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Talking about some selective concepts about UPS system

Nov 12, 2020

UPS (Uninterruptible Power System), that is, uninterruptible power supply, is a constant voltage and constant frequency uninterruptible power supply with an energy storage device and an inverter as the main component. It is mainly used to provide uninterrupted power supply to a single computer, computer network system or other power electronic equipment. When the mains input is normal, the UPS will stabilize the mains and supply it to the load. At this time, the UPS is an AC mains voltage stabilizer, and it also charges the battery in the machine; when the mains is interrupted (accidental power failure) At this time, the UPS immediately uses the power of the battery in the machine to continue supplying 220V AC power to the load through inverter conversion, so that the load can maintain normal operation and protect the load software and hardware from damage.

    UPS, as a protective power supply equipment, its performance parameters are of great significance and should be the focus of our consideration when purchasing. The wide input range of the mains voltage indicates a strong utilization of the mains (reducing battery discharge). The output voltage and frequency range are small, indicating strong adjustment ability to the mains and stable output. The waveform distortion rate is used to measure the stability of the output voltage waveform, and the voltage stability indicates the stability of the output voltage when the UPS is suddenly added from zero load to full load.

    In addition, UPS efficiency, power factor, and conversion time are all important parameters that characterize UPS performance, which determine the protection capability of the load and the utilization rate of the utility power. The better the performance, the stronger the protection capability. In general, the offline UPS has the worst protection to the load, the online interactive type is slightly better, and the online type can solve almost all common power problems. Of course, the cost also rises with the enhancement of performance. Therefore, when purchasing UPS, users should choose different types of UPS according to the load's requirements for power and the importance of the load.

Under what circumstances is UPS generally used?

    UPS is not only used directly on computers, all equipment equipped with computers (such as medical CT, instrumentation in supply stations, etc.), radar stations, military communication systems, program-controlled telephone systems, surgical operating rooms, etc., use UPS instead of generators Used for backup power supply.

How to buy UPS

Due to unstable power quality, computer equipment hardware is often damaged, crashed, and important data is lost. Therefore, the uninterruptible power system (UPS) has gradually become an indispensable standard equipment when purchasing computer equipment. However, how to buy UPS often troubles users. Therefore, Santak website specially sorts out the problems frequently encountered by customers during the sales process and provides explanations. I hope that as users when purchasing UPS Reference.

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What are the types of power problems?

Answer: In addition to the interruption of the mains power supply, there are voltage dips, pulse voltages, transient overvoltages, voltage surges, noise interference, frequency changes, voltage fluctuations and flicker. These problems are caused by computer equipment or precision Software and hardware losses such as instrument crashes, damage to internal components, shortened service life, and data loss.

Why use an uninterruptible power system? What is the long-term cost-effectiveness?

Answer: (1). We will use a computer to illustrate this problem. If the uninterruptible power system is not used today, then when the mains power supply is abnormal, the computer will crash, and even cause hardware failure, and the maintenance fee will be unpredictable. The failure can cost money to eliminate the disaster, but what about the data stored in the hard disk? But if you have money, you can't buy it, so buying an uninterruptible power system for your equipment is like buying insurance.

(2). It must be noted here that the uninterrupted power system does not only operate when the power is cut off. The above-mentioned mains abnormality includes the mains voltage is too low, too high, surge, noise, etc. , Are all power quality problems that can affect the normal operation of the equipment, and equipped with an uninterruptible power system can solve the power problem at one time.

(3). Allen-Segall was entrusted by IBM US Headquarters to evaluate the benefit and cost of various power equipment, which proved that the long-term cost of UPS is the lowest.

Classification of uninterruptible power systems?

Answer: 1. Early uninterruptible power systems are divided into two categories: online and offline. Recently, manufacturers have launched online interactive. Its characteristics are between online and offline, but its operating characteristics and power supply methods are different. In other words, it should be classified as offline.

2. According to the number of input/output phases and voltage, it can be divided into single-phase input and single-phase output, (applied to less than 10KVA, offline, online interactive, online and other small capacities), three-phase input and single-phase output (applied to 10KVA The above online type), three-phase input and three-phase output (applicable to online large capacity above 20KVA).

