March 30, 1965
A. BLEIBTREU ETAL
3,175,089
LOAD TAP CHANGERS FOR TRANSFORMERS
Filed June 19, 19.62
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March 30, 1965
3,176,089
A. BLEIBTREU ETAL
LOAD TAP CHANGERS FOR TRANSFORMERS
Filed June 19, 1962
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March 30, 1965
A. BLEIBTREU ETAL
3,176,089
LOAD TAP CHANGERS FOR TRANSFORMERS
Filed June 19, 1962
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March 30, 1965
A. BLEIBTREU ETAL
3,176,089
LOAD TAP CHANGERS FOR TRANSFORMERS
Filed June 19, 1962
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A. BLEIBTREU ETAL
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LOAD TAP CHANGERS FOR TRANSFORMERS
Filed June 19, 1962
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United States Patent 0 "ice
3,176,089
Patented Mar. 30, 1965
I
2
LOAD TAP CHANGERS FOR TRANSFORMERS
tank, i.e. built into the common tank, which load tap
changers are extremely compact and add relatively little
to the bulk of the composite transformer and load tap
Alexander Bleibtreu, Regensburg, Germany, and Anton
August Schunda, deceased, late of Regensburg, Ger
many, by Wilhelmine Schunda, Anton Schunda, and
Brunhilde Schunda, heirs, all of Regensburg, Germany,
assignors to Maschinenfabrik Reinhausen (lehruder
Scheubeck K.G., Regensburg, Germany, a ?rm of
Germany
changer unit.
In the method of tap changing a current limiting device
must be employed during each transition period from one
tap position to the other. Such current limiting devices
may either be center tapped reactors or resistors. This
invention is particularly concerned with load tap changers
Filed June 19, 1962, Ser. No. 204,029
Claims priority, application Germany, June 22, 1961,
M 49,421
8 Claims. (Cl. 200-18)
This invention has reference to load tap changers for
power transformers as applied, for instance, to maintain a
constant secondary voltage with a variable primary volt
age, to control the flow of reactive kva. between two gen
erating systems, and to control the division of power be
tween branches of loop circuits, etc.
It is a general object of this invention to provide im
proved load tap changers for polyphase transformers, in
particular polyphase high voltage power transformers.
A further object of this invention is to provide load tap
changers for polyphase high voltage power transformers
which are considerably more compact, and involve con
siderably smaller manufacturing cost, than comparable
10 wherein resistors are used as current limiting devices.
Load tap changers utilizing resistors as current-limiting
devices and fast operating transfer switches are known,
or referred to, as “Jansen” type load tap changers. This
type of load tap changers has important advantages over
load tap changers of other kinds. In this type of load tap
changers the current-limiting resistors are in parallel with
respect to the load current and in series with respect to
the circulating currents which flow during transition times
between tap changes. This makes it possible to reduce
the resistance of the current limiting resistors to relatively
low ohmic values without giving rise to large circulating
currents. In “Jansen” type tap changers the movable con
tacts of the transfer switches move at high speeds, or with
a snap action, wiping over the fixed contacts to which the
current limiting resistors are connected. As a result of
this fast motion the transition periods during which the
current limiting resistors must carry load currents are
prior art load tap changers.
very short, say in the order of a few hundredths of a
Load tap changers include selector switches and trans
second. This has two signi?cant advantages: The cur
fer switches. The selector switches serve the purpose of
rent limiting resistors can be made very small and the
30
selecting a particular tap on a tapped transformer wind
voltage ?uctuation resulting from tap changes insigni?
ing intended to be connected into an electric circuit. Se
cant. The rapid operation of the transfer switches is
lector switches do not carry any load currents at the
produced by stored energy means, preferably wound up
time a particular tap is selected, i.e. they are not required
springs which are maintained in a pre-wound, or pre—
to interrupt or close on current-carrying circuits. This
loaded, condition in readiness for the next tap changing
task is performed by the transfer switches. The latter 35
perform all switching operations under load. Therefore
all arcing is restricted to the transfer switches, the se
lector switches merely selecting the particular transformer
tap to which the load is to be transferred.
Polyphase transformers require a selector switch and
a co-operating transfer switch for each phase of the cir
cuit. The selector switch and the transfer switch of each
phase must be electrically insulated from the selector
switch and the transfer switch of each other phase ac
cording to the full voltage between phases. For this rea
son it has become common practice to subdivide poly
phase transformers into separate transformer units. Each
such single phase unit comprises a separate tank, a sepa
rate single phase transformer, a separate load tap changer,
and a separate drive for the latter. A plurality of such
single phase units are integrated into a transformer bank.
Transformer banks tend to be extremely bulky.
It is, therefore, another object of this invention to
provide load tap changers which are less bulky than the
load tap changers normally associated with transformer
banks including a plurality of separate single phase trans
former units.
It is frequently possible to reduce the aggregate size of
a polyphase transformer including load tap changing
means by arranging all the phases of such a transformer
and the selector switches and the transfer switches of
operation. Load tap changers of the “Jansen” type are
well known in the art and have been described in many
printed publications such as, for instance, the book by
H. P. Young, Electric Power Control Systems, London,
England, Chapman 8: Hall Ltd, 1942, and reference may
be had to such publications for a more complete descrip
tion of “Jansen” type load tap changers, and the struc
tural features and operating characteristics thereof.
It is another object of this invention to provide im
proved “lansen” type load tap changers for polyphase
high voltage power transformers.
.
