Technical Field

The invention relates to an electrical motor and more particularly to an outrunner permanent magnet synchronous motor with laminated high-performance hybrid composites yoke, fractional-slot concentrated windings, integrated gear system and control electronic.

State of the art

Electric motors are electromechanical machines which are used to convert electric energy into mechanical energy and, more precisely, into rotational mechanical energy. Electric motors are widely used in terrestrial, industrial, home, marine and space applications just to mention a few fields of use. Electric motors are very different in their architecture and manufacturing characteristics which are mainly dictated by their fields of use as well as their durability and target selling price.

One of the characteristics that all electric motors are trying to maximize is their ability to convert electric energy into mechanical energy, the so-called motor efficiency conversion rate. The higher the efficiency conversion rate of the electric motor, the higher the mechanical energy transformed from electric energy will be. The higher the efficiency conversion rate of the electric motor the less electric energy is required to provide a given amount of mechanical energy. The higher the efficiency conversion rate of the electric motor the less heat will be generated within the motor itself which finally lead to the possibility to manufacture powerful motors in a smaller volume. The possibility to manufacture smaller motors has a direct impact on the motor manufacturing costs as less material is required to manufacture the electric motor.

The ability for an electric motor to deliver high mechanical power outputs within a small volume and at high efficiency conversion rates is a key differentiator for a lot of applications and more specifically for transportation applications. As an example, an electric car that uses less electrical energy to cover a given distance need to carry less batteries and therefore will be lighter and cheaper compared to an electric car that uses a lower efficiency conversion rate electric motor.

The electric motor’s electrical to mechanical energy conversion can be achieved by a multitude of electro-mechanical techniques. The vast majority of those techniques relies on a rotating element, called rotor, which rotates around a fix element of the electric motor which is called the stator. The rotor is forced to move around the stator by magnetic forces. Those magnetic forces are generated by an interaction between magnetic fields located on the stator and magnetic fields located on the rotor of the electric motors. Those magnetic forces can be generated by magnetic attraction or magnetic repulsion or a combination of the two forces. The correct synchronization of the magnetic fields on the stator and on the rotor allow the magnetic forces between the stator and the rotor to spin the rotor in a controlled movement. The rotor is generally connected to the electric motor shaft which deliver the rotational mechanical force to the final user.

The magnetic fields on the stator are most commonly generated by electricity flowing through coils which are fixed to the electric motor stator itself. The magnetic fields on the rotor side can be generated by electricity flowing through coils or by using permanent magnets which do not need electricity to generate the magnetic fields. The correct placement and activation of the electric fields generate magnetic forces that spins the rotor around the stator.

A review of the working principle of a synchronous motor can be for example reviewed at the following link: https://en.wikipedia.org/wiki/Synchronous_motor.

State of the art permanent magnets synchronous motors can be found on both inrunner and outrunner configurations, with the latter widely used for airplanes or drone applications, due to its ability to generate large torque at lower speeds, and the former largely used for automotive applications due to its ability to rotate at higher speeds.

Inrunner and outrunner permanent magnet synchronous motors are based on a round rotor structure with permanent magnets attached to it as well as a stator element with coils attached to it. Inrunner and outrunner motors are described in the following internet site: htps://www.magneticinnovations.com/faq/outrunner-motor/.

A synchronized AC current flows through the stator coils and the generated magnetic fields interact with the rotor permanent magnet’s magnetic fields in such a way that the rotor spins around the stator. The permanent magnets are generally dipole magnets with one magnetic pole oriented toward the inner surface of the rotor and the other magnetic pole oriented toward the coils fixed to the stator.

In order to increase the strength of the magnetic field toward the coils fixed to the stator, and therefore the mechanical power delivered by the electric motor, two adjacent dipole magnetic poles are channeled together by a ferromagnetic material which is generally the rotor yoke itself.

The use of a ferromagnetic material as rotor yoke manufacturing material has the advantage of increasing the magnetic field toward the motor’s coils fixed on the stator, and therefore increase the mechanical power delivered by the electric motor, but has the drawback of being heavy and add a considerable inertia to the electric motor itself which reduces its ability to rapidly accelerate or decelerate as well as limiting the choice of materials to be used to manufacture the rotor yoke itself. Nowadays, high-power motors with high torque are manufactured to be directly coupled with the drive axle through a series of external gear systems. The specific request of a passengers or good transportation vehicle, which requires to provide high torque at low speeds and low torque at high speeds, requires a motor that it’s able to work within a large spectrum of speeds and torques.

As of today, existing systems typically runs at 40% of their maximum speed and 60% of their maximum torque and as a result, and in order to meet the vehicles requirements, the motors rarely work at high efficiency rates which results in large power losses.

Improving urban mobility is crucial to the sustainable development of a city. Well- managed movement of individuals, goods, and services is essential to increase citizens’ welfare, not only by reducing travel times and congestion levels, but also by minimizing air pollution and noise.

Light electric vehicles are seeing a sharp adoption rate increase as those vehicles can solve many of our current city problems. However, there is currently a lack of a simple, light, and compact high-power electric motor with great overall performance and durability dedicated to this market segment. Generally, current small transportation vehicles use electric motors which have low power and use old battery technology. As a result, they are limited to a speed of 25 - 45 km/h, have short ranges and high maintenance costs.

One of the limitations of prior art motors is that they do not comprise an internal gear system, which can extend the torque and speed operation spectrum of the motors, because the vast majority of available solutions uses induction motors which are in runner electric motors and do not have the physical space to integrate a gear system without adding extra weight and volume to the motor itself.

There is therefore a need for an improved and more efficient outrunner motor with integrated gear system to solve the problems presented by prior art motors.

Summary of the invention

It is the aim of this invention to provide an improved electrical motor that solves the limitations of prior art motors. The motor of the invention is particularly well adapted for electrical transport systems such as electrical bicycles, motorcycles, mopeds, cars, trucks, airplanes, drones, rockets, ships and robotic systems that features a rotor yoke that is, at least partially non-ferromagnetic, and to which or in which a Halbach array is arranged. The advantage of using non ferro-magnetic materials to manufacture the rotor yoke is the reduction in weight of the electric motor assembly as well as the reduction in inertial momentum of the motor which yields to faster accelerations and decelerations of the electric motor shaft and also has the potential to reduce the manufacturing costs. In a first aspect the invention relates to an outrunner motor comprising a rotor and a stator. The rotor comprises a rotor yoke having an inner wall that defines a central space being the rotor core defining a virtual central axis. Said yoke comprises on its surface or integrated or embedded inside its wall a plurality of magnetic elements. The plurality of magnetic elements define an inner surface to the side of said rotor core and an outer surface opposite. The stator is arranged in said rotor core.

