Program-controlled switches, data communication processing systems, computers, communication base stations, security monitoring systems and other equipment require AC power supply systems to be out of power during operation. In order to improve the reliability and maintainability of these devices, many enterprises have equipped them with ups power supplies. system. The UPS (Uninterruptible Power) power system consists of a rectifier, an energy storage device, an inverter, and a static switch. At present, there are many kinds of UPS systems in the domestic and foreign markets, and their main functions and principles are basically the same. The following is a brief introduction of their use and maintenance from several aspects.
1 The role of UPS
The use of UPS mainly has two aspects: First, emergency use, to prevent sudden power failure and affect the normal operation of the equipment, causing damage to the electrical equipment; second, to eliminate power surges on the mains, instantaneous high voltage, instantaneous low voltage, power line noise And "power pollution" such as frequency offset, improve power quality, and provide high-quality power for electrical equipment.
The UPS is mainly composed of four parts: a rectification system, an energy storage system, a conversion system and a switch control system. When the power supply system is powered, the rectification system is a device that converts alternating current (AC) into direct current (DC). The inverter is supplied to the inverter or charged to the energy storage system to function as a charger. The energy storage system is a device used by the UPS to store electrical energy. It consists of several batteries connected in series. The size of the battery determines the time it takes to maintain the discharge (power supply). The main function of the energy storage system is to convert electrical energy into chemical energy stored inside the battery when the power supply system is normal; when the power supply system fails, the chemical energy is converted into electrical energy to be supplied to the inverter or the load. A conversion system is a device that converts direct current (DC) into alternating current (AC), which consists of an inverter bridge, a control logic circuit, and a filter circuit. The switch-switching control system is a kind of non-contact switch, which is an AC switch composed of anti-parallel connection of thyristor (SCR). Its closing and opening are controlled by logic controller, which is divided into two types: conversion type and parallel type. Kind. The conversion type switch is mainly used for a two-way power supply system, and its function is to realize automatic switching from one power supply to another; and the switch is mainly used for parallel inverters and power supply lines or multiple inverters. In the system.
2 UPS usage management
Proper use of the UPS power system not only protects it, but also helps to extend its service life. Specifically, you can start from the following aspects:
(1) Regularly check the UPS power supply
When using the UPS power system, not only the main components should be inspected regularly, but also the voltage and internal resistance of each battery unit of the UPS battery pack should be detected. If it is found that the terminal voltage difference of a battery unit of the battery pack is >0.4 V or the internal resistance is >0.08 Ω, the connection wire of the battery unit and the battery pack with abnormal operation should be disconnected, and an external independent charger is used. The battery unit with abnormal operation is separately charged, and its charging voltage (for a 12V battery) is maintained between 13.5 and 13.8 V, and the charging time is controlled to be 10 to 12 hours. It should be noted that during the use of the UPS power supply, the charging of each battery unit in the battery pack may be inconsistent, and the battery unit terminal voltage and the internal resistance of the battery may be unbalanced. These can not be eliminated and corrected by charging the internal charging circuit of the UPS power system. If the unbalanced battery unit is not properly balanced and charged in time, the above problems may be more serious. Therefore, the internal resistance of the battery unit can be restored to 0.03 Ω by charging it separately; and when the battery is fully charged, the battery unit is connected to the battery pack in time, and the UPS charging system is used for unified charging.
(2) First charge
The new UPS should be charged directly to the battery for about 12 hours without load before use. If the UPS power supply is in the floating state for a long time without discharging operation, then the whole UPS is in the storage state. If this state is kept for too long, the battery function may be degraded due to the long-term saving state, and the battery will slowly fail over time. Or scrapped. It is recommended to use UPS battery to supply power to the device once every three months or so, so that the UPS battery is discharged normally, and the battery discharge voltage is controlled above the minimum allowable discharge voltage.
(3) Choice of charging timing
In order to prevent the UPS power supply battery unit from being damaged prematurely due to insufficient long-term charging, the user using the UPS should arrange the battery charging time as much as possible at night to ensure that the battery has sufficient time and stable voltage after discharge. Charge the battery.
