TM 11-6125-261-30
Section IV. MAINTENANCE
3-6 Adjustments
following the table give the method for making these
adjustments. Any deviation from the procedure as listed
will cause improper operation of the inverter.
affect the operation of the inverter. The paragraphs
Table 3-7. Adjustments and Alinements.
Circuit involved
Adjustment procedure
Inverter adjustment
Oscillator circuit
Paragraph
3-7
Output frequency adjustment
Paragraph
3-8
Regulator circuit
output voltage adjustment
Pulser output circuit
Paragraph
3-10
Output distortion
Paragraph
3-9
Current limiting circuit
Short circuit time delay
Paragraph
3-9
Current limiting circuit
Overcurrent limit adjustment
3-7. Output Frequency Adjustment
(11) Check frequency on frequency counter; it shall be
400 0.5 Hz. If the frequency is 4000.5 Hz, proceed to ( 12)
a. To adjust the output frequency proceed as follows:
below. If the frequency is not 400 0.5 Hz, refer to (7)
(1) If the inverter has not been previously opened, do
above.
so as described in paragraph 3-11. Disassemble until
(12) Recheck frequency at A22L101 pin 1, A21L1 pin
printed circuit boards A21 and A22 are accessible.
2 and A21L101 pin 1 to ensure proper frequency before
(2) Disconnect the +28 V dc bus at El, E2, and E3 of
proceeding.
circuit card A14.
(13) Turn off the 28 V dc power to the inverter.
(3) Disconnect the following wires at the A21 PCB.
(14) Replace the wires removed in (2) and (3) above.
Blk
A21E20
A21E21
Gry
NOTE
(4) Connect frequency counter to A22L101 pin 1 or
pin 3 (lower pins).
(5) Apply 28 V dc to the inverter.
made during this adjustment procedure.
b. If no other troubleshooting or adjustment is indicated,
NOTE
reassemble the inverter as described in paragraph 3-12 and
Input current will not exceed 1.0 ampere. If
check inverter for proper operation as described in Section
current is high, troubleshoot inverter as described
V, Final Tests.
in table 3-6.
(6) Check frequency on frequency counter; it shall be
3-8. Output Voltage Adjustment
400 0.5 Hz. If the frequency is not 400 0.5 Hz, proceed to
a. To adjust the Phase A output voltage, proceed as
(7) below.
follows:
(7) If the oscillator frequency is high, increase the
(1) Connect inverter to test fixture as shown in figure
value of C 104. If the frequency is low, decrease the value of
C104.
NOTE
A 0.01 ufd change in capacitance will change
CAUTION
the frequency approximately 5 Hz.
Isolate voltmeter chassis from earth ground to
(8) Connect frequency counter to A21L1 pin 2.
avoid damage in inverter.
(9) Check frequency on frequency counter; it shall be
(2) Set test fixture switches as follows: S 1 -- No load;
400 0.5 Hz. If the frequency is not 4000.5 Hz, refer to (7)
S2 -- WYE; S3 -- phase A; S4 -- +1.0; S5 -- Off; S6
above.
--Off.
(3) Energize the test equipment and slowly (over -
NOTE
approximately 10 seconds) raise the input voltage to +28 V
Refer to table 3-2 for correct capacitor reference
dc. If input current exceeds approximately 15 amperes at
designation for phases B and C.
any point, turn off the equipment and troubleshoot as
described in table 3-6.
(10) Connect frequency counter to A21L101 pin 1.
Change 1
3-20