Said plurality of magnetic elements consists in a number N1 of Halbach arrays. Each Halbach array comprises Halbach array portions. The Halbach arrays are arranged to said inner wall and each of said Halbach array provides a single magnetic pole having a magnetic field H1 that is higher to the side of said inner surface than to the side of said outer surface. The rotor yoke is made, at least partially, of a non ferromagnetic material for enhanced mechanical purposes.

The stator of the motor of the invention comprising a number N2 of slots being the hollow parts of the stator between the stator tooths. The number N2 of slots is equal to the number of stator tooths.

The motor of the invention can be configured to provide either a three-phase or two three-phase or a six-phase coil winding configurations on the stator. There is a number of N3 phases provided by the motor coil windings, in operation of the motor.

The motor of the invention is a fractional-slot motor, meaning that the Slot per Pole per Phase ratio (SPP), equal to the N2/N1/N3 ratio, is not an integer number. The fact that the ratio N2/N1/N3 is not an integer is an essential aspect of the motor of the invention. Preferably the ratio N2/N1/N3 is <1 .

The motor of the invention comprises a concentrated windings architecture. Concentrated windings refer to coil electrical connections in which the coils do not overlap. This has a significant advantage of reducing the axle length of the motor and lowering copper losses. It also has an increased slot fill factor and simplified manufacturing as compared to distributed windings which have coil electrical connections overlapping from one coil to another. Concentrated windings introduce increased electromotive forces harmonics and larger cogging torque, which can be optimized by fractional-slot distribution and skewing. The use of fractional-slot distributed windings generates lower cogging torque due to the elimination of periodicity between slot and poles, it also produces a more sinusoidal electromotive force waveform.

In existing outrunner motors there is no approach to minimize the cogging torque while maintaining a high electromotive force by using fractional-slot concentrated windings. The disclosed motor solve this issue and furthermore, the disclosed electric motor has an improved efficiency that is based on a Halbach array rotor configuration providing an optimized number of rotor poles, slots as well as an optimized number of phases.

In an embodiment, the number N1 of poles is greater than 2, preferably greater than 4, most typically 6, 8, 10, 12, 14 or 16.

In an embodiment, the number N2 of coils and thus equal number of teeth, or slots, is greater than 3, preferably greater than 6, most typically 9, 12, 15, 18, 21 or 24.

In an embodiment, the number N3 of phases is greater than 1 , most typically 3, 6 or 9.

In advantageous embodiments N2/N1/N3 is between 1/16 and 1/2, preferably between 1/8 and 1/2, more preferably between 2/7 and 2/5. In variants N2/N1/N3 is one of: 1/4, 2/7 or 2/5.

The motor of the invention has the following advantages compared to prior art electrical motors.

- it allows to provide a mechanical power that may be at least 3 times higher than the mechanical power of existing motors for the same motor volume.

- it can be up to 20% more compact and lighter and require 15% less permanent magnets to achieve the same torque density. - It can achieve a conversion efficiency rate of 93% over a large portion of the vehicle using conditions compared to a typical 65% to 85% of state-of-the-art motors.

- It has a lower cogging torque thanks to an SPP ratio that allows the frequency of the cogging torque to be raised and its magnitude to be lowered.

The motor of the invention provides a number of advantages and surprising performances such as:

- compared to a similar size motor of the state of the art, the disclosed invention allows up to 20% weight reduction and can be realized in powers ranging from 1 kW to 100 kW.

- it can achieve a much higher power to weight ratio (kW/kg) compared to state- of-the-art motors

- a power output of 10kW for 5 kg of weight may be achieved, which is equivalent to a power to weight ratio of 2kW/kg. State of the art motors typically shows a power to weight ratio of 0.4kW/kg.

- the motor has a longer lifetime compared to the state-of-the-art motors. The reason is that the lower cogging torque generates less vibrations and radial forces which ultimately reduces the damages on the bearings and increase lifetime. The outrunner motor of the invention can be started, accelerated, decelerated and stopped faster than the state of the art as the rotor yoke, at least partially made of non-ferromagnetic material, as well as the lower amount of permanent magnets required allow the rotor to have a lower inertial momentum and therefore achieve a faster speed of rotation rate change.

- the Halbach arrays of the outrunner motor 1 allows to manufacture the rotor yoke in non-ferromagnetic materials as well as using high volumes manufacturing techniques which are less expensive than state of the art manufacturing procedures. - the motor 1 has a slot fill factor of 60%, compared to the typical 30% of state- of-the-art outrunner motors. Also, because of the decrease of Joule losses it allows to achieve a higher efficiency conversion rate.

- the stator coils can be industrialized in large volumes without the need for a large conventional winding machine. Additionally, the manufacturing of the motor is simplified as the stator coils can be easily radially plugged onto the stator teeth or can be directly soldered to a compact control electronic which can be integrated into the motor. This improvement reduces the size and complexity of the installation of the motor of the invention in the vehicle.

- the motor of the invention requires less space and eliminates the intermediate cables between the motor and an external control electronic.

- - more affordable and sustainable permanent magnets may be used such as non-rare earths based permanent magnets more affordable and sustainable permanent magnets may be used such as non-rare earths based permanent magnets.

The stator winding of the outrunner motor of the invention may be realized according to a modular approach. This means that each coil may be produced individually on a separate mandrel, before adapting the coils to the teeth of the stator, which allows to modify the length and width of the coils, the cross section of the coil windings as well as the section of the wire used. It is therefore possible to easily design stator windings for different motor specifications.

In an embodiment, said rotor yoke is made at least partially of a material chosen among: glass fiber, carbon fiber, a high resistance polymer, an aluminum alloy, a titanium alloy, a steel alloy, iron, cobalt, nickel, brass, copper, organic fiber and inorganic fiber or a combination of them.

In embodiments, said high resistance polymer is one of: PEK, PEEK, PAI, PPSU, PPS, PSU, PES, PA, PC, PPA, PET, SPS, TPE, PBT, POM, PMMA, SAN, ABS, PP, PVC.

