Due to the complexity of the power supply and utilization of the mains power grid, such as the insufficient capacity of the mains power grid, the performance and quality problems of power transmission and transformation and various power distribution equipment, the irrationality of the configuration of various electrical equipment, and the inter-equipment Mutual influence, the increase of various non-linear loads in the power distribution system, the wide application of power semiconductor converter devices, as well as the influence of natural lightning, ground electricity and human factors, the AC power output from the power grid is not a stable sine wave , But make the quality of power supply continue to deteriorate, there are various power supply quality problems, for example as follows.
①Voltage surge: refers to the voltage change in which the effective value of the output voltage of the mains power grid is greater than 110% of the rated value, and the duration is one cycle (20ms) to several cycles. This is mainly due to the poor voltage regulation capability of the power transformer of the power grid, and the voltage shock caused by the sudden disconnection of large electrical equipment.
②High voltage spikes: refers to voltage spikes with a peak voltage of 6000V and a duration of 1ms to several cycles. This is mainly caused by lightning strikes, arc discharges, static discharges, and the opening and closing operations of large electrical equipment.
③Temporary overvoltage: refers to a pulse voltage with a peak voltage of up to 2000V and a duration of 1-100μs. This is still mainly caused by lightning strikes, tip discharges, and instantaneous actions of large equipment.
④ Voltage sag: refers to the low voltage state where the effective value of the voltage is between 80% and 85% of the rated value, and the duration is one cycle to several cycles. This is mainly caused by the start of large equipment, large motors, or the connection of large power transformers.
⑤Line noise: Refers to radio frequency interference (RFI), electromagnetic interference (EMI) and other high-frequency interference on the line. The operation of large electric motors, the operation of large circuit breakers, broadcast transmission, microwave radiation, etc. will all cause line noise interference.
⑥Frequency deviation: Refers to the change of the grid frequency exceeding ±3Hz. This is mainly caused by the unstable operation of emergency diesel generators and hydroelectric generators.
⑦Continuous low voltage: refers to the long-term effective value of grid voltage lower than the rated value. This is mainly caused by the operation of large-scale equipment, the switching of main power, and line overload.
⑧ Mains interruption: refers to the interruption of power supply to the power grid, and its duration is greater than two cycles to several hours. This is mainly caused by the tripping of the circuit breaker of the grid, the interruption of the mains power supply, or the grid failure.
According to a survey, when a computer is powered by a mains power supply with the above-mentioned quality problems, on average, it will encounter power supply problems about 120 times a month. These problems will have a great impact on the work of the computer, as shown below.
① Computer memory has high requirements for power supply. It is a storage device that relies on electric energy. It needs to keep refreshing to keep the stored content. Once the power is cut off, the stored content will disappear immediately. If the power is off abnormally, it will cause the information in the memory to be too late to 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. This will cause a waste of manpower and time. Cause huge economic losses.
②For the operating system, if it is not shut down normally, the system information in the memory is not written back to the hard disk, and the operating system may crash and fail to restart.
③Although 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/writing work, or cause files when maintaining the file system. The allocation table is wrong, which will cause the entire hard disk to be scrapped.
④Current operating systems are mostly capable of setting virtual memory. Due to a sudden power failure, the system will not have time to cancel the contents of the virtual memory, resulting in “information fragmentation” in the hard disk, which not only wastes the storage space of the hard disk, but also causes the computer It runs slowly.
⑤The computer’s power supply is a switching power supply. Excessive mains voltage may cause the power rectifier to burn, and the spikes of the mains voltage, intelligent overvoltage and power clutter, etc. may enter the motherboard through the rectifier and affect The normal operation of the computer even burns and sucks the host circuit.
In short, the problem of power supply has a great impact on the work of computers, so with the increasing importance and widespread of computer network applications, safe and reliable power supply has become an important issue that computer network designers and managers have to face seriously.
It can be seen from the above that directly using the electric energy on the mains power grid to supply power cannot meet the requirements of safe and reliable work of the computer, so the UPS power supply must be used for power supply.