US2294536A - Transformer tap changer - Google Patents

Description

F w. BUSH TRANSFORMER TAP CHANGER Filed July 20, 1940 a h 'u za a d d Patented Sept. 1, 1942 2,294,536 TRANSFORMER 'rAr CHANGER Fred W. Bush, Wauwatosa, Wis, minor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis., a corporation of Delaware Application July 20, 1940, Serial No; 346,475

8 Claims. (Cl. 171-119) This invention relates in generalv to encased electrical apparatus and relates particularly to an encased transformer provided with a tap changing mechanism located adjacent the transformer casing and to a new and improved means for interconnecting the transformer and tap changing mechanism.

In step regulators where the tap changing switch mechanism and easing are located on the side of the transformer casing, disadvantages have arisen in connecting the switch contacts and the transformer taps. It is desirable to have separate casings or a casing partitioned to provide separated portions. If an insulating partition is provided between the two casings and provided with conducting studs therethrough, to which connections are made on one side to the tap switch, and on the other side of thetransformer taps, the additional work of making and maintaining these connections is a disadvantage. In a three phase regulator with thirteen leads per phase, there would be seventy-eight such connections. Loose connections provide a source of operating trouble, and bolted connections provide a source of loose connections as well as an added manufacturing cost. If such connections at the insulating partition are brazed or otherwise solidly made, inability to easilyuntank the transformer or switch mech anism is adisadvantage. If these connections are bolted, they may become loose and cause trouble. If the leads are brought from one casing to the other in one piece over the partition separating the oil in the casings, half of the connections are avoided, but only at the expense of exposing the leads to the air and moisture breathed into the transformer and thereby lowering their insulation'value.

It is desirable to have a construction in which the transformer and tap switch mechanism can be and to have the connecting leads entirely in oil or other insultaing fluid throughout their length. It is therefore an object of the present invention to provide a-step regulator avoiding one or more of the above disadvantages and utilizing one or more of the above advantages.

, It is also an object of the present invention to and yet permit the untanking of transformer and tap switch mechanism without disconnecting the leads,

It is a further object of this invention to provide a cover for both casings and to suspend the transformer and switch mechanism from the cover.

It is a further object of this invention to provide means for tightly clamping the connecting leads to withstand short circuit stresses.

It is also an object of this invention to reduce manufacturing cost and to simplify maintenance of a transformer tap changer by including the transformer, the tap changing switch, the interconnecting leads, and the clamping means therefor, in a unitary structure attached to the casing cover.

Objects and advantages other than those above set forth will be apparent from the following description-when read in conjunction with the accompanying drawing, in which:

Fig. 1 is an elevational view, with part of the casing removed, of a transformer tap changer embodying the present invention;

Fig. 2 is a view of the tap changer shown in Fig. 1 showing the transformer and tap changing switch partly removed from the casing;

Fig. 3 is an enlarged end view of the clamping means for the leads interconnecting the transformer tap changer shown in Figs. 1 and 2;

Fig. 4 is a top view of the clamping means shown in Fig. 3; and

- connecting the same, through a partition I'I diprovide a step regulator of theiabove type,.in I

which the transformer and tap switch are in separate casings-with solidleads connecting the transformer'taps and the tap switch, and so arranged as to be in oil throughout their length and IC- viding the casing into portions l5 and it. The

portions II and I! of the casing are maintained separate in order that impurities, dirt and prod-.

nets of arcing of the tap switch contacts ll do not mix with the oil surrounding the transformer 33 in the casing I I. The partition I] has a portion thereof cut out as indicated by the numeral 21. I

The leads III interconnecting the various windings 9' and 34 of thetransformer and the tap switch contacts II are solid leads throughout their length. This avoids bolted connections at thepartition II, which may loosen under operation and cause trouble. These leads II are immersed in insulating q d in both casings ii and their insulation strength is there- ,nection into the circuit-are not shown.

fore high and'their insulation is not esposed to moisture or air above the level of the oil in the Qtransformer ,casing, and therefore subject to i added corrosion.

In order to avoid disconnecting the leads at the partition I! upon untanking of the transformer, the leads ill go through the partition-l1 through a removable portion 3! thereof. Mounted on the plate 3| is a clamping structure which rigidly braces the leads "I against forces due to short circuit current. In order to simplify manufacture and maintenance, the entire transformer structure, the tap changing switch, and-the clamping structure for the leads I are supported from the cover i2 of the casing. In Fig. 2 the transformer and tap changer structure is shown partly removedfrom the casing, and the transformer windings and cores are supported on the cover member by means of staybolts 24.

The tap changing switch 22 is illustrated as an insulating panel 25 on which are mounted con-- tacts H in a dial conformation. The leads l0 from the transformer taps are connected to the contacts H in any suitable manner. The movable member of thetap switch 32 and its con- However, this tap changing switch 32 may be of the type shown" in Patent No. '2,l7'7,l09, granted to L. H. Hill October 24', 1939, for Voltage regulator.