In an embodiment, said Halbach arrays have been magnetized before their fixation to said inner surface. In variants the Halbach arrays may be partially magnetized before their assembly and additionally magnetized after their assembly. The Halbach arrays may be magnetized entirely or at least partially after their fixation to said inner surface of the rotor yoke.

In advantageous embodiments said Halbach array portions may be individual magnetic elements made of AINiCo, NeFeBo, SMCO, Thulium oxides, or ceramic materials such as hard and soft Ferrites.

In an embodiment, said plurality of magnetic elements constitute at least two different Halbach array configurationss.

In an embodiment, the inner surface is a structured surface comprising cavities in which said Halbach arrays are arranged onto.

In an embodiment, Halbach arrays are separated by gaps that have a gap width WG, defined along a circumference of said inner surface, being smaller than the width W of one of said Halbach arrays.

In an embodiment, at least one inner layer of a ferromagnetic material is arranged to said inner surface and said Halbach arrays are realized inside said inner layer. Such inner layer of a ferromagnetic material may be a non-uniform layer and may have thicknesses that vary along its length aid inner layer of a ferromagnetic material may have a thickness between 0.1mm and 10mm, preferably between 3 and 7mm, more preferably between 4 and 6mm.

In an embodiment, said inner layer of a ferromagnetic material is made of a material chosen among: AINiCo, NeFeBo, SMCO, Thulium oxides or ceramic materials such as hard and soft Ferrites.

In an embodiment, a single magnetic ring may be used to form the Halbach arrays. This allows to improve the precision of the positioning of the plurality of the magnetic elements around the rotor yoke and eliminate the need to glue them individually. A single magnetic ring may be arranged on or in the inner surface of said rotor yoke and can be magnetized before or after it has been fixed onto the rotor yoke. The design of the rotor yoke may be adapted to integrate such a magnetic ring. In an embodiment, said single magnetic ring is made of a material chosen among: AINiCo, NeFeBo, SMCO, Thulium oxides or ceramic materials such as hard and soft Ferrites.

In an embodiment, said rotor yoke must not be a uniform yoke but may be composed of at least two longitudinal sections, defined in the length of said virtual axis, having a different arrangement of a plurality of magnetic elements. The advantage of a rotor yoke comprising said two sections is to make the system less noisy, it reduces the asynchronous Magnetomotive force (MMF) harmonics and reduces the motor’s torque ripple.

In an embodiment, the stator comprises a number N2 of slots equal to the number of stator teeth, each stator tooth located between two adjacent slots. The stator tooths have a virtual stator tooth axis oriented to the axis of the motor core, each of said stator tooth having a stator tooth base and a stator tooth tip said stator tooths comprising at their surface at least one coil having a smaller packing density to the side of the stator tooth bases than to the side of said stator tooth tops.

In an embodiment, said teeth and /or slots may have different cross section shapes. In variants, the stator tooth axes do not intersect with said virtual axis.

In an embodiment, the stator is made of a stack of layers, arranged on top of each other in the direction Z of said virtual axis. In an embodiment, said stack is a non- uniform stack having different types of layers.

In an embodiment, the inner surface of the stator defines weak magnetic field locations that face the base of each of said stator tooths.

In an embodiment, said inner surface comprises recesses that are located at said weak magnetic field locations, the shape of said recesses may be circular, or half circular, or square, or rectangular or triangular or a shape defined by a polynomial function or defined by at least one cross section of the 3D shape of the weak magnetic field fluxes. The advantage of providing recesses in the stator and/or in the rotor is to allow to introduce mechanical elements in the recesses, which allow to improve the torque transmission between the rotor and internal systems that may be arranged inside said stator such as a gear system.

In an embodiment, said recesses have an elongated shape in the direction of said virtual axis. In a variant, recesses are located on weak magnetic field locations of the stator.

In an embodiment, the outrunner motor comprises a gear system that is arranged, at least partially, inside said rotor core, and is linked by a mechanical link to said rotor. The advantage of using an integrated gear system is that the electric motor shaft can be directly coupled, for example, to a vehicle wheel via a single stage transmission without the need to add additional gear systems that will use space and add weight to the vehicle itself. Another advantage of using an integrated gear system is that the electric motor output torque will be multiplied by the gear system internal ratio and the electric motor will therefore require less electric energy to generate its torque. In advantageous variants, said mechanical link is a shaft key.

In an embodiment, said gear system is a planetary gear system. In an embodiment, the gear system is arranged, at least partially, onto the stator by one of the techniques consisting in: gluing, soldering, pressing or a combination of them. In advantageous embodiments, cooling pipes are arranged into said recesses.

In an embodiment, the outrunner motor comprising a printed circuit board to which the coils of the stator are connected. The advantage of integrating the control electronics in the electric motor is that the electric motor’s coils can be directly connected onto the control electronics board and reduce the electrical resistances and thus further increase the overall electric motor’s ability to convert electric energy into mechanical energy. In variants of execution said printed circuit board comprises a motor controller and/or motor control electronic.

In a second aspect the invention is also achieved by outrunner motor system comprising the outrunner motor as described, the system comprising an electrical power source wherein said printed circuit board is connected via cables to said electric energy source.

In embodiments the outrunner motor system may have a mechanical to electric power ratio of 2kW/kg and deliver 10kW mechanical power with a motor volume of less than 600 cubic centimeters. The invention is also achieved by an outrunner motor system comprising the outrunner motor and an electrical power source and wherein said Printed Circuit Board is connected via cables to said electric power source.

In another aspect, the invention is also achieved by a method of fabrication of the motor as described herein. The method comprises the steps (A-D) of:

A. providing a rotor yoke having an inner wall defining a central space being the rotor core defining a virtual central axis, the rotor yoke being made, at least partially, of a non-ferromagnetic material;

B. arranging to said rotor yoke, to the side of said rotor core, a plurality of magnetic elements consisting in a number N1 of Halbach arrays each array comprising Halbach array portions arranged to said inner wall, each of said Halbach arrays providing a single magnetic pole having a magnetic field H1 that is higher to the side of said inner surface than to the side of said outer surface;

C. arranging a stator, having an inner stator surface, in said rotor core;

D. adapting to said stator a plurality of electrical conducting coils so as to provide, in operation of the motor, a number N3 of electrical phases, the steps A-D being executed so the ratio N2/N1/N3 is not an integer.

