WO2023099934A1

WO2023099934A1 - An electric motor with a winding configuration

Info

Publication number: WO2023099934A1
Application number: PCT/IB2021/061098
Authority: WO
Inventors: Geoffrey Kwananga MKANDAWIRE
Original assignee: Mkandawire Geoffrey Kwananga
Priority date: 2021-11-30
Filing date: 2021-11-30
Publication date: 2023-06-08

Abstract

An electric having a special winding configuration motor includes a rotor and a stator, the rotor configured to rotate relative to the stator. The rotor defines 2⋅n poles, where n is an integer ≥ 1 and the stator defines 2⋅n⋅k teeth, where k is an integer ≥ 2, the teeth being interspaced by slots. The motor includes a winding configuration comprising a plurality of windings with two windings, namely a first winding and a second winding, being associated with each of the teeth. The first winding of an m th tooth, where m = 1...2⋅n⋅k, is connected in series with the second winding of an m+k th tooth to form a series circuit, there thus being 2⋅n⋅k series circuits. The series circuits spaced k teeth apart are connected in parallel to form a parallel circuit, there thus being k parallel circuits. k pairs of electrical conductors are connected respectively to the k parallel circuits provided for connection to control circuitry.

Description

An Electric Motor with a Winding Configuration

FIELD OF INVENTION

This invention relates generally to electric motors, and it relates more specifically to a winding configuration for stators of electric motors.

BACKGROUND OF INVENTION

The Applicant is aware of various existing winding configurations, including concentrated windings, lap windings, wave windings, etc. To some degree, the windings define the motor functionality. All these windings go around a circumference of the rotor or stator, usually around teeth of the stator defined at in inner circumference of the stator.

The windings are commonly configured in accordance with a number of poles of the motor. An 8-pole motor having 24 slots/teeth may have individual slots centred (at a given moment) with each one of the eight respective poles. The pole centres will cycle or revolve around the circumference as the rotor rotates. Regardless of the winding type, it is usually configured to effect opposite polarity at adjacent poles. Four the 8-pole motor, there should be four north poles and four south poles at a given moment.

The switching of the polarity of poles is also well-established in the technical art of motors. Brushes may be provided to slide along commutator segments (in a brushed configuration). Brushless configurations also exist in which the polarity of the poles is controlled by more advanced, e.g., control circuitry, usually as a function of rotor position. However, such control circuity is also usually heavily depending on the winding configuration.

The Inventor desires an improved winding configuration which may permit construction of larger motors or stronger motors (e.g., having improved torque and better speeds).

SUMMARY OF INVENTION

The invention provides an electric motor which includes: a rotor; a stator, the rotor configured to rotate relative to the stator, wherein: the rotor defines 2-n poles, where n is an integer > 1 ; and the stator defines 2-n-k teeth, where k is an integers 2, the teeth being interspaced by slots, and a winding configuration, comprising a plurality of windings with two windings, namely a first winding and a second winding, being associated with each of the teeth, wherein: the first winding of an m^th tooth, where m = 1 ...2-n-k, is connected in series with the second winding of an m+k^th tooth to form a series circuit, there thus being 2-n-k series circuits; and the series circuits spaced k teeth apart are connected in parallel to form a parallel circuit, there thus being k parallel circuits, and k pairs of electrical conductors connected respectively to the k parallel circuits provided for connection to control circuitry. As is conventional with stators, the teeth are arranged in a ring, and it will be understood that counting of the teeth wraps around the stator. In other words, if there are 12 teeth, and reference is made to the 14^th tooth, this is the 2^nd tooth (14-12=2).

Something that will be noted is that the number of pairs of conductors (k) which exit the motor itself for connection to the control circuitry decreases inversely to the number of poles (2-n) when the number of teeth stays constant. This means that a 2- pole, 12-tooth motor has more pairs of conductors (specifically, 6) then a 4-pole, 12- tooth motor (3 pairs of conductors). This is highly unusual in itself.

The series connected windings (that is, the first winding of the m^th tooth and the second winding of the m+k^th tooth) may be oppositely orientated such that one (e.g., the first winding) will, in use, produce a first polarity (e.g., N) and the other (e.g., the second winding) will produce a second, opposite polarity (e.g., S).

Each of the windings may be in the form of a concentrated coil winding.

The windings may comprise or form part of an armature of the motor.

The motor may be a brushless motor. The motor may be a DC motor. The motor may be a brushless DC (BLDC) motor:

The windings may be configured to receive a current - in accordance with the winding configuration - to drive the rotor.

