Service Manual

GSM-204-323
Power supply module (PSM)
31st Oct 01
Technical Description: Horizon macro outdoor
68P02902W02-A
CONTROLLED INTRODUCTION
Tech. 4–31
Power supply module (PSM)
PSM overview
The PSM is a dc to dc converter, providing a stabilized +27 V output to power all
the main cage equipment.
Only one type of PSM is used in the Horizon
macro outdoor:
 Nominal –48 V (positive earth).
The PSMs are fed from a backplane connector, and use pulse width modulation
to generate output supply. A front panel switch (shown in Figure 4-19) disables
the output, reducing the input current as shown in Table 4-7.
Table 4-7 Input currents for power supply module
Type of PSM Output voltage
full load
Input current
full load
Input load when
output switch off
–48 V nominal dc +27 V 18 A 0.5 A
NOTE There are several manufacturers of the PSMs. Each is
fully compatible with the same type of PSM of a different
manufacturer.
PSM location
and redundancy
The PSMs are located above the digital cage and circuit breaker module. There
are three slots, two for maximum main cage configuration and one for
redundancy. Table 4-8 shows the recommended number of PSMs for different
operational configurations.
Table 4-8 PSM operational configurations
Number of
PSMs fitted
Maximum load capability
1 Complete operation of cabinet for up to three CTUs.
2 Complete operation of cabinet for up to six CTUs.
3 Redundancy and power load sharing (further enhancing
reliability by reducing temperature of operation).