U.S. patent number 3,686,561 [Application Number 05/136,701] was granted by the patent office on 1972-08-22 for regulating and filtering transformer having a magnetic core constructed to facilitate adjustment of non-magnetic gaps therein.
This patent grant is currently assigned to Westinghouse Electric Corporation. Invention is credited to Robert J. Spreadbury.
United States Patent |
3,686,561 |
Spreadbury |
* August 22, 1972 |
REGULATING AND FILTERING TRANSFORMER HAVING A MAGNETIC CORE
CONSTRUCTED TO FACILITATE ADJUSTMENT OF NON-MAGNETIC GAPS
THEREIN
Abstract
A parametric regulating and filtering transformer including a
magnetic core having input, output and saturating regions, input
and output windings disposed in inductive relation with the input
and output regions, and a capacitor connected to the output winding
to provide a tank circuit. Different embodiments of the parametric
transformer develop a non-magnetic gap or gaps, in the output
region of the magnetic core, required to provide the desired
waveform and electrical performance of the transformer, while
facilitating the manufacture and assembly of the transformer.
Inventors: |
Spreadbury; Robert J.
(Murrysville, PA) |
Assignee: |
Westinghouse Electric
Corporation (Pittsburgh, PA)
|
[*] Notice: |
The portion of the term of this patent
subsequent to June 6, 1988 has been disclaimed. |
Family
ID: |
22473981 |
Appl.
No.: |
05/136,701 |
Filed: |
April 23, 1971 |
Current U.S.
Class: |
323/308; 336/165;
336/215; 336/170 |
Current CPC
Class: |
H01F
27/25 (20130101); H01F 38/02 (20130101); G05F
3/06 (20130101); H01F 27/245 (20130101) |
Current International
Class: |
H01F
38/00 (20060101); H01F 38/02 (20060101); H01F
27/245 (20060101); G05F 3/04 (20060101); G05F
3/06 (20060101); H01F 27/25 (20060101); G05f
003/06 () |
Field of
Search: |
;323/6,44,60,61
;336/165,170,178,215 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Pellinen; A. D.
Claims
I claim as my invention:
1. A parametric regulating and filtering transformer,
comprising:
a magnetic core having first, second and third separable
sections,
input and output windings disposed in inductive relation with said
first and third sections, respectively,
said first section being butted against the second section to
provide at least two spaced joints therewith and at least one
magnetic loop,
said third section being disposed adjacent to, but spaced from,
said second section to provide at least one magnetic loop with the
second section having two gaps therein, and at least one magnetic
loop with the first section having two gaps therein,
spacer means disposed in the gaps between the second and third
sections, to maintain predetermined gap dimensions,
means holding the first, second and third sections of the magnetic
core in assembled relation,
and a capacitor connected to the output winding to provide a tank
circuit.
2. The transformer of claim 1 wherein the gaps formed between the
second and third sections are in a common plane.
3. The transformer of claim 1 wherein the first and third sections
include the input and output leg of the magnetic core, and the
second section includes the saturating leg.
4. The transformer of claim 3 wherein the joints between the first
and second sections lie in a common plane which is parallel with
the axis of the input leg, and the gaps between the second and
third sections are in a common plane parallel with the axis of the
output leg.
5. The transformer of claim 3 wherein the second section also
includes substantially all of the yoke portions of the magnetic
core which interconnect the ends of the input, output and
saturating legs.
6. The transformer of claim 1 wherein the magnetic core includes a
plurality of nested turns of magnetic, metallic laminations.
7. The transformer of claim 3 wherein the second section is
substantially rectangular in cross-sectional configuration, with
the first and third sections including yoke portions which
interconnect the ends of the input, output and saturating leg
portions of the magnetic core.
8. The transformer of claim 7 wherein the magnetic core includes a
plurality of nested turns of magnetic, metallic laminations.
9. The transformer of claim 7 wherein the magnetic core includes a
plurality of flat, superposed layers of metallic, magnetic
laminations.
10. The transformer of claim 1 wherein the first section is
substantially E-shaped, having an intermediate leg portion and two
outer portions, forming three spaced joints and two magnetic loops
with the second section, with the input winding being disposed
about the intermediate leg portion, and the third section is
substantially E-shaped having an intermediate portion and two outer
leg portions, forming two loops with the second section, each
having two gaps therein, with the output winding being disposed on
the intermediate leg portion of the third section.
11. The transformer of claim 10 wherein the intermediate leg
portions of the first and third sections have the same width
dimension as their outer leg portions.
12. The transformer of claim 10 wherein the intermediate leg
portions of the first and third sections have twice the width
dimension as their outer leg portions.
13. The transformer of claim 10 wherein the magnetic core includes
a plurality of nested lamination turns formed of magnetic, metallic
strip material.
14. The transformer of claim 10 wherein the magnetic core includes
a plurality of flat, superposed layers of metallic laminations.
15. The transformer of claim 10 wherein the E-shaped first and
third sections each include two substantially C-shaped loops
disposed side-by-side, with their intermediate leg portions being
formed of adjacent portions of the two C-shaped loops.
16. The transformer of claim 10 wherein the second section has a
substantially rectangular cross-sectional configuration, and
includes a plurality of flat, superposed magnetic metallic
laminations.
