GE Industrial Solutions CPS6000 - Manual (Page 25)

CPS6000 –48V Indoor/Outdoor Power Shelf
Issue 21 January 2008
25
Figure 3-1: Recharge Factor vs. Recharge Time
Plant Configuration Examples
1. To illustrate the relationships between mirc, abh current drains, the recharge factor, and
battery recharge current for non-redundant and redundant systems, consider the following
examples. Note that the QS862A rectifier provides 25A at 54.5 Vdc (100-120 Vac) and
30A at 54.5 Vdc (200-240Vac).
A battery plant is required to provide a load current of 50 amperes, have an 8-hour
discharge time (reserve time) and recharge to 95% of battery capacity in 24 hours.
Determine the number of rectifiers required for non-redundant systems.
From Figure 3-1, the recharge factor is 1.38.
mirc = abh x recharge factor
mirc = 50 x 1.38 = 69 amperes
For low line ac using QS862A 25A (100-120 Vac) rectifiers, three rectifiers (69/25 =
2.76) are required to provide the minimum installed capacity of 69 amperes for a non-
redundant system. If one rectifier fails, the remaining rectifiers will provide the abh
capacity.
2. An alternate method to calculate the number of rectifiers necessary is to utilize power. In
the above example, the requisite current is 50A. As most battery plant loads are looking
into constant-power loads, the 50A would increase as the battery voltage decreases during
battery discharge. Assuming the 50A is the current being drawn from the load at the plant
float voltage of 54.5V, the total power being drawn by the load is 2725W (54.5V x 50A).
We can utilize the recharge factors from Figure 3-1 and use a modified mirc formula,