The difference between DC MCCB and AC MCCB

For the power system, molded case circuit breakers (MCCBs) are fundamental equipment that makes the circuit safe. DC and AC systems require entirely different considerations for MCCB design and usage. This paper will explore major differences between AC MCCB and DC MCCB to enable engineers and procurement personnel to make better decisions

Differences in working principle and arc extinguishing mechanism

AC MCCB: AC power has a periodic zero crossing (50/60Hz), and the arc can easily be extinguished when the current naturally crosses zero. Therefore, the arc extinguishing chamber design for MCCB communication is relatively simpler, and usually entails the use of disconnecting grids or gas arc extinguishing technology to meet the demands

DC MCCB: DC current flows only one way and has no natural zero crossing, and the arc simply keeps burning and is not self-extinguished. DC MCCBs thus must use more advanced arc extinguishing techniques, such as magnetic blow coils (which stretch the arc out by a magnetic field) or multi-stage arc extinguishing chamber design, to forcibly interrupt the current

Comparison of Technical Parameters and Standards

Core design differences

Contact Material and Structure
DC MCCB contacts need to withstand higher arc energy, usually using silver based alloys or copper tungsten composite materials, and increasing the contact spacing to reduce the risk of arc reignition
The communication MCCB contact material is mainly silver nickel alloy, and the design pays more attention to the stability of contact resistance

Arc extinguishing chamber design
The DC arc extinguishing chamber needs to be equipped with a magnetic blowing device to push the arc into the arc extinguishing grid through a magnetic field, extending the arc path to accelerate cooling
The communication arc extinguishing chamber relies on the zero crossing characteristic of current, divides the arc through metal grids, and uses a medium (such as air or ceramic) for cooling

Application scenarios and selection suggestions

Typical Applications of DC MCCB
Photovoltaic power generation system: It is necessary to match the open circuit voltage of the components (such as selecting MCCB with 1800V withstand voltage for 1500V system), and consider PID effect protection

Rail transit: used for DC 750V or 1500V contact network protection, must meet the EN 50155 anti vibration standard

Energy storage system: It needs to support high rate charging and discharging impacts, and be equipped with backup protection devices to prevent short circuits

Typical Applications of Communication MCCB
Building power distribution: The main switchgear adopts Class I breaking capacity (≥ 50kA), and the floor distribution box can choose Class II (20kA)

Industrial control: requires integration of overload, short circuit, and ground fault protection, supporting remote communication function

Brand Choice

Choosing ONESTO’s molded case circuit breakers, we offer a variety of DC and AC MCCBs to comprehensively protect circuits from overload and short circuit effects. With 19 years of industry experience, we promise to provide you with the most competitive prices and excellent quality

summarize

It is necessary to understand the difference between DC MCCB and AC MCCB if you are working with electrical systems. The difference in the type of current, structure, internal build, and breaking ability separates these circuit breakers from each other. Therefore, it is necessary to choose the correct MCCB for your application. By investing money in reliable and high-quality MCCBs produced by reputed manufacturers, you can ensure the safety and efficiency of your circuits for the next couple of years.

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