FUNCTIONING OF EQUIPMENT
This chapter provides theory of operation for the power supplies
and power supply test set. The purpose of this chapter is to explain
the circuit operation of this equipment to organizational and inter-
mediate support maintenance personnel.
In addition to the-general section, this chapter contains a func-
tional description section and a detailed theory of operation section.
a. Power Supplies. The power supplies each consist of four her-
metically sealed dc-dc converter power modules (PS1 thru PS4), four
overvoltage protectors (U1 thru U4), a thermal switch (S1), a cooling
fan (blower B1), and an elapsed time meter (Ml). Differences between
the power supplies occur in the voltages provided-by the de-de conver-
ter power modules, and in the types of interface connectors and pin
configurations (see tables 1-1 thru 1-7). Each power supply receives
28 V dc and 3 , 400 Hz, 115 V ac from external primary power sources.
The 28 V dc is applied in parallel to the four converter modules, which
convert it to the dc voltages listed in table 1-1. The remote-sensing
feature of the converter outputs is used to compensate for supply vol-
tage drops across long interconnecting cables. The voltage outputs are
protected from excessive voltage by modular overvoltage protectors con-
nected across all power supply dc outputs. The 3- ac input operates
blower B1, with 1 operating the running time meter. If a power
supply overheats, the thermal switch closes to provide a warning
indication to external equipment.
b. Power Supply Test Set. The power supply test set routes 3-,
40C-HZ ac, and 28-V dc facility line power to the power supplies under
test and receives power supply outputs that have been preselected on
the three-position toggle switch. The power supply output selected is
LOAD, or OVERLOAD. Test jacks are provided, allowing voltage to be