17. A parametric regulating and filtering transformer,
comprising:
a magnetic core having a plurality of superposed layers of
laminations which define first, second and third parallel leg
portions and connecting yoke portions,
each of said layers including a substantially E-shaped lamination
having first and second outer leg portions and an intermediate leg
portion, with the second outer leg portion having a shorter
longitudinal dimension than the first outer leg portion, and a
substantially L-shaped lamination having first and second portions,
with the first and intermediate leg portions of the E-lamination
butting against the first portion of the L-lamination, and with the
ends of the second portion of the L-lamination and the second outer
leg portion of the E-lamination being aligned but spaced apart by a
predetermined dimension to provide a predetermined gap, with the
midpoint of the gap falling on the central axis of the layer which
is perpendicular to the first outer and intermediate leg portion of
the E-shaped lamination,
alternate layers of said magnetic core having their E- and
L-laminations similarly oriented, with the remaining layers being
in 180.degree. rotational symmetry with said alternate layers about
the central axis of the alternate layers, to align the gaps in the
layers and provide a gap in the third leg of the magnetic core,
input and output windings disposed in inductive relation with the
first and third leg portions, respectively, of said magnetic
core,
and a capacitor connected to said output winding to provide a tank
circuit.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates in general to regulating transformers, and
more specifically to regulating and filtering transformers of the
parametric type.
Description of the Prior Art
Co-pending application, Ser. No. 835,953 filed June 24, 1969, now
U.S. Pat. 3,584,290 which is assigned to the same assignee as the
present application, discloses a new and improved three-path
regulating transformer of the parametric type. This new and
improved regulating transformer requires a magnetic core having
input, output, and saturable regions, provided by three spaced
parallel leg portions, input and output windings disposed in
inductive relation with the input and output regions of the
magnetic core, and a capacitor connected to the output winding to
provide a tank circuit. The alternating fluxes produced in the
input and output regions, dictated by a source of alternating
potential connected to the input winding, and the capacitor
voltage, respectively, share the saturable region, with negligible
direct flux linkage of the input and output windings, until the
vector addition of these parallel fluxes reaches a magnitude
sufficient to saturate the saturable region. When the saturable
region reaches saturation, which is typically for about 15.degree.
of each half cycle of the source potential, the flux produced by
the input winding is forced through the output region, linking the
output winding and thus transferring energy into the tank circuit
to sustain oscillation thereof. The short period of direct
transformer coupling, and the fact that the direct coupling occurs
near the voltage zero of the output voltage waveform, provides
excellent filtering of any "noise" in the input voltage waveform,
and the output voltage is regulated to .+-.0.5 percent for a .+-.15
percent change in input voltage from nominal, without closed loop
control.
While this three path parametric transformer may be constructed
without a non-magnetic gap in the output region of the magnetic
core, by proper dimensioning of the magnetic core, in practice the
output region is gapped as it optimizes the output voltage waveform
from the standpoint of harmonic content, it increases the stability
of the transformer, it enhances the decoupling of the input and
output windings, and it controls many operating characteristics of
the transformer, such as the threshold level of the input voltage
required to start the operation of the transformer. Self-starting
at a predetermined voltage less than the nominal input voltage may
be achieved by selecting a gap dimension which is about 20 mils per
square inch of cross-sectional area of the output leg of the
magnetic core.
The magnetic core of the three-path parametric transformer has
first, second and third spaced parallel leg portions interconnected
by first and second yoke portions. When the magnetic core is wound
from magnetic, metallic strip material, the resulting loop is cut
transversely to the leg portions of the core to enable the input
and output windings to be assembled therewith, and the desired gap
in the output region of the magnetic core is formed by machining a
cut end of the leg which is to function as part of the output
region of the magnetic core. This manufacturing approach
effectively presets the non-magnetic gap dimension and thus limits
the amount of adjustment available to take care of tolerances in
the capacitor, magnetic material variations, and the like. Thus, it
would be desirable to provide a new and improved parametric
transformer having a wound magnetic core, i.e., a plurality of
nested turns of magnetic, metallic laminations, which facilitates
manufacture, assembly and adjustment thereof to provide the desired
electrical characteristics.
It would also be desirable to provide a new and improved parametric
transformer having a magnetic core formed of a plurality of
superposed layers of assembled metallic, magnetic laminations,
which also facilitates the manufacture, assembly and adjustment
thereof to provide the desired characteristics.
SUMMARY OF THE INVENTION
Briefly, the present invention is a new and improved parametric
regulating and filtering transformer, and methods of constructing
same, which provides a non-magnetic gap in the output region of the
magnetic core without machining the gap. In one embodiment of the
invention, the magnetic core is wound from a magnetic, metallic
strip material to provide first, second and third spaced parallel
leg portions, and instead of cutting the magnetic core transversely
to the leg portions, the first and third leg portions are severed
from the intermediate portion of the magnetic core by cutting each
yoke portion transversely at two predetermined spaced locations.
The input and output windings are assembled with the first and
third leg portions and the legs reassembled with the intermediate
portion of the core, with non-magnetic spacer means being disposed
between the cut portions of the third leg and the complementary cut
portions of the intermediate core portion.
In other embodiments of the invention an independent magnetic
shunt, in the form of a packet or stack of magnetic, metallic
laminations is used to facilitate the manufacture of the magnetic
core, with both wound and stacked type core constructions.
