Electric cabinet and modular circuit breakers
Electric cabinet and modular circuit breakersDate of publication: 05-01-2024 Update date: 10-04-2026 🕒 8 min read
An electric distribution board connects all points of an electric system, and is also responsible for safety, signalling and circuit control. Considering all these necessary functions, a control cabinet should be fitted with high-quality equipment. A neatly designed cabinet, constructed in line with the best practices, is an electric engineer’s showpiece and, simultaneously, guarantees full users’ safety.
A classic electric cabinet is equipped with electric components that can be classified as follows: switchgear, metering equipment, signalling equipment, protective features and control gear.
Electric cabinet components – tasks
All incoming and outgoing electric cables installed in the distribution board close the current flow in a complete circuit, as they are routed through the equipment inside the cabinet. This is the first function of the distribution board, i.e. it divides the previously designed zones into separate electric circuits. Why is it so important? The answer to this question is quite simple, and we will discuss it using an example of a single-family house. The first and one of the most important reasons for this is the ability to separate an illumination circuit from, for example, electric sockets. When a lamp needs replacing, we deactivate the electric circuit associated with the illumination system in a room, thanks to which we can use a drill connected to a socket that remains operational. Additionally, if the rest of the house runs on a separate circuit, the occupants are not forced to sit in the dark, as the illumination system is fully operational there.
Distribution boards also fulfil the metering function. It does not only involve simple measurements of electricity consumed, but also operates smart energy management features available in more advanced solutions, as well as facilitates remote monitoring or control of the entire electric system, based on various parameters.
A distribution board also comes equipped with components that signal the presence (or lack) of voltage in a given circuit. These components usually communicate with users via indicators using different colour codes to signal various states.
Finally, we must mention the most recognisable distribution board feature, namely, the protection function. Everybody knows the importance of components protecting users against an electric shock possibly resulting from a short-circuit in an electric system. They are responsible for protecting human life and health as well as property, as a short-circuit can result in an electric shock or fire. Short-circuit, overload or overvoltage protections account for a large part of all components installed in the distribution board.
The importance of control gear should also be noted. It facilitates automatic control of electricity consumers by, for example, temporarily switching on or off their power supply, controlling dusk illumination sensors or managing the current flow intensity.
All of these functions are performed by various devices enclosed in an electric cabinet. Correct operation of the entire system usually depends on their quality, precision and reliability. Therefore, it is worth having a closer look at parameters and characteristics of modular equipment offered by market-leading manufacturers.
Modular equipment – types and applications
Modular equipment includes devices designed as cubical modules with standardised dimensions, which fulfil various functions in an electric system. Identical mounting dimensions facilitate their installation on DIN rails. A significant advantage of introducing identical guidelines for all modular equipment solutions consists in the fact that even components provided by several different manufacturers are compatible with one another and can be used to create an operational system. Such features as incredibly easy assembly and disassembly, as well as independence from other, separated distribution board components, facilitate their modifications and replacements.
The TME product catalogue contains modular equipment offered by such global giants as Eaton, Siemens, Schneider, Hager and Legrand. With their long-standing experience in the field of implementing more and more advanced and refined modular components, these industry leaders are virtually unbeatable.
1) Residual current circuit breakers are among the most important and indispensable components enclosed in each electric box. Their principle of operation consists in deactivating the power supply when “differential current”, i.e. voltage, is detected on an electric device enclosure. It usually happens following damage to an electric system resulting from insulation failure and transmission of voltage onto the metal enclosure components. In such circumstances, an imminent risk of electrocution or fire occurs. To prevent these, the device detects the current intensity difference between the phase conductor and the neutral conductor, and cuts off the voltage supply to the system.
Residual current circuit breakers in the TME product catalogue
The residual current circuit breakers offered by Legrand, with the manufacturer’s catalogue number: P 312 B10-30-AC DX, are a perfect example here.
It is designed for 230 V AC systems. Its specifications include: rated current of 10 A, differential current of 30 mA, and maximum surge current that should not cause the module failure of 250 A. The manufacturer specifies that the device’s mechanical strength guarantees withstanding up to 20,000 operation cycles, and its electric life amounts even up to 10,000 operating cycles. The short-circuit strength of this model reaches even up to 6000 A. Such factors as an attractive design and attention to detail confirm Legrand products’ leading position on the electric equipment market.
Residual current circuit breaker with differential current rating of 30 mA
2) Overcurrent circuit breakers protect systems against the adverse effects of a current flow whose intensity exceeds the permissible value. This protection element also trips during short-circuits, thus triggering an automatic power cut-off. The main characteristics of overcurrent circuit breakers include such parameters as the number of overcurrent circuits and poles, or the rated current. The time-current characteristic of a circuit breaker is extremely important, as it determines the time and current at which the protection feature should cause the power supply to be deactivated.
