"Distribution box", also known as distribution cabinet, is the general name of motor control center. Chongqing distribution box is a low-voltage distribution device, which is composed of switchgear, measuring instruments, protective appliances and auxiliary equipment assembled in closed or semi closed metal cabinet or panel according to the requirements of electrical wiring.
1、 Application of distribution box
It is convenient for management and maintenance when circuit failure occurs. Distribution box and distribution cabinet, distribution board, etc. are complete sets of equipment for centralized installation of switches, instruments, etc.
There are two kinds of commonly used distribution boxes: wooden and iron. Now the power consumption is very large everywhere, so the iron is used more. The purpose of the distribution box: of course, it is convenient to stop and send electricity, and plays the role of measuring and judging the stop and send electricity.
2、 The distribution box is mainly composed of two parts
One is a complete set of components, that is, the distribution box shell and its related accessories.
Second, electrical components and related accessories, that is, air switch and its required accessories.
The cabinet consists of the following parts
1、 Circuit breaker
Circuit breaker: both switch, is the main components of the distribution cabinet, commonly used air switch, leakage switch, dual power automatic transfer switch
1. Air switch:
A. Concept of air switch:
Air switch is also called air circuit breaker. It can connect, break and carry rated working current, short circuit, overload and other fault current in the circuit. It can quickly break the circuit and provide reliable protection in case of overload, short circuit, undervoltage and other conditions of line and load.
The design types of moving and static contacts and contact rods of circuit breakers are various, but the main purpose is to improve the breaking capacity of circuit breakers. At present, the current limiting principle of limiting the peak value of short-circuit current when breaking by using certain contact structure has obvious effect on improving the breaking capacity of circuit breaker, and is widely used.
B. Working principle of air switch:
Automatic air switch, also known as low-voltage circuit breaker, can be used to turn on and off the load circuit, can also be used to control infrequent starting motor. Its function is equivalent to the total function of some or all electrical appliances such as knife switch, over-current relay, voltage loss relay, thermal relay and leakage protector. It is an important protective electrical appliance in low-voltage distribution network. Health, safety and Environmental Protection Assistant
Automatic air switch has a variety of protection functions (overload, short circuit, undervoltage protection, etc.), adjustable action value, high breaking capacity, convenient operation, safety and other advantages, so it is widely used at present.
2. Leakage protection switch:
A. Concept of leakage protection switch:
The main function of the leakage protector is to have the function of leakage protection, to trip when people touch the live line, and to ensure personal safety; If the electric equipment is not well insulated and leaks to the shell, the leakage protector will trip to avoid electric shock. At the same time, it has the functions of current on-off, overload protection and short circuit protection.
B. Working principle of leakage protection switch:
Working principle diagram of leakage protector. LH is a zero sequence current transformer, which consists of a permalloy core and a secondary coil wound on the ring core. The phase line and neutral line of the power supply pass through the circular hole and become the primary coil of the zero sequence transformer. The rear outlet of the transformer is the protection scope. Health, safety and Environmental Protection Assistant
C. Function of leakage protection switch:
1. When electric equipment or circuit leakage or grounding fault occurs, the power supply can be cut off before people touch it.
2. When the human body touches the charged object, it can cut off the power supply within 0.1s, so as to reduce the harm of current to the human body.
3. It can prevent fire accidents caused by electric leakage.
3. Dual power automatic transfer switch:
Concept of dual power automatic transfer switch:
The automatic transfer switch of dual power supply is an automatic transfer system of one-out-of-two power supply. When one circuit fails, the automatic transfer switch of dual power supply will automatically switch to two circuits to supply power to the load. If two circuits fail, the automatic transfer switch of dual power supply will automatically switch to one circuit to supply power to the load.
It is suitable for UPS-UPS, UPS generator, UPS utility, utility utility to utility conversion.