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The working process of the linear regulated power supply can be briefly described as follows: After the 220V/50HZ power frequency grid voltage is stepped down through the linear transformer, and then through rectification, filtering and linear voltage regulation, finally output a ripple voltage and stability are in line with the requirements DC voltage.
The advantages of linear regulator power supply:
1, high power stability;
2, the output ripple voltage is small;
3, quick response speed;
4, the line structure is simple, easy to understand and repair;
5, no high frequency switching noise;
6, high reliability.
Disadvantages of linear regulated power supply:
1, internal power consumption, low conversion efficiency, its conversion efficiency is only about 45%;
2, bulky, heavy weight, inconvenient for miniaturization;
3, low filter efficiency, must have a large input and output filter capacitors;
4, the input voltage dynamic range is small, linear adjustment rate is low;
5, the output voltage can not be higher than the input voltage.
Switching regulated power supply:
Switching regulated power supply consists of full-wave rectifier, power switch V, pulse width modulation (PWM) control and driver, freewheeling diode VD, energy storage inductor L, output capacitor C, and sampling feedback circuit, in fact, switching power supply The core part is a DC transformer.
Switching power supply advantages:
1, the internal power loss is small, high conversion efficiency;
2, small size, light weight;
3, wide voltage range, high linear adjustment rate;
4. The filter efficiency is greatly improved, and the capacity and volume of the filter capacitor are greatly reduced;
5, flexible and diverse circuit forms, choices are large.
Disadvantages of switching regulated power supplies:
1. Switching power supply has serious switching noise and interference;
2. The circuit structure is complex and it is not easy to maintain;
3, high cost and low reliability.
There are two types of power supply: centralized power supply and decentralized power supply centralized power supply:
Means that a transformer (switching power supply) provides centralized power to all load devices in the entire line;
Decentralized power supply:
Refers to the independent power supply of each load independently by multiple transformers (brain);
List of maximum current of each wire diameter:
An aluminum core wire (copper core wire) with a square cross-section of 1 mm is calculated as follows: copper wire 5A-8A, aluminum wire 3A-5A
Security system power supply options:
According to the above information, the security system generally does not take into account the size and power consumption of the device. The most appropriate method is to select a linear regulated power supply; distributed power supply and centralized power supply are available; general security equipment is recommended for centralized power supply for ease of management. .
Hazard of power quality problems 1. The scope of voltage change is too large. The power supply is insufficient. The power supply department takes a step-down power supply, or is located in a remote area with excessive losses, resulting in a low voltage. The power grid has too little power, resulting in high voltage, low voltage load can not work properly, the voltage is too high, the service life of the load is shortened, or the load is burned.
2, waveform distortion (or harmonic WaveformDistortion)
Common waveform distortion refers to the multiple harmonics of the standard power waveform. Harmonics in power grids are caused by the use of switching power supplies in power electronics and electrical equipment such as rectifiers, UPS power supplies, electronic speed control equipment, fluorescent lamp systems, computers, microwave ovens, energy-saving lamps, dimmers, or secondary power supplies themselves.
Harmonic harm to the utility grid mainly includes:
1) Make the components in the utility grid generate additional harmonic losses and reduce the efficiency of power generation and transmission and transformation equipment. When a large number of third harmonics flow through the neutral line, it will cause the line to overheat or even cause fire;
2) Affect the normal operation of various electrical equipment, in addition to causing additional losses, but also make the motor produce mechanical vibration, noise and overvoltage, so that the transformer local severe overheating, so that capacitors, cables and other equipment overheating, insulation aging, shortened life expectancy, Resulting in damage;
3) It will cause partial parallel resonance and series resonance in the utility grid, so that the harmonics will be amplified, which will greatly increase the aforementioned hazards and even cause serious accidents;
4) It will lead to relay protection and automatic device malfunction, and make the electrical measurement instrument measurement inaccurate;
5) It will cause interference to neighboring communication systems, light noise will be generated, communication quality will be reduced, and information loss will be caused by serious ones, making the communication system unable to work normally.
3, surge (or surge PowerSurges)
In the instant (in milliseconds), the output voltage has an rms value higher than 110% of the rated value for one or several cycles. It is the main culprit in the destruction of sophisticated electronic equipment.
