240 Power Management Unit Fault Finding TB8100 Service Manual
© Tait Electronics Limited September 2006
13.9 AC Module
Important When removing plug-in cards, we strongly recommend
that you use the TB8100 card remover
1
, as shown in
Figure 15.1 on page 263. A flat-blade screwdriver may
reach too far through the slot and damage the components
or tracks on the card.
These checks will verify the correct operation of the AC converter. The
test procedures require you to power-up the AC converter on approximately
30VDC. Running the AC converter on DC is made possible by carrying
out the following modifications to its standard set-up:
■ Replacing the standard PFC control card with a spare card which has
been modified as described in “Modifying the PFC Control Card” on
page 246.
■ Connecting two variable voltage DC power supplies as shown in
Figure 13.11 on page 243. Note that the control power supply is
connected via back-power protection diodes and a high power resistor.
The variable voltage DC power supplies must be able to provide the correct
input voltages for the AC converter under test. The current capability of
these power supplies will decide how much load you can connect to the
converter. Testing at light loads will be enough to verify if the converter is
working. Variable power supplies with a 3A capability would be sufficient.
Caution Even though the AC converter is running on a low
DC voltage, there is still 400VDC present on the
board.
If you have been directed to this section from “Initial Checks” and the PMU
is still fully assembled, go to Task 1
. This allows you to check the operation
of the 400VDC bus without disassembling the entire PMU (you only need
to remove the top cover). If you have already checked the DC converter
and the PMU is disassembled, go to Task 2
.
Warning!! The AC power on/off switch does not isolate the
PMU from the mains. It breaks only the phase cir-
cuit, not the neutral.
1. The card remover is included in the TBA0ST2 tool kit, which is available
from your nearest Tait Dealer or Customer Service Organisation. It is also
available separately as part number 220-02034-01.
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