In an embodiment, the method allows to provide a motor 1 that is realized according to a modular fabrication method. In such an embodiment the method comprises the steps of:

In an embodiment, the method comprises the steps (E-G) of: E. realizing each of said electrical conducting coils (30-4)1 on a mandrel so that a predetermined length of the wires of the coils, and/or shape and/or width and/or cross section of the coils is obtained;

F. arranging each of said electrical conducting coils (30-41) to the teeth of the stator (302-313);

G. arranging a control electronic board (500) to the motor (1 ) and connecting the coils to said electronic board (500) so that a number N3 of electrical phases may be provided to the motor (1).

Brief description of the drawings

The present invention will now be described in reference to the enclosed drawings wherein:

- Figure 1 shows an outer view of the electric motor of the invention;

- Figure 2 shows a 3D view of the outrunner motor according to the invention;

- Figure 3 shows a detail of a Halbach array comprising five Halbach array portions of which two provide a magnetic field in a plane defined by the Halbach array;

- Figure 4 shows a rotor yoke with an exemplary Halbach array arranged on the inside of the rotor yoke;

- Figure 5 shows a top view of the rotor yoke with an exemplary Halbach array arrangement on the inside of the rotor yoke;

- Figure 6 shows a top view of the rotor yoke with another possible Halbach array arrangement on the inside of the rotor yoke;

- Figure 7 shows a top view of the rotor yoke with a Halbach array arrangement realized in a layer that is arranged to the inside of the rotor yoke; - Figure 8 shows a top view of the rotor yoke with an exemplary Halbach array arrangement on the inside of the rotor yoke made of a stack of different layers;

- Figure 9 shows a top view of the rotor yoke with another possible Flalbach array arrangement on the inside of the rotor yoke made of a stack of different layers;

- Figure 10 shows a top view of the rotor yoke with a Halbach array arrangement realized in a layer that is arranged to the inside of the rotor yoke made of a stack of different layers;

- Figure 11 Shows a top view of the motor stator with the coils arranged to the stator tooths of the stator;

- Figure 12 shows a 3D view of the motor stator;

- Figure 13 shows a top view of the motor stator with the coils arranged to the stator tooths and an exemplary rotor surrounding the stator;

- Figure 14 shows a gear system arranged in the center of the electric motor stator;

- Figure 15 shows a gear system arranged in the center of the electric motor stator with a baseplate attached to the stator;

- Figure 16 shows a side view of the stator with the control electronic board attached to the coils;

- Figure 17 shows a possible stator coil design;

- Figure 18 shows the cross section of a rectangular coil configuration arrangement; - Figure 19 shows the cross section of a pyramidal coil configuration arrangement;

- Figure 20 shows an exploded view of the electric motor of the invention;

- Figure 21 illustrates a motor system comprising the motor of the invention and a power source connected to the motor.

Embodiments of the invention

The present invention will be described with respect to particular embodiments and with reference to certain drawings, but the invention is not limited thereto. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual reductions to the practice of the invention.

It is to be noticed that the term “comprising” in the description and the claims should not be interpreted as being restricted to the means listed thereafter, i.e. it does not exclude other elements.

Reference throughout the specification to “an embodiment” means that a particular feature, structure, or characteristic described in relation with the embodiment is included in at least one embodiment of the invention. Thus, appearances of the wording “in an embodiment” or, “in a variant”, in various places throughout the description, are not necessarily all referring to the same embodiment, but several. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to a skilled person from this disclosure, in one or more embodiments. Similarly, various features of the invention are sometimes grouped together in a single embodiment, figure, or description, for the purpose of making the disclosure easier to read and improving the understanding of one or more of the various inventive aspects. Furthermore, while some embodiments described hereafter include some features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and from different embodiments. For example, any of the claimed embodiments can be used in any combination. It is also understood that the invention may be practiced without some of the numerous specific details set forth. In other instances, not all structures are shown in detail in order not to obscure an understanding of the description and/or the figures.

A pair of two Halbach arrays 202 and 202’ herein defined as a magnetic cell FA that is repeated on a circumference of a rotor yoke 102.

Herein the Slot per Pole per Phase ratio (SPP) is also defined as the SPP value and is equal to a non-integer number equal to N2/N1/N3.

In a first aspect the invention relates to an outrunner motor 1 comprising a rotor 100 and a stator 300. The rotor 100 comprises a rotor yoke 102 having an inner wall 102b that defines a central space being the rotor core 101 defining a virtual central axis 103. Said rotor yoke 102 comprises on its surface or integrated or embedded inside its wall a plurality 200 of Halbach arrays 202, 202’. The plurality 200 of Halbach arrays 202, 202’ define an inner surface 200’ to the side of said rotor core and an outer surface 200” to the side of the rotor yoke 102. The stator 300 is arranged in said rotor core 101.

Said plurality 200 of Halbach arrays 202, 202’ consists in a number N1 of Halbach arrays. Each Halbach array provides a single magnetic pole. The total of magnetic poles by that Halbach arrangement on the yoke 100 is equal to the number N1 of magnetic poles. Fig.3 illustrates a typical Halbach cell FA comprising 2 Halbach arrays 202a-c, 202’a-c, having one Halbach element in common and providing each two magnetic poles H1.

In a preferred embodiment each of the Halbach arrays 202,202’ comprise an arrangement of at least three Halbach array portions 202a-c, 202’a-c that are repeated along a circumference of the rotor yoke 102. Each of said Halbach array portions have their magnetic pattern oriented differently in respect to their neighboring Halbach array portions. In said preferred embodiment a Halbach array portion 202a, 202a’ provides a central magnetic field to each of its sides. A Halbach cell FA may be defined also as two pairs 202a-c, 202’a-c of Halbach array portions that have one common central element 202a, 202a’. The at least three Halbach array portions 202a-202c, 202’a-202’c share at least one Halbach array portion, most typically the Halbach array portion that has its magnetic pattern aligned toward the rotor core 101. In variants, the central element 202a, 202a’ may have any magnetic pattern orientation.

In variants the plurality 200 of Halbach arrays may be a plurality of identical Halbach cells FA, such as illustrated in Fig.5, providing a plurality 200 of Halbach arrays having a geometric arrangement such as a series of identical magnetic cells FA: FA-FA-FA-FA, ..etc.

