First, why use UPS
There is a common misconception that the utility power we use is continuous and constant except for occasional power outages, but it is not. As a public power grid, the mains system is connected to thousands of various loads. Some of the larger inductive, capacitive, switching power supplies and other loads not only get power from the grid, but also in turn cause the grid itself. Affects the deterioration of the power supply quality of the grid or local grid, causing distortion or frequency drift of the mains voltage waveform. In addition, accidental natural and man-made accidents, such as earthquakes, lightning strikes, disconnection or short circuit of power transmission and transformation systems, can impair the normal supply of electricity, thus affecting the normal operation of the load. According to the test of electric power experts, the following problems occur frequently in the power grid and cause interference or damage to computers and precision instruments:
1. Power surges:
It means that the output voltage RMS is higher than the rated value by 110% and lasts for one or several cycles. The surge is mainly due to the high voltage generated by the sudden unloading of the grid when the large electrical equipment connected to the grid is shut down.
2. High voltage spikes:
Refers to a voltage with a peak value of 6000v and a duration from one ten thousandth of a second to one half of a cycle (10ms). This is mainly due to lightning strikes, arcing, static discharges or switching operations of large electrical equipment.
3. Transient overvoltage (switching transients):
Refers to a peak voltage of up to 20,000V, but the duration is between one millionth of a second and one tenth of a second of pulse voltage. The main reason and possible damage is similar to high-pressure spikes, but there are differences in the solution.
4, voltage sags (power sags):
Refers to the low voltage state where the rms voltage is between 80% and 85% of the rated value and lasts for one to several cycles. Powering up large equipment, large motor starting, or large power transformer access can cause this problem.
5, electrical line noise (electrical line noise):
Refers to radio frequency interference (RFI) and electromagnetic interference (EFI) and various other high frequency interference. Motor operation, relay operation, motor controller operation, broadcast emissions, microwave radiation, and electrical storms can cause line noise interference.
6, frequency offset (frequency variaTIon):
Refers to the change in the mains frequency more than 3Hz. This is mainly caused by the unstable operation of the emergency generator or by the power supply with unstable frequency.
7, continuous low voltage (brownout):
It means that the rms voltage of the mains voltage is lower than the rated value and lasts for a long time. Causes include: large equipment start-up and application, main power line switching, starting large motors, and line overload.
8, power failure (power fail):
Refers to the situation where the mains supply is interrupted and lasts for at least two cycles to several hours. The causes are: circuit breaker trip on the line, mains supply interruption, grid failure.
For computers, both the display and the mainframe work require a normal power supply. Especially the memory, the power requirements are higher. It is a storage device that relies on electrical energy and requires constant refreshing actions to keep the content stored. Once the power is turned off, the saved content disappears immediately. If the power is abnormally turned off, the information in the memory cannot be saved to a storage device such as a hard disk, which may result in loss of value due to complete loss or incompleteness, thereby wasting a lot of work effort, time, and even a huge economy. loss. An operating system such as UNIX, if it does not shut down properly, the system information in the memory is not written back to the hard disk, and may also cause the system to crash and cannot be started again. In addition, the hard disk in the computer, although the application of the magnetic storage medium, will not lose information due to power failure, but sudden power failure will damage the physical head of the hard disk that is being read and written, or the system file is in the maintenance of the file system. Causes a file allocation table error, which causes the entire hard disk to be scrapped. In addition, most of the current operating systems can set virtual memory. Due to the sudden power failure, the system can't cancel the virtual memory, which causes the "information fragmentation" in the hard disk, which not only wastes the hard disk storage space, but also causes the machine to run slowly. The computer power supply is a rectified power supply. Excessive voltage may cause the rectifier to burn out. Interferences such as voltage spikes and transient overvoltages and power supply noise may enter the motherboard through the rectifier, affecting the normal operation of the machine and even burning the host line. In short, the power problem is a major threat to computer work. But with the increasing importance and breadth of computer and network applications, safe and reliable power supplies have become an important issue that network design and management personnel have to face seriously. “Need to be the first driving force for social developmentâ€, in this context, UPS (Uninterruptible Power Supply) came into being, and with the development of power electronics technology, constantly innovating, not only created a brand new in the past decade or so. Industry, and moreover, will have a prosperous development and bright prospects over time.
