FED-STD-791D
inside the test cell approximately 38 cm (15 in) to one side of the WADD gear machine.
The test gear heating coil, shown in Figure 5 without the end cover, is mounted inside the
end cover of the WADD gear machine and is connected directly to the load coil
transformer output terminals by removable, silver-plate connectors.
4.1.8 Instrumentation and controls. All except one of the instruments and
controls that require constant attention during test are located on the control console, as
shown on Figure 6. The one item requiring constant attention and not included in the
control console is the induction heater. The induction heater power supply is normally
located abutting the control console for convenience. Attention should be directed to the
instruction manual for the specific induction heater used to determine the exact control
method to use. Items that do not require frequent attention are located inside the test cell.
The functions of most of the instruments and controls are apparent. Therefore, only
selected items will be explained further.
4.1.8.1 Speed measurement and control. An electronic counter (Figure 6, item
10), located on the control panel, measures the speed. This instrument is actuated by
pulses supplied by a variable reluctance pickup (the variable reluctance being provided
by a 60-tooth gear operated from the driven shaft of the step-up gearbox). The rpm
adjustment control (Figure 6, item 28), located on the con-sole, regulates the field
excitation of the dynamic coupling and thus the gear speed.
4.1.8.2 Control of test-run duration. An electric timer (Figure 6, item 16), located
on the console, is used to control the duration of each test run. As soon as the desired test
load and test gear temperature has been reached, the timer is started. After the ten-minute
run is over, the timer automatically turns off the drive motor and opens the load-bypass
valve. The timer switch must be moved to the "stop" position immediately following
coast down of the machine.
4.1.8.3 Support-oil controls. The support-oil pump buttons (Figure 6, item 18) on
the console are connected to the support-oil pressure pump as well as the scavenge
pumps. Pressing the start or stop button controls all pumps at the same time. The
support-oil heater buttons (Figure 6, item 19) control both the electric heaters and the
water cooler through the action of thermoswitches. The support-oil chamber vacuum is
measured by a water manometer located on the test stand. A valve connecting the
chamber to a vent (Figure 2) should be adjusted to give a chamber vacuum of
approximately 2.54 cm (1 in) of water under normal test conditions.
4.1.8.4 Control of load-oil pressure. The control of load-oil pressure has been
explained in 4.1.4.2. The load adjusting valve is air actuated and is controlled by the
load-adjust control (Figure 6, item 6 or 15) located on the console. The load-bypass
valve, is solenoid actuated and is controlled by the load-bypass switch (Figure 6, item 20)
on the console. At the end of a run, the solenoid circuit will automatically be open by the
electric timer. This opens the load-bypass valve, but the load-bypass switch on the
console remains in the "close" position. For this reason, the switch must be turned to the
"open" position prior to the next run.
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