The k pairs of electrical conductors may be controlled or energised independently of each other. The k pairs of electrical conductors may be controlled or energised dependent on a rotational position of the rotor. The motor may be configured to run at a higher speed than a comparable conventional motor having the same number of poles and teeth.

Conceptually, the motor may be considered to define a plurality (more particularly, k) motor circuits from the electrical conductors. Torque provided from the motor circuits may be additive.

It will be noted that the windings (be it the first winding or the second winding) of a given tooth (say, the k^th tooth) may be independent of the windings (be it the first winding or the second winding) of an adjacent tooth (the k-1^th tooth or the k+1^th tooth).

The motor may include conductive tracks or paths outside (that is, radially outwardly of) the stator. The tracks may connect the respective series circuits in parallel. Accordingly, there may be k pairs of tracks, a track for each one of the k pairs of conductors exiting the motor. The tracks may extend circumferentially around the stator, e.g., being mounted to a motor frame which supports the stator.

The control circuitry may be configured to (e.g., switch) polarities of the windings based on a rotational position of the rotor. The control circuitry may include, or may be connected to, a position sensor configured to provide an indication of the rotational position of the rotor.

The control circuitry may be as described, or may include features described, in WO2016207700, particularly FIGS13-15 and their supporting descriptions. More specifically, FIGS 14-15 mention that two or more of these sensing arrangements (as sets) could be affixed to the rotor. There may be k sets of sensing arrangements. BRIEF DESCRIPTION OF DRAWINGS

The invention will now be further described, by way of example, with reference to the accompanying diagrammatic drawings.

In the drawings:

FIG. 1 shows a schematic view of a first embodiment of an electric motor in accordance with the invention, having a winding configuration with only half of the windings illustrated;

FIG. 2 shows a schematic view of the electric motor of FIG. 1 with the other half of the windings illustrated;

FIG. 3 shows a schematic view of a second embodiment of an electric motor (with windings only partially illustrated) in accordance with the invention; and

FIG. 4 shows a schematic view of a third embodiment of an electric motor (with windings only partially illustrated) in accordance with the invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENT

The following description of an example embodiment of the invention is provided as an enabling teaching of the invention. Those skilled in the relevant art will recognise that changes can be made to the example embodiment described, while still attaining the beneficial results of the present invention. It will also be apparent that some of the desired benefits of the present invention can be attained by selecting some of the features of the example embodiment without utilising other features. Accordingly, those skilled in the art will recognise that modifications and adaptations to the example embodiment are possible and can even be desirable in certain circumstances and are a part of the present invention. Thus, the following description of the example embodiment is provided as illustrative of the principles of the present invention and not a limitation thereof. FIGS 1 -2 illustrate a first embodiment of an electric motor 100 in accordance with the invention. These FIGS illustrate a schematic cross-sectional view of the motor 100. Features in the FIGS may not be to scale as they are intended to illustrate the conceptual principle rather than practicable dimensions.

The motor 100 has a rotor 102 and a stator 104. The rotor 102 may be relatively conventional and need not be modified to function with the motor 100; however, its dimensions may be tailored to the stator 104, e.g., by being enlarged. The rotor 102 is mounted to rotate about an axis of rotation within the stator 104; the stator 104 thus being arranged radially around, or outwardly of, the rotor 102. The motor 100 may include many features germane to motors which are not illustrated, e.g., bearings, support frame, etc. but will nonetheless be understood to be part of, or supplemental to, the motor 100.

The rotor 102 defines pairs of poles (north (N) and south (S)) and therefore has an even number of poles; more specifically, the rotor defines 2-n poles, where n is an integer s 1. In this example, n=2 and the rotor 102 defines four poles P1...P4. Their polarity is alternating (e.g., N, S, N, S) but otherwise arbitrary. The rotor 102 may be a permanent magnet rotor.

