Circuit breakers are essential electrical components used in electrical safety. Circuit breakers are divided into high-voltage circuit breakers and low-voltage circuit breakers, each with different applications. Today, the circuit breaker manufacturer will explain the different types and differences between high-voltage and low-voltage circuit breakers.
High-voltage circuit breaker
1. High-voltage circuit breaker (QF) – short circuit, arc extinguishing, normal load
High-voltage circuit breakers possess reliable arc-extinguishing devices with strong arc-extinguishing capabilities. During normal circuit operation, they are used to connect or disconnect load currents. In the event of a circuit fault, they prevent the accident from escalating and ensure safe operation. They can also be used to interrupt enormous short-circuit currents. High-voltage circuit breakers must be able to interrupt arcs of 1500V and 1500-2000A, arcs that can stretch up to 2 meters and continue burning without extinguishing. Therefore, arc extinguishing is a crucial problem that high-voltage circuit breakers must solve.
High-voltage circuit breakers can be classified according to the different arc-extinguishing media into oil-based arc-extinguishing circuit breakers, low-oil circuit breakers, high-voltage circuit breakers, vacuum circuit breakers, sulfur hexafluoride circuit breakers, magnetic blowout circuit breakers, etc.
Types of low-voltage circuit breakers
1. Frame Circuit Breaker (Universal Type) – ACB
Regarding rated current, in principle, a frame circuit breaker is required for a rated current of 630A, while molded case circuit breakers are generally rated below 630A (some new products can reach 1600A). It is evident that the rated current of frame circuit breakers is much higher, typically ranging from 630A to 6300A. Furthermore, frame circuit breakers have a higher breaking capacity than molded case circuit breakers.
In practical applications, circuits with an A rating of 800A or higher, circuits with particularly high segmentation capacity requirements, or circuits requiring more functions should use frame circuit breakers, while circuits with an A rating of 630A or lower generally use molded case circuit breakers.
All parts of a frame circuit breaker are housed within an insulated metal frame. It is typically an open type, allowing for the installation of various accessories and facilitating the replacement of contacts and components. It is commonly used as a main switch at the power supply end. Overcurrent trip units include electromagnetic, electronic, and intelligent types. The circuit breaker offers four protection stages: long-delay, short-delay, instantaneous, and ground fault. The setting values for each protection stage are adjustable within a certain range according to the frame rating.
2. Molded Case Circuit Breaker (MCCB)
It can automatically cut off the current after the current exceeds the tripping setting. Molded case circuit breakers usually contain a thermal-magnetic tripping unit, while larger molded case circuit breakers are equipped with solid-state tripping sensors. Their tripping units are divided into: thermal-magnetic tripping and electronic tripping units.
Also known as a modular circuit breaker, it is characterized by its grounding terminal external contacts, arc-extinguishing chamber, trip unit, and operating mechanism all housed within a single plastic casing. Auxiliary contacts, undervoltage release units, and shunt trip units are often modular, resulting in a very compact structure. Maintenance is generally not a primary concern, making it suitable as a protective switch for branch circuits.
Most are operated manually, while electric opening and closing can be selected for large capacity applications. Due to the application of electronic overcurrent trip units, they can be divided into two types: Class A and Class B. Class B has good three-stage protection characteristics, but due to price factors, Class A products using thermal-magnetic trip units have a higher market share.
Molded case circuit breakers (MCCBs) have two types of overcurrent trip units: electromagnetic and electronic. Electromagnetic MCCBs are generally non-selective, offering only long-delay and instantaneous protection modes. Electronic MCCBs offer four protection functions: long-delay, short-delay, instantaneous, and ground fault protection. Some newly released electronic MCCBs also feature a zone-selective interlocking function.
3. Miniature Circuit Breaker (MCB)
It is one of the most widely used terminal protection electrical devices in building electrical terminal distribution equipment. It is used for protection against short circuits, overloads, and overvoltages of single-phase and three-phase circuits below 125A, including four types: single-pole 1P, two-pole 2P, three-pole 3P, and four-pole 4P.
In civil building design, low-voltage circuit breakers are mainly used for protection and operation of lines in case of overload, short circuit, overcurrent, undervoltage, grounding, leakage, automatic switching of dual power supplies, and infrequent starting of motors (9 types).
Differences between the above types of circuit breakers
The main differences between ACB (Universal Circuit Breaker), MCCB (Molded Case Circuit Breaker), MCB (Miniature Circuit Breaker), and ELCB (Residual Current Circuit Breaker) are:
(1) The breaking ability is different. ACB has a relatively high breaking ability, followed by MCCB, and MCB has the worst breaking ability.
(2) Due to their different installation locations, ACBs are mostly used as main circuit breakers (power supply side main switches) because they have a time delay function, enabling delayed breaking and tripping, and also have good communication and selectivity. MCCBs, on the other hand, are mostly used as distribution devices in the middle of the line because they only have breaking capacity and inverse-time tripping capability, lacking selectivity, and are mostly used as downstream protection switches and emergency stop switches. MCBs are mostly used at the load end because their breaking capacity is relatively low, typically 6000A and 4500A.
(3) Their external dimensions also differ greatly. MCB is small and easy to install, while ACB is the largest and complicated to install. MCCB is in the middle.
