7 Electrical Connection and
Testing
7.1 General
Before the transformer is energized, tests have to be carried out to make sure that all
mechanical 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 motor-drive mechanism is
connected according to section 7.2.
7.2 Connecting and Testing the Motor-
Drive Mechanism and the On-Load
Tap-Changer
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.
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 a position 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-
operation. If the phase sequence is wrong, (three-phase supply), the motor-drive
mechanism will start in LOWER-direction. The motor-drive mechanism will stop when
it has made approximately half of the complete operation and it will operate back and
forth without the on-load tap-changer changes 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!
Run the motor-drive mechanism and check that the red mark on the brake disc stops
within the tolerance of ±25 degrees from exact position, see Fig. 39. For adjustment,
see
1ZSE 5492-126, Maintenance Guide for UCC/UCD.
7 Electrical Connection and Testing
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