In order to prolong the service life of the UPS, the UPS should not be operated at full load for a long time. Backup UPS generally selects 60%-70% of the rated power load, and online UPS generally selects 70%-80% of the rated power load. In order to prolong the service life of the battery, UPS should not run under excessive light load for a long time.
Suppose you want to configure a UPS for a load with a power rating of 500VA and a power factor of 0.9. Calculate as follows based on the assumed load parameters:
500VA/0.8=625VA (When the UPS drives a load with a power factor of -0.9, its driving capacity is 80% of the rated power)
625VA/0.7=892.86VA (Backup UPS generally selects a load capacity of 60% -70% of its rated power)
625VA/0.8=781.25VA (Online UPS generally selects 70% -80% of its rated power load)
From the calculation results, when driving a load with a rated power of 500VA and a power factor of 0.9, if you choose an online UPS, you can choose a load above 780VA, and if you choose a backup UPS, you can choose a load above 892VA.
The capacity selection of UPS should take into account several factors.
1. Actual load situation
P=∑Pi/k(5-3)
1) The sum of all actual loads, plus a certain margin. K is the margin coefficient, generally ranging from 1.1 to 1.3.
2) Reserved expansion: Considering the possibility of the development of the IC trading network volume, additional operational equipment will be added in the future without increasing equipment and site investment
P=P*k(5-4)
In the formula, k represents the margin coefficient, which can be controlled by users according to their actual situation between 1.1 and 1.3.
The load power factor of UPS is treated as a percentage of the output active power: in fact, UPS has a Pythagorean chord relationship with active power, reactive power, and apparent power in a right angled triangle. For example, when the load power factor PF of UPS is 0.8, a UPS with an apparent power S of IKVA can output active power of
P=S*PF=800W
The reactive power is
Q=S*√1-PF2=1*0.6=600var
Instead of 200var reactive power. Moreover, when the dual conversion UPS is operating normally with a linear load with power factor PF=l, the inverter can only provide 80% of the active power instead of 100. This is determined by the inherent characteristics of the inverter.
Using the apparent power sum of nonlinear loads as a criterion to select UPS with mismatched power factors may seem reasonable, but if the power factor is not selected correctly, there may be problems. The ability of UPS to handle nonlinear loads mainly depends on its reactive power. A high reactive power has a strong ability to cope with nonlinear loads. Therefore, reactive power should be used as the standard to select UPS.