UPS (Uninterruptible Power System / Uninterruptible Power Supply) power supply is also called uninterruptible power supply. It is an uninterruptible power supply of constant voltage and constant frequency that contains an energy storage device and an inverter as its main component. Important external equipment for power supply. Strictly speaking, UPS is not a power supply. It does not rely on the conversion of energy forms to provide electrical energy. It only provides an opportunity to switch between two power sources without interruption. This is the main design idea of UPS.

As the name suggests, UPS power supply is such a machine. When the mains power input is normal, the UPS will stabilize the mains power and supply it to the load. At this time, the UPS is an AC mains voltage stabilizer. The internal battery is charged; when the utility power is interrupted (an accidental power outage), the UPS immediately supplies 220V AC power to the load through the inverter conversion method to maintain the load and protect the software and hardware of the load from damage..

Summary: UPS has two main functions in computer systems and network applications: first, emergency use, that is, to prevent sudden power outages, affect the normal operation of electrical equipment, and cause damage to computers. The second is to purify the power supply and eliminate "power pollution" such as surges, electromagnetic interference, instantaneous high and low voltages, wire noise, or frequency shifts on the mains, improving our power quality and providing our computer systems And precision electrical equipment provides high-quality power.

2. UPS uninterruptible power supply principle-composition

From a structural point of view, UPS power can be mainly composed of battery, inverter, rectifier and static switch.

1) Accumulator: It is mainly used as a UPS power storage device. It has several batteries connected in series, and its capacity determines the length of emergency power consumption. Its main function is to convert electrical energy into chemical energy and store it in the battery. When a power failure is required, it can invert the chemical energy in the battery into electrical energy and provide it to our electrical equipment.

2) Inverter: In general, an inverter is a device that converts DC power into AC power. It consists of a filter circuit, a control logic, and an inverter bridge.

3) Rectifier: Rectifier and inverter are opposite, it is a device that converts AC power into DC power, it has two main functions, one is to convert AC power into DC power and provide it to load equipment or inverter after filtering process, and One role is to act as a charging voltage for the battery, like a charger.

4) Static switch: also known as a static switch, it is a kind of non-contact switch, which is formed by two thyristor directions connected in parallel, and its closing and opening are controlled by a logic controller. There are two types of parallel type and conversion type, and the parallel type switch is mainly used for parallel inverter and mains power supply, or multiple inverters. The converter switch is mainly used for power supply of two power sources to realize automatic switching from one channel to the other.

3. The principle of UPS uninterruptible power supply-working process

When the mains power is normally 380/220VAC, the main DC circuit has a direct current voltage, which is supplied to the DC-AC AC inverter to output a stable 220V or 380V AC voltage. At the same time, the mains power is charged after rectification. When the mains voltage is unstable or suddenly loses power at any time, the battery pack feeds power to the DC link through the isolation diode switch. There is no switching time from grid power supply to battery power supply. When the energy of the battery is about to be exhausted, the uninterruptible power supply sends out an audible and visual alarm, and the inverter stops working at the lower limit of the battery discharge, and a long alarm sounds. The uninterruptible power supply also has an overload protection function. When an overload occurs (150% load), it jumps to the bypass state and automatically returns when the load is normal. When a severe overload occurs (more than 200% of the rated load), the uninterruptible power supply immediately stops the inverter output and jumps to the bypass state. At this time, the front input air switch may also trip. After eliminating the fault, as long as the switch is closed, restart the work and resume work.

4. UPS uninterruptible power supply principle-working principle

UPS can be roughly divided into three types: backup (Off Line), online (On line) and online interactive (Line interactive), the following editors explain the working principle of various UPS one by one

1) On-Line UPS

On-Line UPS (On-Line UPS) operation mode is "mains and power equipment are isolated, the mains will not directly supply power to the equipment", but will be converted into DC power when the UPS, and then divided into two Battery, the other way is to charge the battery, and the other way is to switch back to alternating current to supply power to the electrical equipment. When the quality of the mains power supply is unstable or there is a power outage, the battery is switched from charging to power supply. The entire process of electricity use is involved throughout." The UPS power supply keeps its inverter in working state, converts external AC power into DC power through a circuit, and then converts DC power into high-quality sine wave AC power through a high-quality inverter and outputs it to the computer.

The main function of the online UPS under power supply conditions is to stabilize the voltage and prevent radio wave interference; in the event of a power outage, a backup DC power supply (battery pack) is used to power the inverter. Since the inverter has been working, there is no problem of switching time, which is suitable for occasions with strict requirements on the power supply. One of the advantages of online UPS power supply is that it is different from the backup type in that the power supply lasts for a long time, usually a few hours, and some more than a dozen hours. Its main function is to allow you to work as usual in the event of a power outage. It is more suitable for industries such as computers, transportation, banking, securities, communications, medical care, and industrial control, because computers in these fields are generally not allowed to experience power outages.

2) Back-up uninterruptible power supply (Off Line UPS)

The back-up uninterruptible power supply is just a "backup" UPS. The mains power directly supplies electricity to the electrical equipment and also charges the battery (Normal Mode). Once the mains power supply quality is unstable or the power fails, the mains circuit will be automatically cut off. The DC power of the battery will be converted into an AC power supply task (Battery Mode), until the mains power returns to normal, "UPS will not intervene in the power supply until the mains power is cut off", but the AC power converted from DC power is a square wave, limited to power supply For capacitive loads, such as computers and monitors.

Normally, it is in the battery charging state, and the inverter switches to the working state in an emergency, and the DC power provided by the battery is converted into a stable AC power output. Therefore, the backup UPS is also called an offline UPS. The advantages of the backup UPS power supply are: high operating efficiency, low noise, and relatively cheap price. It is mainly suitable for occasions where the mains fluctuation is not large and the power supply quality is not high, which is more suitable for family use.

3) Online interactive uninterruptible power supply (Line interactive UPS)

The basic operation mode of the online interactive uninterruptible power supply is the same as that of the backup type. The difference is that although the online interleaved type is not like the online type full intervention power supply, it is always monitoring the power supply status of the commercial power supply. It has boost and decompression compensation itself. Circuit, when the power supply condition of the city power is not ideal, it can be corrected immediately to reduce unnecessary "Battery Mode" switching and extend battery life.

This is an intelligent UPS power supply. The so-called on-line interactive UPS means that when the input of the mains power is normal, the inverter of the UPS is in reverse operation (that is, the rectifier working state) to charge the battery pack; when the mains power is abnormal When the inverter immediately switches to the inverter working state, the battery pack power is converted into AC power output, so the online interactive UPS also has a conversion time. Compared with backup UPS, online interactive UPS power supply has stronger protection function, inverter output voltage waveform is better, generally sine wave, and its biggest advantage is that it has strong software functions and can be easily connected to the Internet. Remote control and intelligent management of UPS.

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