Note: Descriptions are shown in the official language in which they were submitted.
5~
-- 1 --
PR~FO~MED ~UL~IPLE TURN
TRANSFORMER WINDING
1. Field of the Invention
This invention relates to transformer
construction and more particularly to a constr~ction of
the transformer windings.
Background of the Invention
Transformer design is often the art of
compromising the conflicting requirements of electrical
performance, space requirements and manufacturing and
fabrication costs. The electrical performance
requirements of the windings often conflict with the
difficulties of winding the desired coils with the
proper geometry and mechanical integrity at a reasonable
cost. At the very least, a transformer winding must
have the required number of turns, adequate current
handling capacity and the necessary structural strength
to withstand electrically induced mecha.ical stresses.
Additional considerations include securing good coupling
between the windings and maximizing utilization of the
core windows. Many times the practical difficulties
inherent in winding the transformer coils such as
getting the coil to lay properly, getting proper
tension, positioning in and filling the core windows
reouire compromises that limit ultimate electrical
performance.
A suitable technique for improving electrical
performance while minimizing the aforementioned
difficulties has been to use a preformed winding having
a channel cross section into which another prewound
winding is mechanically inserted. This solves many of
the above mentioned constructiona~ difficulties without
compromising electrical performance. It also
,~
~5~
-- 2
advantageou~ly permits a low profile trans~ormer design
suitable for car-type circuit packsO Such an
arrangemen-t is disclosed in U.S. Patent No. ~,583,068
which issued on August 15, 1986 to F.T. Dickens and W.A.
Peterson, entitled 'ILow Profile Magnetic Structu~e in
Which One Winding Acts ~s Support for a Second Winding".
The arrangement disclosed therein comprises a
transformer having a one turn preformed secondary
winding and further having the primary enclosed within a
channel cross section of the secondary winding. This
arrangement, ho~ever, is limited to situations where a
single turn winding is appropriate since no arrangement
exists permitting the preformed winding to have multiple
turns.
In accordance with one aspect of the
invention there is provided a transformer comprising: a
core having ~irst and second windows around a central
core leg, a first conductor unit threaded through th2
first and second windows to encircle the central core
and having a channel shaped cross section, a second
conductor unit threaded through the first and second
windows to encircle the central core and having a
channel shaped cross section, the first and second
conductor units positioned adjacent to one another with
an open edge of the channel cross section of each of the
first and second conductor units being substantially
adjacent to one another and including means for
electrically insulating the first and second conductor
units from each other, a conducting mechanism
electrically connecting the first and second conductors
in a series connection, a third conductor encircling the
central core leg and included within the channel cross
section or each of the first and second conductor units.
In accordance with another aspect of the
invention there is provided a transformer comprising: a
magnetic core, first and second windings wound to
.../2
~L~5~ 9
- 2a -
interact with the ma~netic core, the first winding
including first and second conducting elements, each
conducting element wound to surround a portion of the
magnetic core and including an elongated cavity, the
first and second conducting elements positioned with th~
cavity of each adjacent to each other, a conducting
mechanism electrically connecting the first and second
conducting elements to form a two turn first winding
surrounding the magnetic core, the second winding
surrounding the magnetic core and being included within
the cavity formed by the first and second conducting
elements.
Summary of the Invention
A preformed two-turn transformer winding
embodying the principles of the invention is designed to
be assembled around another winding so that the two
windings are coaxial. The two-turn winding is formed of
individual turns each having a channel cross section.
The individual turns are stacked on top of one another
so that in one embodiment the channels form a closed
passageway. The two turns are electrically isolated
from each other by a film of insulation coating the two
channels that electrically isolates adjacent edges
except for a series connection employed at the ends of
the individual turns to form a two-turn winding. The
other transformer winding is inserted into the enclosed
passageway. An alternative embodiment of the invention
uses two turns having a channel cross section with one
cross section smaller than the other so that one turn
may be nested within the other. The other transformer
winding is located within the open channel cross section
of the nested turn.
It is readily apparent that this
multiwinding arrangemPnt expands the range of
applicability of preformed windings to a larger power
range since the
~58~3~3
overall t~rns ratio permitted is increased.
