A brief introduction to UPS and its working principle
UPS is an acronym for Uninterruptible Power Supply, meaning "Uninterruptible Power Supply", which is a kind of uninterruptible power supply that contains an energy storage device (commonly batteries) with a constant voltage and frequency with an inverter as the main component. Inverter as the main component of the constant voltage and frequency of the uninterruptible power supply, it can solve the existing power outages, low voltage, high voltage, surge, noise and other phenomena, so that the computer system operation is more secure and reliable. Now it has been widely used in computer, transportation, banking, securities, communications, medical, industrial control and other industries, and is rapidly coming into the family.
Below, let us first briefly understand the working principle of UPS.
When we do not use the UPS, PCs, printers and other terminal equipment is directly connected to the utility to use, with the UPS, the PCs, printers and other terminal equipment connected to the UPS to use, and the UPS then access to the utility. When the utility input is normal, the UPS will be stabilized utility voltage supplied to the terminal equipment (relative to the UPS, we will be these terminal equipment called loads), at this time, the UPS is an AC utility voltage regulator, at the same time, it is also charging their own built-in batteries; when the utility interruptions (for example, blackouts), the UPS will be built-in battery power immediately, the inversion conversion method to the load to continue the supply of The UPS can also be used as a stand-alone system to protect the load's software and hardware systems from damage.
Two, the impact of utility power on home PCs and their terminal equipment
If our PCs, computer networks and other equipment do not use UPS, and what will be affected? Many people have a common misconception that we use the utility power, in addition to the occasional power outage, are continuous and constant. This is not the case. The utility system as a public **** power grid, connected to thousands of various loads, some of the larger inductive, capacitive, switching power supply loads not only from the grid to obtain electricity, but also in turn on the grid itself, deterioration of the power grid or local grid power supply quality, resulting in utility voltage waveform distortion or frequency drift. In addition, accidental natural and man-made accidents, such as lightning strikes, transmission and transformation system disconnection or short-circuit, power plug ground wrong unplugging, etc., will jeopardize the normal supply of electricity, thus affecting the normal operation of the load. In particular, it should be especially pointed out that PCs, network equipment, communication systems, medical equipment, etc. are very sophisticated electronic equipment, the impact on them is particularly prominent.
For PCs, normal power supply is required for the monitor and the host computer to work. Memory, in particular, requires a higher level of power supply. It is a storage device that relies on electrical energy and requires constant refreshing action to maintain the stored content, and once the power is cut off, the saved content immediately disappears. If abnormal power failure results in the information in the memory not being saved to the hard disk and other storage devices in time, it will cause the information to lose its value because it is completely lost or becomes incomplete, thus wasting a lot of work energy and time; and operating systems like UNIX and Linux (nowadays, many computer enthusiasts use this kind of operating system), if they are not shut down normally, the system information in the memory is not written back to the hard disk, may also cause the system to crash, can not start again; In addition, the hard disk in the computer, although the application of the magnetic storage media, will not be due to power outages and loss of information, but a sudden power failure will make the hard disk is reading and writing the work of the physical head damage, or the system files in the maintenance of the file system, resulting in the file allocation table error, so as to make the hard disk to generate a bad sector, serious, and even cause the whole Hard disk scrap; In addition, most of the current operating system can set the virtual memory, due to a sudden power failure, so that the system can not cancel the virtual memory, resulting in hard disk "information fragmentation", not only a waste of hard disk storage space, but also lead to slow machine operation; computer power supply is a kind of rectifier power supply, too high a voltage may cause rectifier burnout. The computer power supply is a rectifier power supply, too high voltage may cause the rectifier burned. The voltage spike and transient overvoltage, as well as the power supply noise and other disturbances may enter the motherboard through the rectifier, affecting the normal operation of the machine, and even burn the host line.
Generally, the standard sine wave (220V, 50Hz) is an ideal state, but in reality, according to the test of electric power experts, there are the following situations that often occur in the power grid and cause interference or damage to computers or precision instruments: surge, high voltage spike pulse, transient overvoltage, voltage sag, wire noise, frequency drift, continuous low voltage, utility power interruption, etc. Interruptions, etc.
1. power surge (Power Surges): refers to the output voltage RMS value is higher than the rated value of 110%, and the duration of one or more cycles. Power surge is mainly due to the grid connected to large electrical equipment shutdown (such as common household air conditioning shutdown), the grid due to sudden unloading of high voltage (we will have such a personal experience: in the evening from 6:00 to 9:00 or so of the time period, is the peak of the power supply, the utility voltage is generally low, the home lighting is darker, the peak of the power supply, such as in the night 10:00 (Around 10:00 pm, you will find that the lighting in your home suddenly flashes and is much brighter, which is one of the most common surge phenomena we see in our daily lives).
2. High Voltage Spikes (High Voltage Spikes): refers to voltages with peaks of up to 6000v and durations ranging from one ten-thousandth of a second to one-half of a cycle (10ms). This is mainly due to lightning strikes, arc discharges, static discharges or switching operations of large electrical equipment.
