Note: Descriptions are shown in the official language in which they were submitted.
~ 683~ Case 252~
This invention relates to a switching
arrangement for an electromagnetic induction device,
and more particularly to an improved switching ar-
rangement for use in a dual voltage transformer
having tap changing capability.
As is well known to those s~illed in the
transormer art, it is a common practice to provide
transformers which have a dual voltage rating. In
general, the term "dual voltage rating" is applied
to trans~ormers which are provided with a low voltage
setting (or level) and a high voltage setting (or
level). It is to be understood that the low voltage
setting may comprise more than one low voltage rating
and the high voltage setting more than one high
voltage rating. In general, the dual voltage of the
dual voltage transformer is provided by means of a
multiple primary winding which may be connected in
either series or in parallel to provide the desired
voltage rating ~or the trans~rmer. For example,
! 20 a transformer primary may be provided with two
12 KV windings. When these two windings are connected
in parallel the voltage rating of the primary of the
transformer will be 12 KV. However, when the two
windings are connected in series, the transformer
primary will have a voltage rating of 2 x 12 KV or
24 KV.
By the use of a series-parallel terminal
board, the appropriate interconnections between the
windings can be made. In simplistic terms the series-
parallel terminal board comprises a board havingelectrically conducting studs located thereon. The
studs are attached, by electrical conductors, to
.,~ ^ ~ ~
1~834~ Case 2524
-to the ends o~ the primary windings. By using
electrically conducting "links" the studs can be
jumpered (or interconnected) in a certain manner to
provide the required series or parallel connection.
The disadvantage of such a system is that the
terminal board is located inside the transformer tank,
and the board is commonly submerged in the transformer
oil. Consequently, if a change in voltage is to be
made, the transformer must be opened, the oil level
must be lowered and then the adjustment can be made.
It is readily apparent that this is not a convenient
method and can easily lead to contamination of the
transformer oil.
To provide a more convenient method of changing
the voltage rating of the transformer it has been
; known to employ a series-parallel switch in lieu of
the previously mentioned series-parallel terminal
board. The series-parallel switch can be operated
externally of the transformer tank and consequently
the trans~ormer need not be opened to be adjusted. The
drawback with this arrangement is that the series-
parallel switch is expensive. With either the
series-parallel terminal board or the series-parallel
switch the voltage can also be adjusted in small
increments by the use of tap changers, as is well
known.
The present invention overcomes the problems
of the prior art methods by employing at least three
tap changers to ad~ust the voltage rating of the
transformer. These tap changers function no only to
change the series~parallel connection of the windings,
but also to provide the fine voltage adjustments
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106~ Case 2524
at each voltage setting that tap changers are generally
noted for.
Statecl in other terms, in a three-phase,
dual-voltage electromagnetic induction apparatus
having for each phase a primary winding and a se-
condary winding, and each phase of the primary winding
comprising a first and a second separate and distinct
winding, switching means for connecting the first and
second distinct windings in one of either a series
or a parallel connection so as to alter the voltage
rating of the primary winding between a first and a
second level, the switching means comprising:
a) at least first, second, and third three-
phase tap changers; b) the first tap changer being
interconnected so as to connect, in each phase, the
first end of the second distinct winding either to
the first end of the first distinct winding, for a
parallel connection of the first and second distinct
windings, or to the taps on the second end of the
first distinct winding, for a series connection of
the ~irst and second distinct wi.ndings; c) the second
tap changer being interconnected 50 as to connect,
in each phase, the taps on the second end of the second
distinct winding to the taps on the second end of the
first distinct winding, for a parallel connection
of the first and second distinct windings, and making
no interconnections for a series connection~ of the
first and second distinct windings; and d) the third
tap changer being interconnected so as to connect.
in each phase, the taps on the second end of the second
dist1nct winding to an output termina~. of the pri.mar~
wlndlny .
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~83~0 Case 2524
The invention will now be described in more
detail with reference to the ollowing drawings in
which:
Figure 1 is a schematic representation of
a typical three-phase transformer winding with which
the invention is employed;
Figure 2 is a schematic representation of
three tap changers and their interconnections to one
phase of the primary winding shown in Figure 1,
according to the present invention;
One preferred embodiment of the present
invention will now be described with reference to
Figures 1 and 2. Figure 1 depicts. schematically
a t~pical transformer winding 10 having a three-
phase pri~lary winding~ll and a three-phase secondary
i winding 12. Primary winding 11 cornprises six separate
and distinct windings 13a, 13b, 14a, 14b, 15a, and
15b (two for each phase of a three--phase system).
Winding 13a has a first end indicated by the letter
a and a second end indicated by the l~tter d; winding
13a also has two taps indicated by the letters b and
; c near the second end of the winding. Similarly,
winding 13b has a first end indicated by the letter
e and a second end indicated by the letter h; winding
13b also has two taps indicated by the letters f and
g near the second end of the winding. For convenience
sake, the ends d and h as well as the taps b, c, f
and g will all be referred to as taps to simplify this
description.
Windings 13a and 13b can be connected in a
series circuit relationship by interconnecting one
of taps b, c, and d of winding 13a to end e of winding
_~~
~ 06~ Case 2524
13b and by also interconnectiny one of taps f, g,
and h to the output terminal k of primary winding 11.