In another embodiment of the invention, modified E- and L-shaped
laminations are assembled to provide a magnetic core having a
non-magnetic gap in the output region of the core, while
alternating the orientation of the laminations from layer to layer
to improve the core magnetically and mechanically.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention may be better understood, and further advantages and
uses thereof more readily apparent, when considered in view of the
following detailed description of exemplary embodiments, taken with
the accompanying drawings, in which:
FIG. 1 is a partially schematic view of a parametric regulating
transformer which may advantageously utilize the teachings of the
invention;
FIG. 2 is a perspective view of a wound magnetic core which may be
utilized in a three-path parametric transformer, illustrating the
cutting thereof according to the teachings of the invention;
FIG. 3 is an exploded perspective view of a parametric transformer
constructed with the magnetic core shown in FIG. 2;
FIG. 4 is a perspective view of the transformer shown in FIG. 3,
after assembly;
FIG. 5 is a perspective view of a magnetic core for a parametric
transformer constructed according to the teachings of the
invention, using two wound C-cores and a magnetic shunt;
FIG. 6 is a perspective view of a magnetic core for a parametric
transformer constructed according to the teachings of the
invention, using two stacked C-cores and a magnetic shunt;
FIG. 7 is a partially schematic view of a parametric regulating
transformer having a magnetic core which includes two C-cores and a
magnetic shunt;
FIG. 8 is a perspective view of a magnetic core for a parametric
regulating transformer constructed according to the teachings of
the invention, using a wound core having three leg portions and a
magnetic shunt;
FIG. 9 is a perspective view of a magnetic core for a parametric
regulating transformer constructed according to the teachings of
the invention, having two core sections each formed of E-shaped
laminations, and a magnetic shunt;
FIG. 10 is a partially schematic view of a parametric transformer
constructed with the magnetic core shown in FIG. 9;
FIG. 11 is a perspective view of a magnetic core for a parametric
transformer constructed according to the teachings of the
invention, using four C-cores and a magnetic shunt;
FIG. 12 is a perspective view of a magnetic core for a parametric
regulating transformer constructed according to the teachings of
the invention, having two core sections formed of E-shaped
laminations and a magnetic shunt, with the middle leg of the
E-shaped laminations being wider than the outer legs thereof;
FIG. 13 is a partially schematic view of a parametric regulating
transformer constructed with the magnetic core shown in FIG. 12;
and
FIG. 14 is a perspective view of a parametric regulating
transformer constructed according to the teachings of the
invention, having a magnetic core formed of modified E- and
L-shaped laminations.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring now to the drawings, and FIG. 1 in particular, there is
shown a three-path parametric regulating and filtering transformer
20 of the core-form type, constructed according to an embodiment of
the hereinbefore mentioned co-pending patent application.
Transformer 20 includes a magnetic core 22, having first, second
and third connected regions 24, 26 and 28, provided by first,
second and third spaced, parallel leg portions, respectively. The
adjacent ends of the regions are joined by upper and lower yoke
portions 30 and 32, respectively, defining first and second windows
or openings 34 and 36, respectively. Magnetic core 20 is wound from
magnetic, metallic strip material, such as grain oriented silicon
steel, to provide a plurality of nested turns 33 which encircle the
first window 34, a plurality of nested turns 35 which encircle the
second window 36, and a plurality of nested turns 37 which encircle
the turns 35 and 37, and therefore both of the windows. The first
and third regions 24 and 28 are outer legs of the magnetic core
structure 22, and the second region 26 is an inner leg. The first
and third regions 24 and 28 are substantially non-saturating input
and output regions, respectively, and the second region is a common
saturable region.
Magnetic core 22 has three magnetic loops or paths, with the first
magnetic path encircling the first window 34 via the first or input
region 24, a portion of the lower yoke 32, the second or saturable
region 26, and a portion of the upper yoke 30. The second magnetic
path encircles the second window 36 via the second or saturable
region 26, a portion of the lower yoke 32, the third or output
region 28, and a portion of the upper yoke 30. The third magnetic
path encircles both the openings 34 and 36 via the first or input
region 24, the lower yoke portion 32, the third or output region
28, and the upper yoke portion 30.
Means 44, including a primary or input winding 46, and a source 48
of alternating potential, are connected to provide a first
alternating flux in the first magnetic path, and means 50,
including a secondary or output winding 52 and a capacitor 54, is
connected to provide a second alternating flux in the second
magnetic path. Means 50 is a tank circuit, with a load circuit 56
being connected across the parallel connected output winding 52 and
capacitor 54.
It is critical for the proper operation of the regulating
transformer 20 that the magnetic core 22 be constructed such that
the second or common region 26 be saturable at a point less than
the vector sum of the first and second alternating fluxes, and that
the input and output regions 24 and 28 be substantially
non-saturating within the design range of the fluxes which will
link them. The input and output windings 46 and 52, respectively,
in conjunction with the capacitor 54, automatically insures that
the alternating flux in the input and output regions adds
substantially inphase in the common saturable region 26 to saturate
the common region during a portion of each half cycle of the
alternating flux therein. The magnetic core 22 is constructed with
the reluctances of the first and third magnetic paths such that the
major portion of the flux produced by means 44 will follow the
first magnetic loop or path, while still providing sufficient flux
in the third magnetic loop or path to directly link the input and
output windings, and induce a voltage in the output winding 52
sufficient to charge capacitor 54 to the point necessary to make
the regulating transformer 20 self-starting.
The common saturating region 26 of magnetic core 22 reaches
saturation during each half cycle of the alternating source
potential 48, with the flux provided by means 44 adding to the flux
provided by the tank circuit 50 in region 26 during one half cycle,
and then the flux provided by means 44 and 50 both reverse their
direction, still additive in the common saturable region 26, but in
the opposite direction, to drive region 26 into saturation during
this half cycle.