Furthermore, it permits a center tapped multiwinding
where such an arrangement is desired.
This arrangement of a preformed winding also
advantageously permits winding arrangements having close
coupling and also fully utilizes the window area of the
core.
Brief Description of_the Drawings
An understanding of the invention may be
readily attained by reference to the following
specification and the accompanying drawings in which:
FIG. 1 is a perspective view of a transformer
utilizing a multiturn winding embodying the principles
of the invention;
FIGS. 2, 3 and 4 are orthogonal projections of
a component of the multiturn winding shown in FIG. l;
FIGS. 5, 6 and 7 are orthogonal projections of
another component of the multiturn winding shown in
FIG. l;
FIG. 8 is a perspective view of another
configuration of a multiturn winding embodying the
principles of the invention;
FIGS. 9, 10 and 11 are orthogonal projections
of a component of the multiturn winding shown in FIG. 8;
FI~ is an exploded perspective view o~
another multiturn transformer winding embodying the
principles of the invention;
FIGS. 13, 14 and 15 are orthogonal projections
of a component of the multiturn winding shown in FIG.
1~, and
FIGS. 16, 17 and 18 are orthogonal projections
o~ another component of the multiturn winding shown in
FIG. 12.
Detailed Description
The transformer arrangement, shown in FIG. 1,
is designed to be board-mounted and to have a very low
profile so one circuit board may be mounted in a housing
-
-- 4 --
in close proximity with another circuit board. The
transformer includes an elongated E shaped magnetic
core 10 and a magnetic core cap 200 The cap 20 is
secured to the core 10 and the entire assembly to the
circuit board 1 by four clips 5 (one is shown) which are
each connected into detents 21 in the cap 20 and snap
into corresponding detents (not shown) located in the
bottom surface of the core 10. The elongated ends 6 of
the clip 5 fit into holes or receptacles 7 in the
circuit board 1.
The transformer windings include a primary
winding 30 formed of a prewound conductor and a
secondary winding formed of two U channel cross
sectioned cond~cting turns or units 41 and 42.
Conducting units 41 and 42 are each oriented so that the
open ends of the channel cross sections face one
another. An insulating film or material 49 is applied
by dipping the individual conducting units in a
liquified insulative material that is then cured into a
solid film so -that when the edges 43 and 44 are
substantially abutted against one another, the two units
~1 and 42 remain electrically isolated along these
edges. The thickness of the side walls 45 and 46 of the
units 41 and 42 and of the bottom wall 47 and 48 may be
varied as needed to accommodate an anticipated power
range of the transformer. Each conducting unit 41 and
42 with the U channel cross section comprises one
complete turn. Units 41 and 42 are stacked on top with
the adjacent edges 43 and 44 electrically insulated from
each other as described above. They are electrically
joined at their ends to form two complete turns.
The ends of the lower conducting unit 42 are
extended to form two L shaped shelves 51 and 52 on a
plane with the bottom of the channel and with each shelf
having a hole 53 and 54 at the end of the L shaped
extension. Shelf 51 and hole 53 are used to facilitate
an electrical connection with the upper conducting unit
_ 5 ~ 3
41.
The extensions S5 and 5~ of the channel ~ottom
of the upper unit 41 are also L shaped shelves. Each
shelf, however, includes a step bend so that the plane
of the shelf is positioned substantially coplanar with
the bottom shelf extensions 51 and 52. The shelf 56 is
directly above the shelf 51 and the holes 58 and 53 are
in register with each other. These two shelf extensions
may be secured together to electrically ~oin the two
conducting units 41 and 42 and create a two-turn winding
by a fastening device such as a bolt or by fusing or
binding such as welding or soldering. When the two
units 41 and 42 are electrically connected, they are
positioned to enclose the primary winding 30. The other
two free shelves 52 and 55 may be used as the end
terminals of the secondary winding and may be secured by
fasteners through holes 57 and 54 to conducting paths 2
and 3 on the circuit board or other conductive media.