The foregoing and other general and special objects
of the invention and advantages thereof will appear more
clearly from the ensuing particular description of the
invention as illustrated in the accompanying drawings,
wherein:
FIGS. la and lb are substantially a vertical section of
a high voltage polyphase load tap changer embodying
the present invention and comprising a plurality of selec
tor switches, a plurality of transfer switches cooperating
with the selector switches and drive meaens for both the
selector switches and the transfer switches, FIG. 1a show
ing the left portion of the structure and FIG. 1b showing
the right portion of the structure, both FIGS. 1a and 1b
being complementary, FIG. la showing at the right side
thereof some structural detail which is also shown in
FIG. lb to the left side thereof;
all the phases in a common tank. Where the voltage of
FIG. 2 is a top plan view of one of the selector switches
a given polyphase transformer is high and its power large,
and of one of the transfer switches of the structure of
the size of such transformers and of their associated load
FIG. 1;
tap changing means tends to become intolerably large, 65
FIGS. Zia-3c are top-plan views of the three transfer
and often exceeds the bulk limits required for transporta
switches of the structure of FIG. 1; and
tion via rail, i.e. on railroad cars.
It is, therefore, another object of this invention to pro
vide polyphase high voltage load tap changers which lend
FIG. 4 is a connection diagram of one phase of a poly
phase transformer provided with a load tap changer em
bodying the present invention.
themselves to be combined with polyphase transformers 70
Referring now to the drawings, the structure shown in
whose various phase windings are arranged in a common
FIGS. 1 and 2 is intended to be accommodated within a
ens/spec
3
6%
transformer tank having a cover on the top thereof.
Neither the transformer tank nor the tank cover have
been shown in FIG. 1. The cover of the tank of the
transformer de?nes an opening which is covered by a
part which may be referred to as a sub-cover. Reference
vessel 11 and are supported by the latter. All of th
voltage distribution control rings 28 are arranged in co
axial relation to parts 11, 14 and 18.
Since contacts 19 and 21 of transfer switches 15, 16,
numeral 115 has been applied in FIG. 1 to indicate the
aforementioned sub-cover.
Sub-cover 19 supports a ves
sel 11 of insulating material including a bottom 12. The
lateral walls of vessel 11 are formed by an insulating
17 part while carrying load currents arcs are kindled be
tween these contacts incident to parting thereof, and these
arcs form hot, ionized products of arcing. In order to
avoid discharge of hot products of arcing formed in
lower transfer switches to the arcing zones of the trans
cylinder or tube as widely applied in high voltage engi~
neering. Vessel 11 is ?lled with an appropriate insu~
lating liquid such as insulating oil. The bottom 12 of
vessel 11 is provided with an opening 13 normally closed
fer switches arranged at a relatively higher stack level,
transfer switches 15, 16, 17 are angularly displaced.
In three phase transformers comprising three transfer
by a screw for draining oil from vessel 11. Tubular
switch support 14 is arranged inside of vessel 11 in co
displacement of the three transfer switches is 120 de
axial relation thereto. Support 14 is made of insulating
material and houses three transfer switches 15, 16 and
switches 15, 16, 17—-one for each phase—-the angular
grees. This has been shown in FIGS. 3a—3c of which
each ?gure is a horizontal section at right angles to
shaft 18 and of which each ?gure shows in top-plan
view one of the three transfer switches 15, 16, 17.
Transfer switches 15, 16, 17 are operatively related
to rotary selector switches 30, 31 and 32, i.e. transfer
switch 15 is operatively related to selector switch 39,
transfer switch 16 is operatively related to selector switch
31 and transfer switch 17 is operatively related to selec
tor switch 32. Selector switches 30, 31 and 32 are
to cooperatively engage a set or group of circularly ar
stacked substantially in the same fashion as transfer
ranged ?xed contacts 21. The set or group of contacts
switches 15, 16 and 17. Transfer switch 15 and selec
19 is pivotally supported at 19a on a rotatable contact
tor switch 36 are arranged substantially at the same level,
carrier 20. Contacts 19 are arranged along a sector of a
transfer switch 16 and selector switch 31 are arranged
circle whose center 19a is spaced from the axis of rota
substantially at the same level, and transfer switch 17
tion of contact carrier 20. The ?xed contacts 21 are 30 and selector switch 32 are arranged substantially at the
supported on the inner surface of the aforementioned
same level. The three selector switches 30, 31 and 32
insulating cylinder or insulating tube 14. When con
are mounted on a common tubular insulating shaft 29.
17 which are arranged in coaxial relation to each other
and to support 14 and vessel 11 and stacked one above
the other. Transfer switches 15, 16, 17 are of the rotary
type and are mounted on, and operated by, a common
shaft 18 adapted to insulate each transfer switch from the
others. As clearly shown in PEG. 2 each transfer switch
comprises a set or group of movable contacts 19 adapted
tact carrier 20 and movable contacts 19 are operated,
Switches 15 and 30 are arranged in the same phase of a
?xed contacts 21 are sequentially engaged by movable con
three phase circuit, e.g. phase U. In a similar fashion
switches 16 and 31 are arranged in the same phase of a
tacts 19, the latter performing a composite rotary and
radial motion as set forth more in detail in US. Patent
2,680,790 to B. Jansen. The two movable contacts 19
on both ends of the sector of movable contacts 19 are
main contacts, and the intermediate contacts of the sector
of movable contacts 19 are switch-over contacts. In a
like fashion the two contacts on both ends of the sector
of ?xed contacts (indicated in some of the ?gures by
reference character 22) 21 are main contacts and the
intermediate contacts of the sector of ?xed contacts 21 are
three phase circuit, e.g. phase S. Finally switches 17 and
32 are arranged in the third phase or phase T of a three
phase circuit. Switches 15 and 39 are interconnected
by relatively short, substantially horizontal leads 33,
switches 16 and 31 are interconnected by relatively short,
substantially horizontal leads 34 and switches 17 and 32
are interconnected by relatively short and substantially
horizontal leads 35.