The stator 104 defines a number (2-n-k) of teeth 106 related to the number of poles of the rotor 102, but a factor (k) greater. In this example, k=2 and there are therefore 8 teeth 106, respectively labelled as T1...T8. The labelling convention of the teeth 106 is arbitrary and could start at any tooth and go in either direction, but in this example, it starts at the top tooth T 1 and goes clockwise. The teeth 106 are interspaced by slots 108 and mounted to an annular stator body 110 (sometimes referred to as a back-iron). Again, a physical structure (e.g., teeth 106, slots 108, and body 110) of the stator 104 may be similar to prior art stators; however, it may be sized and dimensioned differently. Importantly, the motor 100 has a winding configuration which is relevant to this disclosure. Referring first to FIG. 1 , each tooth 106 has two windings 120, 130, namely a first winding 120 and a second winding 130, coupled thereto. The naming order of the first and second windings 120, 130 is arbitrary but, in this example, the first winding 120 is closer to the stator body 110, that is, radially outwardly of the second winding 130 which is closer to the rotor 102; however, this could be the other way around. Each winding 120, 122, 130 may comprise a plurality of coils; the coils themselves are not necessarily germane to this disclosure.

In accordance with the disclosure, the first winding 120 of any given tooth 106, say an m^th tooth, where m = 1 ...2 n k (or 1 ...8 for this stator 104) is connected in series with the second winding 122 of an m+k^th tooth to form a series circuit. This is illustrated schematically in FIGS 1 -2; the solid and dotted lines do not illustrate different structural features but are merely used to distinguish between different sets of windings, to avoid the FIGS becoming too cluttered.

As shown in solid lines, the first winding 120 of tooth Ti is connected in series by a conductor 124 to the second winding 122 of tooth T3. These teeth (T1 and T3) are spaced 2, or k, teeth apart. This connection forms a first series circuit.

Moving around the stator 104 by two teeth in a clockwise direction, a first winding of tooth T3 is connected in series to a second winding of tooth Ts as shown in dotted lines. This forms a second series circuit. This continues for a first winding of tooth Ts connected to a second winding of tooth T7 (solid lines) for a third series circuit and a first winding of tooth T7 connected to a second winding of tooth T1 (or tooth T9 as the numbering wraps around) in dotted lines for a fourth series circuit.

These four series circuits are connected to each other in parallel by means of a pair of tracks 140 provided around, or radially outwardly of, the stator 104. Each series circuit has a pair of leads (labelled as leads 126, 128 in the first series circuit) which connect to respective tracks 140; this forms the first parallel circuit. The electrical tracks 140 are connected to a pair of electrical conductors or terminals 142 for connection to control circuitry (not illustrated). Again, the broken line format of the tracks does not convey any particular technical meaning but rather is used to distinguish the tracks 140 from each other and from other parts of the motor 100.

Referring now to FIG. 2, a second parallel circuit is illustrated. It works on the same principle as that of FIG. 1 , just offset by one tooth, to provide a second parallel circuit. The windings of FIGS 1 -2 are both present together, but are merely separated into two FIGS for clarity of illustration; accordingly, the motor 100 comprises the windings of FIGS 1 -2 superimposed on each other, although the various circuits are separate.

To note from FIG. 2 is that there is a second set of tracks 150 (electrically separate from the first set of tracks 140) which produce a second pair of electrical conductors 152. Accordingly, there are eight (2-n-k =2-2-2) series circuits (four in FIG. 1 and four in FIG. 4) grouped respectively into two (k=2) parallel circuits (one in FIG. 1 and one in FIG. 2), culminating in 2 (k=2) pairs of electrical conductors 142, 152. Each parallel circuit will have 2-n (2-2=4) series circuits.

The k pairs of electrical conductors 142, 152 may then be connected to control or drive circuitry and may be controlled or driven independently of each other. However, the parallel circuits may be controlled based on related criteria, for example, rotational position of the rotor 102 as determined by the control circuitry; thus, their control may be related or synchronised.

The windings of a parallel circuit may be configured to produce opposite polarities in alternating teeth of that parallel circuit. More specifically, referring to the first parallel circuit of FIG. 1 , at a given moment, the teeth 106 may be as follows (due to a current in the windings of that parallel circuit):

The winding configuration of a given parallel circuit provides that alternating teeth 106 in that circuit will have opposite polarities. For the stator 104 as a whole, then, the winding configuration may ensure that teeth 106 spaced k (2, in this case) teeth apart have opposite polarities.

This is exhaustively described as:

1 ^st parallel circuit (illustrated in FIG. 1 ) =

1 ^st series circuit = 1^st winding of Ti + 2^nd winding of T3;

2^nd series circuit = 1 ^st winding of T3 + 2^nd winding of Ts;

3^rd series circuit = 1 ^st winding of Ts + 2^nd winding of T7; and

4^th series circuit = 1^st winding of T7 + 2^nd winding of T1, and

2^nd parallel circuit (illustrated in FIG. 2) =

1 ^st series circuit = 1^st winding of T2 + 2^nd winding of T

2^nd series circuit = 1 ^st winding of T4 + 2^nd winding of Te;

3^rd series circuit = 1 ^st winding of Te + 2^nd winding of Ts; and

4^th series circuit = 1^st winding of Ts + 2^nd winding of T2.

