An article to let you understand the internal structure of the distribution box

Distribution box composition is mainly divided into two parts. One complete set of components, i.e. power distribution box shell and its related accessories. Two electrical components and related accessories, i.e. air switches and their required accessories.

The cabinet is composed of the following parts.

I. Circuit breaker: both switches, is the main components of the distribution cabinet, commonly used air switch. Leakage switch. Double power automatic transfer switch.

1. Air switch.

A. The concept of air switch.

Air switch is also known as the air circuit breaker, in the circuit for connecting, breaking and carrying the rated operating current and short circuit, overload and other fault currents, and can be in the line and load overload, short circuit, under voltage, etc., quickly break the circuit, for reliable protection. The design of dynamic and static contacts and contact bars of circuit breakers are various, but the main purpose is to improve the breaking capacity of circuit breakers. At present, the use of certain contact structure to limit the peak short-circuit current limit principle when breaking, to improve the breaking capacity of the circuit breaker has an obvious effect, and is widely used.

B. Working principle of air switch.

Automatic air switch, also known as a low-voltage circuit breaker, can be used to turn on and break the load circuit, and can also be used to control infrequently starting motors. Its function is equivalent to the sum of some or all of the functions of the gate switch, over-current relay, loss-of-voltage relay, thermal relay and leakage protector and other electrical appliances, and is an important protection appliance in the low-voltage distribution network.

Automatic air switch has a variety of protection functions (overload, short circuit, under voltage protection, etc.), adjustable action value, high breaking capacity, easy operation, safety and other advantages, so it is now widely used.

2. Leakage protection switch.

A. Leakage protection switch concept.

Both with leakage protection function, people touching the charged body will trip to ensure personal safety, is the main function of the leakage protector; electricity-using equipment if the insulation is not good leakage to the shell, the leakage protector will also trip to avoid human touch electrocution. It also has the function of current flow interruption, overload protection and short circuit protection.

B. The working principle of the leakage protection switch.

The working principle diagram of the earth leakage protector. LH in the figure is a zero sequence current transformer, which consists of a core made of PoMo alloy, and a secondary coil wound on a circular core to form the detection element. The phase and neutral wires of the power supply pass through the circular hole and become the primary coil of the zero-sequence transformer. The rear line of the transformer is the protection range.

C. The role of the leakage protection switch:

1, when the electrical equipment or line leakage or grounding fault, can cut off the power supply before the person has touched. 2, when the human body touches an electrically charged object, can cut off the power supply within 011s, thereby reducing the degree of injury to the human body from the current. 3, can prevent fire accidents caused by electrical leakage.

3. Double power automatic transfer switch.

A. The concept of dual power automatic transfer switch:

Dual power automatic transfer switch for power two-choice automatic switching system, after the first road failure dual power automatic transfer switch automatically switch to the second road to the load power supply, the second road failure then dual power automatic transfer switch automatically switch to the first road to the load power supply. Suitable for UPS-UPS, UPS-generator, UPS-utility, utility-utility and any two-way power conversion.

II. SPD

A. The concept of surge protector.

Surge protector, also known as lightning protection, is a variety of electronic equipment, instruments, communication lines to provide safety protection of electronic devices. When the electrical circuit or communication lines because of external interference suddenly produce spikes in current or voltage, surge protector can be shunted in a very short period of time to avoid damage to other equipment in the circuit

B. Surge basic knowledge:

The main function of a surge protector system is to protect electronic equipment from damage caused by "surges". So, if you want to know what a surge protector does, you need to understand two questions: What are surges? Why do electronic devices need their protection?

A surge, also called a surge, is, as the name implies, a momentary overvoltage that exceeds the normal operating voltage. Essentially, a surge is a violent pulse that occurs in just a few millionths of a second. Possible causes of surges are: heavy equipment, short circuits, power switching, or large engines.

A surge or transient voltage is a voltage that substantially exceeds its rated level during the flow of electrical energy. In the United States, the standard voltage for wiring in the average home and office environment is 120 volts. If the voltage exceeds 120 volts, problems can arise and surge protectors help prevent that problem from damaging computers.

C. The role of surge protectors.

The first line of defense should be connected to the user power supply system inlet line between each phase and the earth's high-capacity power supply surge protector. General requirements of the level of power protection device with 100KA / phase above the maximum impact capacity, the required limit voltage should be less than 2800 V. We call CLASS I level power surge protector (referred to as SPD). These power supply surge protectors are designed to withstand the high currents and high energy surge energy absorption of lightning and induced lightning strikes, which can divert large amounts of surge current to earth. They only provide limiting voltage (the maximum voltage that appears on the line when the inrush current flows through the SPD becomes the limiting voltage) as a medium level of protection, because CLASS I protectors are mainly for the absorption of large surge currents. They alone cannot fully protect sensitive power equipment inside the power supply system.

The second line of defense should be installed in the power supply to the important or sensitive power supply equipment at the branch distribution equipment of the power supply anti-surge protector. These SPDs provide better absorption of the residual surge energy that passes through the surge dischargers at the customer's power supply entrance and provide excellent suppression of transient overvoltages. The use of the power supply surge protector requires the maximum impact capacity of 40KA / phase or more, the required limit voltage should be less than 2000V. we call CLASS II power supply surge protector. The general user power supply system for the second level of protection can be achieved by the operation of power equipment requirements.

The last line of defense can be used in the internal power supply part of the power equipment with a built-in power supply anti-surge protector to completely eliminate small transient transient overvoltage purposes. The use of power supply anti-surge protector required for the maximum impact capacity of 20KA / phase or some lower, the required limit voltage should be less than 1800V. For some particularly important or sensitive electronic equipment, with the third level of protection is necessary. It also protects the power equipment from transient overvoltages generated within the system.

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