Testing - ABB VUBB User Manual

3.7 Testing

When testing the transformer, the tap-changer can be
operated either by the hand crank or electrically. When
operating electrically, the motor-drive mechanism must be
connected.
1. Make sure that the motor-drive mechanism and the tap-
changer show exactly the same position. See Fig. 59 and
Fig. 60.
WARNING
If the position indicators on the motor-drive
mechanism and on the tap-changer do not show the
same position, a serious transformer failure could
occur.
To access the position indicator, remove the cover.
See Fig. 60.
2. Operate the tap-changer with the hand crank, counting
the number of turns from the exact position until the tap-
changer operates.
- For BUL – the tap-changer should operate after
11.5 ± 1 turn of the hand crank.
- For BUE – the tap-changer should operate after
19 ± 1.5 turns of the hand crank.
If it does not, one of the shaft couplings of the gears is
incorrectly mounted.
3. Manually crank the motor-drive mechanism to a position in
the middle of the range. See Fig. 59.
4. Turn the control selector switch to the LOCAL position.
5. Send an impulse for a raise operation.
If the phase sequence is incorrect (three-phase supply), the
motor-drive mechanism starts in the lower direction. The
motor-drive mechanism moves back and forth around its
service position until the control selector switch is turned to 0.
6. If the phase sequence is incorrect, reverse two of the
motor supply cables in order to get the correct sequence.
WARNING
Dangerous voltage!
For a BUL2 motor-drive mechanism, continue at step 7.
For a BUE motor-drive mechanism, continue at step 10.
For BUL2:
7. Run the motor-drive mechanism.
8. Check that the center of the notch in the cam disc stops
within ±2 mm of the center of the roller on the brake arm.
See Fig. 57.
If it does not stop within the tolerances, see the
maintenance guide for the motor-drive mechanism.
9. Continue to step 14.
For BUE:
10. Run the motor-drive mechanism.
11. Check that the red mark on the brake disc stops within the
tolerance limits. See Fig. 59.
12. If the brake disc is outside the tolerance limits, increase
or decrease pressure on the springs; see the maintenance
guide for the motor-drive mechanism.
13. Continue to step 14.
For BUE and BUL
14. Check that the position indicator on the motor-drive
mechanism shows the same position as the indicator
inside the cover of the tap-changer. See Figs. 59 and 60.
WARNING
If the position indicators on the motor-drive
mechanism and on the tap-changer do not show the
same position, a serious transformer failure could
occur.
To access the position indicator, remove the cover.
See Fig. 60.
15. Operate one step.
16. Check that the tap-changer follows the motor-drive
mechanism.
17. Operate the drive mechanism electrically between the
end-positions.
18. Check the end-stops. When attempting to operate it
electrically beyond the end-position, the motor should not
start.
19. Check the mechanical end-stop by attempting to manually
crank it beyond the end-position. After a couple of turns of
the hand crank, it should be mechanically stopped.
20. Manually crank back to the end-position.
21. Operate the tap-changer electrically to the other end-
position.
22. Repeat the test procedure above.
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