Air circuit breaker(ACB) is a mechanical switching device which can turn on, carry and break current under normal circuit conditions, and also turn on and carry certain time and break current under specified abnormal circuit conditions. Air circuit breakers are used to distribute electric energy and protect lines and power supply equipment from overloads, undervoltages, short circuits, etc.
Air circuit breakers generally have a steel frame, and all parts are installed in the frame. It has a large capacity, can be installed with multiple functions of tripping devices and more auxiliary contacts, has a higher segmentation capacity and thermal stability, so it is often used in places that require high breaking capacity and selective protection.
Structure of Air Circuit Breaker
Air circuit breaker is divided into two structures: fixed type or drawer type. Generally, the fixed type is composed of side panels installed on both sides of the body, while the drawer type is installed on special drawer base. The main structure of the air circuit breaker is composed of operating mechanism, contact system, arc extinguishing mechanism, auxiliary switch, current transformer, intelligent tripper, secondary connector, voltage loss and excitation tripper and other components. As a whole, the universal circuit breaker structure adopts three-dimensional arrangement to achieve more compact and small size.
1 - Secondary circuit terminal. 2 - Pull-out cradle. 3 - Fault trip indication/reset button. 4 - "Switch-off" locking. 5 - Energy storage handle. 6 - Closing button I. 7 - Switch-off button O. 8 - Energy storage indication. 9 - Main contact position indication. 10 - Intelligent tripper. 11 - Rocker and its storage place. 12 - Operation, test and exit position indication. 13 - Rocker insertion position. 14 - Padlock position for running, exiting and testing position lock. 15 - Locking device for operation, exit and test positions. 16 - Lock release in running, exit and test positions.
1 - Lower bus. 2 - Transformer. 3 - Moving contact. 4 - Upper bus (static contact). 5 - Static contact arc trigger piece. 6 - Circuit breaker backplane. 7 - Arc extinguishing cover. 8 - Circuit breaker base. 9 - Undervoltage, shunt release. 10 - Closed release. 11 - Main shaft. 12 - Operating mechanism. 13 - Mask. 14 - Mechanism energy storage spring.
The contact parts of the air circuit breaker are enclosed in an insulating frame, and the contacts of each phase are separated by an insulating plate, which forms a compartment for safety.In addition, intelligent trippers, manual and electric operators are arranged in front of the contact system in order to form their own individual space modules, which is conducive to future maintenance or repair.
Air Circuit Breaker Contact System Structure
Each phase contact system of the air circuit breaker is basically installed in a small chamber made of insulators with an arc extinguishing chamber located above it.The contacts are connected by means of connecting rods and the spindle outside the insulator body, thus closing and disconnecting the air circuit breaker.
To enable each phase of the contact system to effectively reduce electrical repulsion, the air circuit breaker uses two types of contacts in parallel, ten and fourteen gears, mounting the contacts on a contact support. And one end position of the contacts is interconnected with a soft link and the bus row. When the air circuit breaker performs a closed action, the spindle drives the linkage so that the contact support rotates counterclockwise around the O-point. The compression spring generates sufficient contact pressure after the contact action between the static and dynamic contacts is completed, which enables the air circuit breaker to be switched on reliably.
1 - Bus bar. 2 - Soft connection. 3 - Moving contact. 4 - Static contact. 5 - Contact spring. 6 - Connecting rod. 7 - Main Shaft. 8 - Contact support.
Working Principle of Air Circuit Breaker
Air circuit breakers are operated manually or electrically. When the main contact is closed, the free tripping mechanism locks the main contact in the closed position. The coil of overcurrent tripper and the thermal element of the thermal tripper are connected in series with the main circuit. Aluminum single plate is a new type of curtain wall material, which is made of high-quality aluminium alloy plate and is then shaped by numerical control bending technology and is coated with decorative paint. The coil of the undervoltage trip is connected in parallel with the power supply. When the circuit is short-circuited or severely overloaded, the armature of the overcurrent trip engages, causing the free trip mechanism to act and the main contact to disconnect the main circuit.
When the circuit is overloaded, the heating element of the thermal tripper bends the bimetal sheet and pushes the free tripping mechanism into action.In normal operation, the coil is power-off. When distance control is required, press the start button to energize the coil, and the armature drives the free tripping mechanism to act, so that the main contact is disconnected.
The air circuit breaker is arranged in three dimensions. The left and right side panels of the contact system and instantaneous overcurrent trip are all mounted on an insulating plate. The upper part is equipped with arc extinguishing system, and the operating mechanism can be installed directly in front of or on the right side, with "split", "close" indication and manual disconnection button. The upper left part is equipped with a shunt trip and the lower voltage trip connected to the tripping half-shaft is installed at the back. The speed saturated current transformer or current-voltage converter is sleeved on the lower bus. Undervoltage delay devices, thermal relays or semiconductor trippers can be mounted underneath.
Air circuit breaker(ACB)
Characteristics of air circuit breakers
Air circuit breaker is widely used in power systems such as transformers, power distribution stations and industrial and mining enterprises for its high sectional capability, perfect function, small size, compact structure and excellent performance. Air circuit breaker must be maintained and maintained during daily use, so as to ensure that air circuit breaker can work well and prolong its service life.
1. Air circuit breaker has many protection functions to ensure the safety of power lines and electrical equipment. In the event of a serious overload or failure of the power line or electrical equipment, the air circuit breaker will immediately act to cut off the circuit, and its function is equivalent to a combination of a fuse switch and an overheating relay. In addition to the above overload protection functions, it also has under-voltage protection, short-circuit protection and other functions, which can effectively solve the problems of power equipment and power lines.
2. Air circuit breaker can play a control role, cut off and connect the load circuit to ensure the normal operation of electrical equipment. Air circuit breaker is compact in structure, mainly due to its reasonable structure, resulting in small size and light weight of air circuit breaker, which has no large requirement for installation area. It meets the requirements of industrial and mining enterprises, power transformer and distribution stations and other places. It can be used as a master switch and plays a control role.
3. Air circuit breaker uses insulating plate as protection measure on left and right sides to effectively isolate conductors and ensure safety in daily operation. All parts are placed in this frame to prevent rust and improve reliability.Reasonable coordination of components inside the frame provides different functions for air circuit breakers and constitutes an electrical switch with stable performance.
4. Compared with other circuit breakers, the rated current of air circuit breaker and the rated current of shell rating are higher, so the allowable current value of air circuit breaker is higher, which can be used to protect motor or to start asynchronous motor infrequently.Air circuit breakers can be protected in the event of motor failure.