From its development history, UPS has gone through two stages: rotary UPS and static conversion UPS.

    Rotary UPS is composed of rectifier, battery, DC motor, diesel (gas) diesel engine, flywheel and generator. In the case of city power supply, the motor drives the flywheel and generator to supply power to the load; when the power is off, due to the inertia of the flywheel, it will continue to drive the rotor of the generator to rotate, so that the generator can continue to provide power to the load (electric energy-kinetic energy) -Electricity), play a buffer role, and start the diesel (gas) oil engine at the same time. When the engine speed is the same as that of the generator, the engine isolation device is connected to the generator to complete the conversion from the mains to the engine. This is an earlier form of UPS. Although it is simple to maintain and relatively stable, the system is large, inconvenient to operate, low in efficiency, noisy, and low in power quality. The limitations of technical conditions force people to use this simplest one. solution.

   With the continuous emergence of computer networks, medical equipment and precision instruments and a large number of applications, rotary UPS has been difficult to meet the requirements. Therefore, with the development of power electronics technology, another form of UPS --- static conversion UPS has emerged, which is the most common type of UPS we currently see.

   Technically speaking, static UPS is divided into three categories: offline (, online and online interactive. Generally speaking, this kind of UPS mainly has two working states, which work in different mains environments. When the power is normal, (refers to the voltage amplitude, frequency and waveform that the UPS can accept and approve is larger than the range that the load accepts), the commercial power supplies the load through the UPS. The UPS filters, stabilizes and adjusts the frequency of the mains After that, it provides a more stable and clean power supply to the load. At the same time, the UPS converts electrical energy into chemical energy through the charger and stores it in the battery. When the UPS detects an abnormality in the mains power, it switches to battery power and uses the inverter to convert the chemical energy. It can be converted into AC power and supplied to the load to ensure uninterrupted power supply to the load. This kind of UPS also has a bypass working state, which can directly output the input after high-frequency filtering when it is just turned on or the machine fails. Ensure the power supply to the load.

 1. Online and backup

   In terms of working principle, UPS can be divided into two types: backup type and online type. From the stand-by time, it can be divided into standard type and long-acting type.

   In principle, the main difference between the online UPS and the backup UPS is that the backup UPS only regulates the mains power when there is mains power, the inverter does not work and is in a waiting state. When the mains power is abnormal, the backup UPS will quickly switch to the inverter state, inverting battery power into alternating current to continue to supply power to the load. Therefore, the backup UPS will have a conversion time when it is reversed from the mains, generally less than 10ms, and the online UPS will reverse after turning on The converter is always in working condition, so there is no interruption time when the mains power is abnormal to the battery discharge, that is, 0 interruption.

2. Online interactive

   In addition to the above two types of UPS, there is also a type called online interactive, such as the Inter series of UPS power supplies. The so-called online interactive UPS means that when the mains power input is normal, the UPS inverter is working in reverse to charge the battery pack. When the mains power is abnormal, the inverter will immediately start inverter work to convert the battery pack voltage to AC power. Output, so the online interactive UPS also has a conversion time.

   Compared with the backup UPS, the online interactive UPS has stronger protection function, the inverter output voltage waveform is better, generally sine wave, and its biggest advantage is that it has strong software functions, such as UPS power supply Inter series UPS random With monitoring software, remote control and intelligent management of UPS can be conveniently performed online.

3. Standard and long-acting type

   In addition to the above three categories, according to the backup time, UPS can also be divided into standard machines and long-term machines. The standard machine uses a built-in battery, and the backup power supply time is short, usually 5-15 minutes. The long-acting machine can increase the battery capacity configuration according to user needs to extend the backup time. But this requires a larger charger to meet the needs of battery charging current and charging time, so manufacturers will enlarge the charger capacity or install parallel chargers in the design.

  In terms of standby time, UPS can be divided into two types: long-term and standard. Generally speaking, the standard machine is equipped with a battery pack, which can maintain power for a short time after a power failure (generally no more than 25 minutes); the long-term machine does not have a battery in the machine, but a charger is added. Need to connect multiple sets of batteries to extend the power supply time.

So why use UPS?

