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Auxiliary Inverter (Controller)
Troubleshooting
The Auxiliary Capacitor Panel remains charged for
at least 15 minutes after engine shutdown. Be
certain LED's D1 and D2 (4, Figure 3-9) are OFF
before working on Auxiliary Blower Control cir-
cuits.
The following items should be checked if an auxiliary
Inverter failure is suspected.
1. Observe the two LED's on top of the Auxiliary
Power Filter Capacitor Bank (AXCAP); Both
LED's should be ON (lit) when the Aux. Inverter
is running and OFF after the circuit has dis-
charged.
2. Check for loose wires and check resistance be-
tween the terminals on the Aux Snubber panel.
Measurements from 1 to AF1, 2 to AF2, & 3 to
AF3 should all be 0 ohms. Measurements from
1 to either AF2 or AF3 and similarly from 2 & 3
should be 2 ohms.
3. Check continuity from PH+ to INV+ and from PH-
to INV-. These circuits connect the Aux Phase
Control, Aux Inductor, Aux Capacitors, & Aux
Inverter. The resistance should be 0 ohms for
these two measurements to verify continuity
through the Aux Inductor.
4. Check the fuses on the Aux Capacitor panel. (The
fuses must be removed from the circuit to check.)
5. Check for loose connections on all wires associ-
ated with the Aux Inverter circuits.
6. Check Aux Inverter Phase Control SCR's (see
Table below). Measure between AC input termi-
nals 1, 2, & 3 and DC output terminals PH+ & PH-.
A reading of less than 100 ohms indicates a
shorted SCR. Good SCR's will measure more
than 100K ohms. Replace at least the connected
pair of SCR's if one is shorted (preferably replace
all 6 SCR's).
Measurement Points
AC Input 1
AC Input 2
Term 1
PH+
Term 2
Term 1
PH-
Term 2
E03015 3/01
AC Input 3
PH+
Term 3
PH+
PH-
Term 3
PH-
AC Drive System Electrical Checkout Procedure
(Release 17 Software)
7. Whenever it is determined that an Aux Inverter
input SCR has failed, both AC Input fuses must
be replaced and the old ones discarded.
8. Check pin and wire continuity between Aux con-
troller CNX connector (7, Figure 3-12) and ap-
propriate PSC & TCI connectors.
9. Disconnect the blower motor cables from AM101,
201, & 301 (4) and megger the Aux Blower motor
and its wiring. Be sure to reconnect properly to
assure proper rotation direction.
10. Check the Gate Drive Power Supply AC input
fuses GDFU1 & 2 and replace if necessary.
11. Disconnect the main rectifier Filter Panel wires
T103, T203, & T303 at the rectifier bus bars.
Using an analog VOM on the ohms scale, meas-
ure between T103 & T203, between T203 & T303,
and between T303 & T103. A capacitance deflec-
tion should show on each measurement.
12. Disconnect the main rectifier from the circuits and
perform a standard diode check with a VOM and
back-bias each diode with a 1000 volt megger.
13. After all checks are made, and repairs completed
if required, reconnect all wiring to their proper
terminals and reinstall fuses.
E3-41
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Table of Contents
Troubleshooting