Overcurrent circuit breakers in the TME product catalogue
Eaton overcurrent circuit breakers mounted on DIN rails
Eaton Electric’s extensive modular equipment assortment includes overcurrent circuit breakers designated as CLS6-B10/3. It is a 3-pole protection device with the rated current of 10 A. Its mechanical strength ensures even 8000 operation cycles, while its high short-circuit strength guarantees safe operation even at 6000 A. The CLS6 series overcurrent circuit breakers come with tripping indicators which report the current switching times with a green or red colour code. The time-current characteristic for this model is specified as B, which means that instant tripping occurs when the rated current value is exceeded 3 or 5 times. Such solutions are perfectly suitable for socket or illumination circuits in household applications.
3) Motor breakers, commonly known as thermal overload relays, are tasked with protecting electric motors. Such protection devices are typically used in workshops or industrial facilities where large electric motors are operated. The instantly cut off supply voltage, once a short-circuit, overload or phase failure occurs. Motor circuit breaker ensure safe machinery start-up, as well as convenient motor operation control and monitoring.
Motor breakers in TME product catalogue
Hager is one of the leading modular equipment manufacturers, and the MM506N circuit breaker designed as an ergonomic module is an example of a device in which every detail is refined to perfection. Its rotational toggle lever facilitates motor switching on and off. Its enclosure is fitted with an overload trigger setting knob scaled in amperes. The setting range is 1 ÷ 1.6 A, and the maximum permissible motor power handled by this circuit breaker is 0.55 kW. The module is neatly designed, and its connection to an electric system and operation will not cause any problems even for an inexperienced DIY enthusiast.
Circuit breaker for motors with maximum power rating of 0.55 kW
4) Surge arresters are components that are vital to ensure the safety of electric devices connected to the mains. They are commonly known as lightning arresters, and they are designed with a view to limiting the mains voltage and stabilise it at a level that is safe for consumers. A proper module protects devices from the effects of voltage surges caused by a nearby lightning strike. Sophisticated electronic equipment is usually highly sensitive to overvoltage, so even minor fluctuations can affect its operation. Surge arresters are designed to protect it against any adverse impact.
Surge arresters in the TME product catalogue
Surge arrester, type 2+3
Schneider Electric offers tried-and-tested, high-performance surge arresters. A9L08400 is a 4-pole, 2+3 type arrester. This designation informs us that the module is designed to ensure protection against medium to low overvoltage, which makes it a perfect solution for household distribution boards to protect the above-mentioned sensitive electronic equipment. As specified by the manufacturer, the permissible surge current rating is 8 kA, at the operating temperature even up to 60°C. Thanks to their reliability, Schneider Electric products are leaders on the modular equipment market.
5) Switch disconnectors are designed to disconnect power supply in industrial-grade control cabinets. They are usually installed on a cabinet enclosure to facilitate cutting off the current supply without opening it. Due to the fact that they frequently operate in adverse environmental conditions, such disconnectors feature a high IP rating, and are located within the operator’s sight. It is particularly important in emergencies when an instant response is required.
Switch disconnectors in the TME product catalogue
Siemens is well-known to virtually everyone. It is one of the electric equipment industry leaders and offers a broad range of modular automation equipment. Therefore, let us present the 3LD2022-0TK11 switch disconnector offered by this manufacturer. This product, designed with attention to every detail, comes with the IP65 degree of protection to handle even most adverse operating conditions. Its basic parameters include the maximum switched power of 7.5 kW and rated current of 16 A. It comes with an ergonomic 0/1 knob, and the entire module dimensions are 49 x 49 mm. The highest quality of materials used in its design ensures its fault-free operation.
Panel-mounted Siemens disconnector
The models presented in this article are just examples of products that are available in the modular equipment category of the TME product catalogue. The available range of circuit breakers is obviously much broader, thanks to which you can always select a perfect solution for any system, whether it is to protect a small flat or single-family home, an extensive industrial installation or a cutting-edge network in office buildings.
Transfer Multisort Elektronik (TME) is one of the world’s largest global distributors of electronic components, electrotechnical parts, workshop equipment, and industrial automation. The catalog includes over 1,500,000 products from 1,300 leading manufacturers. TME’s modern logistics centers in Łódź and Rzgów (Poland), with a combined area of over 40,000 m², ship nearly 6,000 packages daily to customers in more than 150 countries.
TME also invests in the development of knowledge and skills of young engineers and electronics enthusiasts through the TME Education project, and supports the tech community by organizing the TechMasterEvent series, promoting innovation and experience exchange.
