Factory circuit design principles - solutions - Huaqiang Electronic Network

Industrial Router Crystal 3.2*2.5mm 3225 26M (26.000MHZ) 12PF 10PPM 20PPM 30PPM

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1. In recent years, with the rapid development of industry, electrification has become increasingly popular. If electrical equipment is selected, poorly configured or improperly maintained, or due to various external factors, such as external impact, vibration, high temperature, high humidity, overload or Improper use causes poor contact, loose wiring, damaged insulation and aging, and leakage, short circuit, etc. can cause electrical accidents, and even electric shock or electrical fire accidents. In particular, the number of low-voltage equipment lines in the factory is quite large, so the safe use of low-voltage equipment and lines becomes the primary task of power consumption in factories.

Second, the potential problems of low-voltage electricity in the factory

In general, electrical equipment requires appropriate electrical protection devices (such as non-fuse switches, earth leakage circuit breakers, etc.) and piping wiring or cable wiring, depending on its holding and use environment. In addition, it has special safety requirements for wet, high temperature or corrosive places. At present, the safety of low-voltage electricity is always caused by the fact that operators (or users) do not have electricity safety knowledge, insufficient information or to reduce expenditures, perfunctory of electrical installers, unclear concepts or sloppy construction, and often non-electrical technology. Any change or addition of temporary electrical wiring and equipment by personnel can cause the following common problems with overall power safety.

(1) Improper location of electrical equipment

Dispose of electrical equipment in a wet location, corrosive location, or high temperature location without taking appropriate measures to prevent insulation degradation or leakage. For example, electrical equipment should be avoided in places with moisture. If it is difficult to configure, use electrical equipment with equivalent waterproof function and install appropriate leakage protection device.

(2) improper wiring configuration

The wires are placed at the work site of the employee or vehicle implement, where they are likely to be touched, and no appropriate measures are taken to prevent insulation damage. Or the wires are placed in a wet place, a corroded place or a high temperature place, and the measures for preventing insulation aging are not taken. For example, the wires are placed directly on the walkway or on the wet ground.

(3) The power cords are often connected to each other and the connection is not handled properly.

In principle, the power cord of the electrical equipment should be connected to the power supply directly with a plug or a connecting terminal. However, when the power cord of the electrical equipment of the factory is damaged or the length is insufficient, there are often interconnections. Sometimes the connection method or the winding of the insulating tape is quite simple and casual, and the construction is not carried out according to the regulations, which often causes the connection portion to be loose or poorly contacted. And the entangled insulating tape often falls off, causing the copper wire to be exposed. In addition, even if the connection is good, if there is moisture in the connection or immersed in water, leakage will occur.

(4) Poor handling of the connection terminals of the power supply

In the electrical box (switch box) or the connection terminal in the electrical machinery and equipment, the live terminal and other parts are not insulated, so that the live terminal is exposed, which may cause accidental contact with the live part. In addition, the connection between the electric wire and the connecting terminal is not strong, and under the action of vibration or external force, the contact is poor or the electric wire is loose, which may cause local high temperature and even cause electrical fire or electric leakage accident.

(5) The polarity of the fire line and the neutral line are reversed

There is sometimes a problem of polarity connection in connection with the neutral line and the live line. If the connection between the neutral line and the live line is reversed, it is the so-called reverse solarity. For example, the polarity of the power line of the electric drill is reversed. When the single-button switch of the electric drill is cut off, even if the electric drill itself stops moving, the electric drill itself The internal wiring is still energized. At this time, if maintenance or other factors touch the internal wiring of the electric drill, an electric shock may occur. Therefore, in the case of such polarity reversal, the shunt switch must be turned off to actually cut off the live line.

(6) Incorrect connection of the line

1. The power supply side and the load side of the non-fuse switch are short-circuited by some lines, causing the safety device to fail to protect the line and electrical equipment connected to its load side.

2. The safety protection device is installed on the line, but some of the lines have not passed the safety protection device, so the part of the line and the connected electrical equipment cannot be protected by this safety protection device.

3. The line connection of the safety device is wrong. For example, the neutral line on the load side of the leakage circuit breaker is used together with the ground line. The ground line passes through the zero-sequence current transformer of the leakage circuit breaker, and the line on the load side of the leakage circuit breaker is “re-grounded”. In this case, the leakage circuit breaker may not operate when the load machine leaks.

(7) Improper selection of safety protection devices

1. The overcurrent (overload) safety protection device installed on the line, such as the no-fuse switch or the fuse (fuse), has a rated current greater than the rated (current) capacity of the subsequent connected line, when the line exceeds its rated current capacity. There is a case where the fuseless switch trips or the fuse blows. Such a line, such as an overcurrent, a fuseless switch or a fuse, has not been cut off, and continuous use of electricity for a long period of time may cause high temperature of the line to cause insulation aging or re-melting of the insulation, causing a short-circuit phenomenon of the wire. .

2. Ground fault safety protection devices installed on the line, such as earth leakage circuit breakers, do not use high-inductance type (below 30 mA) and fast (less than 0.1 second) circuit breakers for the purpose of preventing induced leakage.

(8) Insufficient protection measures

For example, the outer casing of the electrical equipment is not grounded as specified; or the grounding measures have been taken, but only the equipment is grounded separately, and the ratio of the grounding resistance value to the system grounding resistance is not low enough (usually almost not too low), when When a leakage accident occurs, when the contact voltage to which the low-voltage equipment grounding resistance is distributed is greater than the safety voltage, when a person touches the outer casing of the electrical equipment, an electric shock may occur. Therefore, such as the outer casing of electrical equipment, it may cause an electric shock. Therefore, if the grounding of the outer casing of the electrical equipment is grounded separately, it is best to use a ground fault safety device. For example, an earth leakage circuit breaker can cut off the circuit immediately in the event of a leakage accident.