Each selector switch 30, 31, 32 comprises a plurality
switch-over contacts (indicated in some of the ?gures by
of ?xed radially outer contacts 36 of which each is secured
reference character 23). The aforementioned ?xed main 45 to an insulating rib 37. Fixed contacts 36 are adapted
contacts 21 are conductively connected to the particular
to be cooperatively engaged by the two bridge elements
tap of the transformer winding which has been selected,
or bridge contacts 38 which may be turned about the
while the aforementioned ?xed switch-over contacts 21
center of a circle along which ?xed contacts 36 are posi
are conductively connected to switch~over resistors or
tioned. The current-carrying bridge elements or bridge
tap-changing resistors 24 in the fashion shown in FIG. 4.
contacts 38 are mounted on insulating tube 29. Insulating
Each transfer switch 15, 16, 17 comprises in essence
tubes 39 extend parallel to insulating tube 29—i.e. both
three sector-shaped spaces of which one is occupied by the
are vertical-and the latter support slip rings 49 clearly
set of movable contacts 19 and the two others 25 are oc
shown in FIG. 2 for connecting ?xed leads to rotary
cupied by the aforementioned switch-over or tap-chang 55 bridge contacts 33. As shown in FIG. 1 annular mem
ing resistors 24. The location of the latter has been
bers or rings 41 are arranged above each ?xed contact
clearly shown in FIG. 2 as well as in FIGS. Zia-3c.
36 of each selector switch 30, 31, 32 for controlling the
The carriers 20 for the movable contacts 19 are secured
voltage distribution in the region of contacts 36. Annular
to composite shaft 18. This shaft comprises tubular sec
metal members or rings 28’ for the control of the voltage
tions 26 of insulating material alternating with sections
distribution in axial direction are also arranged on the
60
formed by metal rods 27. Each of the two sections
top and at the bottom of the stack formed by the three
formed by metal rods 27 is interposed between a pair of
selector switches 30, 31, 32.
sections 26 of tubular insulatin<7 material. The latter
Insulating tubes 39 integral with the stack of selector
sections 26 separate and insulate each transfer switch 15,
switches 30, 31, 32 are operable by means of a Geneva
16, 17 from the transfer switch or transfer switches im
65 gear 42 shown in FIG. 1 arranged above the stack of
mediately adjacent thereto.
selector switches 30, 31, 32. Geneva gears are widely
Reference character 28 has been applied to indicate
applied in the art for operating selector switches of load
annular members for controlling the voltage distribution,
tap changers and, therefore, Geneva gear 4-2 provided at
i.e. the distribution of the electric ?eld, around transfer
the top of the stack of selector switches 311, 31, 32 does
switches 15, 16, 17 along parts 11 and 14. At least two 70 not call for a detailed description. Gear train 43 ar
such voltage control members 28 are anranged at each
ranged above Geneva gear 42 is provided for operating
axial end of each transfer switch 15, 16, 17. As shown
the latter. Gear train 43 is operated from a shaft 45
by the intermediary of a transmission which may include
in
23 FIG.
are arranged
1 some of
inside
the of
voltage
insulating
distribution
tubing control
14» and sup”
a clutch or coupling 44.
ported by the latter, and others are arranged outside of
Shaft 45 is driven by an elec
tric motor (not shown) which drives also the three trans~
3,1 76,089
5
6
fer switches 15, 16, 17 shown to the left of FIG. 1.
This is achieved by means of gear 46 and an eccentric
47 operating a link or rod 48 loading a spring 49 upon
rotation of shaft 45. Reference numeral 50 has been
21 of transfer switch 15, movable contact 19 of transfer
switch 15 engaging the aforementioned ?xed contact 21
thereof, contact support 20, lead 104, ?xed contact K of
reversing switch 54, movable contact D, ?xed contact
applied to indicate a tripping latch for releasing spring
49 when the particular taps intended to be inserted into
B’, lead 102, lower transformer winding 190.
In the embodiment of the invention shown in FIGS. 1,
the load circuit have been selected by means of the three
2 and 3a, 3b, 30 each transfer switch comprises but one
selector switches 31}, 31 and 32. Operation of the latch
single substantially sector-shaped set of movable contact
?ngers 19 and one single set of ?xed circularly arranged
carrying contacts 38 of the three transfer switches 15, 16, 10 contacts 21 cooperating with contact ?ngers 19. Where
17 from their original positions to their pre-selected posi
prevailing current intensities are very large it may be
tions. Operation of the three transfer switches 15, 16, 17
necessary, or desirable, to provide each transfer switch
by spring 49 is effected by the intermediary of an eccen
15, 16, 17 with more than one substantially sector-shaped
tric to which reference character 51 has been applied.
set of movable ?nger contacts 19, and with an equal
The aforementioned drive comprising spring 49 and the 15 number of sets of ?xed circularly arranged contacts 21.
50 results in an instantaneous movement of the current
transmission means for loading the same and for tripping
the same are arranged within a gear housing 52 which is
mounted on top of horizontal plate or cover 10 on the top
The aforementioned sets of movable and ?xed contacts
of the transformer tank. Gear housing 52 is provided
must be assigned to each single set of contacts. In such
a plural contact set arrangement there is less room with
on the upper side thereof with an opening or window 53
making it possible to readily determine the particular
position of the stack of transfer switches 15, 16, 17 and
are connected in parallel into each phase of a polyphase
circuit, thus limiting the current carrying duty which
in the space occupied by the transfer switches 15, 16, 17
for accommodating tap changing resistors 24.
to inspect the constituent parts or elements of the drive
housed within gear housing 52.
