TM 5-6115-434-12
.Figure 1-8. Power unit electrical system schematic
(Sheet 1 of 2).
(Located in back of manual)
.Figure 1-8. Power unit electrical system schematic
(Sheet 2 of 2).
(Located in back of manual)
tacles, and interconnecting wiring and connectors. The 60 Hz system neutral conductor is not grounded. Control
components in the 60 Hz system are powered from the 24v dc system.
(3)
400 Hz electrical system (fig. 1-7 and 1-8). The 400 Hz electrical system provides 120/208v ac, 400 Hz,
three phase power for operation of the conditioned air system compressors, condenser cooling fans, air circulating fans,
hot and cold water pumps, and water hose heaters, 24v dc battery charger, and for 400 Hz power requirements in other
elements of the MUST hospital. The 400 Hz system consists of a brushless, self-excited, aircooled generator, voltage
regulator, generator protective panel, output power receptacles, and interconnecting wiring and connectors. The 400 Hz
generator incorporates an integral cooling fan and receives additional cooling air from the engine cooling fan. The 400
Hz system neutral conductor is grounded. Control components in the 400 Hz system are powered from the 24v dc
system.
d.
Conditioned Air System (fig. 1-9, 1-10, and 1-11). The conditioned air system supplies cooled air, heated air, or
ventilating air under slight pressure to other elements of the MUST hospital. The system is a recirculating system with
recirculating fans in the return air plenum. Adjustable vents in the return air compartments permit adding make-up air to
the system. The conditioned air system consists of a cooled air system, a heated air system, and a ventilating air
system. The three systems function independently but use some components interchangeably between systems. The
four conditioned air outlets are located at the rear of the power unit and provide connection flanges for attaching the
distribution ducts. The four return air inlets are located on the right side of the power unit and provide connection flanges
for attaching the return air ducts. Covers are provided for the outlets and inlets when not in use. The four return air
inlets are provided with permanent high-velocity-type cleanable air filters. Two temperature sensors are located at each
of the four return air inlets to provide temperature control of the output air in response to temperature changes in the
return air. Also, a remote temperature sensor may be connected to an electrical connector provided on the return air
inlet panel to provide temperature sensing and control in MUST hospital elements that do not utilize the return air ducts.
(1)
Cooled air system (fig. 1-9, 1-10). The cooled air system uses two independent 10 ton (refrigerating
capacity) refrigeration systems for maximum flexibility of operation. The two refrigeration systems may be operated
individually or together to provide 20 tons cooling capacity. Each refrigeration system is a vapor cycle closed loop
system consisting of an electric-motor-driven refrigerant compressor with an integral overtemperature switch, an air-
cooled refrigerant condenser, two condenser cooling fans, a refrigerant receiver, an expansion valve, an evaporator, two
recirculating fans, a refrigeration solenoid valve, a compressor bypass solenoid valve, an overpressure switch, a
refrigeration de-icing system, and associated tubing, fittings, and refrigerant level sight gages. All electric motors in the
refrigeration system are powered by the 400 Hz electrical system and all control components are powered by the 24v dc
electrical system. Output temperature control of the refrigeration systems is automatic with variable adjustment
provided. Refrigeration output temperature control is accomplished by three solenoid-operated valves, a refrigerant flow
control valve, a compressor bypass valve, and a de-icing valve. The de-icing system functions automatically to prevent
ice formation on the evaporator core.
(2)
Heated air system (fig. 1-9, 1-11). The heated air system uses two independent control and mixing
systems connected to a single source of heated air. Each system uses hot compressed air from the gas turbine engine
compressor through the engine load control valve. The heated compressed air passes through one or both
thermostatically controlled, electrically actuated flow control
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