Jim MURRAY III
Elliptical Rotor Alternator / Generator / Motor
" Dynaflux " design reduces Lenz Law
resistance for ultra-high efficiency
TOROIDAL MOTOR DESIGN HAVING BACK EMF
CROSS REFERENCE TO RELATED APPLICATIONS
 This application is related to the concurrently filed
application Ser. No. ______, titled “Controller For Toroidal Motor
Having Back EMF Reduction,” which is incorporated entirely herein
FIELD OF THE INVENTION
 The disclosed inventions relate to the field of direct
current (“DC”) electric motors, and more particularly to DC motors
having a toroidal stator winding and externally driven commutation
to drive a rotor by interaction with a rotating magnetic field.
 As described in this inventor's prior patents, conventional
geometry motors are affected by Speed Voltage Back EMF that is
parasitic in nature and, among other things, degrades the source
potential supplied to the motor. This inventor has implemented
novel geometries to reduce Speed Voltage Back EMF, such as those
disclosed in co-pending application Ser. No. 13/562,233, titled
“Multi-Pole Switched Reluctance D.C. Motor with a Constant Air Gap
and Recovery of Inductive Field Energy,” which is hereby
incorporated by reference in its entirety.
 In most conventional DC motors, the energizing current to
the motor is delivered via some type of commutation in
communication with the motor coils. Typically, commutation may be
accomplished by a mechanical commutator (e.g., commutator bars and
carbon brushes), or by electronic commutation (e.g., an
electronically controlled switching circuit). In most existing
devices the commutator operates in conjunction with the rotor,
either by being physically coupled to the rotor by a common shaft
(e.g., mechanical commutation), or electronically by relying on
information relating to the position of the rotor (e.g.,
 Many drawbacks and limitations are present in existing DC
motors. In addition to the above-mentioned degradation of source
potential, existing designs are inconvenient for applications
desiring a constant torque output with an unvarying input current.
Likewise, existing designs do not lend themselves easily to
creating an output horsepower that increases with the rotational
speed of the rotor. Other drawbacks of traditional designs also
 One advantage of the presently disclosed system and method
is that it addresses the drawbacks of existing systems.
 Accordingly, another advantage of some embodiments of the
disclosed invention is that they provide a toroidal DC motor that
reduces Back EMF and, therefore, minimizes the degradation of
source potential. In addition, embodiments of the disclosed
invention provide a motor that provides constant torque at
constant current irrespective of the speed of the rotor. Likewise,
some embodiments of the disclosed inventions provide output
horsepower that increases with the rotational speed of the rotor.
Other advantages and features of the disclosed invention also
exist and may be apparent to those of skill in the art.
 Exemplary non-limiting embodiments are disclosed herein,
however, it should be appreciated that other appropriate
embodiments are encompassed by the present disclosure, the
possible variations being too numerous to illustrate. It is
understood that one skilled in the art would recognize that other
potential arrangements are capable of supporting the principles
disclosed herein. Other aspects and advantages of the presently
disclosed systems and methods will now be discussed with reference
to the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
 FIG. 1 is an overview of a DC toroid motor in
accordance with some embodiments of the disclosed inventions.
 FIG. 2 shows a close-up view of a driven commutator
30 in accordance with some embodiments of the disclosed
 FIG. 3 shows a close-up view of some embodiments of
the rotor/stator assembly 40.
 FIG. 4 is a close-up view of toroidal stator 44 with
the cover removed.
 FIG. 5 shows a series connection scheme for stator
coils 50 in accordance with some embodiments of the invention.
 FIG. 6 shows a schematic diagram of an embodiment of
a toroid stator and rotor assembly 40 and a representation of
the rotating magnetic flux 80 and Dead Zones 70.
 FIG. 7 shows a perspective view of a rotor/stator
assembly 40 in accordance with some embodiments of the
 FIG. 8 illustrates a side view of a commutator
housing configured for parallel connection of stator coils 50 in
accordance with some embodiments.
 FIG. 9 shows a perspective view of a rotary switch
for use with the brush holder ring 302 of FIG. 8 and utilized in
embodiments of parallel coil configuration.
 FIG. 10 shows a side view of an embodiment of a
brush holder ring 302 of FIG. 8 and also showing the conductors
322 which are to be connected to power the coils 50.
