Hobart Brothers 6910, Operation And Maintenance Manual With Illustrated Parts List

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D. Preparation for Power Delivery (Normal Automatic Voltage Control)
The following are power delivery preparation procedures to be followed after the engine is started.
(1) Check and position switches and controls.
(a) Loosen fastener
(3, Fig. 1)
and pull generator control tray outward. Place automatic-manual
switch (33) in AUTOMATIC position. Close tray and secure.
(b) Loosen fastener
(3)
and pull protective relay tray outward. Place test bank switch
(34)
in AIR-
CRAFT position if the aircraft being serviced is equipped with 28.5-V DC interlock relay system.
(If not, place in TEST BANK position.)
Slide tray in and secure.
(c) Meter switch (5) may be in any position except pointing straight DOWN.
(2) Connect output cable plug connector to aircraft receptacle. Be sure connectors are mated fully
and securely.
E. Power Delivery (Automatic Voltage Control)
(1) Place engine-generator control switch
(18, Fig. 1)
in BUILD-UP-VOLTAGE position momentarily,
then allow it to position itself in GEN position. The electric governor will immediately increase engine
speed to 2000 RPM and maintain it.
(2) Observe generator instruments. Frequency meter (1, Fig. 1) should indicate exactly 400 Hz. Volt-
meter
(2)
should indicate 115 V AC when line switch
(6)
is in LINE-TO-NEUTRAL position.
(3) The final step in delivering power is closing the load contactor. When satisfactory frequency and
voltage values are indicated by the instruments, close the load contactor by momentarily placing the
load contactor control switch
(20) in the top (spring loaded), CLOSE position. The green indicating
light (22) should glow at once to indicate that the load contactor is closed and power is available at
the aircraft. As soon as the light glows, release the switch. It will automatically return to the center ON
position.
NOTE: If the indicating light (22) should “go-out” as soon as the switch is released, and no fault lights
are ON, it indicates that 28.5-V DC holding current is not being supplied from the aircraft to the
plug-interlock relay. Correct the condition an again operate the load contactor control switch (20) as
above.
(4) It is recommended that the operator check output voltage and current in each of the three phases
early in the power delivery run. Use the meter switch
(5) to select the phase. Use the line switch (6) to
select line-to-line or line-to-neutral voltage. If the load is changing, it is good operating practice to ob-
serve the instruments until load conditions stabilize.
(5) A condition of overvoltage, undervoltage, underfrequency, overfrequency, or overload in the out-
put circuit will automatically open the load contactor and turn on the applicable indicating light to sig-
nal the operator which of the above faults caused the protective monitor system to operate. After the
fault has been corrected, press the reset switch
(7) to turn off the indicating light and reset the protec-
tive relay system. Proceed with power delivery by operating the load contactor switch.
F. Preparation for Power Delivery (Manual Voltage Control)
Preparation for power delivery using manual voltage control is exactly the same as for automatic con-
trol [Para. 2, D,
(1) thru (2) above] except:
(1) Place automatic-manual switch
(33)
in MANUAL position.
(2) Set the manual voltage control rheostat (32) near its mid-range position.
OM-2028
1-3 August 31/90 Revised
Page 6