What are the components of the plastic shell low voltage circuit breaker and what are the functions

The structure (components) of different working principles of circuit breakers are also different, there are thermal type, there are hydraulic electromagnetic type, there are electronic type, I will say hydraulic electromagnetic type. There are mainly terminal blocks, load terminals, contact arms, detach components, coils, delay tubes, shells, manipulators, nickel skeletons, and some will also have auxiliary switches.

A low-voltage circuit breaker (formerly known as an automatic switch) is a kind of switching appliance that can not only turn on and off normal load current and overload current, but also turn on and off short-circuit current. In addition to playing a controlling role in the circuit, the low-voltage circuit breaker also has certain protection functions, such as overload, short circuit, undervoltage and leakage protection. There are many classification methods of low-voltage circuit breakers, according to the use of categories, there are selective type (protection device parameters are adjustable) and non-selective type (protection device parameters are not adjustable), according to the arc extinguishing medium, there are air type and vacuum type (at present, most of the domestic ones are air type).

The capacity of the low-voltage circuit breaker is wide range, from a minimum of 4A to a maximum of 5000A. Low-voltage circuit breakers are widely used in low-voltage power distribution systems at all levels of feedout lines, power control of various mechanical equipment and control and protection of power terminals.

The low-voltage circuit breaker is composed of a contact, an arc extinguishing device, an operating mechanism and a protection device.

1.Contact system.

Contacts (static and moving) are used in circuit breakers to make or break circuits.

The basic requirements for contacts are:

1) It can safely and reliably turn on and break the circuit current of the limit short-circuit current and below;

2) Long-term working current;

3) Within the specified number of electrical life, there will be no serious wear after switching and breaking.

The contact types of commonly used circuit breakers are butt contacts, bridge contacts and plug-in contacts. Butt and bridge contacts are mostly surface contact or line contact, and silver-based alloy inserts are welded on the contacts. In addition to the main contact, the large circuit breaker also has secondary contacts and arc contacts in each phase.

The sequence of action of the circuit breaker contact is that when the circuit breaker is closed, the arc contact is closed first, then the secondary contact is closed, and finally the main contact is closed; When the circuit breaker is broken, on the contrary, the main contact carries the load current, the role of the secondary contact is to protect the main contact, and the arc contact is used to bear the arc ablation when the current is cut off, and the arc is only formed on the arc contact, so as to ensure that the main contact is not ablated by the arc and works stably for a long time.

2.Arc extinguishing system.

Arc extinguishing systems are used to extinguish the arcing between contacts that occurs when the circuit is disconnected. The arc extinguishing system consists of two parts: one is a strong spring mechanism, which makes the circuit breaker contacts quickly separated; One is to provide an arc extinguishing chamber above the contact.

3.Actuating mechanism.

The operating mechanism of the circuit breaker includes two parts: the transmission mechanism and the tripping mechanism.

1) Transmission mechanism:

According to the different operation modes of circuit breakers, it can be divided into: manual transmission, lever transmission, electromagnet transmission, and motor transmission; According to the closure method, it can be divided into: storage closure and non-storage closure.

2) Free Trip Mechanism:

The function of the free trip mechanism is to realize the connection between the transmission mechanism and the contact system.

4.Protector.

The protection device of the circuit breaker is realized by various trippers.

The types of trippers of circuit breakers include: undervoltage trippers, overcurrent trippers, shunt trippers, etc. Overcurrent trippers can also be divided into overload trippers and short-circuit trippers.

The undervoltage tripper is used to monitor the fluctuation of the operating voltage, when the grid voltage is reduced to 70% to 35% of the rated voltage or when the grid fails, the circuit breaker can be immediately disconnected, and when the supply voltage is below 35% of the rated voltage, it can prevent the circuit breaker from closing. Undervoltage trippers with delayed action prevent voltage fluctuations caused by sudden load spikes that could cause the circuit breaker to break inappropriately. The delay time can be 1s, 3s, and 5s.

Shunt trippers are used for remote control or thermal relay action disconnect circuit breakers.

Overcurrent trippers are used to prevent overloads and short-circuits on the load side.

Generally, the circuit breaker also has a short-circuit locking function, which is used to prevent the circuit breaker from being closed before the fault is eliminated after the circuit breaker is broken due to a short-circuit fault. Under the condition of short circuit, the circuit breaker is broken, and the locking mechanism is operated to keep the circuit breaker mechanism in the breaking position, and the circuit breaker closing mechanism cannot be operated and the circuit cannot be connected before the locking mechanism is not reset.

Structure summary: The low-voltage circuit breaker is composed of an operating mechanism, a contact, a protection device (various trippers), an arc extinguishing system, etc. It can realize short circuit, overload, and loss of voltage protection.