 FIG. 11 shows a perspective view of another
embodiment of a rotor.
 In the following detailed description, reference is made to
the accompanying drawings that form a part hereof, and in which
are shown by way of illustration specific embodiments in which the
invention may be practiced. These embodiments are described in
sufficient detail to enable those skilled in the art to practice
the invention, and it is to be understood that other embodiments
may be utilized and that various changes may be made without
departing from the spirit and scope of the present invention. The
following detailed description is, therefore, not to be taken in a
 The operation of a DC Motor of standard design requires
that sets of magnetic field producing coils be
electro-mechanically, or electronically switched, so as to secure
an output torque and continuous rotary motion. This is typically
achieved by timing the switching of the coils, such that the coil
windings spend a maximum amount of time beneath the magnetic poles
of the motor such that the electromagnetic force (F) described by
the Lenz force relationship,
 (where B is the magnetic field, l is the length of the
conductor, and I is the current) can be fully exploited. However
in the invention herein disclosed, two opposing magnetic fields
are created within the toroidal windings of the stator, and come
together at two points (i.e., 180 mechanical degrees apart) where
they exit the confines of the stator iron, traverse the air gap,
and enter the rotor structure which is positioned across a
diameter of the toroid. Accordingly, the reluctance forces
associated with this rotor structure will cause the rotor to align
itself with the flux lines, producing a torque, and providing a
closed path for the flux to travel through the rotor, cross the
air gap on the other side, and return to the stator, thus,
allowing each flux line to return to its associated coil group.
This is discussed in more detail with reference to FIG. 6 below.
Thus, a very large value of restoring torque may exist within the
motor, rotor, and drive shaft whether rotation ensues or not.
Rotation is a secondary feature of this arrangement, and is
determined by the switching frequency of the windings. Therefore,
when rotation is desired, a switching sequence is initiated which
turns off and isolates one coil in one coil group, while
simultaneously turning on one coil in the other complementary coil
group. This action will advance the position of the rotor by 360/n
degrees, where n is the total number of coils arranged around the
periphery of the toroidal stator. The switching sequence is
repeated for the next adjacent set of coils in each group and
rotation may be sustained at a speed related to the rate of
 The areas where the rotating flux field dynamically
interacts with the windings are at the two positions where the
flux exits out of the stator and enters the rotor, and exists out
of the rotor and enters the stator. Therefore, depending upon the
arc length required by the physical dimensions of the rotor, a
certain number of windings are electronically eliminated from the
overall circuit within these two regions, thereby providing a
“Dead Zone,” or an isolated segment at each end of the rotor's
immediate position, thereby insuring that speed-related Back EMF
will be kept to an absolute minimum.
 Therefore, a motor operating in accordance with this
scheme, will sustain a rotating field of flux 80, and a rotating
Dead Zone 70, which possess the same angular velocity, but not
necessarily the same phase relationship. Depending upon the load
applied to the motor, the Dead Zone 70 may be advanced or
retarded, or broadened or narrowed, with respect to the rotor's
position, in order to minimize any flux coupling between the
rotating field and the DC windings. This control feature may be a
function of some embodiments of the electronic controller 90, and
is disclosed in greater detail in concurrently filed, related
application Ser. No. ______, titled “Controller For Toroidal Motor
Having Back EMF Reduction.”
 FIG. 1 is an overview of a DC toroid motor system in
accordance with some embodiments of the disclosed inventions. As
shown, some embodiments may comprise a DC toroid motor 10 further
comprising an appropriate power supply 20. Of course, the
particular power supply 20 may vary in accordance with factors
such as the intended use of the motor 10, the environment motor 10
is intended to operate in, the desired electric inputs, the
desired torque outputs, the desired RPM, or the like.
 Some embodiments of motor 10 may comprise a commutator 30
assembly. As shown, some embodiments may comprise a commutator 30
that is located apart from the rotor/stator assembly 40. Further,
in embodiments where commutator 30 comprises an electro-mechanical
device, a powered driver 32 may also be included. Powered driver
32 may comprise any suitable motor, or other prime mover, capable
of imparting the desired rotational motion to commutator 30.
