When purchasing UPS power supply, you not only need to understand the load, use environment, volume and weight of the UPS, but the choice of UPS also depends on the technical performance and after-sales service. Generally speaking, it is best to choose a reliable and big brand. Some small brands may have quality problems. You can directly contact the UP system power supply factory purchased by UPS power supply, and the UPS system power supply factory directly docks the terminal. Now, I will specify the purchase of UPS power supply. The following aspects should be considered:
1. Load type
As mentioned above, although the ratio of active power and reactive power is different for each load, the UPS must provide sufficient active power and reactive power for the load at the same time, so the actual output capacity is limited by the load type. For computer loads, the UPS can basically output the rated power. If the load is resistive or inductive, the output power of the UPS must be reduced, thereby increasing the UPS capacity. For example, a 1kVA UPS with a power factor of 0.7 can carry the full 1kVA with a computer load, but can go up to 700VA with a purely resistive load (700 watts active in this example), and less with an inductive load. Therefore, resistive and inductive loads that express power in W must be converted to VA when calculating load capacity. A typical calculation method is: resistance load VA value = W value _ 0.7. Inductive load VA value = W value 0.3.
2. Environmental conditions
The operating temperature of the UPS should be controlled between 0 and 40. The temperature is too high and the ventilation conditions are not good, which is not conducive to heat dissipation, so the amount should be reduced. Also, altitude can be affected. If the altitude exceeds 1000 meters, the UPS will be reduced by 5% for every additional 1000 meters.
When considering the capacity problem in the matching process of UPS power supply in the computer room, the factors related to the capacity determination should be listed, and the specific relationship between each factor and the capacity should be clarified. The main factors that determine the size of UPS capacity include actual load capacity, load type, capacity utilization, environmental conditions, UPS type and actual load capacity, and potential expansion requirements that need to be considered in actual applications.
4. Actual load capacity
This is the most basic factor in determining the size of the UPS power supply. The output capacity of the UPS power supply must meet or exceed the load requirements to ensure normal power supply. In practical applications, it is necessary to consider whether the UPS power supply is a centralized power supply or a distributed power supply. The total load of the centralized power supply must be the total power of all UPS power loads in the computer room. Distributed power is determined by the load carried by each UPS.
The load capacity of electrical equipment is generally called long-distance power, represented by S, and the unit is VA. According to different powers, it includes active power P (unit W) and reactive power Q (unit Var). The size relationship is S2=P2 Q2. Here, we call it the ratio power factor of active power and off-site power. The power factor of pure resistive load is 1, and the power factor of capacity load is usually 0.6 ~ 0.7. 5. UPS power supply capacity utilization
Since the equipment in the computer room has various non-linear loads, such as switching power supplies and various types of printer loads, these loads have larger inrush currents. The UPS capacity of the power supply is too small, and long-term heavy-duty operation will easily lead to waveform distortion and output power drop. The heat generated by the overcurrent and heavy load of the device has obvious hazards to the reliability of the system. For large-capacity UPS, it is generally recommended that the capacity utilization be controlled between 0.6 and 0.8.
Of course, the capacity of UPS cannot be too large. A small load UPS helps with reliability, but running an overloaded UPS is a waste of investment. Second, when the mains power is cut off for a long time, the discharge current of the battery is very small, and it is easy to be damaged by deep discharge.
If you can choose online UPS with all the above indicators, it will be the most cost-effective product. For output voltage stability, harmonic distortion, three-phase load unbalanced capacity, etc., they can generally meet the requirements, and have little impact on the price, so generally there is no need to focus on it. Regarding MTBF, it is a very important metric, but how meaningful it actually is is debatable.