What is a circuit breaker? Automatically scratched electrical switch that designed to protect the depreciated electrical circuit cause to any overload or short circuit. Its main function is to interrupt the current flow after detecting an error.
Not like the fuse, That operates once and then it will be change place from another place. manually or automatically the circuit breaker can be reset to recommence general operation.
Circuit breakers are made in miscellaneous cities that protect low-current circuits or separate domestic machinery from small devices, Up to large switchgear designed to defend, exalted voltage circuits feeding an all in the city. The generic function of a circuit breaker, or fuse, is often abbreviated as OCPD (over-current protection device) as an automatic way to remove power from a faulty system.
Thomas Edison described the initial appearance of the circuit breaker in the 1879 patent application, though his commercial electricity distribution system used fuses. The purpose is to protect the light circuit wiring from accidental short circuits and overloads.
In 1924 a modern miniature circuit breaker, like the one now used by Brown, Bowery, and C.I., patented. Hugo Stotz, an engineer who sold his company to the BBC, credited with being the inventor of DRP 458392.
The interconnection of many generators on the electrical grid required the improvement of circuit breakers with increasing voltage rating and increased the ability to safely intercept short circuit currents created by the networks.
Normal air-brake manual switches made dangerous auras when discontinuing at high voltages. This oil gives different forms of cooling and disrupting associated contacts and pressure by pressurizing airflow or pressurized oil.
By 1935, singularly designed circuit breakers applied in the Boulder Dam project used 8 series breaks and pressurized oil flows at three cycles of AC power frequency to obstruct drawback up to 2,500 (MVA).
All things very remarkably depending on the voltage class, current rating, and like of circuit breaker but All circuit breaker systems have common features in operation. The circuit breaker must first detect an error condition. In small Maine and low voltage circuit breakers, this is usually done within the device. Typically, the heating or magnetic effects of an electric current employed.
Circuit breakers for large currents or high voltages are usually equipped with protective relay pilot devices to understand a faulty condition and to conduct the opening process. These typically needed an individual power source like a battery, although some high-voltage circuit breakers are self-dependent with current transformers, resistant relays, and an interior control power source.
Once the fault detected, the breaker contacts must be opened to stop the circuit being disrupted; this is often usually done using the mechanically stored power contained within the breaker, like a spring or compressed gas to separate the contacts. Circuit breakers are also used to isolate faulty contacts, such as thermal expansion or magnetic field, for faulty reasons.
Smaller circuit breakers usually have manual control levers to switch offloads or reset tripod breakers. But larger units use solenoids and electric motors to trip the mechanism to return power to the fountain. Circuit breaker contacts must carry the load current without excess load, and also prevent the heat of the arc produced when the circuit disrupted. The contacts are made of copper or copper mixtures, silver mixtures, and other highly conductive materials. The service life of the contact limited by the loss of the material of the contact due to the current interrupting. A pressure created when a high current or voltage obstructed.
The length of the pressure is usually proportional to the voltage while the intensity (or heat) is proportional to the current. This pressure must in a controlled manner, cooled and extinguished so that the gap between the contacts can again withstand the voltage of the circuit. Different circuit breakers make a vacuum, air, insulating gas or oil in medium size. Their several techniques used to relieve stress:
- To lengthen or remove the pressure
- Intensive cooling (in the jet chamber)
- Partially RK divided
- Zero-point zeroing (contacts are open at the AC current of zero current, no-load current broken when opening effectively The zero-crossing doubles the line frequency; that is, 100 times per second for 50 Hz and 120 bar Hz per AC). In seconds
- Connect the capacitors in parallel to the DC circuit contacts.
Low-voltage miniature circuit breakers (MCBs) use air alone to quench the pressure. These circuit breakers contain so-called arc coots, a stack of mutually heated parallel metal plates that share pressure and cool. Splitting the pressure into smaller pressures causes the pressure to cool down when the pressure voltage increased and acts as an additional resistor that limits the currents through the circuit breaker.
The current-carrying parts closest to the contacts easily suppressed by the magnetic force of the current path, although magnetic blot coils or adjustable magnets can split the pressure in the arc Kutter (used in circuit breakers for higher rating).
At larger ratings, oil circuit breakers rely on the evaporation of some oil to cause the oil jet to explode through pressure. Gas (usually sulfur hexafluoride) circuit breakers sometimes extend the pressure using a magnetic field and then rely on the dielectric strength of sulfur hexafluoride (SF6) to suppress the expansion pressure.