3. Transient overvoltage (Switching Transients): refers to the peak voltage of up to 20000V, but the duration of the pulse voltage bounded by millionths of a second to ten thousandths of a second. Its main reason and may cause damage similar to the high-voltage spike pulse, just in the solution will be different.
4. Voltage sag (Power Sags): refers to the utility voltage RMS value between 80% and 85% of the rated value of the low voltage state, and the duration of one to several cycles. Large equipment start-up, large motor start-up, 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), as well as a variety of other high-frequency interference. The operation of the motor, the action of the relay, the work of the motor controller, radio transmissions, microwave radiation, and electrical storms, etc., will cause line noise interference.
6. Frequency shift (Frequency Variation): refers to the change in utility frequency of more than 3Hz. This is mainly due to the unstable operation of the emergency generator, or by the frequency instability of the power supply.
7. sustained low voltage (Brownout): refers to the utility voltage RMS value is lower than the rated value, and continue for a long time. Its causes include: large equipment startup and application, main power line switching, starting large motors, line overload (many parts of our country have this problem).
8. utility interruptions (Power Fail): that is, we usually encounter power outages. The causes are: tripping of circuit breakers on the line, interruption of the utility supply, grid failure.
Three. Classification of UPS
UPS has evolved from rotating generators in the 1960s to today's static, fully electronic circuits with a degree of intelligence, and continues to evolve. At present, UPS generally refers to stationary UPS, according to its mode of operation can be divided into backup, online interactive and online three categories.
1. Backup UPS: When the utility power is normal, directly from the utility power to the load power supply, when the utility power exceeds its operating range or blackout, through the conversion switch to the battery inverter power supply. Characterized by: simple structure, small size, low cost, but the input voltage range is narrow, the output voltage stabilization accuracy is poor, there is a switching time, and the output waveform is generally a square wave. The schematic diagram is as follows:
2. Online interactive UPS: In the utility power normal directly from the utility power to the load power supply, when the utility power is low or high, through the UPS internal voltage regulator line voltage regulator output, when the utility power is abnormal or blackout, through the conversion switch to the battery inverter power supply. It is characterized by: a wide range of input voltage, low noise, small size and other characteristics, but there is the same switching time, but compared with the general backup UPS, this model has a stronger protection function, the inverter output voltage waveform is better, generally sinusoidal. The schematic diagram is as follows:
3. On-line UPS in the utility power normal, rectified by the utility power to provide DC voltage to the inverter work, the inverter to provide AC power to the load, in the utility power abnormalities, the inverter from the battery to provide energy, the inverter is always in the working state, to ensure that there is no interruption to the output. It is characterized by an extremely wide input voltage range, no switching time and high accuracy of output voltage stabilization, which is especially suitable for occasions with high power requirements, but at a higher cost. At present, the power greater than 3KVA UPS is almost always online UPS. schematic diagram as follows:
UPS according to the size of the output capacity is divided into a small capacity of 3KVA, small and medium-capacity 3KVA ~ 10KVA, medium and large-capacity 10KVA or more.
UPS can be divided into three categories according to the input/output mode: single-phase input/single-phase output (referred to as single-input single-output), three-phase input/single-phase output (referred to as three-input single-output), and three-phase input/three-phase output (referred to as three-in-three-out).
For the user, the three-phase power supply utility power distribution and load distribution is easy, each phase is responsible for part of the load current, and thus the medium and high power UPS more than three-phase input/single-phase output or three-phase input/three-phase output power supply mode.
Backup UPS is mainly used to provide power protection for a single PC, and is characterized by small size, low price and simple operation, which is very suitable for home use, so when you buy a UPS for your home computer, please buy a backup one.
Online UPS can solve almost all common power problems, in the presence of utility power, the function is to stabilize the voltage and prevent power fluctuations interference, because of its function is more complete, so its cost also rises with the enhancement of the performance, the price is much more expensive than the backup UPS. On-line UPS is mainly used for some computer equipment, medical equipment, etc. with very strict power requirements, generally used in series with multiple external batteries to extend the power supply time, mostly for the unit configuration.
Intelligent UPS is a major development trend of today's UPS, with the UPS in the network system on the application of network managers to emphasize the entire network system for the protection of the object, I hope that the entire network system in the power supply system failures, but still can continue to work without interruption. Therefore, the UPS internal configuration microprocessor to make it intelligent is the new trend of the UPS, UPS internal hardware and software combination, greatly improving the function of the UPS, you can monitor the operation of the UPS work status, such as: UPS output voltage frequency, grid voltage frequency, battery status and fault records. Can also be detected through the software on the battery, automatic discharge charging, as well as remote control switching and so on. Network managers can analyze the quality of power supply according to the information, according to the actual situation to take appropriate measures. When the UPS detects an interruption in the power supply grid, the UPS automatically switches to the battery power supply, and immediately notifies the server to make preparations for shutdown when the battery power supply capacity is insufficient, and shuts down itself before the battery runs out. Intelligent UPS through the interface to communicate with the computer, so that network administrators can monitor the UPS, so the function of its management software is extremely important.