The development of low voltage electrical appliances generally refers to the evolution of devices such as power circuit breakers, molded case circuit breakers, control appliances, electronic motor protectors, soft starters, terminal equipment, miniature circuit breakers, residual current circuit breakers, terminal combination appliances, and low voltage surge protectors.

Power Circuit Breakers

Development Direction of Power Circuit Breakers
Power circuit breakers, as one of the most important products in low voltage electrical appliances, have always been highly favored. The competition is fierce in terms of new products launched. New generations of air circuit breakers (ACB) have not only significantly improved overall performance and key technical indicators but also emphasized practicality in their improved technical performance. Large current integral structures have become a mainstream development trend for new generations of high-specification air circuit breakers. The new generation features reduced size for each product specification and a decrease in the total number of specifications in the series. Most new generation air circuit breakers adopt a single breakpoint structure in their contact extinguishing system. Many employ modular designs for internal and external accessories, facilitating standardized assembly production, easy disassembly, replacement, and maintenance. Electronic controllers in these breakers are now highly functional, and all new-generation products are equipped with communication interfaces, compatible with major industrial field bus systems, with some using internal bus systems.

MCCB

Molded Case Circuit Breakers (MCCB)
The new generation of MCCBs has made significant breakthroughs in product structure, operating mechanisms, contact extinguishing systems, adjustable thermal magnetic trip units, and electronic trip units, greatly enhancing overall technical and economic indicators. The development of new-generation MCCBs focuses on reducing size while improving technical performance, hence the increasing attention to new double breakpoint breaking technology.

With increased short-circuit breaking capacity, many products now feature Ics=Icu. Higher current models in some series have Icw ratings, enabling selective protection between upper and lower levels of MCCBs. The size and frame rating of many new-generation products have significantly decreased. The adoption of electronic trip units across the full range due to their reduced size and cost is a clear trend, enhancing the protective performance of MCCBs equipped with them.

The new generation of MCCBs features ground fault protection and residual current protection. In terms of structure, they generally use either a twin structure or a modular assembly structure. The twin structure is smaller and easier to maintain and replace, while the modular structure offers flexible derivations.

To meet system requirements, increasing emphasis is placed on the development of accessories, offering a rich selection of internal and external accessories. The new generation of MCCBs has communication capabilities, easily connecting to various field bus systems (such as Profibus, Devicenet, Modbus) through external communication adapters, enabling remote monitoring.

 

Development of Miniature Circuit Breakers (MCB)
As a primary product in terminal electrical equipment, the development of MCBs has always led the way in this field. The introduction of MCBs with selective protection, like ABB’s S700, has completely solved the issue of selective protection in terminal distribution systems, significantly improving the safety and reliability of electricity usage. The P+N structure MCB has rapidly developed in recent years, with larger capacity and higher breaking capacity models emerging. With technological breakthroughs in the P+N structure and MCBs, even smaller models (expected to be 12mm wide per pole) will soon be available, heralding another peak in MCB development. These MCBs have various tripping characteristics to meet different standards and distribution system requirements, catering to the needs of globalized trade. Besides their own technological development, the range of accessories for MCBs is becoming more comprehensive. New installation methods, from screw to rail mounting, make MCB installation more convenient. The increasing adoption of busbar connection and integrated installation technology by more MCBs improves production efficiency.

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Development of Residual Current Circuit Breakers (RCCB) and RCBOs
In recent years, the development of RCCBs and RCBOs has mainly focused on Type B RCCBs and self-testing RCCBs. The introduction of new technologies has not only enhanced the protective performance and functionality of RCCBs but also continually reduced their size. The emergence of small-sized Type B RCCBs has improved residual current protection performance and laid the foundation for broader applications in the future. The advent of self-testing RCCBs is another bright spot in the RCCB family, significantly enhancing the safety and reliability of end-use.

 

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Development Trends of Low Voltage Surge Protectors (SPD)
With the advancement of electronic technology, lightning protection technology and products are receiving increasing attention worldwide, with comprehensive product ranges being launched. Besides tiered products, many have introduced combined Type I+II SPDs for direct use in protection from LPZ0 to LPZ2, simplifying installation and wiring, and reducing costs.

Development Trends in Control Appliances
With the rapid development of electronic technology, control appliances are evolving ever faster, especially control and protection switchgear, electronic motor protectors, soft starters, and frequency converters. In recent years, many have developed two generations of products, demonstrating rapid technological progress.

Control and Protection Switchgear (CPS)
In recent years, the concept of integrated solutions has been introduced into motor control and protection devices, combining motor circuit breakers, contactors, and protective relays into compact motor starters (like MOELLER’s Xstart series). Component design considers appearance, size, terminal connections, and performance compatibility. With technological advancements and increasing demand, integrated CPS (like Schneider’s TesysU series) have emerged, more compact and powerful. The high level of integration not only reduces the size compared to combined types but also offers complete protection and powerful functionality, making integrated CPS likely the future mainstream in CPS development.

Electronic Motor Protectors
Electronic motor protectors, born from the advancement of electronic technology, are specialized for motor protection, ranging from high to low-end products. High-end protectors, like those in the MM2 and GEMultlin series, are mainly used in low voltage motor control centers. These protectors offer a range of functions beyond motor protection, extending to other equipment protection like substation and transformer protection. The mechanical structure and functionality of low and mid-range electronic motor protectors are similar to traditional thermal overload relays, capable of being directly combined with contactors of the same grade to form compact motor starters, but with stronger functions, gradually replacing thermal relays in motor control and protection.

Soft Starters
Soft starter technology has rapidly evolved, largely replacing traditional reduced-voltage starters like autotransformer starters. Soft starters, generally available in economical and advanced series, have become an important type of motor starter. Economical soft starters are simple, with only soft start functionality and no additional protection features, but are cost-effective, compact, and can sometimes double as semiconductor contactors. Advanced soft starters, in addition to soft start, have various protection functions.

Variable Frequency Drives (VFDs)
Variable frequency drives, which adjust motor speed by altering the output frequency of the power supply, are widely used in industrial control systems requiring speed control. The overall characteristics of the new generation of VFDs include high performance; user-friendliness with simplified installation and initial setup; a wide power range with excellent speed and torque control; modular power structure and control units supporting plug-and-play; intelligent design supporting multiple bus communications and an open field-programmable structure; high power density and compact size; minimal EMI/RFI harmonic interference. With advancements in VFD control technology, high-end models offer high control performance, capable of controlling both AC induction and permanent magnet synchronous motors, reaching the performance level of universal servo controllers. Integrated motor VFDs and modular VFDs have rapidly developed, likely becoming the main trend in small VFD development.

Development Trends in Terminal Electrical Equipment
The development of terminal electrical equipment saw rapid growth in the 1990s and has since stabilized, with complete product ranges, high technical performance standards, modular dimensions, and rail-mounted installation.

Development of Terminal Combination Appliances
After nearly two decades of development, the protective enclosures of terminal combination appliances are mostly made of high-strength engineering plastics with innovative structures, attractive appearances, and bright colors. The protection level of enclosures has continuously increased from IP30, IP40 to IP55, IP65. Modular dimensions allow for both standalone and combined assembly use. More and more terminal combination appliances are adopting busbar connection and integrated installation technology, likely becoming the mainstream structure for protective enclosures.