Referring now more particularly to FIG. 4, this ?gure
shows to the left thereof three windings 100 of a poly
phase transformer. All three windings 100 pertain to the
same phase-say phase U-and only the center winding
100 is tapped. The center winding 1% has ten taps of
According to FIG. 4 tap number seven is included in
the circuit of the transformer and the load tap changer
thereof. Assuming now that it is desired to change from
tap number seven to tap number eight. Such a change
involves the following steps to be carried out in the fol
lowing sequence: Contact 38 which, heretofore, has been
in engagement with the ?xed selector switch contact num
30
which each is connected to one of the ten ?xed contacts
ber six is moved from the latter position into engagement
36 of one of the selector switches, say selector switch 30.
with ?xed selector switch contact number eight. This
In order to make it clear that the center windings of the
change of position of one of contacts 38 of each selector
other phases S, T are also tapped and also connected to
switch 30, 31, 32 does not involve the flow of any circu
selector switches in the same fashion as the center wind
lating currents. Nor does it involve any change in re
ing of phase U, the reference characters 31 and 32 have
gard to the active windings of the transformer. Con
been added in parentheses in FIG. 4 after reference char
comitant with the aforementioned change of the position
acter 30. The FIGURES 1 to 10 at the left of FIG. 4
one of contacts 38 of each of the selector switches 30, 31,
have been applied to distinguish between the ten ?xed
32 the spring 49 for instantaneous or snap-action opera
contacts 36 of selector switch 30. Transfer switch 15 has
tion of transfer switches 15, 16, 17 is loaded, and thus
been shown to the right of the selector switch 30 and refer 40 readied to effect an instantaneous operation of said trans
ence characters 16 and 17 have been added in parentheses
fer switches. Upon tripping of latch 50 the movable set
after reference character 15 to indicate that the transfer
of contacts 19 of each selector switch 15, 16, 17 perform
switches 16 and 17 are related in the same fashion to
a composite or rolling motion thereby sequentially en
selector switches 31 and 32 as transfer switch 15 is re
gaging the ?xed contacts 21 thereof. As a result of this
lated to selector switch 30. Each transfer switch 15, 16,
motion the following switching operations are performed
17 is provided with six ?xed contacts 21 of which each of
sequentially. The upper tap changing resistor 24 of FIG.
the four inner contacts 21 is connected to one of four
4 is inserted into the circuit, the two upper tap-changing
tap changing resistors 24. The latter are, in turn, con
resistors 24 of FIG. 4 are inserted into the circuit, the
nected to the rotary contacts 38 of selector switches 30,
two tap changing resistors arranged in the center of FIG.
31, 32 by the intermediary of leads 33, 34, 35.
4 shunt the part of center winding 1% situated between
Reference numeral 54 has been applied to indicate a
taps number seven and number eight for a very short
reversing switch of the kind widely applied in connec
tion with load tap changers. Reversing switch 54 com
prises a ?xed center contact K and four additional ?xed
contacts A, A’, B, B’. Lead 101 connects the lower ter
minal of the upper transformer winding 160 to the ?xed
contact A’ of the reversing switch 54 and lead 102 con
nects the upper terminal of the lower transformer winding
100 to the ?xed contact B’ of the reversing switch 54. 60
period of time, the two lower tap-changing resistors 24
Fixed contacts A and B of reversing switch 54 are con
of FIG. 4 are inserted into the circuit, but the lowest tap
changing resistor of FIG. 4 is inserted into the circuit, and
?nally only the lowest of movable contact 19 engages the
lowest ?xed contact 21 providing a direct current path
not including any of the tap-changing resistors 24. At
this point of the tap changing operation contact 38 en
gaging ?xed contact 36 of tap number seven does not
carry any current any longer, all the current being carried
by the other contact 38 in engagement with ?xed contact
36 of tap number eight.
The next operation of the load tap changer may either
nected by leads 103 and 103a to the upper terminal of
transformer center winding 10%. Fixed center contact K
of reversing switch 54 is connected by lead 104 to the sup
port 20 of movable contacts 19 of the transfer switch 15.
consist in a return of the constituent parts thereof to
In the position of the reversing switch 54 shown in FIG.
their original positions indicated in FIG. 4, which is a
4, the ?xed contacts A and A’ are conductively inter
reversal of the operation which has been previously de
connected by movable contacts C and the ?xed contacts
scribed in detail, or the next operation of the load tap
K and B' are conductively interconnected by the mov
changer may consist in a switching operation from taps
able contact D. The current path of phase U shown in 70 number eight of selector switches 3t}, 31, 32 to taps num
FIG. 4 is as follows: upper transfer winding 100, lead
ber nine thereof. The last mentioned operation is a du
101, ?xed contact A’, movable contact C, ?xed contact
plication of the switching operation which has been de
A, lead 103, center winding 10!), ?xed contact 35 of
scribed above, i.e. a switching operation from taps num
selector switch 39 at tap number seven, bridge contact
ber seven of selector switches 31), 31, 32 to taps number
38, slip ring 40, lead 33, lead 105, upper ?xed contact 75 eight thereof.
7
Provision of reversal switch 54 makes it possible to re
duce the number of taps of center winding 1% for a
given or predetermined control duty since it makes it pos
sible to use the voltage in the tapped center winding 1%
selectively either for the purpose of boosting or for the
purpose of bucking.