The clamping structure, as shown more clearly in Figs. 3 and 5, comprises a series of wooden blocks i8 each having half-round holes in one or sense that it has no bolted or equivalent parts where it passes through the partition l1.

Although but one embodiment of the present invention has been illustrated and described, it

will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from thespirit of the I invention orfrom the ,scope of the appended claims. v

It is claimed and desired to secure by Letters Patent:

1. In a regulating device, a tapped transformer winding immersed in a casing containing insulating liquid, a second casing adjacent said transformer casing, switch contacts immersed in insulating liquidin said second casing, means .for connecting said switch contacts and said winding :comprising solid leads maintained below the level of said insulating liquid, and means whereby said winding and said switch are removable'from said casings while maintaining said both edges thereof. When clamped together, the half-round holes in adjacent blocks form a clamping means for a-lead III. In order to prevent the free flow of oil from one part of the casing to another, a felt gasket 2| is placed between the boards l8 and around the leads l0. While this joint is not oil tight, it sufllciently separates the casing Hi from the casing i5 in that particles of 'dirt, carbon, or other are products cannot move from one casing to the other.

' In assembling the, device, the transformer 33 and the tap changing switch 32 are mounted on the cover l2, and then all connections at both ends of the leads I0 are made. The clamping boards IB are then positioned around the leads in the manner shown more clearly in Figs. 3

and 5. In a transformer of the three-phase.

type shown, there are thirtgenine of these leads from the transformer to thtap changing switch, thirteen for each phase. The clamping boards M are then clamped togethher by long bolts l9 running through the board as shown more clearlyinFigJi.

Clamped along the. top and bottom edges of the clamping board by means of, the bolts I9 are metal'angles 20 which add rigidity to the clamping means for positioning the clamping board on the plateil. The angles 20 are then clamped to the plate 3las by means of bolts 22.

The plate 3| has an opening therein practicallycoinciding with the clamping boards l8 when clamped together. The. plate 3| is securely clamped to the cover l2 by means of clamps 80.

After the transformer, tap switch, clamping" structure and cover are lowered as a unitary construction into the casings l5 and it, as shown in Fig. 1, the plate 3| is securely clamped to the partition H by means of. the clamps 23 which inspection plates ll.

The term solid connection used-in reference are easily positioned and tightened through theleads connected to said winding and said contacts.

2. In combination, a. casing divided with a partition provided with a removable portion. a

positioned adjacent to and without said trans-- former casing for enclosing said tap changing switch contacts, a cover for said casings, nondetachable conductors connecting said taps and said contacts, and means for rigidly clamping said conductors to said cover...

4. In combination, a casing divided with a partition, a transformer in one portion of said cas-.

ing, switch contacts in another portion of said casing, insulating liquid in saidcasings, nondetachable leads connecting said transformer and said switch contacts, means for rigidly clamping said leads to said partition, said clamping means forming a part of said partition below the level of said liquid, and means whereby said part of said partition is removable therefrom simultaneously with removal of said trans-- former and said switch contacts from said portions of said casing.

5. In a transformer tap changing device, a

transformer winding provided with taps thereon,

.tap changing switch contacts, separate casings for said transformer and said tap changing switch, means for non-detachably connecting said taps and said contacts, means for wholly immersing said connecting means in insulating liquid, and means wherebyv said transformer windin said switch contacts and said connecting means are removable from said separate casings as a unitary structure.

tothe leads l0 defines a conductor that is con- -tinuous, unbrokenend non-detachable in the 6. In a transformer tap changing device, a transformer winding provided with taps thereon, tap changing switchcontacts, separate casings for said transformer and said tap changing switch provided with a common wall portion, means for nofi-detachably connecting 'said taps 7 and said contacts, means for wholly immersing said connecting means in insulating liquid, and

'means for' rigidly clamping said connecting transformer winding provided with taps thereon,

tap changing switch contacts, separate casings for said transformer and said tap changing switch, means for non-detachably connecting said taps and said contacts,. means for wholly immersing said connecting means in insulating liquid, means for rigidly clamping said connecting means intermediate the ends thereof, and means whereby said transformer, said clamping means and said tap changing switch contacts are removable from said casings as a unitary structure.

8. In combination, a casing divided by a partition provided with a removable portion, a transformer winding having a plurality of taps thereon in one fixed portion of said casing, a plurality of switch contacts in another fixed portion of said casing, insulating liquid in both said fixed portions of said casing, and means comprising a plurality of electrical conductors extending through said removable portion of said partition below the level of said liquid, whereby said transformer winding, said switch contacts, said removable portion of said partition and said conductors are removable from both said fixed portions of said casing as a unitary structure.

FRED W. BUSH.

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