When source potential 48 is connected to input winding 44, an
alternating flux will be produced which divides between the first
and third magnetic paths according to their relative reluctances,
with the geometry of the core dictating relatively weak direct
transformer coupling between the input and output windings 46 and
50 via the third magnetic path, and a much stronger flux in the
first magnetic path. The weak transformer coupling between the
input and output windings, however, is unopposed by flux provided
by the tank circuit 50 during startup, and thus the regulating
transformer may be constructed to induce sufficient voltage into
output winding 52 to charge capacitor 54 to the magnitude necessary
to start and sustain oscillations in the tank circuit 50. The
threshold voltage necessary to start and sustain oscillations in
the tank circuit 50 depends upon the magnitude of the load across
the tank circuit. Once the tank circuit starts to oscillate, its
flux in the second magnetic path adds to the flux provided by means
44 in the common saturable region 26, driving region 26 to the knee
of its hysteresis curve. Upon reaching saturation, region 26 is no
longer a low reluctance path for the flux provided by means 44,
forcing the flux provided by means 44 around the third magnetic
path, strongly coupling the input and output windings 46 and 52 and
inducing a voltage into the output winding 52 which charges
capacitor 54 to provide the energy required to sustain the
oscillations of the tank circuit. Region 26 only stays in
saturation for a few degrees, typically less than 15, of the half
cycle of the source potential, with the strong transformer coupling
occurring only during this very short interval of time. During the
remaining portions of each half cycle of the source potential, the
input and output windings are effectively isolated. Thus, it will
be readily understood that the output voltage waveform is not
substantially affected by noise in the input voltage waveform. For
a cyclic disturbance, i.e., waveform distortion and/or periodic
spikes, the regulating transformer 20 will integrate the overall
energy level and provide a filtered, stable output voltage.
A non-magnetic gap 60 is provided in the output region 28, which
linearizes the output region and changes the output waveform of the
tank circuit 50 from substantially a square wave to a sine wave.
Thus, the dimension of gap 60 controls the harmonic content in the
output voltage waveform. The gap 60 also eliminates the possibility
of low frequency amplitude modulation of the desired output
voltage, and it improves the stability of the tank circuit.
Further, it enhances the decoupling of the input and output
windings 46 and 52, respectively.
The dimension of gap 60 is somewhat of a compromise between
harmonic content of the output voltage waveform, and power
capability of the parametric regulating transformer, with a
dimension of about 20 mils per square inch of cross-sectional area
of the output leg providing a good sine wave output voltage without
undue sacrifice of power output capability.
In the manufacture of parametric regulating transformers,
variations in the magnetic materials and windings, and capacitor
tolerance, often make it necessary to establish the dimension of
gap 60 during tests. This is difficult for unskilled personnel, as
the gap 60 is usually disposed within the confines of the output
winding 52. Further, the gap dimension is established by a
relatively costly machining operation, after the magnetic core 20
is cut into two halves along a centerline or axis disposed
perpendicularly through the three legs of the wound core. If the
first gap dimension selected is too small, the magnetic core input
and output windings are disassembled and the cut end of one of the
halves is machined again to remove additional material. If the gap
dimension selected is too great, the magnetic core is a costly
reject.
The first embodiment of the invention discloses a new and improved
parametric regulating transformer of the core-form type, having a
wound magnetic core which provides the required gap in the output
region without machining, while facilitating the manufacture,
assembly and test of the transformer. FIG. 2 is a perspective view
of a magnetic core 62 which is cut according to the teachings of
the invention. Magnetic core 62 is wound in the same manner as
magnetic core 20 shown in FIG. 1, and it includes first, second and
third leg portions 64, 66 and 68, respectively, and upper and lower
yoke portions 70 and 72, respectively, all of which cooperate to
define first and second windows 74 and 76, respectively, for
receiving portions of the input and output windings.
Instead of transversely cutting the three leg portions of the
magnetic core, along a common cut-plane, as illustrated in FIG. 1,
this embodiment of the invention teaches cutting each yoke portion
transversely thereto at two predetermined spaced locations, with
the predetermined spaced locations being selected to sever the
first and third leg portions 64 and 68 from the intermediate
portion of the magnetic core 62. Very little yoke is included with
the severed first and third leg portions 64 and 68. The selected
cut planes intersect the windows 74 and 76 immediately adjacent to
where the severed legs join the yoke portions. If the corners of
the windows are curved, such as illustrated at corner 78, the point
of intersection of each cut plane with a window is preferably where
the curved corner ends and the straight portion of the window which
defines the yoke begins. Thus, as indicated in FIG. 2, yoke 70 is
cut transversely along the two spaced cut planes indicated by
arrows 80--80', respectively, and yoke 72 is cut transversely along
two spaced cut planes indicated by arrow 84 and arrows 86--86'.
Although four total cuts are involved, only two cutting steps are
required to make the four cuts, as the two cut planes for severing
each leg portion are in alignment. Thus, the cut planes represented
by arrows 80--80' and 84 are in alignment, and the cut planes
represented by arrows 82--82' and 86--86' are in alignment.
FIG. 3 is an exploded perspective view of a parametric regulating
transformer 90, constructed with the magnetic core 62 shown in FIG.
2. After the step of cutting the magnetic core 62 to sever the
outer leg portions 64 and 68 from the intermediate portion of the
magnetic core, which includes the intermediate leg 66 and yoke
portions 70 and 72, input and output windings 92 and 94,
respectively, are provided, which are telescoped over the first and
third leg portions 64 and 68, respectively. The first leg portion
64 may then be reassembled with the intermediate portion of the
magnetic core, with their complementary cut portions being butted
together. The third leg portion 68 is also reassembled with the
intermediate portion of the magnetic core, but instead of butting
the complementary cut portions tightly together, they are spaced
apart by a predetermined dimension to provide the required total
gap dimension in the output loop of the parametric regulating
transformer 90. While the dimensions of the two gaps, i.e., the gap
between yoke 70 and leg 68, and the gap between yoke 72 and leg 68,
are preferably the same in order to simplify the manufacture and
assembly of the transformer 90, they may be different if desired.
The gaps are established and maintained by inserting insulating
spacer members 96 and 98 between the cut portions of yokes 70 and
72, respectively, and the complementary cut portions of leg 68, as
the leg 68 is assembled with the intermediate portion of the core
62. Insulating spacer members 96 and 98 may be formed of any
suitable material which will maintain their dimensions in the
operating environment of the transformer 90, such as one of the
laminated plastic materials.