FIG. 3 provides another example of a motor 200 with a different rotor 202 in that it only has two poles Pi, P2 and thus n=1 . As there are still eight teeth (as in FIGS 1 - 2), however, k=4 in this motor 200. A notable difference in the winding configuration is that there will now be fewer, that is, only two (2-n=2-1 =2), series circuits per parallel circuit and more, that is, four (k=4), parallel circuits. The same or similar numerals amongst the FIGS may relate to the same or similar features.

Consequently, there will be four (k=4) sets of electrical conductors 140... emanating from the motor 200. Accordingly, and perhaps counterintuitively, as the number (n) of poles decreases for a fixed number of teeth 106 (12 in FIGS 1 -3), the number of conductors 142, 152 exiting the motor 100 increases.

Once again, the windings of a parallel circuit may be configured to produce opposite polarities in alternating teeth of that parallel circuit. More specifically, referring to the first (and only illustrated) parallel circuit of FIG. 3, at a given moment, the teeth 106 may be as follows:

There will be an additional three parallel circuits (not illustrated) each comprising two series circuits, as follows:

1 ^st parallel circuit (illustrated in FIG. 3) =

1 ^st series circuit = 1^st winding of Ti + 2^nd winding of Ts; and

2^st series circuit = 2^nd winding of Ti + 1^st winding of Ts_;

2^nd parallel circuit =

1 ^st series circuit = 1^st winding of T2 + 2^nd winding of Ts; and

2^st series circuit = 2^nd winding of T2 + 1^st winding of Te_;

3^rd parallel circuit =

1 ^st series circuit = 1^st winding of T3 + 2^nd winding of T7; and

2^st series circuit = 2^nd winding of T3 + 1^st winding of T7, and

4^th parallel circuit =

1 ^st series circuit = 1^st winding of T4 + 2^nd winding of Ts; and

2^st series circuit = 2^nd winding of T4 + 1^st winding of Ts.

FIG. 4 provides another example of a motor 300, but scaled up so that its rotor 102 has four poles (n=2 and there are 2 n=2-2 poles) and its stator 304 has 12 teeth 306 (k=3 and there are 2-n-k= 2-2-3 teeth). The poles are labelled as P1...P4 and the teeth 306 are labelled as T1... T12.

FIG. 4 is reminiscent of FIG. 1 except that the series circuits are now spaced three (k=3) teeth apart. The winding configuration will be as follows:

1^st parallel circuit (illustrated in FIG. 4) =

1^st series circuit = 1^st winding of T1 + 2^nd winding of T

2^nd series circuit = 1 ^st winding of T4 + 2^nd winding of T7;

3^rd series circuit = 1^st winding of T7 + 2^nd winding of T10; and

4^th series circuit = 1^st winding of T10 + 2^nd winding of T1,

2^nd parallel circuit =

1^st series circuit = 1^st winding of T2 + 2^nd winding of T5;

2^nd series circuit = 1 ^st winding of Ts + 2^nd winding of Ts;

3^rd series circuit = 1^st winding of Ts + 2^nd winding of T11; and

4^th series circuit = 1^st winding of T11 + 2^nd winding of T2, and

3^rd parallel circuit =

1^st series circuit = 1^st winding of T3 + 2^nd winding of Te;

2^nd series circuit = 1 ^st winding of Te + 2^nd winding of T9;

3^rd series circuit = 1^st winding of T9 + 2^nd winding of T12; and

4^th series circuit = 1^st winding of T12 + 2^nd winding of T3.

