value but does not reach the short-circuit level (e.g., motor stalling), the bimetallic strip bends due to the thermal effect of the current, pushing the mechanical mechanism to trigger tripping.
Short-Circuit Fault: When the current surges to several times or even dozens of times the rated value (e.g., line short-circuit), the electromagnetic coil generates a strong magnetic field, which attracts the iron core to quickly strike the tripping mechanism, achieving “instantaneous tripping”.

Step 3: Circuit Interruption and Arc Extinguishing

After the tripping mechanism acts, it drives the movable and fixed contacts of the circuit breaker to separate quickly, cutting off the main circuit. Meanwhile, since DC current has “no zero-crossing point and a long arc duration”, the built-in DC-specific arc-extinguishing chamber (usually containing metal grid plates and insulating partitions) splits and cools the arc, forcing it to extinguish. This prevents the arc from burning the contacts or causing safety accidents.

2. Key Designs: Core Differences for Adapting to DC Scenarios

Compared with AC circuit breakers, the working principle of DC MCCBs includes two key optimizations to adapt to DC characteristics:

Arc-Extinguishing System Optimization: To address the difficulty of extinguishing DC arcs, the arc-extinguishing chamber adopts a “multi-grid splitting + strong magnetic field drive” design. This splits long arcs into multiple short arcs, rapidly reducing arc energy and ensuring the circuit is completely de-energized after interruption.
Tripping Characteristic Adaptation: DC circuits have no current zero-crossing point, and short-circuit current peaks are higher with longer durations. Therefore, electromagnetic trip units have higher sensitivity and faster response speeds, capable of triggering interruption within milliseconds to prevent equipment from enduring excessive inrush current.

Types of DC Molded Case Circuit Breakers （DC MCCB）

DC MCCBs are classified based on core functional characteristics and application scenarios to meet diverse protection needs of DC circuits. The main types include:

By Tripping Mechanism
- Thermal-Magnetic DC MCCBs: Integrate dual protection of “bimetallic strip (for overload)” and “electromagnetic coil (for short circuit)”. Suitable for general DC scenarios (e.g., industrial auxiliary circuits, small energy storage systems) with simple structure and cost-effectiveness.
- Electronic DC MCCBs: Adopt electronic current sensors and microprocessors for precise current monitoring. Support adjustable protection parameters (e.g., overload trip time, short-circuit current threshold) and are ideal for complex DC systems (e.g., large-scale photovoltaic stations, rail transit traction circuits) requiring flexible protection.
By Breaking Capacity
- Low Breaking Capacity DC MCCBs: Designed for low-current DC circuits (usually ≤ 10kA breaking current), used in household energy storage, communication base station auxiliary circuits, etc.
- High Breaking Capacity DC MCCBs: With breaking current up to 50kA or higher, they withstand large short-circuit energy and are applied in high-power scenarios (e.g., industrial DC drives, ship propulsion systems).
By Installation and Structural Form
- Fixed DC MCCBs: Fixed on electrical cabinets or distribution boards via screws, with stable installation. Common in stationary DC power systems (e.g., ground traction substations, industrial control cabinets).
- Plug-In DC MCCBs: Can be plugged into matching sockets, enabling quick disassembly for maintenance. Suitable for scenarios requiring frequent device replacement (e.g., modular energy storage cabinets, mobile power supplies).
By Special Application Adaptability
- Environmentally Resistant DC MCCBs: With enhanced protection (e.g., IP65 dustproof and waterproof, corrosion-resistant materials) for harsh environments like marine (high salt spray), deserts (high dust), or high-altitude areas (low pressure).
- Rail Transit-Specific DC MCCBs: Feature vibration resistance (complying with EN 50155) and wide temperature adaptability (-40℃ to 85℃), used in subway onboard circuits and ground traction power distribution.
- New Energy-Specific DC MCCBs: Optimized for photovoltaic/storage characteristics (e.g., anti-PV array reverse current, compatible with battery charging/discharging fluctuations), applied in PV combiner boxes and energy storage PCS circuits.