It will be apparent from the foregoing that a polyphase
load tap changer embodying the present invention com
prises a plurality of substantially identical transfer
switches 15, 16, 17 each connected into one phase of a
polyphase circuit and superimposed in substantially co
axial relation to form a transfer switch stack.
The trans
fer switches comprised in said stack are angularly dis
placed a number of degrees equal to 360 divided by the
number of the phases of the polyphase transformer. As
a result of this angular displacement the hot products of
arcing formed at load current switching operations of the
transfer switches which are arranged at relatively low
levels of the aforementioned stack are substantially kept
away from the arcing zones of the transfer switches
which are arranged at relatively high levels of the afore~
mentioned stack. The particular embodiment of the in
vention described above is a load tap changer for a three
phase transformer and its transfer switch stack com
prises three transfer switches. The three transfer switches
are angnlarly displaced 360:3:120 degrees, as best
shown in FIGS. 3a, 3b and 3c.
The aforementioned an
gular displacement of the constituent transfer switches
15, 16, 17 of the transfer switch stack is generally su??ci»
changers embodying the present invention comprise a
plurality of substantially identical selector switches 39,
31, 32 each connected into one phase of a polyphase
circuit and superimposed in substantially coaxial relation
to form a selector switch stack arranged in proximity of,
or immediately adjacent to, the aforementioned transfer
switch stack. The vertical spacing of the constituent
transfer switches of the transfer switch stack and the
vertical spacing of the constituent selector switches of
the selector switch stack is substantially equal. Hence
each transfer switch and each selector switch pertaining
to the same phase are situated at substantially the same
level, and each transfer switch is operatively related to
one of the selector switches by leads 33, 34, 35 which
are substantially horizontal or, in other words, do not
extend beyond the two horizontal planes which form the
upper and the lower boundary of a pair of associated
and cooperatively related transfer switches and selector
switches. These leads are, therefore, arranged in equi
potential spaces, i.e. spaces throughout which there is
substantially the same potential. To be more speci?c,
the required insulation of the leads 33, 34, 35 between
cooperating transfer switches and selector switches is but
that called for by the difference in voltage between con~
.. secutive or contiguous taps.
This is a minimum of in
sulation requirement. The tap change resistors 24 for
limiting the flow of circulating currents incident to chang
ing from one tap to another are preferably arranged with
in the above equipotential areas, forming integral parts
of the transfer switches 15, to, 17 to which they are opera
ently effective to provide for a rapid dielectric recovery
tively related. The gear means for operating the trans
of the ionized gaps formed between the parting contacts
fer switches 15, 16, 17 and for operating the selector
of transfer switches 15, 16, 17. If desired baffles may be
switches 39, 31, 32 are arranged on top of the transfer
provided between the various levels of a stack of transfer
switch stack and on top of the selector switch stack.
switches to keep the hot products of arcing of one trans
It will also be apparent from the foregoing that the
fer switch away from the arcing zone of the other trans 35
leads 33, 34, 35 operatively relating the transfer switch
fer switches and to control the upward ?ow of products
and the selector switch pertaining to the same phase do
of arcing in a predetermined desired fashion.
not cross with like leads operatively relating transfer
The aforementioned angular displacement of transfer
switches and selector switches of other phases.
switches 15, 16, 17, i.e. of the sets of ?xed contacts 21
It is a feature inherent in the above described struc
and the sets of movable contacts 19 thereof makes it nec
ture that the constituent switches 15, 16, 17 of the trans
essary to angularly displace the tap-changing resistors 24
fer switch stack and the constituent switches 39, 31, 32
in the same fashion. This has been clearly shown in
of the selector switch stack may jointly be insulated
FIGS. 3a-3c in which structure the tap-changing resis
against ground, which results in much more economical
tors 24 of transfer switches 15, 16, 17 are angularly dis
placed 120 degrees.
and compact structures than where cooperating pairs of
It appears further from the foregoing that each of the
transfer switches 15, 16, 17 of polyphase load tap
changers embodying the present invention includes a
plurality of ?xed circularly arranged contacts 21, a set
of movable contacts 19 and current-limiting tap change
resistors 24 within the cylindrical space de?ned by said
circularly arranged ?xed contacts 21.
The present invention contemplates the use of transfer
switches of the general type disclosed and claimed in
United States Patent 2,680,790 to B. Jansen, Load
Changeover Switch for Tapped Transformers Using a
Combination of Contact Movements, June 8, 1954 and
United States Patent 2,833,873 to B. Jansen, Multi-Pole
transfer switches and selector switches are separately in
Tap Switch for Changing Transformer Taps Under Load,
sulated against ground. Since the impulse strength of
insulation against ground must be relatively high, this
feature is one which is of considerable importance.
The common drive means for all transfer switches 15,
16, 17 and for all selector switches 30, 31, 32 of the load
tap changer is a feature greatly reducing prime cost and
space requirements. Since the volume of oil involved for
insulating load tap changers embodying this invention is
relatively small, and since inspection of the aforemen~
tioned common drive and of the switches integrated into
the transfer switch stack and of the switches integrated
into the selector switch stack is relatively simple, the cost
of maintenance of load tap changers embodying the
May 6, 1958, and reference may be had to the two afore 60 present invention are minimized.
Load tap chargers embodying this invention lend them
mentioned patents as to further details in regard to the
transfer switches intended to be used for carrying the
selves to manual as well as to automatic supervisory con
present invention into effect.
trol.