In variants, the plurality 200 of Halbach arrays may be a plurality of different magnetic cells. For example, a first type of magnetic cell FA may be followed by a second magnetic cell type FB to provide a series having a geometrical arrangement of the type FA-FB-FA-FB-FA., and so on. For example, in embodiments there may be two different magnetic cells of the type of Fig 3 or of a different type.

In variants, the plurality 200 of Halbach arrays may be a plurality of more than two different magnetic cells (FA, FB, FC) providing a geometric arrangement of the type FA-FB-FC-FA-FB-FC and so on.

In variants the plurality 200 of Halbach arrays may be a series of continuously different magnetic cells (FA, FB, FC, FD, FE, FG, etc..) providing a geometric arrangement of the type FA-FB-FC-FD-FE-FG- etc..

The at least three Halbach array portions 202a-202c and 202’a-202’c may be arranged inside a rotor yoke 102 or may be realized by magnetizing the rotor yoke 102 or a layer arranged onto the rotor yoke 102. The rotor yoke 102 is made, at least partially, of a non-ferromagnetic material. The stator 300 of the motor 1 of the invention comprises a number N2 of coils 30- 41. Each coil 30-41 is arranged, preferably, on a tooth of the stator.

The described motor 1 may be arranged with either a three-phase or two three- phase or a six-phase coil windings configuration on the stator 300. The number of phases N3 of the motor windings is related to the number of coils N2 and number N1 of Halbach arrays 202, 202’

The Slot per Pole per Phase (SPP) ratio of the motor 1 is the value of the ratio N2/N1/N3 and is not an integer number.

The disclosed electric motor 1 shown on Fig.1 is an outrunner permanent magnet synchronous motor with fractional slot concentrated windings.

Realizing the winding of electrical wires onto a motor stator is known to the skilled person and is, for example, described on the following internet page, included herein in its entirety: htps://things-in-motion.blogspot.com/2019/02/An outrunner electric motor consists on an architecture with the rotating part of the electric motor showed on Fig.4, also called the rotor 100, being located at the exterior of the stator 300 as shown in Figures 2, 13, 20. The electric motor 1 of the invention can generate large torque which is essential for usages in the transportation sector.

The disclosed electric motor 1 features a plurality permanent magnets Halbach array portions 202a-202c, 202’a-202’c of at least three magnetized Halbach array portions 202a -202c, 202’a-202’c, which are placed with their magnetic orientations in a configuration to form an Halbach array as shown on Fig.3 The Halbach arrays 202, 202’ are located on the inner surface 102b of the rotor 100 shown on Fig4. The Halbach array portions 202a-202c, 202’a-202’c made of at least three magnetic portions or elements, illustrated on Fig.3, has the advantage of creating a strong magnetic field H1 on one side of the Halbach array while creating a weak magnetic field H2 on the opposite side of the Halbach array, as shown on Fig.3.

Each of said strong magnetic field H1 generated by the Halbach array portions 202a-202c, 202’a-202’c provides a rotor pole. The permanent magnets or the magnetic portions which form the Halbach arrays are located on the inner part 102b of the rotor yoke. The Halbach array 202 and 202’ define an outer surface 200” and an inner surface 200’. The outer surface 200” of the Halbach array is in contact or is integrated to the inner surface 102b of the rotor yoke 102. In the inner part of the rotor yoke, multiple Halbach arrays, each of them composed of at least three magnets or three magnetized portions, are arranged next to each other along the entire circumference of the inner part of the rotor yoke as shown on Fig.4. In the case the Halbach array portions are separate components that can be glued, soldered, press-fitted or screwed onto the inner part of the rotor yoke as shown on Fig.4.

The multiple Halbach arrays 202,202’, each of them composed of typically at least three magnets or three magnetized portions 202a-202c, 202’a-202’c, are sequentially arranged next to each other along the entire circumference of the inner part of the rotor yoke as shown on Fig.4. The sequentially arrangement means that an Halbach array 202 is followed by an Halbach array 202’, followed by an Halbach array 202 and again by an Halbach array 202’ and thus along the entire circumference of the inner part of the rotor yoke as shown on Fig.5.

In an embodiment, the at least three permanent magnets that form the Halbach array can be made for example of AINiCo, NeFeBo, SMCO, Thulium oxides or ceramic materials such as hard or soft Ferrites or any other ferromagnetic materials, or a combination of such materials. The at least three permanent magnets that form the Halbach array can be magnetized before or after their fixation onto the inner surface of the rotor yoke 102b.

The disclosed motor features permanent magnets disposed at or in the inner surface of the rotor yoke, like any state of the art out runner motors available today. Nevertheless, such magnets are arranged to the rotor yoke in a Halbach array configuration which creates a strong magnetic field H1 toward one side of the Halbach array and a weak magnetic field H2 toward the other side of the Halbach array. The Halbach array surface that is arranged to the rotor yoke is preferably the weak magnetic field side H2 of the Halbach array as shown on Fig.3. For an outrunner electric motor, the Halbach array, arranged to have its weak magnetic field H2 onto the inner surface of the rotor yoke 102b allows to direct the Halbach array strong magnetic field H1 toward the location where the stator of the motor, shown on Fig.11 is located. The stronger the magnetic field toward the motor’s stator, shown on Fig.11 , the higher the electric to mechanical energy conversion efficiency rate of the motor will be.

The plurality 200 of Halbach arrays 202,202’ can be realized by using at least three independent single poled permanent magnets as shown on Fig.3. Alternatively, the Halbach array can be realized by using a single ferromagnetic element which is magnetized in an Halbach array configuration before or after it’s fixation onto the inner surface 102b of the rotor yoke as shown on Fig.6. In a variant the Halbach array configuration may be arranged into the yoke 102. Multiple single Halbach arrays 202,202’ can be attached next to each other along the entire circumference of the inner part of the rotor yoke as shown on Fig.6. They may be in contact to each other or they may present a gap having a gap width WG.

Alternatively, the full circumference of the inner surface 102b of the rotor yoke 102 can be covered by a single layer of ferromagnetic material which is magnetized in a multiple Halbach array configuration as shown on Fig.7. Alternatively, the ferromagnetic material layer that covers the full circumference of the inner part of the rotor yoke 102b can be an independent ring shaped ferro magnetic part which is fixed onto the inner surface of the rotor yoke as shown on Fig.7. A plurality 200 of Halbach arrays 202,202’ can be created also on the ring-shaped ferromagnetic material by a post magnetization process.

