Many people believe that the mains power we use is continuous and stable, except for the occasional power outage. In fact, as a public power grid, the municipal power system connects thousands of various loads, among which some large inductive, capacitive, switching power and other loads not only obtain power from the grid, but also in turn affect the grid itself, deteriorate the power supply quality of the grid or local grids, and cause the distortion of the voltage waveform or frequency drift of the municipal power.
 
In addition, unexpected natural and man-made accidents, such as earthquake, lightning stroke, open circuit or short circuit of power transmission and transformation system, will endanger the normal power supply, thus affecting the normal work of the load. According to the test of power experts, the problems that often occur in the power grid and cause interference or damage to computers and precision instruments mainly include the following:
 
1. Power Surges:
It means that the effective value of the output voltage is 110% higher than the rated value and lasts for one or more 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 Spikes:
It refers to the voltage with a peak value of 6000v and a duration from one thousandth of a second to one half of a cycle (10ms). This is mainly caused by lightning stroke, arc discharge, static discharge or switching operation of large electrical equipment.
3. Switching Transients:
It refers to the pulse voltage with a peak voltage up to 20000V, but the duration is between one millionth of a second and one thousandth of a second. Its main causes and possible damage are similar to high voltage sharp pulse, but there are differences in solutions.
4. Power Sags:
It refers to the low voltage state in which the effective value of the mains voltage is between 80% and 85% of the rated value and lasts for one to several cycles. Large equipment startup, large motor startup, or large power transformer connection may cause this problem.
5. Electrical Line Noise:
It refers to radio frequency interference (RFI), electromagnetic interference (EFI) and other high-frequency interference. The operation of motor, the action of relay, the operation of motor controller, broadcast emission, microwave radiation, and electrical storm will cause line noise interference.
6. Frequency Variation:
It means that the change of mains frequency exceeds 3Hz. This is mainly caused by the unstable operation of the emergency generator or the power supply with unstable frequency.
7. Continuous low voltage (Brownout):
It means that the effective value of mains voltage is lower than the rated value and lasts for a long time. The causes include:
Large equipment startup and application, main power line switching, large motor startup, line overload.
8. Power failure:
It refers to the situation that the mains power is interrupted and lasts for at least two cycles to several hours. The causes include tripping of circuit breaker on the line, interruption of municipal power supply and power grid failure.
For a computer or server, the monitor and host need normal power supply. In particular, memory requires higher power supply. It is a kind of storage device that depends on electric energy, and needs to refresh constantly to keep the storage content. Once the power is cut off, the saved contents will disappear immediately. If the power is cut off abnormally, the information in the memory will not be saved to the hard disk and other storage devices in time, which will cause the information to lose its value due to complete loss or becoming incomplete, thus wasting a lot of work energy, time, and even causing huge economic losses. However, if an operating system such as UNIX does not shut down properly and the system information in memory is not written back to the hard disk, it may also cause the system to crash and fail to start again. In addition, although the hard disk in the computer uses magnetic storage media, 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 cause an error in the file allocation table when maintaining the file system, resulting in the retirement of the entire hard disk. In addition, most current operating systems can set up virtual memory. Due to sudden power failure, the system has no time to cancel the virtual memory, resulting in "information fragments" 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 rectifier power supply, and excessive voltage may cause the rectifier to burn out. The voltage spike, transient over-voltage, power supply noise and other disturbances may enter the main board through the rectifier, affecting the normal operation of the machine, or even burning the main circuit.
In short, the power problem is a major threat to computer work. But with the increasingly important and extensive application of computers and networks, safe and reliable power supply has become an important problem that network designers and managers have to seriously face. "Needs are the first driving force of social development". Under this background, UPS (Uninterruptible Power Supply System) came into being. With the development of power electronics technology, it has constantly pushed through the old to bring forth the new. In more than ten years, it has not only created a new industry, but also will have vigorous development and bright prospects as time goes by.
Do you know?
According to IDC statistics, 45% of all computer failures are caused by power problems; In China, the average number of power outages in large cities is 0.5 times/month, that in medium-sized cities is 2 times/month, and that in small cities or towns is 4 times/month; Therefore, it is necessary to equip the computer with a UPS from the perspective of improving the quality of power supply.
In addition, precise network equipment and communication equipment are not allowed to have power interruption. It is self-evident that the network center with the server as the core should be equipped with UPS. Even an ordinary computer, whose software value such as data files after three months of use has exceeded the hardware value, so it is very necessary to equip UPS to prevent data loss.
Power failure is rare where the equipment is used. Can UPS not be used?
According to statistics, power failure only accounts for a small part of the power problems, and imperceptible power problems, such as high voltage, low voltage, surge, surge, etc., are the main power problems. UPS is designed to provide comprehensive power protection for your extremely important loads. It includes voltage stabilization, prevention of sudden wave damage, avoidance of high-frequency interference, prevention of any form of power supply interruption or floating, etc., and can provide unlimited long delay power supply.