 Some embodiments also may comprise a number of conductors
42 in electrical communication with stator coils and commutator 30
contacts 38. For clarity, the figures only illustrate a single
conductor 42, but, of course, as many conductors 42 as desired may
be implemented. In addition, any suitable connection mechanisms
may also be implemented, such as ribbon cables, multi-conductor
cables, modular connectors, connection busses, or the like.
Likewise, any suitable conductors 42 are possible and may vary
with the intended use, power, speed, number of coils, or
environment considerations. Optional controller 90 and optional
energy recapture 100 are discussed below and may also be provided
in some embodiments.
 FIG. 2 shows a close-up view of commutator 30 in accordance
with some embodiments of the disclosed invention. As shown,
embodiments of commutator 30 may include a slidable contact by
which energizing power from power supply 20 may be fed to the
stator coils of rotor/stator assembly 40. For example, embodiments
may comprise a slidable contact such as slip rings 34 which
receive power from power supply 20 via input power brushes 33. As
shown in FIG. 2, two input power brushes 33 are in slidable,
electrical contact with two slip rings 34 to accommodate the two
poles of DC current (e.g., positive and ground, or positive and
negative). Other configurations are also possible.
 Embodiments of commutator 30 also may comprise a rotating
assembly 36. Rotating assembly 36 may be driven by commutator
driver 32 (e.g., via a common shaft, coupled shafts, gearing,
pulleys, or the like) causing the rotating assembly 36 to slide
over contacts 38. Embodiments of rotating assembly 36 may also
comprise one or more switching brushes 39 per rotor pole that
facilitate the transfer of input power from input power brushes 33
and slip rings 34 to contacts 38, and then to the stator coils via
conductors 42. As discussed in more detail below, the rotating
assembly 36, in association with its brushes, will create two Dead
Zones 70 which rotate in sync with the rotor 46, thus, nullifying
the interaction between the rotating flux field and the windings
located in the Dead Zones 70.
 FIG. 3 shows a close-up view of some embodiments of the
rotor/stator assembly 40. As shown, conductors 42 carry input
power from the contacts 38 to the toroidal stator 44 and may be
connected to the stator coils in any suitable configuration as
discussed in more detail below. As shown, toroidal stator 44 is
generally annular in shape and arranged to allow rotor 46 to
rotate within the center space of the toroid.
 As shown in FIG. 3 some embodiments of rotor 46 may
comprise an un-excited (e.g., coil-less) rotor 46. For some
embodiments rotor 46 may be generally rectangular with ends shaped
to conform to a curvature that generally matches the curvature of
the inner circle of the toroid stator 44 to ensure a constant air
gap, and allow free rotation. Other embodiments may include coils
(not shown) on rotor 46 in order to, among other things, provide a
mechanism for increasing motor 10 torque output.
 Other shapes and configurations for rotor 46 are also
possible. For example, rotor 46 may comprise a disc of varying
magnetic permeability. A portion of such a disc may include a
relatively high permeability material that provides a preferential
flux path through the rotor 46. Other shapes and configurations
for rotor 46 are also possible.
 FIG. 11 is an illustration of an embodiment of such a
disc-shaped rotor 460. As shown, a magnetically permeable path 462
is provided in a lower permeability material 464. Of course, other
shapes, paths, and configurations are also possible.
 In some embodiments, it may be preferable to couple motor
10 with other machines, instruments, or devices, therefore, output
coupler 48 may be provided on a shaft coupled to rotor 46. Output
coupler 48 may comprise one or more pulleys, gears, shafts, or
 FIG. 4 is a close-up view of toroidal stator 44 with the
cover (e.g., end bell) removed. As shown, stator 44 may comprise a
number of toroidally wound stator coils 50. For some embodiments,
stator coils 50 may comprise a number of individually wound coils.
 A variety of connection schemes for stator coils are
possible. FIG. 4 illustrates a series connection for stator coils
50 in that each coil is connected to the next in a series fashion.
In some embodiments, a series connection may be accomplished by
connecting commutator contacts 38 located 180 mechanical degrees
apart (i.e., opposite sides of a diameter) with opposite switching
brushes 39 on the rotating assembly 36.
