GE Industrial Solutions CPS6000 - Manual (Page 24)

CPS6000 –48V Indoor/Outdoor Power Shelf
Issue 21 January 2008
24
3 Engineering and Ordering
Engineering Information
Introduction
This section discusses the factors to be considered in determining the number of rectifiers and
ringers required in both non-redundant and redundant battery plants.
Rectifier Sizing (Non-Redundant Systems)
In non-redundant systems, the installed rectifier capacity of the battery plant must be
sufficient to provide the current required for the load during normal operations as well as the
current required to recharge the battery following ac power outages.
For the telecommunications industry, the system load current is known as the average busy-
hour current. (The average busy-hour current drain is defined as the average busy-hour
current drain during busy season with the plant operating at the normal voltage.) Therefore,
the minimum installed rectifier capacity (mirc) is the sum of the average busy-hour (abh)
current and the required battery recharge current, or
mirc = abh + recharge current
The battery recharge current is determined by two system considerations: the maximum time
the system is required to operate in the absence of ac power (reserve time), and the time
allocated to recharge the battery after ac power returns. These two times and Figure 3-1 may
be used to determine the recharge factor. This factor, when multiplied by the average busy-
hour current, determines the minimum installed rectifier capacity, or:
mirc = abh x recharge factor
The mirc divided by the individual rectifier capacity determines the number of rectifiers (of
equal capacity) required for a non-redundant system.
Rectifier Sizing (Redundant Systems)
In redundant systems, a spare on-line rectifier is included so that the loss of any one rectifier
will not cause the available plant capacity to fall below the required minimum installed
rectifier capacity. Thus, the loss of a rectifier will not affect the normal system operation nor
will it cause the batteries to discharge, and will allow the batteries to recharge in the required
time.
In cases where the additional spare rectifier will provide the required battery recharge current,
the mirc satisfies the requirements for both non-redundant and redundant systems. In other
cases, rectifiers in addition to the redundant rectifier may be required to provide the battery
recharge current. Typically, the number of spare rectifiers required for a redundant system is
the larger of one spare rectifier or 200% of the rated load.