The combined gap dimensions may be greater than the preferred 20
mils per square inch of cross-sectional area of the output leg, as
this value was established for a single non-magnetic gap disposed
within the output winding. When the gap or gaps are disposed
outside of the output winding, there is more flux fringing at the
gap.
FIG. 4 is a perspective view of transformer 90 after assembly,
illustrating that the three separable sections of the magnetic core
62, and the input and output windings 92 and 94, respectively, may
be easily held in assembled relation by a conventional core band
100. The transformer 90 is complete in FIG. 4, except for
connecting a capacitor (not shown) to the output winding 94 to
provide a tank circuit.
It should be noted that the gaps in the output loop of magnetic
core 62 are established and maintained without requiring an
additional machining step. The gap dimensions are easily
established, merely by selecting the thickness dimension, or
dimensions, of the insulating spacer members 96 and 98.
Establishing different gap dimensions merely requires selecting
spacer members having the desired dimensions.
The non-magnetic gap may also be easily established and maintained
in the output loop of the magnetic core of a three path parametric
regulating transformer, by constructing a separate or discrete
magnetic shunt and assembling it with easily manufactured and
assembled core elements or components. FIGS. 5, 6 and 7 illustrate
an embodiment of the invention which illustrates the use of a
magnetic shunt with core-form construction.
More specifically, FIG. 5 is a perspective view of a magnetic core
110 for a core-form parametric regulating transformer, which
utilizes a discrete magnetic shunt 112, first and second wound
C-cores 114 and 116, respectively, and insulating spacer means 118
which establishes and maintains first and second non-magnetic gaps
120 and 122 in the output loop portion of magnetic core 110.
The magnetic shunt 112 is formed of a plurality of thin,
rectangularly shaped laminations 124 which are superposed to
provide a stack of laminations, with the integrity of the stack
being maintained for easy handling by bonding the laminations
together. The laminations 124 are preferably formed of grain
oriented magnetic material, such as silicon steel, having at least
one preferred direction of magnetic orientation. The at least one
direction of magnetic orientation should be parallel with the
longitudinal axis of the laminations. For 60 H3. applications, the
laminations are preferably formed of magnetic material having a
thickness dimension of about 12 mils.
The first and second C-cores 114 and 116 may be formed by winding a
strip of grain oriented steel into a rectangular or circular loop
having the desired window dimensions and number of turns, bonding
the nested turns of the loop together, and then cutting the loop to
provide first and second C-cores. Since the output winding requires
more window volume than the input winding, the wound loop is
preferably designed such that it may be cut off-center, and provide
close fitting windows for both the input and output windings.
In the assembly of the magnetic core 110, an input winding (not
shown) is telescoped or slipped over one leg of C-core 114, such as
over leg 126, and the resulting assembly has the cut ends of the
legs of the C-core butted tightly against one side of magnetic
shunt 112, with the selected side of the shunt preferably being one
of the sides formed by the edges of the stack of laminations.
An output winding (not shown) is telescoped over one leg of C-core
116, such as leg 128, but instead of butting the cut ends of the
legs of C-core 116 directly against the magnetic shunt 112, the
insulating spacer member 118 is disposed against the side of the
shunt which is opposite to that associated with the first C-core,
and the cut ends of the C-core 116 are butted tightly against the
insulating spacer member 118. Since the insulating spacer 118, in
this embodiment, is not disposed inside a winding opening, it may
be in the form of a single sheet, as illustrated, instead of using
two members which are sized to closely fit the gap created between
the assembled core members. However, the gaps 120 and 122 may be
formed by using two separate spacer members, if desired.
In the assembly of magnetic core 110, the cut ends of the two
C-cores 114 and 116 are aligned, just as they were prior to
cutting, i.e., legs 126 and 128 are aligned with one another, and
the remaining legs are aligned with one another, enabling the
resulting assembly to be easily banded to hold the various core
members and windings in the desired assembled relation.
FIG. 6 is a perspective view of a magnetic core 110', which is
similar to magnetic core 110 shown in FIG. 5, except the two
C-cores are formed of a plurality of C-shaped laminations, bonded
together and stacked. Like reference numerals in FIGS. 5 and 6
indicate like components, and like reference numerals except for a
prime mark in FIG. 6 indicate like functions but slightly modified
structure.
More specifically, magnetic core 110 includes a magnetic shunt 112
and an insulating spacer member 118, as hereinbefore described
relative to FIG. 5, and first and second C-core members 114' and
116', respectively. The C-core member 114' is constructed of a
plurality of substantially C-shaped magnetic, metallic laminations
115, and C-core member 116' is constructed of a plurality of
substantially C-shaped magnetic metallic laminations 117. In order
to provide closely fitting windows or openings for the input and
output windings, the length dimensions of the C-shaped laminations
may be different for the first and second C-cores 114' and 116'. In
other words, the length of the leg portions of the C-shaped
laminations for core section 114' is preferably less than the
length of the leg portions of the C-shaped laminations for the
magnetic core section 116'. The assembly of the magnetic core with
associated input and output windings is the same as described
relative to FIG. 5.
FIG. 7 is a partially schematic view of a core-form parametric
regulating transformer 130 constructed with the magnetic core 110
shown in FIG. 6, but the construction would also be the same when
using the magnetic core 110 shown in FIG. 5. An input winding 132
is disposed about leg 126' of the first C-core 114', with the input
winding 132 being adapted for connection to a source 134 of
alternating potential. The ends of the outwardly extending legs of
the first C-core 114' are butted tightly against the magnetic shunt
112. An output winding 136 is disposed about leg 128' of C-core
116', and a capacitor 138 is connected to the output winding 136 to
provide a tank circuit. The output winding may also be adapted for
connection to a load circuit 140. The capacitor and load voltages
need not be the same. For example, as illustrated, the capacitor
138 may be connected across only a predetermined portion of the
output winding 136.
