The difference between an air circuit breaker vs. MCCB types is not only functional; it includes a variation in ratings, size, cost, and installation methods. Find out how the two devices differ below. We will also discuss their distinct uses.
Air Circuit Breaker (ACB) Definition
An air circuit breaker (ACB) is a type of breaker designed for high-voltage systems and high-current circuits. It utilizes air to quench arcs, which is also where it derives its name.
The typical ACB is a reasonably large unit with a robust metal housing. Inside the enclosure are trip units, which are either thermal-magnetic or electronic.
You will often find the ACB on the supply mains protecting downstream devices, including smaller-sized breakers. It also usually has adjustable settings. These enable users to customize the device’s operation.
Molded Case Circuit Breaker (MCCB) Definition
An MCCB, or molded case circuit breaker, is a breaker that comes enclosed in a case of molded plastic. The case provides a robust, compact, and highly insulating housing to protect internal components.
One thing that distinguishes MCCBs from other breakers, such as MCBs, is their ability to handle higher fault levels. They are also available with adjustable settings. This feature lets you match their operation with system needs.
Molded case circuit breakers are typically installed in the distribution boards of power systems. Here, they protect branch circuits. Their tripping components are thermal-magnetic, but they can also utilize electronic parts.
Air Circuit Breaker vs. MCCB
While they both protect electrical equipment and circuits, there’s a distinct difference between air circuit breakers and molded case circuit breakers. Here is an overview of these variations and how they impact usage and other aspects.
Voltage and Current Ratings
Air circuit breakers operate at higher system voltages than molded case breakers. They can also handle higher currents, such as short circuits, with ratings ranging from 400A to 6300A.
MCCB voltage ratings are comparatively lower but higher than those of low-voltage breakers, such as MCCBs. Additionally, they handle lower currents in the range of 16A to 3200A.
Breaking Capacities
The breaking capacity of ACBs is way higher, from 50 kA to over 150 kA. This capacity is suitable for transmission circuits supplying electricity to commercial buildings and industrial facilities.
The MCCB breaking capacity is relatively lower. It ranges from 6 kA to 100 kA or higher. These capacities suit load circuits for wiring and equipment protection needs.
Size Differences
ACBs are generally larger than molded case circuit breakers. That’s because they house more components. Their parts are also heavier to withstand the higher currents.
MCCBs are compact devices that you can install in tight spaces. They are typically 2 to 3 times smaller than ACBs and available in a broad range of physical sizes.
Trip Times
ACBs are meant to trip less frequently as they protect larger systems with other protection devices. They usually come with specified durations before tripping. The delay allows downstream devices to act first.
Molded case breakers are more sensitive. They trip more readily than ACBs since they protect individual loads and sub-distribution circuits. This feature defines a critical usage difference between them and ACBs.
Location Difference
The ACB location is usually upstream, where it protects power distribution circuits, ensuring they remain safe in the event of a fault, such as system overloads and short-circuits.
In comparison, we use molded case circuit breakers on the load side of an electrical circuit. Here, the breakers protect electrical equipment from damage by fault currents.
It’s also good to note that the location of ACBs makes them trip less frequently. On the other hand, MCCBs are more likely to trip as their breaking capacity is lower.
Installation and Mounting
The installation of ACB breakers differs from that of MCCBs. Molded circuit breakers mount on panels using bolts. They remain fixed to the panel until you need to replace them.
The ACB breaker mounting method can be a fixed (bolted) or withdrawal type. A draw-out/rack-out install makes inspection easier. It also reduces disruptions during maintenance.
Cost Comparison
ACBs cost more, given their larger sizes, both in terms of physical dimensions and ratings. They also include sophisticated mechanisms and components to match their application requirements.
Molded case circuit breakers are compact units with lower ratings compared to ACBs. They generally cost less. However, you cannot use them in the higher voltage current circuits that ACBs protect.
Key ACB Application Areas
As discussed earlier, ACBs are designed to interrupt high fault currents. They also operate in high-voltage systems. These attributes make them suitable for protecting entire electrical installations.
You install them in the mains of industrial and commercial power distribution systems. Apart from utility power, the ACB may also protect the circuits of UPS installations and large backup generators.
Use an ACB if you need a protection device for a facility’s entire power system with high potential fault currents. You must also correctly size the breaker to match the application’s protection requirements for safety.
Key MCCB Application Areas
Molded case circuit breakers have lower voltage, current, breaking capacity, and other ratings than ACBs. They are, therefore, suitable for protecting the load side of power distribution circuits.
Their application is generally in individual equipment or circuit protection. You will usually find them in the power systems of commercial buildings and manufacturing facilities.
Use a molded case breaker if you’re protecting branch circuits. The device is also suitable for protecting heavy equipment, such as industrial motors and machinery.
Conclusion
Air circuit breakers and molded case circuit breakers are popular electrical safety devices. One protects higher voltage and current installations, while the other is designed for lower ratings. These differences define their distinct applications. Understanding them is critical when seeking a protection device for your power system.