Second, what is UPS
UPS (Uninterrup TIble Power System), an uninterruptible power supply, is a constant voltage constant frequency uninterruptible power supply that contains an energy storage device and uses an inverter as a main component. 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 supplies the mains voltage to the load for use. At this time, the UPS is an AC mains voltage regulator, and it also charges the internal battery; when the mains is interrupted (accident blackout) At the same time, the UPS immediately supplies 220V AC power to the load through the inverter conversion method, so that the load maintains normal operation and protects the load soft and hardware from damage.
As a protective power supply device, UPS's performance parameters are of great significance and should be considered when we purchase. A wide range of mains voltage input indicates strong utilization of utility power (reducing battery discharge). The output voltage and frequency range are small, indicating that the power supply adjustment capability is strong and the output is stable. The waveform distortion rate is used to measure the stability of the output voltage waveform, while the voltage stability indicates the stability of the output voltage when the UPS suddenly loads from zero load to full load.
UPS efficiency, power factor, and conversion time are all important parameters that characterize UPS performance, which determines the protection of the load and the utilization of the utility. The better the performance, the stronger the protection. In general, the offline UPS has the worst protection against the load, the online interaction is slightly better, and the online type can solve almost all common power problems. Of course, the cost also rises as performance increases. Therefore, when purchasing a UPS, the user should select different types of UPS according to the requirements of the load on the power and the importance of the load.
Third, the type of uninterruptible power supply (UPS)
1. What is an offline uninterruptible power supply (Off Line UPS)
Offline uninterruptible power supply, also known as backup uninterruptible power supply. Normally, the mains supply directly supplies power to the load through the bypass, and the inverter inside the machine is in a stopped state. At this time, the UPS power supply is essentially equivalent to a poor performance mains voltage regulator, except for the mains voltage. In addition to the improvement in amplitude fluctuations, there is basically no improvement in adverse effects such as voltage instability, waveform distortion, and interference from power grid intrusion. Only in the event of a power outage, the battery energy is converted to AC by the inverter to provide power to the load. Offline uninterruptible power supply features:
(1) When the mains supply is normal, the off-line UPS outputs the load directly to the load without any treatment to the mains, so the ability to suppress the mains noise and surge is poor;
(2) There is a conversion time;
(3) The worst protection performance;
(4) The structure is simple, the volume is small, the weight is light, the control is easy, and the cost is low.
2. What is an online uninterruptible power supply (On-Line UPS)
When the mains supply is normal, it first rectifies the mains AC power into a DC power supply, then performs pulse width modulation and filtering, and then reconverts the DC power to a sine wave AC power supply to supply power to the load. Once the mains is interrupted, the DC power provided by the battery is immediately supplied to the load to provide sinusoidal AC power to the load. Therefore, for the online UPS power supply, under normal conditions, whether or not there is mains supply, it is powered by the inverter of the UPS power supply, thus avoiding all the voltage fluctuations and interference caused by the mains grid. The impact of coming. Obviously, the power quality of the online UPS power supply is significantly better than that of the backup UPS power supply. Because it can achieve the frequency stabilization, regulated power supply of the load, and when the power is converted from the mains supply to the battery, the conversion time is zero. It provides users with high-quality, regulated and frequency-stabilized pure sine wave power supplies to provide power protection that meets the needs of network systems. Online UPS features:
(1) The output power is processed by the UPS, and the output power quality is the highest;
(2) No conversion time;
(3) The structure is complicated and the cost is high;
(4) The best protection performance, the strongest suppression of commercial noise and surge. ·
3. What is the online interactive uninterruptible power supply (Line interacTIve UPS)