The Halbach arrays 202,202’, which generate a weak magnetic field H2 toward the inner rotor yoke surface 102b on which the permanent magnets are attached to it, allow to use non ferro-magnetic materials as rotor yoke manufacturing materials. Non ferro-magnetic materials can be used to manufacture the rotor yoke 102 as the weak magnetic fields H2 of the Halbach array which is attached to the rotor yoke do not necessarily requires a ferro-magnetic material to channel the magnetic fields. In embodiments the rotor yoke 102 to which Flalbach arrays are arranged, shown on Fig.5, Fig.6 and Fig.7 can be made of a single non ferro-magnetic material. The Flalbach arrays are arranged preferably to the inner surface 102b of the rotor yoke but could be arranged into the thickness of the wall of the rotor yoke. In a variant, the material of the rotor yoke 102 may be chosen so that the Flalbach array can be arranged to the outside of the rotor yoke 102. For example, in the case of a rotor yoke made, at least partially of a polymer or a rotor yoke that has apertures made into its wall.

Additionally, the rotor yoke 102 with the Halbach array configurations shown on Fig.5, Fig.6 and Fig.7 attached onto the inner surface 102b of the rotor yoke can be made of a plurality of different materials which can be a combination of ferro magnetic and non-ferro magnetic materials as shown of Fig.8, Fig.9 and Fig.10.

- Figure 5 Shows a top view of the rotor yoke with a plurality of separate Flalbach arrays, each made of three single Flalbach array portions, arranged inside of the rotor yoke made of a single non-ferromagnetic material.

- Figure 6 Shows a top view of the rotor yoke with a plurality of separate Flalbach arrays arranged inside of the rotor yoke made of a single non ferromagnetic material.

- Figure 7 shows a top view of the rotor yoke with a Flalbach array arrangement realized in a single layer that is arranged to the inside of the rotor yoke made of a single non-ferromagnetic material.

- Figure 8 Shows a top view of the rotor yoke with a plurality of separate Flalbach arrays, each made of three single Flalbach array portions, arranged inside of the rotor yoke made of a stack of layers of equal or different ferromagnetic and non-ferromagnetic materials.

- Figure 9 Shows a top view of the rotor yoke with a plurality of separate Flalbach arrays arranged inside of the rotor yoke made of a stack of layers of equal or different ferromagnetic and non-ferromagnetic materials. - Figure 10 shows a top view of the rotor yoke with a Halbach array arrangement realized in a single layer that is arranged to the inside of the rotor yoke made of a stack of layers of equal or different ferromagnetic and non ferromagnetic materials.

In an embodiment the rotor yoke 102 may be made of a non-homogenous material or may be realized by different section or different layers. The use of a combination of equal or different materials to manufacture the rotor yoke allows to realize a rotor yoke with different mechanical and magnetic properties which can be achieved in different ways. As an example, the rotor yoke 102 could be manufactured by a multi-layer of carbon fiber sheets which are oriented in a different way sheet after sheet in order to achieve a given mechanical resistance.

In an embodiment, the rotor yoke 102 may be manufactured with a layer of ferro magnetic material in combination with a layer of fiber glass material to allow the rotor yoke to channel magnetic fields while reducing the overall rotor weight at the same time.

In an embodiment, a layer of ferromagnetic material is placed between the inner surface 102b of the rotor yoke 102 and the outer surface 200” of the multitude 200 of Hal bach arrays.

Said layer of ferromagnetic material improves the channeling of the magnetic field between each Halbach array portions.. This allows to reduce potential reverse magnetic fields locations, usually the corners of the Halbach array portions, that can irreversibly demagnetize parts of the Halbach array portions. Said irreversible demagnetization process especially occurs on Halbach arrays made of at least three Halbach arrays portions as the magnetic pattern between each Halbach array portion change abruptly thus creating highly saturated magnetic field locations.

Said channeling of the magnetic field between each Halbach array portions, and the resulting prevention of irreversible demagnetization, further increases the amplitude of the Halbach array strong magnetic field H1 and prevent changes on the strong magnetic field H1 overtime. The ferromagnetic layer can be made of iron, a steel alloy, cobalt or nickel, or a combination of these materials and has a typical thickness between 0.01mm and 5mm, preferably between 0.05mm and 2mm, more preferably between 0.1 and 1mm.

In embodiments, the rotoryoke 102 can be manufactured fully or partially by glass fiber, carbon fiber, a high resistance polymer, an aluminum alloy, a titanium alloy, a steel alloy, iron, cobalt, nickel, brass, copper, organic fiber and inorganic fiber or a combination of them.

In embodiments, the rotoryoke 102 is manufactured by using milling, lathe, EDM, sintering, injection molding and 3D printing techniques. In embodiments the rotoryoke parts can be glued, soldered, press-fitted or mechanically fixed to each other.

Each of the plurality of Halbach arrays generate the strong magnetic fields H1 , also called rotor poles, that will interact with the stator magnetic fields S1 as shown on Fig.11 , which will provide the necessary magnetic forces to spin the rotor 100 around the stator 300.

The stator magnetic fields S1 , S2 shown on Fig.11 are generated by flowing electric current through the coils 30-41 arranged on the stator 300. If no current is flowing through the stator coils consequently no stator magnetic fields S1 and S2 are generated.

In order to generate magnetic fields on the motor stator as shown on Fig.11 and, more specifically to generate only the stator magnetic field S1 and S2 showed on Fig.11 , the two coils 38 and 39 have to be activated by flowing current through them. The two adjacent activated coils, which combined, generate, in operation, the desired stator magnetic fields S1 and S2, have to generate two different magnetic poles orientations in order for the magnetic fields of both coils to be combined and maximize the strength of the generated stator magnetic field and ultimately to increase the ability of the motor to transform electric energy into mechanical energy. In a preferred execution, the stator magnetic fields S1 and S2 generated by the at least two coils 30-41 are channeled by the stator on one side of each coil and, by the air gap between stator teeth, on the other side of each coil as shown on Fig.11.

