Abstract: At present, there are many varieties of UPS introduced in China, and different products come from different countries and manufacturers. The working principle and specific circuit design of these UPSs are different. In particular, some manufacturers often erase the logo on the type of integrated circuit for commercial needs. All of these factors present certain difficulties in using and maintaining the UPS. However, some commonalities can still be found for some commonly used UPS usage rules. Here are some clues for proper use and maintenance of the UPS for your reference.
(1) In the backup UPS design, in order to reduce the production cost, it uses the same main power transformer in both the mains supply and the battery supply. When this type of UPS is powered by a battery, its AC output live and neutral positions are fixed and the user cannot change their mutual order. Since the neutral line of the mains input of the UPS is the ground of the UPS control line, the user must follow the relevant regulations on the manufacturer's product specification when using the UPS.
(2) The actual usable capacity of all the batteries in the UPS is closely related to the discharge current of the battery, the environmental operating temperature of the battery, the length of the storage time, and the load properties (resistance, inductance, and capacitance). If the UPS is not used correctly, the actual available capacity of the battery is only a small part of the nominal capacity of the battery. For this reason, users should pay attention to the following points when using the battery:
A. Over-discharge of the battery and the long-time open circuit of the battery are not used, which will cause a large amount of lead sulfate to be generated inside the battery and be adsorbed to the cathode of the battery to form a so-called cathode "sulfation", which results in a battery. The internal resistance increases and the charge and discharge performance of the battery deteriorates. The current life of the commonly used M-type sealed lead-acid battery is about 3-5 years.
B. For most current UPS, after each discharge of the battery, the battery can be floated by the battery charging circuit inside the UPS. In order to ensure that the battery is placed in a saturated state of charge, the charging time is generally 10 to 12 hours. Insufficient charging time will cause the battery to be undercharged. At this time, the actual usable capacity of the battery is much lower than the nominal capacity of the battery. For some UPSs, when the mains voltage is lower than 200V, it is impossible to saturate the battery with the charging circuit inside the UPS.
C. Some users use the method of reducing the actual load power of the UPS or increasing the battery capacity to extend the discharge time of the battery.
D. When the UPS battery encounters one of the following conditions during use, in order to resurrect the chargeable and discharge characteristics of the battery, a balanced charging method should be used to solve the problem. The so-called equalization charging is an operation method in which each battery unit is connected in parallel and charged with a uniform charging voltage. The situations in which the battery needs to be balancedly charged are:
• Excessive discharge causes the terminal voltage of the battery to be lower than the discharge termination voltage allowed by the battery. For the 12V M-type lead-acid battery, the discharge final voltage is about 10.5V;
E. In order to ensure the battery has good charging and discharging characteristics, for long-term idle UPS (experience data is UPS shutdown for more than 10 days), before restarting the use, it is best not to load, let the UPS use the charging circuit inside the machine Recharge the battery after 10 to 12 hours. For the backup UPS users, if the UPS is working in the backup mode for a long time, it is recommended that the UPS be in the inverter for at least 2-3 minutes every other month to activate the battery.
(3) For most UPSs, when they are in the inverter power supply state, their load characteristics are generally required to be purely resistive or capacitive. When the load is capacitive, its power factor requirement is greater than about 0.8. Therefore, for those with inductive loads, care should be taken to adjust their total load reactance to meet the conditions of power factor greater than 0.9 as much as possible. Otherwise, the actual load power that the UPS can bear will decrease. Manufacturer's recommendation: The maximum starting load of the UPS is preferably controlled within 80% of the rated output power of the UPS. For a sine wave output UPS, when the load is less than 30% of the UPS rated output power, its output voltage waveform distortion factor will increase slightly. Practice has proved that for most UPS, it is the best way to control the load within 30%~60% of the rated output power of the UPS. Therefore, users who have requirements for AC input waveforms should pay attention to this.
(4) For the backup UPS, when it is in the backup working state of the mains supply, although it has anti-interference automatic voltage regulation function, it does not have the output short-circuit automatic protection function (usually realized by AC input fuse) Limiting). Therefore, for this type of UPS user, the capacity of the fuse in the AC input circuit must not be increased arbitrarily. Only when this power supply is in the inverter power supply state, it has automatic voltage regulation and output short circuit automatic protection.
(5) For the UPS of the backup square wave output, because there is no technical means to accurately adjust the square wave operating frequency in its control circuit, when this power supply is in the inverter power supply state, sometimes its The square wave operating frequency is likely to deviate significantly from 50 Hz. In addition, for a square wave output UPS, when it is powered by the inverter, it is not suitable for long-term no-load operation.
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