The online interactive UPS power supply is also called a 3-port UPS power supply, using a power frequency transformer. From the perspective of energy transfer, there are three energy flow ports in the transformer: port 1 is connected to the mains input; port 2 is connected to the battery through the bidirectional converter; port 3 is output. When the utility power is supplied, the AC power flows into the transformer through the port 1, and the appropriate transformer tap is selected under the control of the voltage stabilizing circuit, and the output on the port 3 is jointly adjusted by the energy conversion of the battery under the action of the bidirectional converter of the port 2. The voltage is used to achieve a better voltage regulation effect; when the mains is powered down, the battery supplies power to the transformer through the bidirectional converter via port 2, maintaining the AC output on port 3. Online interactive UPS power supply In the process of transformer tap switching, the bidirectional converter works as an inverter. The battery is powered, so that the output voltage can be uninterrupted, and there is no conversion time in the switching process from the mains supply to the battery supply. The circuit of the online interactive UPS power supply is simple to implement, and there is no separate charger, which brings about a reduction in production cost and an increase in reliability. Such products do not have AC/DC, DC/AC conversion when the utility power supply works, which improves the efficiency of the whole machine. The online interactive UPS combines many of the advantages of a backup UPS and an online UPS, and is a very good form of transformation. However, because it uses a power frequency transformer, it also has the problem of being bulky and bulky. Online interactive UPS features:
(1) With bidirectional converter design, UPS battery recharge time is shorter;
(2) There is a conversion time;
(3) The control structure is complex and the cost is high;
(4) The protection performance is between the on-line and off-line UPS, and the ability to suppress the mains noise and surge is poor.
4. How long does it take for the uninterruptible power supply (UPS) to supply power?
UPS can have enough time to implement emergency measures when power is abnormal. In general, a backup time of 5-10 minutes is sufficient. If you need a longer backup time, you can purchase a UPS with long delay.
5. How to calculate the capacity of the uninterruptible power supply (UPS)
Most of the uninterruptible power supplies (UPS) currently on the market use VA as the capacity unit. V is the voltage, A is the current, V & TImes; A is equal to the power, that is, the capacity of the uninterruptible power supply. For example, a 425VA uninterruptible power supply, if its output voltage is 110V, the maximum current that the UPS can provide is 3.86A. Exceeding this current value is overload. Another way to express power is W, W for real work, and VA for virtual work. The difference between the two is the power factor. The power factor is generally between 0.6 and 0.8. If it is lower than 0.5, the UPS design is not good. When purchasing the UPS, the power factor should be considered.
How to extend the power supply time of the uninterruptible power supply (UPS)
There are two ways to extend the power supply time of an uninterruptible power supply:
1. Increase battery capacity.
The number of batteries can be increased according to the length of time required for power supply, but this method will cause a relative increase in battery charging time, and also increase the number of corresponding maintenance equipment, increase product volume, and increase the overall cost of the UPS;
2. Purchase a larger UPS.
Not only can this method reduce maintenance costs, but if you need to expand the load equipment, the larger capacity uninterruptible power supply can still work normally.
Seven, what is the power monitoring software
Power monitoring software is used in conjunction with an uninterruptible power supply (UPS) to improve the performance of uninterruptible power supplies. During the process of using the uninterruptible power supply, the user can accurately grasp the working state of the uninterruptible power supply and record the stability of the commercial power for the technician to analyze. When the utility power is interrupted or the battery power is terminated, the functions of document storage, system shutdown, and shutdown of the UPS can be automatically performed. The new generation of power monitoring software also has functions such as UPS remote monitoring and UPS timer switching.
8. Must I purchase the corresponding monitoring software when purchasing UPS?
In order to improve and effectively play the full performance of UPS, it is necessary to choose a set of UPS monitoring software. What the average user wants to know most is whether the mains input and battery status are normal. When the mains electricity is abnormal and the corresponding power monitoring software is not installed, if the user is at the site, you can use the power provided by the UPS to take emergency measures, such as storing documents and shutting down the system. However, if the mains supply is abnormal and the monitoring software is not installed, and the user is not in the field, when the UPS battery is exhausted, the data is lost, and the internal components of the computer and peripheral devices are damaged. Therefore, when purchasing a UPS, it is best to purchase power monitoring software at the same time to achieve perfect power protection.