Load tap changers embodying the present invention
It will be understood that although but one embodi
further comprise insulating means for insulating the con
ment of the invention has been illustrated and described
stituent transfer switches 15, 16, 17 of the transfer switch
in detail, the invention is not limited thereto. It will also
stack in accordance with the voltage prevailing between
be understood that the structure illustrated may be modi
phases. The aforementioned insulating means include
?ed without departing from the spirit and scope of the
the body of oil inside of vessel 11 in which the transfer
invention as set forth in the accompanying claims.
switches 15, 16, 17 are immersed, and the aforement
It is claimed:
tioned insulating means further include the common shaft
13 for jointly operating the constituent transfer switches
15, 1d, 17 of the transfer switch stack which shaft is at
least in part of insulating material.
it appears also from the foregoing that load tap
1. A load tap changer for polyphase transformers
comprising in combination with a plurality of tapped
phase windings of a polyphase transformer:
(a) a horizontal cover plate;
3,176,089
9
(b) an oil ?lled cylindrical vessel attached to said plate
and projecting from the lower surface thereof;
10
ranged ?xed contacts engageable by said pair of
rotary contacts, each of said plurality of ?xed con
(c) a plurality of stacked transfer switches each artacts of each of said plurality of selector switches
ranged within said vessel in coaxial relation thereto,
being conductively connected to one tap of one of
each of said plurality of transfer switches including 5
said plurality of .phase windings, and said pair of
?xed contacts and movable contacts cooperating with
rotary contacts of each of said pair of selector
said ?xed contacts in a predetermined sequence;
switches being conductively connected to said second
(d) a shaft coextensive with the axis of said vessel
end of said constituent resistors of one of said plu
projecting transversely through said cover plate for
rality of groups of resistors.
joint operation of said plurality of transfer switches; 19
3. A load ta-p changer for polyphase transformers com
(e) a plurality of groups of resistors arranged Within
prising in combination with a plurality of tapped phase
said vessel each at substantially the same level as one
of said plurality of transfer switches, the constituent
windings of a polyphase transformer:
(a) a plurality of stacked transfer switches each in
resistors of each of said plurality of groups of re
sistors having a ?rst end conductively connected 15
to some of said ?xed contacts of one of said plural-
operating with said ?xed contacts in a predetermined
ity of transfer switches and the constituent resistors
of each of Said plurality 6f groups of resistors 113V"
ing a second end;
(f) a plurality of stack selector switches each arranged 20
(1;) a vertical shaft for gang-operating said plurality
of transfer switches including insulating means for
insulating said plurality of transfer switches from
each other;
at substantially the same level as one of said plurality
of transfer Switches and One Of Said plurality of
groups of resistors, each of Said plurality of Selector
SWllIClli-ZS including 21 pair Of rotary contacts, and each
of Said plurality of Selector Switches including 3 p111— 25
(c) a plurality of stacked groups of resistors each ar
ranged at substantially the same level as one of said
plurality of transfer switches, the constituent resis
tors Of each of said plurality of groups of resistors
having a ?rst end conductively connected to some
Tamil 0f circularly arranged ?xed cc?mcts engageable
by Said Pair of TOtaYY Contacts, each of Said plurality
of ?xed contacts of each of said plurality of selector
switches being conductively connected to one tap of
0116 Of Said plurality of Phase windings, and Said 30
Pair of rotary Contacts of each 0f Said Pail‘ of 5615Ctor switches being conductively connected to said
second end of said constituent resistors of one of said
plurality of groups of TeSiStOYS;
(8) an insulating column Parallel to Said Shaft Pro‘ 35
fulcra for said pair Of I'OtZlI‘y contracts Of Each
of said plurality of sel?ctof Switches; and
(h) drive means for said plurality of transfer switches
and for Said plurality of Selector Switches SUPPOTWd
of said ?xed contacts of one of said plurality of
transfer switches and the constituent resistors of each
cluding ?xed contacts and movable contacts co
sequence;
of said prurarity of gmups of resistors having a Sec
end end;
(d) a plurality of stacked selector switches each ar
ranged at substantially the same level as one of said
plurality of transfer Switches and one of said p111
ramy of groups of resistors, each of Said p1ura1ity 0g
selector switches including a pair of rotary contacts,
and each of said plurality of selector switches in
a plurality of circularly arranged ?xed Con_
tacts engageable by said pair of rotary contacts, each
of Said pmramy of ?xgd Contacts of each of Said
plurality of selector switches being conductively con~
by Said Cover Plate, Said drive maans including a 4"
nected to one tap of one of said plurality of phase
loaded Operating Spring arranged ab?ve Said Cover
Plate for Operating Said ?rst Shaft and a Geneva gear
dIiW for gang Op?fati?g Said Pair of rotary Contacts
of each of Said ‘plurality of Selector SWilChQS2- A 10215 tap Changer for Polyphase transf?fmers C0111" 4,
‘prising in Combination With a plurality of tappad Phase a
windings Of 51 13013111112186 transformer:
windings, and said pair of rotary contacts of each
of said pair of selector switches being conductively
connected to said second end of said constituent re~
sistors of one of said plurality of groups of resistors;
(e) a vertical insulating column in the center of said
plurality of selector switches providing fulcra for
said pair of rotary contacts of each of said plurality
(a) an oil ?lled substantially cylindrical vessel;
(11) an insulating Cylinder arranged inside Said vessel
Of Sglegtor switches;
(3‘) additional vertical insulating columns providing
in coaxial relation thef?'w;
5O
(C) a plurality of Stacked transfer Switch?s ‘each HT‘
ranged within said vessel in coaxial relation thereto,
each of said plurality of transfer switches including
?xed contacts and movable contacts cooperating with
said ?Xcd Contacts in a predetermined Sequence, 55
said ?xed contacts of each of said plurality of trans
fer switches being supported by said insulating cylin
der;
(d) a plurality of groups of current-limiting resistors
arranged within the space bounded by said insulating 69
cylinder each arranged at substantially the same
level as, one of said plurality of transfer switches,
the constituent resistors of each of said plurality of
groups of resistors having a ?rst end conductively
connected to some of said ?xed contacts of one of
said plurality of transfer switches and the constituent 65
resistors 01“ each of Said plurality of groups of Te‘
SiStOI‘S having a Second end; and
(e) a plurality of stacked rotary selector switches each
arranged at substantially the same level as one of said 70
plurality 0f transfer Switches and one 0f said Plural‘
ity of groups of current-limiting resistors, each of
said plurality of selector switches including a pair
of rotary contacts, and each of said plurality of selector switches including a plurality of circularly are 75
mechanical ties between each of said pair of rotary
contacts of each of said plurality of selector switches;
and
(g) a Geneva gear drive arranged above said plurality
of salector Switches coopayatively engaging tbs upper
ends of said additional insulating columns for gang
operating said plurality of selector switches.