When the pressure is very small (less than 2-3 mm (0.08-0.0 inches)) it is less. Vacuum circuit breakers often used in modern medium-voltage switchgear at 38,000 volts. Air circuit breakers can use compressed air to disperse pressure, or alternatively, as contacts quickly turn into a small sealed chamber, the escape of displaced air thus suppressed.
Circuit breakers usually able to finish all current very quickly: Depending on the device’s age and construction, the pressure usually lowered to between 305 ms and 150 ms after the process broken. Determines the maximum current value and the quality of the let-throw energy circuit breakers.
Circuit breakers rated both by the simple current. And the most short circuit current that they can safely intercept which they supposed to carry. This next image is the Breaker’s Ampere Disruptive Capacity (AIC). Under short-circuit. The most likely short circuit to calculated or measured as a condition may be many times the normal rated current of the current circuit.
When electrical contacts are open to impede a huge current, open contacts have a tendency to create pressure that allows the current to continue. This condition can create conductive ionized gases and molten or vaporized metals. It can cause further continuity of pressure or the creation of additional short circuits, possibly leading to the explosion of the circuit breaker and the equipment installed on it.
Therefore, circuit breakers must integrate various features in order to split and relieve the pressure. The maximum short circuit that the breaker can interrupt determined by the current test. The application of a breaker to a circuit with a potential short-circuit current. And it can safely prevent any defect from the failure of the breaker compared to the breaker’s ability to interrupt the rating.
In the worst case, the breaker can successfully interrupt the fault, only to explode when reset. Common domestic panel circuit breakers rated for 10 kA (10000A) short circuit current barriers.
Panelboards may not have sufficient barrier capability to used on panel boards used to protect control circuits or small appliances; These circuit breakers called “complementary circuit protectors” to distinguish them from distribution-type circuit breakers.
Standard current ratings
Circuit breakers use a custom number system to cover different ratings by setting values. Smaller circuit breakers have a specific trip setting; To change the operating current value it is necessary to change the whole circuit breaker.
While larger circuit breakers permitted to apply standard components. There may be adjustable trip settings with a setting intended to improve safety. For example, a circuit breaker with a 400-ampere “frame size” could keep its overcurrent detection set to secure only one feeder cable, operating at 300 amperes only.
Low-voltage for example (less than 1,000 vac) used these types like commercial, domestic and industrial applications.
- Smaller circuit breaker (MCB) 125A current trip features are generally not permanent. Thermal or thermo-magnetic activity. The breakers described above are in this section.
- Molding Case Circuit Breaker (MCCB) Thermal or thermo-magnetic operation up to 1,600 current. Trips may be adjustable to current larger ratings.
- Power circuit breakers for Low-voltage can mounted on a low-voltage switchboard or in switchgear cabinet for the multi-tier.
The direct current circuit breaker consists of a blow-out coil that creates a magnetic field that rapidly expands the pressure.
The design includes the following elements:
- Activator lever – Used to manually trip and reset the circuit breaker. It also indicates the status of the circuit breaker (on or off / tripod). Most breakers designed so that they can trip even when the lever held or locked in an “on” position. It referred to as a “free trip” or “positive trip” operation for the sometimes.
- Actuator mechanism – merges or separates contacts.
- Contacts – Allow currents to touch and brake currents when removed.
- Bimetallic Strip – Separates contacts in response to short, long-term overdose
- Calibration screw – Allows the manufacturer to adjust the trip current of the device properly after assembly.
- Solenoid – Communicates quickly in response to high overcurrent
- Arc separator/fire extinguisher
Medium voltage circuit breakers, rated between 1 and 72 kV. It can integrated into metallic closed switchgear lineups for indoor use or individual components. And that can be installed externally at a substation. Air-brake circuit breakers replaced the oil-filled unit for indoor applications. They replaced by vacuum circuit breakers (up to about 40.5kV). The features of MV breakers offered by international standards such as IEC 62271.
Medium-voltage circuit breakers almost always use separate current sensors and protective relays, without relying on built-in thermal or magnetic overcurrent sensors.
by high-voltage breakers will protect and controlled Electric power transmission networks. The definition of high voltage varies according to the latest definition of the International Electronic Technology Commission (ICC). But generally considered to 72.5 kV or more in the case of power transmission. Defensive relay schemes at substations can be complex, protecting equipment and buses from various types of overload or ground/earth defects.
Here have described the ground fault circuit interrupter (GFCI), or Residual Current Device (RCD).