Design of apcups power supply system in the center of telecommunication data room

1. Determination of apcups power capacity

According to the load capacity and nature, choosing the appropriate apcups power supply can not only ensure the power supply quality of apcups, reduce the failure rate, but also save investment and improve economic benefits. Generally speaking, the capacity of UPS should meet the needs of current load, and the following factors should also be considered.

① The influence of load properties on the output power of ups. At present, the output power given by most UPS manufacturers in the product manual refers to the load power factor of When the load is pure resistive or inductive, the active power of the inverter will decrease under the rated apparent power. Therefore, when considering UPS capacity, power conversion should be carried out for different load power factors. Generally, it can be estimated that if the load power factor is 0.8 (lagging) and the rated power of UPS is 1kVA, the output power is 0.74-0.77kw, then when the power factors are 0.9 (lagging) and 1.0, the output power is 0.9-0.92kw. For impact load, as long as the peak coefficient of load is within the allowable range of apcups power supply, UPS can basically output rated power; for resistive or inductive load, it is necessary to increase the capacity of apcups power supply as appropriate.

② . apcups power supply capacity should not be too large to avoid over light load operation. Although excessive light load operation is conducive to reducing the probability of inverter damage, it may cause the battery discharge current to be too small and the discharge time to be too long when the power supply is cut off, and the battery pack will be deeply discharged when the battery protection device fails, resulting in permanent damage.

③ . the capacity of apcups power supply should not be too small to avoid long-term heavy load operation. This can save some investment, but because the inverter is in the state of heavy load operation, its output waveform will be distorted, and the output voltage amplitude jitter is too large. In this way, it can not provide high-quality power for the load, and it is very easy to cause damage to the final drive elements of UPS inverter. At present, some ups manufacturers recommend that the load of UPS should not exceed 80% of its rated capacity for a long time.

④ . in case of large area of communication room and continuous expansion of load by stages, the medium and long-term development trend shall be properly considered when configuring UPS capacity in the first phase, and the models that can be combined or operated by multiple machines shall be selected in the selection, so that the output capacity can be expanded through UPS when the medium and long-term load capacity is the largest. Accordingly, when the apcups power input and output distribution panel is configured, the input switches of multiple ups and load shunt switches in the medium and long term shall be reserved for future expansion.

2. Electrical isolation and grounding of power supply system

In order to reduce the cost, some manufacturers take the output isolation transformer as an option for users to choose. But generally speaking, there are often differential mode interference and common mode interference in the power grid, which have different degrees of interference to the normal operation of the equipment in the computer room. In addition, the offset of zero line potential will also affect the operation of electronic equipment. Therefore, when considering apcups power supply scheme, measures should be taken to minimize these impacts, and isolation transformer must be considered. Traditional apcups power supply realizes electrical isolation and voltage matching between load and power grid through internal power frequency input and output transformers, and suppresses common mode interference voltage and differential mode interference voltage from power grid, so that it is not coupled to power supply of electronic equipment. The output zero point of this apcups power supply is taken from the neutral point of the secondary y-winding of the isolation transformer. In order to ensure that the output zero voltage is not offset, a separate lead shall be connected to the output point from the AC working grounding bar of the communication machine room.

In recent years, apcups power supply with high frequency chain structure without output isolation transformer has appeared. Because the high frequency transformer is used instead of the power frequency transformer, its volume and weight are obviously reduced, but because its output end is directly output through the transformation element, there is a risk of DC high voltage entering into the load to some extent, and there is also the zero point of the electric voltage in the case of three-phase load imbalance