 FIG. 5 shows a series connection scheme for stator coils 50
in accordance with some embodiments of the invention. As shown in
FIG. 5 the opposite side of contacts 38 may comprise one or more
terminals 52 that are in electrical communication with conductors
42. As also shown, for a series connection some embodiments may
include electrical connections between terminals 52 on half of
stator 44 being connected to half of the coils 50 and the
remaining half of terminals 52 being connected to the other half
of the coils 50 on stator 44, but varying the connection as the
contacts 38 slide, thus, creating a mechanically driven rotating
magnetic field. This, in conjunction with the connection of
switching brushes 39, which are in turn connected to opposite
poles of the input DC power, enables the creation of a rotating
stator magnetic field having two paths with each path being of
opposing magnetic polarity (e.g., North and South).
 The operation of some embodiments demands that motor-driven
commutator assembly 32, rotates the rotating assembly 36, such
that the two sets of switching brushes 39 will make and break
contact with the commutator contacts 38, and thereby switch the
appropriate stator coils 50 in and out of the supply 20 circuit.
The switching is so performed that no current is allowed to flow
through the coil 50 windings which lie between each respective
pair of brushes 39, thus, isolating those coils 50. This selective
form of switching, then creates a series of “inactive and isolated
coils” which constitute two Dead Zones 70 located 180 mechanical
degrees apart on the stator 44, and rotate in synchronism with the
rotor 46. These traveling Dead Zones 70, then, represent windows
for the flux 80 to pass through with minimal, if any, inducing of
a Back EMF Voltage, or a Back Torque, either of which could reduce
motor 10 performance.
 As with any magnetic field, the flux lines 80 created by
the energized coil 50 windings will travel from one pole to the
other (e.g., North to South). Rotor 46, which for some embodiments
may comprise steel or some other magnetically responsive material,
provides a preferred path for the flux lines to travel through,
and complete the magnetic circuit, but in so doing, will align the
rotor 46 so that the end faces of the rotor line up with the Dead
Zone 70 created in the coil 50 windings. This is illustrated in
FIG. 6 which shows a schematic diagram of a toroid stator and
rotor assembly 40 and a representation of the rotating magnetic
flux lines 80 and Dead Zones 70. As shown, rotor 46 may be
generally rectangular with ends shaped to conform to a curvature
that generally matches the curvature of the inner circle of the
toroid stator 44 to ensure a constant air gap 76, and allow free
rotation. At the instant depicted in FIG. 6, active coils 50 on
the “left half” of the toroid stator 44 generate magnetic flux
lines 80 that cross air gap 76, enter the rotor 46 through Dead
Zone 70 a, traverse the rotor 46, and exit the rotor 46 and cross
air gap 76 through Dead Zone 70 b to complete the magnetic
circuit. Likewise, active coils 50 on the “right half” of the
toroid stator 44 traverse a corresponding route on the other side
of the toroid stator 44.
 In the above-described manner, the Back EMF due to rotation
of the rotor 46 in the presence of the stator 44 magnetic field is
reduced by controlling the characteristics of the rotor 46 and
coil 50 interactions. Creation of the Dead Zones 70 insures that
no current is present in the adjacent coil 50, and consequently
minimal, or no, Back EMF Voltage or magnetic field is generated in
that coil 50, when rotor 46 is adjacent to the coil 50.
 Such an arrangement creates a motor 10 that delivers
constant torque at varying rotor 46 speeds. Furthermore, the
torque is adjustable by changing the input current, and, thus, the
magnitude of the resultant stator 44 magnetic field. At given
current setting the motor 10 output torque will remain relatively
constant irrespective of speed. Further, motor 10 output
horsepower (HP), can be determined from:
 HP=(Torque×speed)/K, where K is constant that depends upon
the units used.
 It is apparent that for embodiments of motor 10 that the HP
increases as RPM increases, and, output torque will stay constant
for a given current (and magnetic field strength), thus,
horsepower can be varied with the speed of the rotor 46 which is
determined by the switching frequency, or by changing the current
at a given speed. Other advantages also exist.
