
43
1ZSE 5492-118 en, Rev. 4
8 Electrical connection and testing
8. Electrical connection and testing
8.1 General
Before the transformer is energized tests have to be made to make sure that all mechanical
and electrical connections are correct, and to check the proper functioning of the on-load
tap-changer and the motor-drive mechanism.
When testing the transformer, the on-load tap-changer can be operated either by the hand
crank or electrically. When operating electrically the Motor-Drive Mechanism is connected
according to section 8.2.
8.2 Connecting and testing
Connect earth connection from the transformer to the earth terminal on the on-load tap-
changer flange.
Connect earth connection from the transformer to the earth terminal on the motor-drive
mechanism.
To check that the shafts have been correctly assembled, the motor-drive mechanism should
be placed in the exact position according to Figs. 13 or 14. Operate the tap-changer with
the hand crank counting the number of turns from the exact position until the tap-changer
operates.
With BUL the tap-changer should operate after 11,5 ± 1 turn of the hand crank.
With BUE the tap-changer should operate after 19 ± 1,5 turns of the hand crank.
If not, one of the shaft couplings of the gears are incorrect mounted.
Hand crank the motor-drive mechanism to a position in the middle of the range.
Connect the motor supply and the control supply to the correct terminals in the motor-drive
mechanism as shown by the circuit diagram supplied with the on-load tap-changer.
Turn the control selector switch to position LOCAL. Give an impulse for RAISE-operation.
If the phase sequence is wrong, (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.
If the phase sequence is wrong, reverse two of the motor supply cables in order to get the
correct sequence.
WARNING
Dangerous voltage!