4. A load tap changer for polyphase transformers com
prising in combination with a plurality of tapped phase
windings of a polyphase transformer:
(a) a plurality of stacked, jointly operable rotary selec
tor switches electrically insulated from each other,
each being at a predetermined potential, each of said
plurality of selector switches including a plurality of
circularly arranged ?xed contacts each connected
to one of the taps of one of said plurality of tapped
Phase windings of said transformer’ and each of said
plurality of selector switches further including a pair
or" movable contacts each cooperating with said
plurality of ?xed contacts;
(b) a mummy of smacked jointly opgmble namfer
switches electrically insulated from each other, each
being ‘at a predecermined potential, each of said plu
rality of transfer switches having a plurality of cir
cularly arranged ?xed contacts including outer main
contacts and inner auxiliary contacts and each of
3,176,089
1. i
said plurality of transfer switches further having a
plurality of movable contacts each cooperating in
comprising in combination with a plurality of tapped
phase windings of a three phase transformer:
a predetermined sequence with one of said plurality
of ?xed contacts, each of said plurality of transfer
switches being arranged at substantially the same
level as one of said plurality of selector switches
‘being at the same potential; and
(a) a plurality of stacked jointly operable rotaryyse
c
a
luralit
of
V lector switches electrically insulated from each other
and at different potentials, each of vsaid plurality of
selector switches having circularly arranged ?xed
contacts conductively connected to the taps of one of
Said plurality of phase windings of said transformer
rou s of switchingO resistors ) the
constituent resistors of each of said plurality of
groups of switching resistors having a ?rst end and
having a second end and being connected with said
?rst end. thereoiC to said pair of movable contacts
of one of said plurality of selector switches, and being
and a pair of movable contacts cooperating with said
?xed contacts;
_
(b) a plurality of groups of stacked switching resistors
having a spacing substantially equal to the spacing
of said plurality of selector switches, the constituent
resistors of each of said plurality of groups of switch
ing resistors having a ?rst end and having a second
end and being conductively connected with said ?rst
connected with :said second end thereof to said ?xed
auxiliary contacts of one of said plurality of transfer
switches, and each of said plurality of groups of
switching resistors being arranged at substantially
end thereof to said pair of movable contacts of one
the same level as one of said plurality of selector
switches and one of said plurality of transfer switches.
5. A load tap changer for polyphase transformers corn- e0
prising in combination with a plurality of tapped phase
windings of a polyphase transformer:
of said plurality of selector switches; and
(c) a plurality of stacked jointly operable rotary trans
fer switches electrically insulated from each other
and at different potentials, each of said plurality of
said transformer and each of said plurality of se
transfer switches having a plurality of circularly ar
ranged ?xed contacts including outer main contacts
and inner auxiliary contacts and each having an
equal number of movable contacts cooperating in a
predetermined sequence with said ?xed contacts, said
plurality of transfer switches having a spacing sub
stantially equal to the spacing of said plurality of se
lector switches and said ?xed auxiliary contacts of
le‘ctof Switch‘? hailing 2} Pail‘
each of said plurality of transfer switches being con
(a) a plurality of stacked jointly operable rotary selec
vtor switches electrically insulated from each other and
at different potentials, each of said plurality of se
lector switches having a plurality of circularly ar
ranged ?xed contacts each connected to one of the
taps of one of said plurality of phase win-dings of
movabla c‘om'acts 30
e'ach c‘o‘ope‘r‘anng wl‘th Sam plurality of ‘?xed Comm“;
(b) means for controlling the voltage distribution along
‘the Stack foamed by Said plurality of semen” switches
ductively connected to said second end of said constit
uent resistors of one of Said plurality of groups of
switching resistors, said plurality of ?xed contacts
‘tending to @Smabush ‘a Plural“? of equitlolemial Zoms
eallh Occupied by Om of ‘Sand mummy of Selector 35
and said movable contacts of each of said plurality
of transfer switches being angularly displaced 120
Swltch?s;
degrees and encompassing an angle of less than 180
.
. .
(c) ‘.1 plumhty 10f stacked iomtly Can-Mable transfer
degrees, each of said plurality of groups of switching
switches electrically 1nsulated from each other each
resistors bang arranged immediately adjacent Said
being at a different pawl-M131’ each ‘of Sand i’lutamy
of transfer switches having a plurality of circularly 49
plurality of ?xed contacts and immediately adiacent
go said movable contacts of one of Said plural'ity of
transfer switches and angularly displaced 120 de
arranged ?xed contacts including outer main contacts
and inner auxiliary contacts and each of said plu
rality of transfer switches further having a plu
rality of movable contacts cooperating in a pre
determined sequcnce with one of said plurality of
?xed contacts, each of said plurality of transfer
switches being arranged at substantially the same
level as one. of said plurality of selector switches;
(d) means for controlling {the voltage distribution along
the stack
formed . by said plurality
of transfer
switches
.