 FIG. 7 shows a perspective view of a rotor/stator assembly
40 in accordance with some embodiments of the invention. As shown
for this embodiment (with coils 50 removed for clarity),
rotor/stator assembly 40 may be housed in an appropriate housing
54. For example, depending upon factors such as the intended
environment, the intended use, the cost of materials, the
conductive and magnetic properties, and the like, housing 54 may
comprise an artificial material (i.e., man-made plastics, resins,
polymers, or the like), a natural material (i.e., wood, metal, or
the like), or combinations of the same (e.g., alloys, composite
 Furthermore, embodiments of housing 54 may also comprise
shapes other than generally cylindrical, or multi-piece housings,
again as appropriate with factors including the intended use and
environment. For example, FIG. 7 shows an embodiment with a
separate end cover 54 (shown as plastic or plexi-glass), a housing
ring 58, and a housing base 60. Other configurations are also
 FIG. 8 illustrates a side view of a commutator 30
configured for parallel connection of stator coils 50 in
accordance with some embodiments. Parallel connection in the
present disclosure means that each stator coil 50 is independently
connected to a DC power supply (e.g., supply 20) so that it may be
independently energized to create a resultant magnetic field.
Further, in accordance with the disclosure herein, the magnetic
field flux lines 80 (and Dead Zones 70) may be created using two
sets of brushes per stator winding (e.g., brush 304 and brush 306)
so that at any given time a portion of the stator coils are
energize with one polarity (e.g., positive) and the other portion
are energized with the opposite polarity (e.g., negative).
Likewise, by turning off the power to, and electrically isolating,
a specific coil group, a rotating Dead Zone 70 may be created in
accordance with the principles outlined herein.
 Control of the switching of the various power cycles for
the coils 50 may be achieved in any suitable manner. For example,
an electronic control circuit may be implemented to give separate,
customizable control over the energizing of each coil 50. For
example, a controller 90 housing appropriate control circuitry as
shown in FIG. 1 may optionally be provided for some embodiments
where electro-mechanical commution is undesirable. An exemplary
control circuit is disclosed in the concurrently filed co-pending
application Ser. No. ______, titled “Controller For Toroidal Motor
Having Back EMF Reduction,” which is hereby incorporated by
reference in its entirety.
 As shown in FIG. 8, some embodiments may comprise a brush
holder ring 302 with active brushes (e.g., 304 and 306) for
providing the appropriate polarity of current in each coil 50.
Likewise, four slip-rings, or other slidable contacts 308 and 310
are provided (in pairs of two) in order to provide input power to
the active brushes and to harvest recaptured power. A shaft 312
may be provided to turn the slidable contacts 308, 310, as well as
the mating conductor (not visible in FIG. 8) for the brushes 304,
 FIG. 9 shows a perspective view of a rotating switch for
use with the brush holder ring 302 of FIG. 8. As shown, a
non-conducting disk or wheel 314 may be provided as support to a
number of conducting ring segments 316, 318, 319 and 320. While
four rings ( 316, 318, 319, 320) are shown in FIG. 9, more could
be implemented for embodiments that require more than two poles or
additional pairs of polarities of input current. Ring 316 and 318
mate with the brushes 304, 306 in brush holder ring 302 and
complete the electrical contact to supply input power to the coils
 For some embodiments, rings 316 and 318 may be formed into
additional segments as indicated at 319, 320 so that materials of
different conductivity can be inserted to add additional control
over the energizing of the coils 50. For example, non-conducting
segments could be used to turn off brushes 304, 306 and create a
Dead Zone 70 in the magnetic field of the coils 50. Other
configurations are also possible.
 FIG. 10 shows a side view of a brush holder ring 302 of
FIG. 8 and also shows the conductors 322 that power the coils 50.
For the embodiment shown, conductors 322 may comprise two separate
conductors (for each independently powered coil 50 of the toroidal
stator 44). Of course, other configurations are also possible.
 For some embodiments, parallel configuration of the
toroidal stator 44 enables fine tuning and customization of the
resultant magnetic field, the Dead Zones 70, and the relative
motion of both. In such a manner, it is possible to customize or
adapt the motor 10 operative characteristics to suit the intended
use, environment, or other parameters. Such control parameters may
employ high speed adjustments made by micro-processors imbedded
within the electronic control circuitry of controller 90.
 The torque and speed characteristics of the motor disclosed
here-in are quite straight forward. Because there is little or no
Back EMF, the torque is proportional to the applied current
regardless of the angular speed. The RPM is dependent upon the
effectiveness of the switching frequency, which controls the
movement from one coil 50 set to the next. Accordingly, the
inductive reactance of the individual coil 50 windings become a
limiting factor where speed is concerned, as said reactance will
impede or limit the rise time of the magnetic field for a given
voltage selection. However, this impedance becomes a matter of
engineering design choice because of the effects which are brought
to bear by the toroidal coil 50 windings.
