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OM-2065 / Operation and Maintenance Manual
90SB51 / Spec. 7015-3 / Frequency Converter
Fault Indicators - (cont.)
Trouble, Sympton and Condition
7. Ø LOSS - Phase-Loss on
ALARM II
8. IMB/GND on ALARM II
(Indicates excessive current in
neutral output conductor.
9. DC FUSE on ALARM III
10. A,B,C,D (E,F not used) on
ALARM I
CAUTION
* Check transistors according to instructions in Section 3-4, and install replacement transistors
observing torque values in Section 2-1.
Chapter 3-2
Page 2
Probable Cause
a. Input voltage on one or
more input phases below
specification.
b. Input voltage too low.
a. Load imbalance more than
10% between phases.
b. Output phase grounded.
a. Shorted + and - DC bus.
b. Shorted transistor module
indicated by A, B, C, D
lights on ALARM I
a. Inverter section A,B,C,D
overcurrent due to
excessive current.
b. Shorted output.
c. Shorted transistor(s).
When unit is connected to AC input, dangerous voltages are present inside the
unit. turn off input power and disconnect output cable from aircraft. check to be
sure that no voltage remains on DC filter capacitors before attempting any
repairs inside the unit.
Test, Check, And Remedy
Check input(s) voltage. (See
para. 2, F on procedure for
restoring to operation).
Check and correct load
balance. (See para. 2, G on
procedure for restoring to
operation).
Remove ground.
Visually inspect the inside fro
sight of shorted parts
connected to + and - bus and
repair as necessary.
Inspect all transistors and
replace if found defective
(shorted)*. SOFT-START unit
(as described in Sect. 3) before
restarting.
Remove excess load, reset and
start.
Remove short, reset and restart.
Replace defective items *.
SOFT-START the unit
(as described in Sect.3)
before starting.
Nov 01/90
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