(4) Use UPS power supply to prevent over discharge
It is well known that the number of overdischarges of the UPS power supply should be minimized during operation because the number of overdischarges directly affects battery life.
When the power supply system is powered off and the UPS battery pack outputs current to the inverter, the UPS power supply will normally sound an alarm every 4 to 5 s, prompting the user that the UPS power supply is in the battery power state; when the alarm sounds time period When it becomes very short, it indicates that the battery has entered or is about to be over-discharged. At this time, emergency treatment should be done before the UPS power supply is over-discharged, and the generator set should be used instead of the power supply system to supply power to the UPS power supply, thereby avoiding excessive discharge of the UPS battery pack. If the over-discharge of the UPS battery pack is not repaired in a timely and effective manner, the service life of the UPS battery pack will be greatly reduced.
(5) Select a suitable charging protection work point
Currently used UPS power supplies are generally maintenance-free sealed batteries. The charging system basically uses a constant voltage load-stop charging circuit. This circuit can set an overvoltage protection working point for the battery, which has a good protection effect on the battery, but the protection working point cannot be set too high or too low. Because the protection of the working point can directly lead to overcharging or insufficient charging of the battery. In many cases, due to the improper selection of the charging protection working point, the charging causes overcurrent or overvoltage to the battery, which causes the battery life to be greatly reduced. In severe cases, the battery may expand and deform, or even explode, directly threatening the safety of people and property. .
(6) Maintain indoor temperature
The working environment of the battery is closely related to the storage capacity of the battery. The UPS power supply has higher requirements on the ambient temperature, generally 0 to 40 ° C, and the optimum temperature is 25 ° C ± 5%. If the temperature is too high, the inverter will stop working and alarm, and it will also affect the battery life; if the temperature is too low, it will affect the output capacity of the battery. In summer, the temperature is very high. If the ventilation is not good, the large amount of heat generated by the operation of the equipment itself cannot be discharged in time, and the temperature will rise rapidly. If it exceeds 55 °C, the inverter will stop working. The working environment with too high or too low temperature will directly affect the life and working performance of the UPS power system.
3 UPS maintenance
Proper maintenance and maintenance are beneficial to the working life and reliability of the UPS power system.
(1) Regular maintenance
According to the above analysis, it is not difficult to find that the working environment of the UPS power supply directly affects the life and working quality of the UPS power supply. Therefore, when using the UPS power supply, the surrounding environment should be regularly inspected or tested. If the environment changes greatly, the temperature and humidity are too low. Or too high may directly affect the normal operation of the UPS. At the same time, the battery pack should be regularly maintained to extend the life of the UPS battery pack.
(2) do a load connection
It is very important that the load connection of the UPS power supply is correct, because the current of the battery pack is very large, and special tools with good insulation effect should be used for connection and maintenance. When connecting the circuit, you must follow the relevant provisions in the product manual or the manual to ensure that the connected live, neutral, and ground wires meet the requirements. Users should not change their mutual order at random. They should be in accordance with the ground, neutral, and live wires. The order is made correctly and reliably.
(3) Precautions
1 Strictly follow the correct power-on and power-off sequence to avoid the UPS power supply not working properly due to the sudden load or sudden load shedding of the UPS power supply.
2 It is forbidden to turn off and turn on the UPS power frequently: Generally, after turning off the UPS power, wait at least 6 s before turning on the UPS power again. Otherwise, the UPS power supply may enter the state of “startup failureâ€, that is, the UPS power supply enters a state of neither power supply nor inverter output.
3 prohibit overload use: the maximum starting load of the general UPS power supply is preferably controlled within 80% of full load. If it is overloaded, it will often break down the inverter tube in the inverter state. It is more suitable to control the load of the UPS power supply within the range of 30% to 60% of the rated output power.
4 battery discharge requirements: General UPS has protective measures for battery discharge, but after the battery is discharged to protect the shutdown, the battery can be restored to a certain voltage value. Do not reboot at this time, otherwise the battery will be over-discharged. The UPS battery must be recharged before it can be put into normal use.
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