Each individual coil of the array of coils 30-41 of the stator shown on Fig.11 is located on a stator tooth 302-313 of the stator 300. In an example of execution stator 300 depicted on Fig.11 has 12 stator tooths 302-313 and 12 individual coils 30-41 located on each of the 12 stator tooths 302-313 of the stator 300. The magnetic fields S1 , S2 of the stator 300, as shown on Fig.11 are generated not all at the same time but in a precise order, that follow the electrical phases of an AC current, in operation of the motor 1. The sequence of generation of the magnetic fields, i.e. the N2 coils, depend on the number N1 of Flalbach arrays placed on the motor rotor 100. This allows having a well-defined number N1 of strong magnetic fields H 1 to interact with the generated stator magnetic fields.

In embodiments, the virtual axes 302’-313’ of the stator teeth 302-313 do not intersect with the virtual rotation axis 103 of the system, i.e. the stator teeth 302-313 may present a 3D orientation that is not orthogonal to the axis 103 of the system.

The disclosed electric motor 1 is a synchronous motor as the rotation of the rotor around the stator is synchronized with the generation of the magnetic fields on the motor stator and ultimately synchronized with the current flowing through the motor stator coils shows on Fig.11.

The disclosed electric motor 1 is may be defined as a fractional slot concentrated windings motor, because the number of coils 30-41 arranged around the stator 300 shown of Fig.11 is not an integer multiple of the sum of the Flalbach arrays 202 and 202’ fitted onto the internal surface 102b of the rotor yoke 102. The disclosed electric motor 1 has, in a preferred configuration, 12 coils evenly distributed around the stator of the motor as shown on Fig.11 and the rotor 100 has, in said preferred configuration, 14 permanent Flalbach arrays evenly distributed in the inner part of the rotor as illustrated in Figs. 5-10. In a preferred embodiment, in order to minimize the cogging torque and maximize the electromotive force and ultimately the overall motor ability to convert electric energy into mechanical energy, the ratio N2/N1/N3 of Slots per Pole per Phase (SPP) of the motor may be from 1/16 to 7/6, and preferably between 2/7 and 2/5.

In embodiments, the motor 1 of the invention may be fitted with a minimum of 3 and a maximum of 24 coils that are evenly distributed around the stator 300 and with a minimum of 2 and a maximum of 16 Halbach arrays evenly distributed around the inner part 102b of the rotor yoke 102.

In an exemplary execution, the stator 300 of the motor 1 shown on Fig.12 is made of a stack of ferro-magnetic sheets which are fixed together by a point soldering process or by the use of epoxies. The ferro-magnetic sheets can have a thickness between 0.1mm to 4mm but most typically between 0.2 mm to 1 mm. The ferro magnetic sheets that composes the motor stator shown on Fig.12 can be manufactured by stamping, laser cutting, EDM or 3D printed technologies just to mention a few methods of fabrication.

In an exemplary execution, the stator 300 of the motor 1 shown on Fig.12 is made of a stack of different types and shapes of ferro-magnetic sheets. Using different types and shapes of the ferro-magnetic sheets, especially at the two extremities of the stator stack 300, allows to better fill the air gap between the stator tooths 302-313 and the inner portion 301” of the coils 30-42. An example of a single coil 301 is illustrated in Fig.17.

In embodiments, the stator 300 of the outrunner motor 1 typically has a series of stator tooths 302-313 sticking out of a donut shaped central portion of the stator. The number of stator tooths 302-313 mainly depends on the type of motor 1. For example, the motor 1 has typically 12 stator tooths 302-313 evenly distributed around the stator as shown on Fig.11 and Fig.12. Each stator tooth 302-313 accommodates a coil 30- 41 which generates, in operation, the magnetic fields as shown on Fig.11. In embodiments, the electric motor 1 presents a plurality of material recesses 300’ on the stator 300 located on the inner portion of the stator 300 at the base of each coil 30-41 support as shown on Fig.12 The shape of the recesses 300’ can be circular, half circular, square, rectangular or triangular or any other geometry or free form shape. In the variant shown on Fig.12 the recess locations are located on a weak magnetic field location of the magnetic field S2 on the motor stator 300. Placing the recesses 300’ on a weak magnetic field location of the stator 300 ensures that the magnetic fluxes S2 are not perturbed or reduced by the lack of ferro magnetic material due to the recesses 300’ and ultimately maintain the motor’s efficiency conversion rate unchanged.

In an advantageous embodiment, the motor 1 comprises a mechanical gear system 400 located at the center of the stator as shown in Fig.13, Fig.14 and Fig.20. Such mechanical gear system 400 can be for example a planetary gear system.

In embodiments, the motor 1 all or a portion of the stator recesses 300’ shown on Fig.12 are used to insert round, square, rectangular, triangular or any other shaped shaft key. A shaft key is a machine element used to connect a rotating machine element to a shaft. The shaft key prevents relative rotation between the two parts and may enable torque transmission.

Shaft keys can be used to rotationally lock the gear system located at the center of the stator as shown on Fig.14.

In variants, the recesses 300’ of the stator shown in Fig.12 can be all or partially used to electrically connect the stack of ferro-magnetic sheets which build up the stator shown on Fig.12. Additionally, the recesses 300’ on the stator can be all or partially used to insert cooling pipes between the stator and the gear system to remove heat generated by the stator or by the gear system as shown on Fig.14, Fig.15 and Fig.16. Such a heat dissipation technique has the advantage of not requiring extra space and weight on the electric motor while increasing the performances and the durability of the electric motor itself. In embodiments, at least one of the recesses 300’ on the stator stack shown on Fig.11 comprises at least one sensor that can be used to monitor the electric motor. Such sensors can be for example temperature sensors, Hall sensors, magnetic sensors, air pressure sensors, tensile strength sensors, gas sensors, liquid sensors, acceleration sensors, vibration sensors, optic sensors or shock sensors to mention a few.

In embodiments the coils 30-41 which are fixed to the stator tooths 302-313 can be woven on the stator tooth or manufactured independently on a separate step and then fixed to the stator tooths as shown on Fig.14-16. A wide variety of coils manufacturing techniques may be used.

In an advantageous embodiment, the stator winding of the outrunner motor of the invention may be realized in a modular manner and realized by a batch process. This means that each coil may be produced individually on a mandrel which allows to modify the length and width of the coils, the cross section of the coil windings as well as the section of the wire used. In such an embodiment it is therefore possible to easily design stator windings for different motor specifications. Also, furthermore, the coils may then be easily changed when damaged or replaced to provide an upgrade of the motor.

