IL 44-751-1
Instruction Leaflet
Page 12 November, 2001
The common installation feature, regardless of other options chosen, is that each deck of the
DTW tap changer mounts to the transformer superstructure with six glass-fiber bolts. There are
one or two DTW decks installed per phase depending on the design of the transformer.
Following are the steps required to properly install a DTW de-energized tap changer:
1. Remove the DTW deck from the shipping carton and verify that it is in position number 1.
Note: for Left Hand Drive, the number 1 position will be as shown in figure 14 and for Right
Hand Drive the number 1 position will be as shown in figure 15. All DTW tap changers are
shipped in position number 1.
2. Once the transformer superstructure has been prepared with holes for the mounting bolts, the
tap changer can be bolted onto the transformer superstructure. Six glass-fiber bolts and
twelve glass-fiber nuts are needed for each DTW deck (not supplied). The nuts should be
tightened.
3. Prepare the ends of the tap leads from the coil. If the leads are wire-cable, a flat connector
will have to be attached to each lead. Make sure that each tap lead is the correct length. If
the leads are flat copper strap of sufficient size, no additional termination connector will be
required. Appropriately spaced holes should be drilled to match the hole spacing on the tap
changer stationary contact posts. NOTE: It might be easier to prepare the tap leads from the
coil if the DTW deck is not mounted to the superstructure.
4. If the decks are not mounted to the superstructure in Step 2, now is the time to do so. The
leads are connected to the tap changer’s Stationary Contact Copper Mounting Post
according to the transformer specifications. Each lead is fastened with two bolts (not
supplied). The bolt head should on the inner side of the copper mounting post as shown in
Figure 16. Note that the Stationary Contact Copper Mounting Post has a recess, which
accepts the bolt head and prevents the bolt head from rotating during the tightening process.
Each tap lead requires two mounting bolts, two flat washers, two cup-washers, two lock-
washers and two nuts. See Figure 16. NOTE: If the number of leads from the coil is less
than the number of mounting posts on the DTW deck, the transformer specification should be
reviewed for correct placement of any additional jumper cables.
Figure 16. Strip wire leads from coil connected to the copper mounting posts.
5. Assemble the Inter-Phase Shaft to the worm gear ball end fitting. The Inter-Phase Shaft
slides onto the ball end fitting so that the slot in the shaft is aligned with the hole in the ball
end fitting. When this is done, place a Spacer ring into the hole; this ring should ride in the
groove of the ball end fitting. Bolt this assembly together using the Nylock bolt, lock washer,
cup washer and shield washer (see Figure 17). Tighten the bolt.