The components of the low-voltage circuit breaker are mainly as follows:

1. The operating mechanism is generally composed of mechanical mechanisms such as four connecting rods and five connecting rods;

2. The shell is composed of insulating materials, mainly nylon, etc.;

3. The contact system is composed of dynamic contacts and static contacts, which may be single breakpoints or double breakpoints;

4. Arc extinguishing system, extinguishing the arc generated when the contact is broken;

5. The overload protection mechanism is generally composed of hot bimetallic components, and there is also an oil cup type;

6. The short-circuit protection mechanism is generally composed of an iron core, a coil, a reaction spring, etc.

7. The locking mechanism is generally composed of metal or plastic. The locking mechanism is rarely mentioned, but in practice it can also be incorporated into the operating mechanism.

Plastic shell circuit breakers (hereinafter referred to as circuit breakers) are generally used for power distribution, but also for the protection of motors. Under normal circumstances, the circuit breaker can be used for infrequent conversion of the line and infrequent starting of the motor. Circuit breakers for power distribution are used in the distribution network to distribute electrical energy and to protect lines and power supply equipment from overload, short circuit and undervoltage.

Circuit breaker for protection motor, used in the power distribution network for starting and breaking of squirrel cage motors and as overload, short circuit and undervoltage protection of rat motors.

The working principle of the plastic shell circuit breaker is to destroy the vertical, mechanical interlocking device, generally using wire rope or lever mechanism, to ensure that the operation handle of the isolation switch is not slender before the circuit breaker cuts off the power supply. Electrical interlocking device, electrical interlocking generally has two interlocking methods, one is to control the handle of the isolation switch through the linkage auxiliary contact on the operating mechanism. When the circuit breaker is not disconnected, the operating handle of the disconnector cannot be operated.

Another type of electrical interlocking is to use the linkage auxiliary contact on the distance switch operating mechanism to control the circuit breaker. When the handle of the disconnector is pulled, the linkage auxiliary contact makes the circuit breaker act to cut the old state break circuit, so as to prevent the accident of pulling the distance switch with load.

If it is **: frame circuit breaker body, control unit, cradle (without, fixed without), rear wiring horizontal mode (standard is horizontal), phase spacer, secondary terminal cover, energy storage motor, closing coil MF, shunt coil MX, plus accessories (standard configuration does not need to add);

As long as the plastic shell is selected, the cutting and control unit will have a face price, and the price of the accessories will come out after the face price is discounted.

The classification of low-voltage circuit breakers is larger, and the circuit breakers that meet the standards (commonly known as switches and molded case switches) are generally called low-voltage circuit breakers (AC 1500V DC 1000V below, rated current 6A 6300A (the latest circuit breaker to 8000A)), molded case circuit breakers, circuit breakers with leakage function, frame circuit breakers (also known as universal circuit breakers), electronic circuit breakers (also known as intelligent circuit breakers), some miniature circuit breakers (in line with the standard, the general shell current is 100A), etc.

Function: Circuit breaker standard definition: A mechanical switching electrical appliance that can turn on, carry and break the current under normal circuit conditions, and can also be turned on and carried for a certain time and breaking current under the specified abnormal circuit.

It is mainly used to automatically disconnect the circuit, protect the circuit and the equipment in the circuit in the case of overload and short circuit (leakage circuit breaker and leakage current protection).

The circuit breaker has a good arc extinguishing ability, and will automatically trip in the case of short circuit and high current; In high-voltage and high-current circuits, it is often used as an operating electrical appliance for power outage, power transmission, and switching on and off loads;

The function of the disconnector:

1. After opening, establish a reliable insulation gap, and separate the equipment or line that needs to be overhauled from the power supply with an obvious disconnection point to ensure the safety of maintenance personnel and equipment.

2. According to the needs of operation, change the line.

3. It can be used to divide and combine the small currents in the line, such as the charging current of bushings, busbars, connectors and short cables, the capacitance current of the switching voltage equalizing capacitor, the circulation current when the double bus is replaced, and the excitation current of the voltage transformer.

4. According to the specific situation of different structure types, it can be used to divide and combine the no-load excitation current of a certain capacity transformer.

High-voltage disconnectors can be divided into the following according to their different installation methods:

Outdoor high-voltage disconnector and indoor high-voltage disconnector.

Outdoor high-voltage disconnector refers to a high-voltage disconnector that can withstand wind, rain, snow, dirt, condensation, ice and heavy frost, etc., and is suitable for installation on terraces.

According to the different insulating pillar structure, it can be divided into single-column disconnector, double-column disconnector and three-column disconnector. Wherein single-column disconnector directly uses vertical space as the electrical insulation of the fracture under the overhead bus, therefore, has the obvious advantage that it saves floor space, reduces the lead wire, and the state of opening and closing is particularly clear simultaneously. In the case of ultra-high voltage transmission, after the substation adopts a single-column isolation switch, the effect of saving floor space is more significant.

The main circuit breaker with a current of more than 800A is a frame circuit breaker. The main circuit breaker of 100 630A is molded case circuit breaker. The main circuit breaker of 1 63A is a miniature circuit breaker.

This question is correct, the current of the frame test is more than 400A, and the maximum can be 4000A