【 Weak current College 】 power factor matches and UPS selection problem--UPS power factor and load properties

The vast majority of computers, communications equipment, control systems, precision equipment with switching power supply as the primary power source, according to the above discussion on load properties, most computer equipment input power factor for micro-capacitive 0.7. And the UPS load is primarily targeted at those only precision equipment, based on the reason all UPS design uses output power factor match 0.7 ~ 0.8 parameters, thereby maximizing the UPS load capacity. Match the power factor, namely, computer load input power factor for micro-capacitive 0.7, and UPS output power factor is also intended to 0.7, load of VA and VA UPS's ratio is 1: 1. In other words 1VA capacity ups without considering the impact, capacity and other factors may bring margin 1VA such loads. If the power factor does not match, for example, resistance load capacity ups 1VA can only load resistance with 0.7VA, UPS appear overload (even if the number is greater than VA UPS with this number VA load). Here it should be noted that some UPS manufacturers propaganda ups output power factor is 0 ~ 1 actually is one-sided, such as interactive UPS and generation have online compensation function of the three ports on the ups, when the mains power supply can be directly loaded by transformer power supply or by compensation match UPS load, you can match the other load power factor, and when the city electricity have a power, UPS loses compensation function, the UPS output power factor matches only one value, but the vast majority of manufacturers will be the match click around 0.7. If you have does not match with load factor exceeds the UPS load capacity overloads, UPS will appear more serious disruption or failure. So the UPS in the load selection issues you need to consider issues of power factor matches. If the load is resistive or sensibility, should be appropriately increased UPS capacity. The following example of a practical example of how to choose UPS capacity of power factor of factors: the load on the above, in accordance with the power factor concept and match with the UPS. The sum of the previous load capacity cannot be a simple algebraic addition draw 6.2kVA. The correct calculation methods are as follows: to load 3 's apparent power is divided into active energy and reactive power in two parts
Active power sections to 1400W
Reactive power is 1430Var
PLx=SLx·cosΦ
QLx=√SL2x-PLx2
Will load 4 apparent power is divided into active energy and reactive power in two parts
Active power part 1540W
Reactive power is 1570VarP = P load 1 + 2 + P load ... + P load n
P=1000W+1000W+1400W+1540W
P=4940W
Q = Q load 1 + 2 + Q load ... + Q load n
Q=1430Var+1570Var
Q=3000Var
S=√PLx2+QLx2
S=√49402W2+30002Var2
S=5780VA
cosΦ=PL/SL=4940W/5780VA≈0.85