The insulating spacer member 118 is disposed on the side of the
magnetic shunt 112 which is opposite to the side associated with
the first C-core 114', and the second C-core 116' is butted against
the insulating spacer member 118 such that its legs are aligned
with the legs of the first C-core 114'. The first magnetic loop,
through which the flux provided by winding 132 is primarily
directed, thus includes the first C-core and the magnetic shunt
112, and the second magnetic loop, through which the flux provided
by the output winding 136 is primarily directed, includes the
second C-core 116' and the magnetic shunt 112. A first alternating
flux provided by the input winding 132 is thus primarily directed
through a first magnetic loop which includes the first C-core and
the magnetic shunt 112, and a second alternating flux provided by
the output winding 136 is primarily directed through a second
magnetic loop which includes the second C-core and the magnetic
shunt 112. A third magnetic loop, which effectively directly
couples the input and output windings only when the magnetic shunt
112 saturates due to the vector sum of the first and second
parallel alternating fluxes flowing through the magnetic shunt, is
provided by the first and second C-cores and the portions of the
magnetic shunt which couple the aligned ends of the C-cores.
The manufacture and assembly of the core-form parametric regulating
transformer 130 is greatly facilitated by the construction shown in
FIG. 7, as the non-magnetic gaps 120 and 122 in the second or
output magnetic loop are formed without machining, and they may be
increased or decreased in dimension by merely changing the
thickness dimension of the insulating spacer member 118.
FIGS. 8, 9 and 10 illustrate an embodiment of the invention which
illustrates the use of a magnetic shunt with shell-form magnetic
core construction. More specifically, FIG. 8 is a perspective view
of a magnetic core 150 for a shell-form parametric regulating
transformer, which utilizes a discrete magnetic shunt 152, formed
of a plurality of stacked metallic, magnetic laminations 154, first
and second wound E-shaped core elements 156 and 158, respectively,
and insulating spacer means 160 which establishes and maintains
non-magnetic gaps 162, 164 and 166 between the ends of the legs of
the second core portion 158 and the magnetic shunt 152.
The first and second substantially E-shaped core elements 156 and
158 may be formed by winding a strip of grain oriented silicon
steel to form two side-by-side core elements, and then winding a
plurality of turns of the magnetic strip about the side-by-side
core elements, to provide a wound magnetic core structure such as
illustrated in FIG. 2. However, instead of cutting the magnetic
core as illustrated in FIG. 2, it is cut transversely to the leg
portions, and it may be cut off-center in order to provide window
volume according to the relative volumes of the input and output
windings to be assembled with the magnetic core.
The first substantially E-shaped core element 156 includes first,
second and third leg portions 168, 170 and 172, which are joined by
a back portion 173, and the second substantially E-shaped core
element 158 includes first, second and third leg portions 174, 176
and 178, which are joined by a back portion 179. In the assembly of
the magnetic core 150, an input winding (not shown) is telescoped
over the second or inner leg portion 170 of the E-shaped core
element 156, and the substantially E-shaped core element 156 has
its cut ends butted tightly against one side of the shunt 152, with
the side of the magnetic shunt selected preferably being one of the
sides formed by the edges of the stack of laminations which make up
the magnetic shunt.
An output winding (not shown) is telescoped over the second or
inner leg portion 176 of the substantially E-shaped core element
158, but instead of butting the cut ends of the legs of core
element 158 tightly up against the magnetic shunt 152, the ends are
spaced from the magnetic shunt by a predetermined dimension. The
insulating spacer means 160 is disposed between the ends of the
core element 158 and the magnetic shunt 152, to establish and
maintain the desired gap dimension for the gaps 162, 164 and
166.
In the assembly of the magnetic core 150, the cut ends of the
E-shaped core elements 156 and 158 are aligned, just as they were
prior to cutting, enabling the resulting assembly to be easily
banded to hold the various core elements and windings in assembled
relation.
FIG. 9 is a perspective view of a magnetic core 150', which is
similar to the magnetic core 150 shown in FIG. 8 except the two
E-shaped core elements are formed of a plurality of E-shaped
laminations bonded together in stacks. Like reference numerals in
FIGS. 8 and 9 indicate like components, and like reference numerals
except for a prime mark in FIG. 9 indicate like functions but a
slightly modified structures.
More specifically, magnetic core 150' includes a magnetic shunt 152
and insulating spacer member 160, as hereinbefore described
relative to FIG. 8, and first and second substantially E-shaped
core elements 156' and 158', respectively. The first E-shaped core
element 156' is constructed of a plurality of substantially
E-shaped magnetic, metallic laminations 157, and the second
E-shaped core member or element 158' is constructed of a plurality
of substantially E-shaped magnetic metallic laminations 159.
Similar to the construction shown in FIG. 8, the leg portions of
the E-shaped core elements all have the same width dimension. The
assembly of the magnetic core 150' with the input and output
windings is the same as described relative to FIG. 8.
FIG. 10 is a partially schematic view of a shell-form parametric
regulating transformer 180 constructed with the magnetic core 150'
shown in FIG. 9, but it will be understood that the assembly would
be the same using the magnetic core 150 shown in FIG. 8. An input
winding 182 is disposed about the intermediate leg portion 170' of
the first E-shaped core element 156', with the input winding 182
being adapted for connection to a source 184 of alternating
potential. The first E-shaped core element 156' has the ends of its
outwardly extending legs butted tightly against one side of the
magnetic shunt 152.
