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PowerIT Vacuum Cast Coil Dry Type
Distribution Transformers
Tap changer operation
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
Previous warnings.
Before you make the tap position change, you must take into
account next warnings and local regulation for working in HV
electrical systems:
 This operation must be carried out without voltage in
transformer, and its terminals must be connected to earth.

The suitable tool for operating the tap changer is a 10 mm or
19 mm wrench depending on what is the screw size. The
screw size is M6 or M12 according to the transformer
characteristics.
Picture 1 A 10 mm or
19mm wrench will be used,
depending the needs.
Steps
The dry type transformers, are supplied with the tap changer in the position corresponding to the
transformer voltage nominal values. If the tap change is necessary you must act as the next table
shows.
Prepared By: Vanessa John
Date: 15/04/2004
Approved By: Carlos García
Date: 16/04/2004
Applicability:
Lang: English
Document No.
1LES100007-ZB
ABB
Rev.
No: 0
Page No:
Page 2 of 3
Title:
1.0
Tap changer operation
1. Look up in rating plate the required
position according to the electrical
system characteristics. This table
shows the suitable tap position to
obtain the nominal BT voltage value,
from each HV voltage value.
2. Slack the screws carefully, by means
of the wrench. Separate the entire
group made up with 2 hexagonal-head
screw, 1 connection plate, 2 washers,
and 2 lock washers.
3. Be extremely careful and don´t mislay
any tap group item. If necessary, the
replacement of one item must be by
another
item
with
the
same
constructive characteristics.
Washer
Connection
plate
Lock
Washer
4. Fit the group between the suitable
terminals that you want to link. Screw it
after you make sure that between the
bolt and connection plate surfaces
there are not any foreign body, and
mentioned surfaces are clean of dust
or dirt.
5. Screws must be adjusted with a
tightening torque of 8 N·m in M6
screws and 60 N·m in M12 screws.
You must be sure that both surfaces
are perfectly coupled in flat form.
Note. The tapping in different coils of a transformer must be always in the same position.
Tightening torque:
8 N·m in M6 screws
60 N·m in M12 screws
Prepared By: Vanessa John
Date: 15/04/2004
Approved By: Carlos García
Date: 16/04/2004
Applicability:
Lang: English
Document No.
1LES100007-ZB
ABB
Rev.
No: 0
Page No:
Page 3 of 3
Title:
1.0
Tap changer operation