Circuit Breakers

Single phase / three phase circuit breakers / fuses

Automatic fuses

Automatic fuses or also called automatic circuit breakers are electromechanical components in the electrical circuit that protect the power transmission and power line, as well as the consumers connected to it. Circuit breakers are an important part of electrical systems and play a crucial role in protecting electrical installations and devices from electrical system overloads and short circuits. They are designed to ensure safety and prevent possible damage to electrical appliances or prevent accidents such as fire. Its main function is to interrupt the phase line when a problem occurs, unlike the ordinary fuse which is used once, the circuit breaker is reset manually or automatically. Circuit breakers are designed to react quickly and interrupt the electrical current when an irregularity is observed in the system.

Automatic fuses are designed to react quickly and interrupt the electrical current when an irregularity is observed in the system. They can react to an overload, short circuit or contamination of the electrical network. When the automatic fuse detects such an anomaly, it automatically shuts off, cutting off the electrical current. One of the great advantages of automatic fuses is that they are automated and do not require constant monitoring. They can function independently and react quickly in case of need. This makes them extremely convenient and reliable for use in various environments and applications. Also, automatic fuses are economical and effective. They can save energy and prevent unnecessary losses by reacting quickly and interrupting the electric current when necessary. This helps prevent damage to electrical devices and maintain system efficiency.

Features when choosing a fuse/circuit breaker?

• voltage class
• the magnitude of the current
• fuse type
• off curve(response time)
• single-phase
• single phase with zero break
• three-phase

How do circuit breakers work in the event of a problem?

For a fuse to operate, a fault must first occur. In small mains and low voltage mains fuses this happens within the device itself, usually using the process of heating when an electric current flows or magnetic effects of the electric current. High current or high voltage fuses are usually equipped with protective relay pilot devices to sense a fault condition and operate the opening mechanism. They usually require a separate power source, such as a battery, although some high-voltage circuit breakers are self-contained with current transformers, protective relays and an internal control source.

Once a fault has occurred in the fuse circuit, the circuit breaker contacts must open to break the circuit. This is usually done by using mechanically stored energy contained in the circuit breaker, such as a spring or compressed air, to separate the contacts. Circuit breakers can also use the higher current caused by a fault to separate the contacts, such as thermal expansion or a magnetic field. Small fuses usually have a manual control lever to switch off the load or restore an already broken line, while larger units use solenoids to switch off the mechanism and electric motors to restore spring energy.

Amortization of contacts

The circuit breaker contacts must be able to withstand the load current without overheating and must also withstand the heat caused by the arc produced when the circuit is broken (opened). Contacts are made of copper or copper alloys, silver alloys and other highly conductive materials. The service life of the contacts is limited by the erosion of the contact material due to wear of the contacts and due to wear of the mechanical element. Miniature and molded case circuit breakers are usually discarded when the contacts wear out, but high power circuit breakers and high voltage circuit breakers have replaceable contacts. There are various methods of dealing with arcing caused by opening the contacts.

Important when choosing a circuit breaker

Automatic fuses or fuses, in addition to being selected according to the rated current that will flow through them, have a parameter and a maximum short-circuit current that they can safely interrupt. In the case of a short circuit, when the electrical contacts open to interrupt the huge current that is passing, an arc forms between the two poles of the open contacts, which would allow the current to continue to flow. This condition can create conductive ionized gases and molten or vaporized metal, which can cause further arcing or create additional short circuits, potentially exploding the circuit breaker, equipment and installation in which it is installed. Typical household panel circuit breakers are designed to interrupt short-circuit currents in the order of 6~10 kA (6000 ~ 10,000 A)

What should we look for when choosing a fuse?

Amount of current

Automatic circuit breakers are an essential part of the construction of electrical networks. They are usually rated at 1A, 2A, 4A, 6A, 10A, 13A, 16A, 20A, 25A, 32A, 40A, 50A, 63A, 80A, 100A. Before we estimate the magnitude of the current fuses we need to build the electrical circuits that will control each of the fuses. For example, will they be large consumers such as an oven, water heater, air conditioners or lighting, sockets and others. Usually, during construction, a main automatic fuse of size 63A or 50A is installed, which is responsible for the entire electrical system of the room, house, apartment, office, warehouse, shop. For the remaining circuits, breakers are usually chosen to play the role of a fuse, with a current size of 20A or 25A. For individual consumers, a fuse with a current size of 16A, 10A or 6A can be chosen. The choice of a fuse is an extremely important choice, because if it has too much current compared to consumers, it will not work in case of damage, and if it is too small, it will switch off the electrical circuit permanently and will not allow the normal operation of electrical appliances.

Exclusion curve

Trip curve is the reaction time of the corresponding circuit breaker in case of overload or failure of the electrical system, which is extremely important to preserve operation and prevent burning or damage to electrical appliances. A tripping curve is denoted by the letter B, C or D, which indicates the instantaneous tripping current - i.e. the minimum value of current which causes the circuit-breaker to open without intentional delay (ie for less than 100 ms) expressed in terms of In: for curve B above 3 In, for curve C from 5In to 10In, for curve D from 10In to 20In etc.

Types of automatic fuses / circuit breakers:

• low voltage circuit breakers
• medium voltage circuit breakers
• high voltage circuit breakers
• electromagnetic switches
• thermomagnetic circuit breakers
• magnetic - hydraulic breakers
• Smart fuses