.
.
.
wndmg m0‘ egt‘abhs‘h '21 plulr'ahty o'fpeqmplotemmal Zon?s
grees.
7. A load tap changer as speci?ed in claim 6 com
prising a common vertical shaft for jointly operating said
plurality of transfer switches, said shaft comprising in
sulating sections alternating with metallic sections, each
of said insulating sections being arranged between con
tiguous of said plurality of transfer switches and each of
said metallic sections being substantially coextensive with
50
the height of one of said
luralit
of transfer switches.
8. Atload tap changer fofpolyplilase transformers com
ealaghocimp Led ‘by one of smd p‘ummy of {mm/fen.
prising in combination with a plurality of tapped phase
SW1” .e’sf
windings of a polyphase transformer:
.
_
‘
.
.
__
.
_ ,‘
(e) a iam‘mlmypf gmd'ps Of iswl‘icmil'g “661.8%”, e’zi'ch
(a) a plurality of stacked jointly operable rotary selec
‘Off smd mummy Of gl‘l‘lpsof‘swlichmg ‘resl‘sltors banig 55
tor switches electrically insulated from each other
‘a‘pmngeid at s‘ilbist'mmmy. th‘? SW26 laid
of 88.1d
phlarhty ‘of trans?” “MP6s, ‘116 ‘coml‘l‘mtmi ‘regs-
and at different potentials, each of said plurality of
selector switches having circularly arranged ?xed
tor? of each of Sald plurality of gsqups of Switching
resistors having a ?rst end and having a seE-ond end
contacts conductively connected to the taps of one
of Said plurality of phqse windings of said trans_
t
.
v
1
“mp
Sf‘
U
'
“
‘L’,
r
“
‘v
I
imQd befmg coyqirfmted wlm‘ Qald ?rst end.i e €Of.to 60
of transfer switches- and
.
’
.
g.
.
(f)pairs
'2.‘ P1‘???
of sillbsémtllgnii hoi‘ilmnéa?y. extgli‘dlgg
o ea s,eac or sat p‘ura‘ty o pair's o ea s
.
.
.
.
conductively
connecting
said
pair
01.c movable con- 7,
c
L c
I
former and a pair of movable contacts cooperating
uald ?ked auMh-arl’ contacts ‘of ‘one of ‘Sam p1“ahty
with said ?xed contacts‘
b
a
‘
.
luraht
of
’
.
. .
rou s of current-limitm
.
1m ed
( bzincesp
each if saidgplufality of groups of imiedaiices
in ’ If n ed t bt t. H
e g. a .a g ., a ,Su
s
an m y, the
same level as one
.
taots of one of said plurality of selector switches 4:0 6”
giggéigégsragyegihseéicgcg
thgf 2051;511:262;
said second end of the constituent resistors of one
impndances having a ?rst end ,md giving a second
of mad mummy ‘of, grit’lup‘s :mf sfl'tchgnli
end and being conductively connected with said ?rst
and each _of ‘531d 1mm? fly 0' pjaus 0'
end thereof to said pair of movable contacts of one
“'2? ‘ ' ~l¥1=
arnauged in one of said plurality of equipotential 70
ZQHES '0‘¢C>uP~1e_‘(1 ‘by {me of ‘said plurality 0'? ‘S‘ekctfn'
switches and in one of said plurality of equipotentlal
limes o‘ccup'ied by One of Said Plumli'iy 01f mimfel‘
switches.
6. A load tap changer for three phase transformers 75
of Said plurality of selactor switches;
(c) cylindrical contact supporting means of insulating
material; and
(d) a plurality of stacked jointly operable rotary trans
fer switches electrically insulated from each other
and at different potentials, each of said plurality of
3,176,089
141
rel
a
transfer switches having a plurality of circularly ar
ranged ?xed contacts including outer main contacts
and inner auxiliary contacts supported by said cylin
drical contact supporting means and each having
movable contacts cooperating in a predetermined se
quence with said ?xed contacts, each of said plu
rality of transfer switches being arranged at sub
stantially the same level as one of said plurality of
selector switches and one of said plurality of groups
of irnpedances, said ?xed auxiliary contacts of each 10
of said plurality of transfer switches being conduc
tively connected to said second end of said constituent
impedances of one of said plurality of groups of im
References Cited in the ?le of this patent
UNITED STATES PATENTS
611,088
1,004,089
1,215,549
1,985,927
2,253,183
2,680,790
2,691,079
2,723,318
2,833,873
pedances, said plurality of transfer switches being
angularly displaced a number of degrees substan 15
tially equal to 360 divided by the number of phases
of said polyphase transformer.
Von Zweigbergk ______ __ Sept. 20,
Sessions _____________ __ Sept. 26,
Koontz _____________ __ Feb. 13,
Jansen ______________ __ Jan.
1,
Le ‘Count ____________ __ Aug. 19,
Jansen _______________ __ June 8,
Jansen _______________ __ Oct. 5,
Jansen ______________ __ Nov. 8,
Jansen ______________ -_ May 6,
1898
1911
1917
1935
1941
1954
1954
1955
1958
FOREIGN PATENTS
1,262,715
France _____________ __ Apr. 24,
1961