This results in windings 13a and 13b (in series)
forming one phase o~ primary winding 11. When windings
13a and 13b are so connected in series (and likewise
winding 14a in series with winding 14b, and winding
15a in series with 15b) the voltage rating o:E the
primary winding 11 oE the transformer will be referred
to as the "high" voltage level, as opposed to the
"low" voltage level of primary winding 11 when the
windings 13a and 13b are connected in parallel (and
similarly 14a in parallel with 14b and 15a in parallel
with 15b). The highest voltage rating of primary
winding 11 is obtained when the windings 13a and 13b
are series connected with tap d connected to end e
and tap h connected to terminal k. Only windings
13a and 13b will be considered to simplify this
description: it is to be understood that windings 14a
and 14b, as well as windings 15a and 15b, will be
interconnected in an analogous fashion to windings
13a and 13b. Other variations of the series inter-
connection (e.g. connecting e to c rather than e
to d) produce small discrete changes (i.e. lower)
to the voltage rating of primary winding 11, but all
the series interconnections produce what will be
referred to as a "high" voltage level on winding 11
in contrast to the "low" voltage level obtained on
primary winding 11 when windings 13a and 13b are
connected in parallel.
When windings 13a and 13b are connected in
a parallel circuit relationship, first end a of
winding 13a is connected to first end e of winding
-5-
` ` ~o6~34~ Case 2524
13b. The taps are connected such that d, h and k
are interconnected, or c, gr and k are interconnected,
or b, f, and k are interconnected, depending upon
the exact voltage rating desired on primary winding
11,
Winding 13a is made as nearly identical as
possible to winding 13b. Conse~uently, the relationship
of the voltage rating oE primary winding 11, when
windings 13a and 13b are connected in series, to the
voltage on primary winding 11, when winaings 13a
and 13b are connected in parallel, is 2:1.
The foregoing has been a brief description
of a well known method of interconnnecting the various
windings of a known transformer construction to
produce a variety of different voltage ratings of the
primary winding. Figure 2 depicts, in simplified
form, the novel means of the present invention for
accomplishing the aforementioned interconnection of
the windings. In this preferred e~nbodiment, three
tap changers are employed. Although each tap changer
is for a three-phase application, only one phase of
each tap changer is shown in Figure 2 to simplify the
description. The remaining two phases of each tap
changer ~unction in a completely analogous manner.
Figure 2 depicts one phase of each of tap
changers 16, 17 and 18. Each tap changer 16, 17 and
18 has seven electricall~ conducting terminals each
indicated as a small circle and enclosing a letter.
These letters correspond to the taps and ends of
windings 13a and 13b of Figure 1. Each tap changer
has six mechanical positions indicated on the Figure
by the numerals 1 through 6. Each tap changer 16, 17
~0~3~ Case 252~
and 18 has a shorting contact l9a, l9b, or l9c
respectively which serves to provide an electrical
connection between two adjacent terminals. Tap changer
16 is shown with its shoxting contact l9a in position
2 and contact l9a is thus connecting first end e
of winding 13b to tap d of winding ]3a. Similarly,
the shorting contact l9b of tap changer 17 is shown
in position 1 and contact l9b is thus connecting
tap d of winding 13a to tap d of winding 13a (in
otherwords, making no interconnection at all).
Similarly, the shorting contact l9c of tap changer
18 is shown in position 2 and contact l9c is thus
connecting tap h of winding 13b to terminal k of
primary winding 11. In cummary, tap changers 16,
17 and 18, as shown in Figure 2 are joining e-d and ]~-h
and are thus connecting windings 13a and 13b in a
series circuit relationship. The position of, and
connection made by each tap changer 16, 17, and 18,
is given in Figure 2, undqrneath the respective tap
changer and under the headings "Position" and "Connect".
The first horizontal line in Figure 2 indicates the
position and the connections made by the tap changers
16, 17 and 18 in their illustrated pcsition and results
in the voltage rating indicated as HVl, The next
four horizontal lines indicate four more possible
arrangements of the tap changers to provide a series
circuit relationship for windings 13a and 13b resulting
in the voltage ratings HV2 to HV5. The last three
horizontal lines of the chart indicate the settings
of the tap changers to produce a parallel circuit
'relationship of windings 13a and 13b resulting in
the voltage ratings LVl, LV2 and LV3. It should
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10~3~0 Case 252~
be noted that the data given in Figure 2 must b~ read
along a horizontal line to get the correct setting
~or each tap changer 16, 17 and 18. For example,
to obtain a voltage rating HV5 on primary winding
11, tap changer 16 is set on position 6 and thus first
end e is connected to tap b, tap changer 17 is set
on position 1, with end d connected to end d (thus
no effective interconnection is made), and tap changer
18 is set on position 6 and thus terminal k is connected
to tap f.
The foregoing has been a description o~
the preferred embodiment of the present invention,
as envisioned by the inventor. It is to be understood
that the device depicted and described in this
specification is for one specif c application of the
invention onl~, and variations can be made therefrom
depending upon the particular application. Accordingly,
the device described herein should not be considered as
a limitation of the invention in any manner whatsoever,
bu~ rather, considered solely as an example for
illustrative purposes.
