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How to configure Communication UPS Power supply system
1 introduction.
Nowadays, the technology development trend of communication network is the increasing integration of IT (information technology) and CT (communication technology). In order to ensure the safety and reliability of power supply, the next generation communication network (NGN), which is based on the core network technology based on softswitch technology, will still use DC power as the basic power supply mode, but on the business support system platform, the AC power supply mode will also exist at the same time. Based on a large number of applications of computer devices, UPS system devices are more and more used in communication networks. Its power supply object has developed from a single computer device to business terminals, network servers, network devices, data storage devices, business support platform and even the entire communication network. The scope of power supply objects mainly involves computer terminals, servers, routers, switches, displays, disk storage arrays, minicomputers and so on. The way of power supply has also evolved from the decentralized power supply of small UPS to the centralized power supply of large UPS. In order to ensure the reliability of power supply, the power supply mode of Number1 parallel hot backup system and even dual-bus UPS system is even adopted. A well-designed UPS power supply system can provide high-quality power to the load, but in practical application, many problems are often caused by the UPS power supply system. Therefore, how to establish a reasonable and safe UPS power supply system has become an issue of concern. This paper will discuss this problem from the point of view of UPS power supply system design.
Configuration of 2UPS system capacity.
The carrying capacity of UPS is the first question that users should consider when choosing UPS, that is, how much capacity of UPS, is needed? what is the capacity of selected UPS to carry load under various circumstances? it needs to be taken seriously. UPS is not like a transformer, as long as the load power does not exceed its rated output capacity (kVA) value, no matter what load, the output capacity of UPS is not only related to the size of the load, but also related to the nature of the load. Reasonable allocation of system capacity can not only ensure the power supply quality of UPS, reduce the failure rate, but also save investment and improve economic benefits.
2.1 Select system capacity according to load size in UPS.
When selecting the type, we must pay full attention to it. In order to pursue the high reliability of UPS operation, we should not unilaterally think that the larger the capacity of UPS, the higher the reliability. If the UPS runs under light load for a long time, it will help to reduce the damage probability of the inverter, but it will increase the possibility of battery failure in the UPS. Because the discharge current of the battery is too small and the discharge time is too long, it is easy to cause deep discharge and be permanently damaged. If the UPS is in heavy-load operation for a long time, it can save some investment, but because the inverter is in heavy-load operation, the output waveform will be distorted and the output voltage amplitude jitter will be too large. This can not provide high-quality power for the load, but also easily cause damage to the driving components of the UPS inverter, so even from an economic point of view, the loss outweighs the gain. According to the current recommendations of some UPS manufacturers, the UPS single machine is configured with a load of 60% and 80%, and each machine is configured with a load of 35% and 40%.
In addition, the capacity expansion of the load system should also be considered when selecting the UPS, and the pre-increased load is about 20%. For the situation that the area of the communication computer room is large and the load continues to expand by stages, when configuring the UPS capacity in the first phase, the medium-and long-term development trend should be properly considered, and the models that can be run by parallel machines or multiple machines should be selected in the type selection, so that when the medium-and long-term load capacity increases, the output capacity can be expanded through UPS. Accordingly, when configuring the UPS input and output distribution panel, multiple UPS input switches and medium-and long-term load shunt switches should be reserved for future expansion. For example, if the actual load of UPS is 60kVA, the minimum selected capacity of UPS can be estimated as (60kVA+60kVA × 20%) / 60%=120kVA.
2.2 Select system capacity according to the nature of the load.
The nature of load is generally divided into linear load (including resistive load or power factor corrected load, inductive load, capacitive load) and nonlinear load (rectifier filter load with electrolytic capacitor).
According to the above table, it can be seen that different loads have different power factors and peak factors, so when choosing UPS, we must consider the nature of the load.
The input power factor of most computer equipment is micro-capacitive 0.7, and the load of UPS is mainly aimed at these intelligent precision equipment. For this reason, all UPS designs need to adopt the output power factor matching parameters of 0.7-0.8, so as to maximize the load capacity of UPS. In the case of power factor matching, that is, when the input power factor of the computer load is 0.7 and the output power factor calibrated by UPS is 0.7, the ratio of the VA number of the load to the VA number of UPS is 1:1. That is to say, the UPS of 1VA capacity can carry this kind of load of 1VA when the remaining factors such as shock and Zeng capacity are not taken into account. If the power factor does not match, such as the resistive load, the UPS of the 1VA capacity can only carry the resistive load of the 0.7VA, otherwise the UPS will overload (even if the VA number of the UPS is greater than the VA number of the load).
In order to select the load capacity, the impulse current of different loads should also be taken into account. Usually, the peak factor of UPS is 3 1, which is suitable for the peak factor requirements of computers and other nonlinear loads in normal work. However, when the impact is large, the current capacity of UPS and other power supply equipment multiplied by 3 is not enough to meet the instantaneous current requirements of the load. In this case, it is necessary to consider increasing the capacity of the power supply equipment, so as to improve the current supply capacity. Usually, when the computer load is turned on, it will produce a large impulse current many times higher than usual. It usually exceeds the peak factor capacity of UPS, so it is necessary to consider load fluctuation and impact margin when selecting UPS capacity, and appropriately increase UPS capacity to resist load fluctuation. Choose UPS capacity margin as: UPS capacity (VA number): computer load capacity (VA number) = 10.7.
For some special loads, a strong impulse current will be generated in the process of starting or working, and the load capacity will increase several times in an instant (sometimes as high as 6 times). For this kind of load, the surplus should be further increased on the basis of the proportion of ordinary capacity margin.
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