Bias windings ~ and 8 of the transformer are positioned
in the bottom of core and may, as shown, comprise loose
wire or may comprise a printed circuit winding.
The assembly of the transformer begins with
placement of the bias windings 7 and 8 into the core
cavity. The primary winding is inserted in the cavity
of the lower conducting unit 42, and the upper unit 41
is placed in top of it enclosing the primary winding
within the desired passageway ~ormed by the upper and
lower units 41 and 42. The two conducting units 41 and
42 are then secured together by suitable fastener
hardwire passing through holes 53 and 58. The assembled
winding is then dropped into place in core 10, and then
core 10 and cap 20 are secured together by the clips 5,
which facilitate mounting the unit on a circuit board 1.
The details of the lower conducting unit 42
and upper conducting unit 41 are shown in the orthogonal
pro~ections in FIGS. 2, 3, 4, 5, 6 and 7, respectively.
The bottom unit 42 has a channel cross section as shown
~58~
-- 6
in FIG. 4 and the base of the channel has two L shaped
shelf e~tensions 51 and 54 as shown in FIG. 2. The
shelf extensions are ofEset in length so that one 5~ may
serve as a winding terminal and the other 51 a
midwinding connection of the two-turn winding. The
upper unit 41 has a channel cross section as shown in
FIG. 7 and two L shaped shelf extensions 55 and 56 as
shown in FIG. 5. Each shelf extension has a step which
is nearly coplanar with a mating surface of a shelf
extension of the bottom unit 42.
A variation of a secondary winding arrangement
embodying the principles of the invention unit is
disclosed in FIG. 8 comprising two identical conducting
units 141 and 142. The two units are joined together
along their edges, with a primary winding positioned
within the resulting enclosed passageway. An insulating
film 144 coating the units electrically isolates the two
windings from each other at the adjacent edges. The two
windings 141 and 142 are electrically connected in
series by a conductive spacer 150 conductively joining
the L shaped shelf extensions 148 and 149 respectively
to create a two-turn winding. The outer L shelves 146
and 147 are used to provide the start and finish
termination leads of the completed secondary winding.
As is apparent from the detailed drawing of
FIGS. 9 through 11, the two individual units 141 and 142
are identical in geometry and are of the same
handedness. They mate together, as shown in FIG. ~,
form a two-turn winding with and enclosed passageway.
A third winding arrangement is disclosed in a
perspective view in FIG. 12 in which the two winding
units 241 and 242 are sized differently so that the
upper conducting unit 241 may be nested into or fit
within the channel cross section of the bottom
conducting unit 242 with the opening of the channels
facing in the same direction for both conducting units.
The conductive cross sectional area of both conducting
~l~5~ 3~3
-- 7
units is selected so that both units have the same
conductive cross sectional area. Hence, a thinner
conductive material is used for the lower shell winding.
This matching of conductive area allows for equalization
of disspative losses in each individual conducting unit.
The two turns are insulated from each other by a layer
of insulation (possibly epoxy) on the surfaces of the
two units.
Each turn has the base of its channel extended
into L shaped shelves 251-25~. The shelf extensions
251-252 of the top unit 241 are oriented in a direction
opposite to the extension direction of shelves 253 and
254 of the bottom unit 242. Holes are in shelves 252
and 253 permit attachment of the conducting units to
each other to form two series connecting turns. Holes
in shelves 251 and 254 are used for terminating the two
turns.
The prewound primary winding is inserted in
the open channel 246 of the upper turn 241 which is left
uncovered. The arrangement has very low leaka~e
inductances between the two turns and is imminently
suitable for application when the individual turns of
the secondary conduct alternately when the winding is
center tapped and current is switched between the two
turns.
The two winding units 241 and 242 differ in
handedness as shown in ~IGS. 13, 14, 15, 16, 17 and 18,
respectively. This permits the shelf extensions 251 and
254 to clear each other and be used as winding
termination connections.
It is readily apparent that by successive
nesting arrangements the arrangement o~ FIG. 12 may be
extended beyond two turns to multiple turns. Such
arrangements are believed to be readily apparent to
those skilled in the artO