In addition to being caused by lightning, the main cause is the high voltage generated by the sudden unloading of the power grid when large electrical equipment connected to the power grid is turned off and on.
Surge hazards:
The development of computer technology so far, multi-layer, ultra-scale chip set, circuit-intensive, tend to be more integrated, smaller component gaps, thinner wires. A few years ago, one square centimeter of computer chips had 2,000 transistors and today's Pentium machines have more than 10,000,000. This increases the probability of a computer being damaged by a surge. Because the design and structure of the computer determines that it should work within a specific voltage range. When the surge exceeds the level that the computer can tolerate, the computer will appear garbled data, the chip is damaged, and the components are prematurely aged. These symptoms include: unexpected data errors, failure to receive/transmit data, loss of documents, malfunctions, and frequent Needs maintenance, unexplained failures, hardware issues, and more. Lightning surges far exceed the level to which computers and other electrical equipment can withstand. In most cases, computers and other electrical equipment are immediately destroyed, or data is lost forever. Even the start-up or shut-down of a small, 20-hp induction engine can generate 3,000-5,000 volts of surges, making computers that share the same distribution box with it damaged or disturbed during each surge. The frequency of surges is very high.
The effects of power surges on sensitive electrical and electronic equipment are the following types:
Breakdown voltage breakdowns semiconductor devices;
Destruction of components metallized surface;
Destruction of printed circuit board printed circuit or contact points;
Destroy the three-terminal dual thyristor/thyristor....
Interference locked, thyristor or triac uncontrolled;
Partial destruction of data files;
Data processing program error;
Received, transmitted data errors and failures;
Unexplained failures....
Prematurely aged components are prematurely aged, and their lifespan is greatly shortened;
Output sound quality, picture quality decreased.
Which electrical equipment will be destroyed by power surges?
Electrical equipment containing microprocessors is vulnerable to power surges. This includes computers and auxiliary equipment, program controllers, PLCs, fax machines, telephones, and answering machines; program-controlled switches, radio and television transmitters, video equipment, and microwaves. Relay equipment; home appliance industry products include televisions, stereos, microwave ovens, video recorders, washing machines, dryers, refrigerators and so on. The survey data shows that 63% of the electrical equipment that had problems during the warranty period was caused by power surges.
4, spikes (or high-voltage spike Spikes)
Refers to a peak voltage of 6000V and lasts from one-tenth of a second to one-half cycle (10ms). This is mainly due to lightning strikes, arcing, static discharges, or switching operations of large electrical equipment.
harm:
5. Transient overvoltage and temporary overvoltage
Refers to a pulse voltage with a peak voltage of up to 20000V, but with a duration ranging from one millionth of a second to one ten-thousandth of a second. The main reason and possible damage are similar to high-voltage spikes, which are mainly caused by lightning.
harm:
Advanced electronic devices such as measurement, monitoring, protection, communications, and computer networks that use large-scale integrated circuits as their core components are widely used in various fields such as power, aviation, defense, communications, broadcasting, finance, transportation, petrochemical, medical, and other modern lives. These electronic devices composed of large-scale CMOS integrated components have the disadvantages of transient overvoltage and weak overcurrent tolerance. Transient overvoltages not only cause malfunctions in electronic devices, but also cause interference to electronic devices. Loss of data, or temporary failure, can cause breakdown of components and burning of circuit boards in severe cases, leaving the entire system paralyzed.
6, Sag & Brownouts
Refers to a low voltage condition where the mains voltage rms is within 80-85% of the nominal value and lasts for one to several cycles or even longer. The reasons for this include: start-up and application of large-scale equipment, start-up of large-scale motors, or access of large-scale power transformers, switching of main power lines, and overload of lines.
harm:
Voltage sags are the most common power problem and account for 87% of power problems.
The power supply may cause a short voltage drop for some reason. Its impact on the computer is such that the keyboard and other interface devices suspend operations, and the data loss and file destruction are caused. The voltage sagging also destroys the components inside the computer, which shortens the life.
Security power selection manual
Classification of regulated power supply: linear regulator power supply and switching regulator power supply linear regulator power supply: