TM 32-5811-018-14&P
monitored by an external oscilloscope or voltmeter. Front-panel
indicators are used to monitor the status of the power supply
over-temperature sensors. The power supply external sense inputs are
provided by the power supply test set to compensate for test cable
loss.
The main power inputs are protected by ac and dc circuit breakers
mounted on the power supply test set front panel. Relays are
included to protect the power supplies from overheating by
interrupting dc power if ac (blower) power is absent. The ac and dc
power input lines are routed through EMI filters to eliminate
high-frequency line noise.
Eleven interface cables, including the power input cables, are
provided with the power supply test set. Instructions for operating
the test set are included in Chapter 6.
Section III.
DETAILED THEORY OF OPERATION
General.
This section provides detailed circuit theory for the power
supplies. Since the three power supplies use sealed converter and
overvoltage Protector modules, the theory of operation in this
section is limited to a description of the main chassis of the power
DC-DC Converter Power Modules.
The dc-dc converter power modules for each power supply are
designated PS1 thru PS4. 28 V dc is applied in parallel to all of
the converter modules. Regulated dc outputs from the converter
modules are routed to the various system units via appropriate
interface connectors. Remote-sense dc returns are obtained from the
system units via interface connectors. Remote sensing permits a
converter module to regulate to the actual voltage at the load
because of the negligible voltage drop across the remote-sense return
line. For those modules not using the remote-sense feature (see
the converter module terminals.
Overvoltage Protectors.
Overvoltage protectors U1 thru U4 are connected across the outputs
of the converter modules. For those converter modules providing both
positive and negative voltage outputs, the overvoltage protectors are
connected between positive and negative outputs. If an output
voltage or pair of voltages should exceed the limit set for the
corresponding overvoltage protector, crowbar action will cause the
protector to trip and present a low impedance that reduces the output
voltage to less than 1 V within 15 s. When the cause of overvoltage
is removed, normal operation can be restored by momentarily deenergiz-
ing the power supply.
