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1ZSE 5492-115 en, Rev. 5
7 Electrical connection and testing
7. Electrical connection and testing
7.1 General
Before the transformer is energized, tests have to be carried out to make sure that all me-
chanical and electrical connections are correct, and to check the proper functioning of the
motor-drive mechanism and the on-load tap-changer.
When testing the transformer, the on-load tap-changer can be operated either by the hand
crank or electrically. When operating electrically the drive mechanism is connected as per
section 7.2.
7.2 Connecting and testing
For bolted-on design, connect the earthing terminal on the on-load tap-changer to the
transformer tank.
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.
Operate the motor-drive mechanism by means of the hand crank to one of the positions in
the middle of the range, but not in a through position (= a position with a letter in).
Turn the control selector-switch to position LOCAL. Then give an impulse for RAISE opera-
tion. If the phase sequence (three-phase supply) is wrong, the motor-drive mechanism will
start in LOWER direction. The motor-drive mechanism will stop when it has made approxi-
mately half of the complete operation and it will operate back and forth without the on-load
tap-changer changing position until the control selector switch is turned to position ”0”. If
the phase sequence is wrong, reverse two of the motor supply cables in order to get the
correct sequence.
WARNING
Dangerous voltage.
Operate the on-load tap-changer electrically. Check that the ywheel in the motor-drive
mechanism stops with the brake between the outer marks on the ywheel. For any adjust-
ment needed, see 1ZSE5492-123 Maintenance Guide for UZE/UZF.
Operate the driving mechanism electrically between the end positions. Check the end stops.
When trying to operate it electrically beyond the end position, the motor should not start.
Check the mechanical end stop by trying to hand crank it beyond the end position. After a
couple of turns on the hand crank it should be mechanically stopped. Hand crank back to
the end position (where the indicator ag is white). Operate the on-load tap-changer electri-
cally to the other end position and repeat the test procedure above.
CAUTION
The transformer should in no case be energized with an end stop out of order.
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