Nine, many brands of UPS now emphasize management functions, is this suitable for general users?
In the past, most PC users used the DOS operating system to process personal data. When the utility power is abnormal, the loss of data is limited to personal data. However, for the current popular computer network systems, such as WINDOWS, NT, and UNIX, the system is responsible for the management and use of the entire workstation data. Even for a short power outage, the damage caused by the system itself and the loss of a large amount of data cannot be Estimated. Therefore, users should take the network management function into consideration when purchasing an uninterruptible power supply (UPS) from the perspective of their future development.
Ten, what are the communication interfaces of the uninterruptible power supply?
The communication interfaces currently available on the market for uninterruptible power supplies (UPS) are as follows: Relay connection; RS-232 interface; AS400 interface; SNMP interface; USB interface.
The AS400 interface is mainly designed for IBM computers. SNMP, on the other hand, enables UPS to connect to the network without having to go through a computer device, while monitoring the UPS over the network. The relay connection and RS-232 interface are the most common. The function is briefly described as follows: The relay connection mode enables the UPS to monitor whether the utility power is normal, whether the battery voltage is too low, and provides automatic storage of documents and systems. Turn off and other functions. In addition to all the functions of the relay connection, the RS-232 communication interface can monitor the voltage, current, frequency, load capacity, etc. of the uninterruptible power supply in real time through the monitoring software, and can set the UPS on/off time and broadcast function. USB (Universal Serial Interface) is the development trend of communication interfaces in the future, and the use of USB interfaces will become more and more popular.
11. What kind of battery is used for the uninterruptible power supply (UPS)?
Most of the uninterruptible power supplies (UPS) currently on the market use sealed maintenance-free lead-acid batteries.
12. How long is the battery life?
The source of the uninterruptible power supply is discharged from its internal battery. In addition to external environmental factors, there are also factors such as chemical changes in the battery. Even if the battery is left unused for a long time, the battery corner will age. In general experience, the battery life is 2-3 years.
Thirteen, how to maintain the battery
Regular charging and discharging of batteries is the key to battery maintenance. If the user-purchased UPS has battery monitoring, the UPS can perform this function automatically on a regular basis. If the user's UPS does not have this function, you can unplug the UPS power input terminal, simulate the mains interruption, and then observe whether the battery discharge time is long enough? If the discharge time is insufficient, you should consider replacing the battery to ensure that the battery has sufficient discharge time when the power is interrupted, to ensure the storage of the file and the complete shutdown of the system.
14. Where can I replace the battery?
When the user's purchased UPS needs to replace the battery, you can contact the service provider or dealer of the product.
Fifteen, what is SNMP
SNMP is the abbreviation of Simple Network Management Protocol. The protocol enables UPS to connect directly to the network with its peripherals without going through a computer, and is included in the network system management. Upscale UPSs typically have an SNMP network management interface that makes it easy to connect to the network.
XVI. What is an isolation transformer?
When the instrument is used in conjunction with an ordinary UPS, the instrument may malfunction due to zero ground voltage. In order to avoid this situation, the high-end UPS designed a UPS with an isolation transformer for this problem. After special design, the zero-ground voltage of the output can be less than 1 volt, thus avoiding the above problems. In addition, The isolation transformer also has functions such as noise filtering.
17. What is Boost and Buck?
Boost is boost and Buck is buck. When the mains voltage is too low or too high, the regulator will raise or lower the voltage too low or too high to within the specified range, so that the UPS or related equipment can operate normally.
Eighteen, what is AVR
AVR is the abbreviation of Automatic voltage Regulation.
19. What should I pay attention to when purchasing an on-line UPS?
Pay attention to the following when purchasing an on-line UPS:
(1) Does the UPS have a high power factor?
(2) If the load of the UPS is an inductive or capacitive load, the UPS using a full-bridge soft-switching converter should be selected.
(3) Some computers or precision instruments have special requirements on the voltage value between the neutral line of the UPS output and the earth. For example, some instruments require that the voltage be less than 3V, and some even require less than 1V. You need to consider this issue when purchasing a UPS.
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