An output winding 186 is disposed on leg 176' of the second
E-shaped core element 158', a capacitor 188 is connected to the
output winding 186 to provide a tank circuit, and the output
winding is adapted for connection to a load circuit 190. This
example again illustrates that the capacitor and load voltages need
not be the same with the load circuit 190 being connected across
only a predetermined portion of the output winding 186.
The insulating spacer member 160 is disposed on the side of the
magnetic shunt 152 which is opposite to that associated with the
first substantially E-shaped core element 156', and the second
E-shaped core element 158' is butted against the insulating spacer
member 160 such that its legs are aligned with the legs of the
first E-shaped core element 156'.
A first alternating flux provided by the input winding 182 divides
substantially equally to circulate about the windows or openings
182 and 183, proceeding, on one half cycle, through the leg 170',
dividing and proceeding in opposite directions through the magnetic
shunt 152, through the outer leg portions and into the back portion
156' and then returning to the intermediate leg 170'. On the next
half cycle, the flux circulation will be in the opposite direction.
A second alternating flux in the magnetic core is provided by the
output winding 186, with the flux, on one half cycle, proceeding
out of the intermediate leg portion 176' and dividing equally to
flow in opposite directions through the magnetic shunt 152, in the
same directions as the first alternating flux provided by the input
winding 182. This flux then enters the outer legs 174' and 178',
proceeds through the back portion 158', and returns to the
intermediate leg portion 176', thus encircling the two windows 185
and 187. The input and output windings 182 and 186 are effectively
isolated from one another, until the vector sum of the first and
second alternating fluxes in the magnetic shunt 152 saturate the
magnetic shunt 152, forcing the first alternating flux to link the
output winding 186 for the short interval of saturation,
transferring energy into the tank circuit to sustain its
oscillation.
The manufacture and assembly of the shell-form parametric
regulating transformer 180 shown in FIG. 10 is greatly facilitated
by the disclosed structure, as the non-magnetic gaps 162, 164 and
166 between the second core element 158' and the magnetic shunt 152
are formed without machining, and the dimensions of these gaps may
be increased or decreased by merely changing the thickness
dimension of the insulating spacer member 160. The insulating
spacer member 160 may be a single sheet, as illustrated, or three
separate insulating spacer members may be used, if desired.
FIGS. 11, 12 and 13 illustrate another embodiment of the invention
which uses a magnetic shunt with shell-form magnetic core
construction. In the shell-form magnetic core structure shown in
FIGS. 8, 9 and 10, the three leg portions of the E-shaped core
elements all have the same cross-sectional area. Thus, the outer
portions of the magnetic loops have one-half the flux density of
the inner portions of the magnetic loop, which has the advantage of
reducing iron losses, but the disadvantage of requiring more iron.
If it is desired to work all of the iron at the same flux density,
the middle leg of the E-shaped core elements should have a width
dimension which is twice that of the outer leg portions. FIG. 11
illustrates how this may be easily accomplished using wound type
magnetic cores, while FIG. 12 illustrates a stacked magnetic core
which provides the same result.
More specifically, FIG. 11 is a perspective view of a magnetic core
200 for a shell-form parametric regulating transformer, which
utilizes a discrete magnetic shunt 202 which is formed of a
plurality of laminations 204 which are stacked and bonded together
to maintain the integrity of the magnetic shunt. Magnetic core 200
has first and second substantially E-shaped core elements 206 and
212, with the first E-shaped core element 206 being formed of two
C-cores 208 and 210 which are assembled in side-by-side relation
such that their adjoining leg portions form a single intermediate
leg 211. The remaining leg portions of the C-cores 208 and 210
provide the outer legs 209 and 213 of the E-shaped core element.
The second substantially E-shaped core element 212 includes first
and second C-cores 214 and 216, disposed in side-by-side relation,
with the adjoining leg portions of the two C-cores providing the
intermediate leg portion 217 of the E-shaped element. The remaining
leg portions of the C-cores 214 and 216 provide outer leg portions
215 and 219 of the E-shaped core element. The four C-cores required
to construct the magnetic core 200 may be formed by winding
magnetic, metallic strip material to provide two magnetic loops
each having the desired window opening and required number of
nested lamination turns, and then the two loops are severed,
preferably off-center, as hereinbefore explained, to provide
C-cores. For example, the C-cores 208 and 214 may be formed from a
single magnetic loop, and the C-cores 210 and 216 may be formed
from a single magnetic loop. It will be noted that this structure
provides inner leg portions 211 and 217, upon which the input and
output windings are disposed, which have twice the cross-sectional
area of the outer leg portions of the magnetic core elements.
FIG. 12 is a perspective view of a magnetic core 200' which is
similar to the magnetic core 200 shown in FIG. 11, except the two
substantially E-shaped core elements 206 and 212 are formed of
substantially E-shaped laminations, stacked and bonded together.
Like reference numerals in FIGS. 11 and 12 indicate like
components, and like reference numerals except for a prime mark in
FIG. 12 indicate like functions but slightly modified structure.
Magnetic core 200' shown in FIG. 12 is similar to the magnetic core
150' shown in FIG. 9, except the width of the intermediate leg
portions 211' and 217' is twice the width of the outer leg portions
of the E-shaped laminations, while in the magnetic core shown in
FIG. 9 the intermediate leg portions have the same width dimension
as the outer leg portions.
FIG. 13 is a partially schematic view of a shell-form parametric
regulating transformer 226 constructed with the magnetic core 200'
shown in FIG. 12, but the construction would be the same using the
magnetic core 200 shown in FIG. 11. An input winding 228 is
disposed about intermediate leg portion 211' of the first E-shaped
core element 206', and it is adapted for connection to a source 230
of alternating potential. The outwardly extending ends of the
E-shaped element 206' butt tightly against the magnetic shunt
202.
