Lister Petter T Series, Руководство оператора, Страница: 54 / 81

9
ALTERNATOR OpERATORS' hANdbOOk
Low voltage
on load
1) Check speed
2) Check UFRO
3) Follow excitation test
procedure
RESIdUAL VOLTAGE ChECk
With the set not running, gain access
to the Automatic Voltage Regulator
(AVR) by removing the side cover of
the terminal box.
Remove leads F+ and F- from the
AVR (Noting correct polarity).Start the
set and check voltage across terminals
7-8. If it is less than 5V stop the set
and carry out the following field flash
procedure.
Reconnect F+ and F- to the AVR
with a 12V DC supply (Noting correct
polarity).Fit a 1000V 1A diode between
the positive terminal and the supply.
Restart the set and note the output
voltage, which should be approximately
nominal voltage. (The voltage across
AVR terminals 7-8 should be 170-250V).
Stop the set and remove the DC supply
and diode. The set should now operate
normally.
SEpARATE ExCITATION TEST
pROCEdURE
The alternator windings, diode
assembly and AVR can be checked
as follows:
1. With the set not running, gain access
to the Automatic Voltage Regulator
(AVR) by removing the side cover of
the terminal box.
2. Remove leads F+ and F- from the
AVR. Connect a 60W 240V household
lamp (or 2 X 120V lamps in series)
to AVR terminals F+ and F- (only
required for AVR Function Test.).
3. Connect a 0-12V 1.0A DC supply to
leads F+ and F- (positive to F+ and
negative to F-).
GENERATOR WINdING ANd
ROTATING dIOdES
CAUTION
The resistances quoted apply to a
standard winding. For alternators
having windings or voltages other
than those specified refer to factory
for details.
Ensure all disconnected leads are
isolated and free from grounding. This
procedure is carried out with leads F+
and F- disconnected at the AVR and
using a 12V DC supply to F+ and F-.
1. Start the set and run at rated speed
on no load.
2. Measure the voltages at the main
output terminals (AC). These should
be balanced and within 10% of the
nominal alternator voltage.
bALANCEd mAIN TERmINAL
VOLTAGES
If all voltages are balanced within 1% at
the main terminals, it can be assumed
that all exciter windings, main windings
and main rotating diodes are in good
order and that the fault is in the AVR.
(See AVR Function Test).
If the voltages are balanced but low,
there is a fault in the main excitation
windings or rotating diode assembly.
Proceed as follows:
RECTIfIER dIOdES
The diodes on the main rectifier
assembly can be checked with a
multimeter. The flexible leads connected
to each diode should be disconnected
at the terminal end, and the forward
and reverse resistance should be
checked. A healthy diode will show
very high resistance in the reverse
direction and a low resistance in the