The polarity (at a particular moment) from the 1^st parallel circuit may be:

The Applicant believes that the invention as exemplified may include one or more of the following advantages:

1 . With Hall sensors (as may be used in prior art motors), start-up is not always smooth and sometimes the motor fails to start. These limitations of Hall using position sensors combined with the availability of powerful and economical microprocessors have spurred the development of sensorless control technology. There is one major disadvantage to sensorless BLDC motor control: when the motor is stationary, no back EMF is generated, depriving the MCU (Motor Control Unit) of information about the stator and rotor position. On the brushed motor side, the commutator poses serious limitation on the speed large motors can attain as high speeds can damage, even, shatter the commutator segments assembly. As the dimensions of the motor increase, the size commutator assembly also increases and thus necessitating lowering of speed. In addition, brushes increase losses and friction. The advantage of the motor 100, 200, 300 in accordance with the present invention is that the motor is able to start at all times and positions. There is no complex algorithms. The control systems presented in WO2016207700 can be fitted to any size of motor and does not need MCUs and simply controls DC power supply without need to convert to AC as in Hall sensors and sensorless systems.

2. Another advantage is that the speed of the motor 100, 200, 300 is not limited by the frequency of the power supply and the number of the poles as in BLDC motors or the size of the commutator segment assembly as in brushed DC motors. Thus, according to this invention even large multi-pole motors are able to attain high speeds.

3. Having the armature (comprising the various windings) mounted on the stator 104 provides better cooling as opposed to brushed motors which have the armature on the rotor where it is difficult to dissipate the heat. The advantage of this invention is that even large motors will benefit from this cooling advantage.

4. The presence of the windings forming separate parallel circuits as independent units in this invention enables better parameter selection for optimal factors in designs for torque, loss minimisation, and motor speed. It should be clearly seen that better cooling in large motors with higher speeds implies the motor is able to carry higher power densities than the conventional motors. 5. Although permanent magnet DC motors are also built with poles, these poles do not impact speed like with AC motors because there are several other factors in play with DC motors. The number of wire turns in an armature, the operating voltage of the motor, and the strength of the magnets all affect motor speed. However, in the present invention, the presence of unit circuits is also amenable to enabling the motors run on higher flux densities and better speeds than would be practical in the conventional motors. This is because by design the back electromotive forces are not additive.

6. Back electromotive forces (EMFs) are not additive and so are circuit resistances The increase in the number of poles affects the circuit units individually and independently but strengthens the torque of the motor.

Claims

CLAIMS What is claimed is:

1. An electric motor which includes: a rotor; a stator, the rotor configured to rotate relative to the stator, wherein: the rotor defines 2-n poles, where n is an integer > 1 ; and the stator defines 2-n-k teeth, where k is an integers 2, the teeth being interspaced by slots, and a winding configuration, comprising a plurality of windings with two windings, namely a first winding and a second winding, being associated with each of the teeth, wherein: the first winding of an m^th tooth, where m = 1 ...2-n-k, is connected in series with the second winding of an m+k^th tooth to form a series circuit, there thus being 2-n-k series circuits; and the series circuits spaced k teeth apart are connected in parallel to form a parallel circuit, there thus being k parallel circuits, and k pairs of electrical conductors connected respectively to the k parallel circuits provided for connection to control circuitry.

2. The electric motor as claimed in claim 1 , in which the series connected windings (that is, the first winding of the m^th tooth and the second winding of the m+k^th tooth) are oppositely orientated such that one will, in use, produce a first polarity and the other will produce a second, opposite polarity.

3. The electric motor as claimed in any one of claims 1 -2, which is a brushless motor.

4. The electric motor as claimed in any one of claims 1-3, which is a DC motor.

5. The electric motor as claimed in any one of claims 1 -4, in which the k pairs of electrical conductors are controlled or energised independently of each other.

6. The electric motor as claimed in claim 5, in which the k pairs of electrical conductors are controlled or energised dependent on a rotational position of the rotor.

7. The electric motor as claimed in any one of claims 1 -6, which is considered to define a k motor circuits from the electrical conductors and in which torque provided from the motor circuits is additive.

8. The electric motor as claimed in any one of claims 1 -7, in which the windings of a given k^th tooth are independent of the windings of an adjacent k-1^th tooth or k+1^th tooth.

9. The electric motor as claimed in any one of claims 1 -8, which includes conductive tracks or paths outside the stator, the tracks configured to connect the respective series circuits in parallel.

10. The electric motor as claimed in claim 9, in which there are k pairs of tracks, a track for each one of the k pairs of conductors exiting the motor.

11. The electric motor as claimed in any one of claims 9-10, in which the tracks extend circumferentially around the stator and are mounted to a motor frame which supports the stator.

12. The electric motor as claimed in any one of claims 1 -1 1 , in which the control circuitry: - 16 - is configured to control polarities of the windings based on a rotational position of the rotor; and includes, or is connected to, a position sensor configured to provide an indication of the rotational position of the rotor.