An output winding 232 is disposed on intermediate leg portion 217'
of the second E-shaped core element 212', and a capacitor 234 is
connected across the output winding 232 to provide a tank circuit.
In this embodiment, a separate load winding 236 is provided, which
is also disposed about the intermediate leg portion 217', which
winding is connected to a load circuit 238. However, a single
output and load winding may be utilized, as shown in other
embodiments of the invention. The operation of the shell-form
transformer 226 is the same as hereinbefore described relative to
the shell-form transformer 180, which is illustrated in FIG.
10.
FIG. 14 is a perspective view, shown partially in phantom, of a
core-form parametric regulating transformer 250 constructed
according to still another embodiment of the invention. Transformer
250 includes a magnetic core 252 of the stacked type, shown
partially completed, and input and output windings 254 and 256,
respectively. The input and output windings 254 and 256 are shown
in phantom to more clearly illustrate the construction of the
magnetic core 252.
Magnetic core 252 includes a plurality of stacked or superposed
layers 258 of metallic, magnetic laminations, such as 12 mil, grain
oriented steel for 60 Hz. applications, with each layer of
laminations including a modified E-shaped lamination 260 and an
L-shaped lamination 262. The E-shaped lamination 260 includes
first, second and third spaced-parallel leg portions 264, 266 and
268, respectively, joined by a back or yoke portion 270, with the
third leg portion 268 having a shorter length dimension than the
first and second leg portions 264 and 266. The L-shaped lamination
262 includes first and second connected portions 272 and 274,
respectively, with portion 272 functioning as a yoke portion of the
magnetic core and with the second portion 274 cooperating with the
third leg 268 of the E-shaped lamination to complete a leg portion
of the magnetic core, which leg portion functions as the output leg
upon which the output winding 256 is disposed.
In the assembly of each layer of laminations, the ends of the first
and second leg portions 264 and 266 of the E-shaped lamination butt
against one side of the first portion 272 of the L-shaped
lamination 262. The portions 268 and 274 of the E- and L-shaped
laminations which cooperate to provide the output leg of the
magnetic core 252, are dimensioned to provide a gap 276 between
their aligned ends, such as a gap having a dimension of 20 mils per
square inch of cross-sectional area of the output leg. The gap 276
is oriented such that its midpoint bisects dimension 278 of the
magnetic core, i.e., that dimension between the outer surfaces of
the yoke portions 270 and 272 of the E- and L-laminations. This
orientation of the gap 276 enables the layers to be flipped over
from layer to layer while maintaining the location and dimension of
the gap 276. In other words, with the top layer oriented as
illustrated in FIG. 14, the next layer which is referenced 280 and
illustrated outside of the assembled laminations and windings, will
have its E- and L-laminations 260' and 262', respectively, in
180.degree. rotational symmetry with the E- and L-laminations of
the top layer, about an axis 282 which passes perpendicularly
through the first and second leg portions of the E-lamination and
through the gap, with arrow 284 illustrating how layer 280 has been
rotated about this axis.
In the assembly of transformer 250, the windings 254 and 256 are
placed in a fixture and the E- and L-laminations are built-up about
the windings. First, an E-lamination would be inserted with its
first and third leg portions entering the openings in the input and
output windings, respectively, from one end of the windings, and
the L-lamination would be placed adjacent to the opposite ends of
the windings such that the ends of the first and second legs of the
E-lamination butt against one side of the first portion 272 of the
L-lamination, and the second portion 274 of the L-lamination enters
the opening in the output winding to complete the output leg of the
layer while establishing the gap 276 therein. The next layer of
laminations would then be placed in position, after flipping them
over, and placing them at opposite ends of the input and output
windings, compared with their positions in the previous layer, with
the first and third legs of the E-lamination still entering the
input and output windings, and with the portion 274 of the
L-lamination entering the output winding. This stacking procedure
is repeated until the required stack build dimension is achieved.
The E- and L-laminations may all have openings therein, such as
openings 290 in the L-lamination and openings 292 in the
E-lamination, through which bolts may be inserted when the magnetic
core has been completed, to hold the laminations and input and
output windings in the desired assembled relation. The gap 276 is
automatically formed is this embodiment of the invention, within
the output winding 256. The magnetic core construction of this
embodiment makes it practical to easily change the dimensions of
the gap after the magnetic core is assembled, by making the holes
in the laminations larger than the bolts, or making the holes
elongated. Thus, the laminations may be tapped into the desired
positions and them clamped with the bolts. A varnish dip will then
lock the laminations together.
If it is desired to reduce the cross-sectional area of the inner
leg portion of the magnetic cores 252, compared with the
cross-sectional area of the outer leg portions, the width dimension
of the inner leg portion of the E-shaped laminations may be
reduced, or the width dimensions of the legs may be the same, with
an effective reduction in cross-sectional area being achieved by
forming a notch 294 in the intermediate leg of the E-shaped
lamination, which effectively reduces the cross-sectional area of
the intermediate leg portion. Another approach would be to utilize
a certain number of the E-type laminations, which have the
intermediate leg portion of the E removed, which laminations would
be interspersed with the other laminations.
In summary, there has been disclosed new and improved parametric
regulating transformers, and methods of constructing same, which
establish a non-magnetic gap in the output region of the
transformer without requiring a machining step. Further, the gap
may be established and changed at will, merely by changing the
dimension of the spacer member, enabling unskilled personnel to
quickly and easily establish the required operating characteristics
of the transformers.
* * * * *