 The geometry of the toroid 40 tends to create a condition
which is very natural to the confinement of a magnetic field. This
property may be exploited by running the flux 80 density up close
to saturation, which not only produces high torque in the rotor
46, but which also drives down the inductive reactance of the coil
50 windings in much the same way as experienced in a saturable
reactor. One result of applying this concept may be the approach
of the coil 50 windings to a pure resistive impedance as the flux
80 density approaches saturation, and an associated diminution of
the coil 50 rise-time. Therefore, as impedance (Z) approaches
resistance (R) in value, the time (t) will become very small, and
allows switching speeds of a very high order indeed and will
produce a substantially square wave current in the windings.
 Such an arrangement also allows for reasonably constant
torque at any current setting, with current (I) being limited
mostly by the value of resistance (R), and a variable speed
function which will support a wide range of angular speeds and
high values of acceleration. Under such conditions, the shaft
horsepower is substantially linear at a given value of current,
with angular velocity being the independent variable. Thus, a
graph of shaft horsepower versus RPM is expected to be almost
linear in nature.
 Although inductive reactance is greatly reduced by the use
of controlled saturation of the back iron, it cannot be eliminated
completely, especially when lighter torque settings are arranged.
Accordingly, where there is inductance (L) and current (I), there
will be stored energy (E) in keeping with the relationship E=1⁄2LI
<2>. Therefore, when coil 50 windings collapse their
magnetic fields at the start of each Dead Zone 70, the stored
field energy will be converted back into electrical energy in very
short intervals of time, and provisions preferably exist to
contend with this recaptured power, such as those described and
 In various embodiments where electro-mechanical commutation
is employed, the recapture feature (e.g., energy recapture 100,
FIG. 1) may be handled by the active, switching brushes (e.g.,
39), and their connections to the outside world via the slip-ring
assemblies (e.g., 34, 33). However, in one embodiment of an
electronically controlled motor of toroidal design, the recapture
function 100 may be achieved by fly-back diodes supplied as part
of the controller 90 circuitry. But, in both cases, the reclaimed
energy may be stored in a separate capacitor bank, or other
storage device, and may be used either for powering a load
external to the motor proper, or actually fed back to the motor
input circuit (e.g., 20) where it can be used to lessen the power
demand from the main line supply.
 As also shown in FIG. 1, embodiments of the controller 90
may also communicate with a recaptured energy system 100. The
concepts of recapturing energy from the collapse of the magnetic
flux 80 fields in each coil 50, has been previously disclosed in
co-pending application Ser. No. 13/562,233, titled “Multi-Pole
Switched Reluctance D.C. Motor with a Constant Air Gap and
Recovery of Inductive Field Energy,” which is hereby incorporated
by reference in its entirety.
 In brief, each collapsing flux 80 field in coil 50 produces
an electrical output pulse which represents the re-captured field
energy. These pulses may be then directed by the controller 90 to
a recaptured energy system 100, and then may be stored, for
example, in a capacitor bank or other storage that comprises part
of recapture system 100. In some embodiments, energy from this
recapture system 100 could be removed if desired, and used to
supply power to external appliances (not shown).
 In some embodiments, recapture system 100 may operate in
“Open System Operation,” which means that energy recaptured from
the motor's inductive components during its operation, will be
applied to a capacitive storage element, and then utilized to
supply power to some electrical load external to the motor itself,
such as a lamp, a resistor, a pump, etc. Of course, any suitable
external load may be powered in this manner.
 Likewise, power inverters or other devices can be used to
convert the recaptured power to alternating current (AC).
Unconverted direct current (DC) power from recapture system 100
may be used to power DC loads. Other configurations of Open System
Operation are also possible.
 In addition, some embodiments may be designed for “Closed
System Operation,” which means that energy recaptured from the
motor's inductive components during its operation, may be applied
to a capacitive storage element in recapture system 100 and then
utilized to send power back to the motor power supply by means of
a DC to DC converter operating in conjunction with an electronic
feedback controller, or the like. Other configurations of Closed
System Operation are also possible.