There is a common misconception that the mains power we use is continuous and constant except for occasional power outages, but this is not the case. As a public grid, the utility power system is connected to thousands of various loads. Some of the larger inductive, capacitive, switching power supply and other loads not only obtain electric energy from the grid, but also cause the grid itself. Affect and deteriorate the power supply quality of the power grid or local power grids, causing distortion of the mains voltage waveform or frequency drift. In addition, unexpected natural and man-made accidents, such as earthquakes, lightning strikes, open circuits or short circuits in power transmission and transformation systems, will endanger the normal supply of power and affect the normal operation of the load. According to the test of electric power experts, the main problems that often occur in the power grid and cause interference or damage to computers and precision instruments are as follows:

1. Surge: It means that the effective value of the output voltage is higher than 110% of the rated value, and the duration is one or several cycles. The surge is mainly due to the high voltage generated by the sudden unloading of the power grid when the large electrical equipment connected to the power grid is shut down.

2. High-voltage spike: refers to a voltage with a peak value of 6000v and a duration from one ten-thousandth of a second to one-half cycle (10ms). This is mainly caused by lightning strikes, arc discharges, static discharges or switching operations of large electrical equipment.

3. Transient overvoltage: refers to pulse voltage with peak voltage as high as 20000V but duration within one millionth of a second to one millionth of a second. The main reason and possible damage are similar to high-voltage spikes, but there will be differences in the solution.

4. Voltage sag: refers to the low voltage state where the effective value of the mains voltage is between 80% and 85% of the rated value, and the duration is one to several cycles. The startup of large equipment, the startup of large motors, or the connection of large power transformers may cause this problem.

5. Wire noise: Refers to radio frequency interference (RFI), electromagnetic interference (EFI) and various other high-frequency interference. The operation of the motor, the operation of the relay, the operation of the motor controller, broadcast transmission, microwave radiation, and electrical storms, etc., will cause line noise interference.

6. Frequency deviation: Refers to the change of the mains frequency exceeding 3 Hz. This is mainly caused by the unstable operation of the emergency generator or the power supply with unstable frequency.

7. Continuous low voltage means that the effective value of the mains voltage is lower than the rated value and lasts a long time. The causes include: large-scale equipment startup and application, main power line switching, large-scale motor startup, and line overload.

8. Mains power interruption: refers to the situation where the mains power is interrupted and lasts for at least two cycles to several hours. The reasons are: circuit breaker tripping, mains supply interruption, power grid failure.

    For computers, normal power supply is required for the display and host to work. Especially memory has higher requirements for power supply. It is a storage device that relies on electrical energy and requires constant refresh actions to maintain the stored content. Once the power is off, the saved content disappears immediately. If the power is off abnormally, the information in the memory cannot be saved to the hard disk and other storage devices, which will cause the information to be completely lost or become incomplete and lose its value, thus wasting a lot of work energy, time, and even a huge economy loss. However, if an operating system such as UNIX is shut down abnormally and the system information in the memory is not written back to the hard disk, the system may crash and cannot be restarted. In addition, although the hard disk in the computer uses a magnetic storage medium, it will not lose information due to power failure, but a sudden power failure will damage the physical head of the hard disk that is reading and writing, or the system files will be maintained when the file system is maintained. , Causing file allocation table errors, resulting in the scrapping of the entire hard disk. In addition, most of the current operating systems can set virtual memory. Due to the sudden power failure, the system cannot cancel the virtual memory in time, resulting in "information fragmentation" in the hard disk, which not only wastes hard disk storage space, but also causes the machine to run slowly. The computer power supply is a rectifier power supply, and an excessively high voltage may cause the rectifier to burn out. Interferences such as voltage spikes, transient overvoltages, and power noise may enter the motherboard through the rectifier, affecting the normal operation of the machine, and even burning the host circuit. In short, power problems are a major threat to computer work. But with the increasing importance and widespread of computer and network applications, safe and reliable power supply has become an important issue that network designers and managers have to face seriously. "Needs are the first driving force of social development". Under this background, UPS (Uninterruptible Power Supply) came into being, and with the development of power electronics technology, it has continuously introduced the old and brought forth the new. In more than ten years, it has not only created a brand-new The industry, and with the passage of time, there will be vigorous development and brilliant prospects.