In embodiments, as illustrated in Fig.17, the coil winding can be achieved by using, but not limited to, round, oval, triangular, rectangular, square, trapezoidal and hexagonal cross section wires. The disclosed motor primarily uses coils with larger wire sections which are manufactured independently and then fitted on the stator tooths.

The coil windings according to the embodiment of Fig.17 can be made at least partially of, but not limited to, aluminum, copper, gold, silver, silicon, or superconductive material and can be machined by, but not limited to, extrusion, casting, sintering, lithographic processes and 3D printing methods. Additionally, the coil windings shown in Fig.17 can be made of, but not limited to, solid, hollow or Litz wires. A Litz wire is a particular type of multistrand wire or cable used in electronics to carry alternating current (AC) at radio frequencies. The wire is designed to reduce the skin effect and proximity effect losses in conductors. It consists of many thin wire strands, individually insulated and twisted or woven together.

Typical coil windings use wires with cross sectional dimensions ranging from ten micrometers (10pm) to ten millimeters (10mm). The coil windings can be overcoated with, but not limited to, resin, epoxies, polymers, glass, diamond or graphene in order to create an electrically insulating layer around the coil windings.

The cross section of the coil windings can be of rectangular shape as shown on Fig.18 or of pyramidal shape as shown on Fig.19. The pyramidal winding coil cross section shown on Fig.19 is typically achieved by stacking layers of the same winding wire on top of each other. Typically, in outrunner electric motors, pyramidal cross section shaped coils show a larger number of wires stacked on top of each other at the tip 302b-313b of the stator tooth 302-313 while shows a fewer number of wires stacked on top of each other at the base 302a-313a of the stator tooths 302-313 as shown in Fig.11 , Fig.13, Fig.14, Fig.15 and Fig.16.

The advantage of using pyramidal-shaped cross section winding coils as shown on Fig.19 is that the coils achieve a higher filling factor compared to coils with a rectangular cross section as shown on Fig.18. The higher the coil filling factor, the higher the efficiency of the electric motor will be as a stronger magnetic field S1 and S2 can be generated by the same coils with the same current flowing through them.

The coils 30-41 fitted on the stator tooths as shown Fig.14, Fig.15 and Fig.16 have typically two coil electrical connections 30T as shown on Fig.17. The two coil electrical connections 30T shown on Fig.17 are electrically connected to the control electronic which send the electric current through each coil in a controlled way in order to generate the stator magnetic fields S1 and S2 necessary to spin the rotor around the stator.

In an embodiment, the motor 1 features an integrated control electronic board 500 as shown in Fig.15 on which the two coil electrical connections 30T shown on Fig.17 are electrically connected. The two coil electrical connections as shown on Fig.17 can be soldered, press fitted, glued or connected via a connector to the motor control electronic board 500 shown on Fig.15 and Fig.16.

Directly electrically connecting the coils to the control electronic board as shown on Fig.15 and Fig.16 greatly reduces the electrical power losses as well as the number of cables that will exit the electric motor enclosure. The control electronic board 500 of the execution of Fig.15 and Fig.16 is configured to sends the correct AC signals to the different coils in order to generate the stator magnetic fields S1 and S2 as shown on Fig.11 that will interact with the Halbach array, and more specifically with the strong magnetic field H1 , fixed on the rotor. The correct interaction between the rotor’s Halbach arrays strong magnetic fields H1 and the stator coil magnetic fields S1 generates the magnetic forces that will allow the rotor to spin around the stator.

The electronic control electronic board 500 may have several high-power electrical components fixed on it. Such electrical components can be for example Silicon carbide Mosfets needed to switch the current into the proper coils at the right time. The control electronic board 500 can be fixed to the base plate of the motor in order to better dissipate the heat generated by the electronic components fixed on the control electronic board 500. The interface between the control electronic board 500 and the motor baseplate 3 can be made in such a way that the thermal resistance between the two parts it’s reduced as much as possible. The thermal resistance between the electronic control electronic board 500 and the motor baseplate 3 can be reduced by using a heat conductive paste or by using heat pipes that will facilitate the heat transfer between the control electronic board 500 and the motor baseplate 3.

The Control electronic board 500 that may be a PCB based board has the characteristics that only two power cables are required to be connected between the control electronic board 500 and the energy source that may be a battery 1000. The fact that only two power cables are required between the electric power source and the control electronic board greatly simplify the installation of the motor on the hosting vehicles as well at it reduces the amount of electrical power connections and therefore the electric power losses as well as the overall price of the electric motor. The control electronic board 500 may have a third cable connected between the control electronic board 500 and the energy source that may be a battery 1000. The third cable may be an additional power cable, a ground cable, a communication cable, a liquid cooling pipe, a heat pipe or a combination of those.

The motor baseplate 3 is the electric motor component on which the rest of the electric motor parts are fixed upon. The electric motor baseplate 3 may be the mechanical interface between the electric motor and the vehicle’s frame on which the electric motor 1 is fixed. The electric motor baseplate 3 can be used to cool or heat the different components of the electric motor depending on their needs. The cooling and heating process of the electric motor’s baseplate 3 can be performed by forced air, liquid cooling or Peltier elements or a combination of those. The cooling or heating energy is transferred to the different parts of the motor by simple mechanical interface or by using thermal conductive elements such as thermal conductive paste, gel, patches, or heat pipes.

In an embodiment the electric motor baseplate 3 has a central hole on which the electric motor’s shaft 5 is extending outside of the electric motor’s case as shown on Fig.16 and Fig.21. The electric’s motor shaft 5 shown on Fig.16 and Fig.21 extending outside of the electric motor’s baseplate 3 can be directly connected to the rotor 300 or having a gear system between the shaft 5 and the rotor 100.

In an advantageous embodiment a gear system 400 is arranged between the electric motor shaft 5 and the rotor 100 shown on Fig.4. The gear system 400 may be a planetary gear system. The use of a gear system between the electric motor shaft 5 and the rotor 100 greatly increases the output torque of the electric motor at lower speed without the need to generate the torque by increasing the current flowing through the motor’s coils. This approach greatly increases the overall motor’s efficiency conversion rate at lower speeds.

The electric motor has preferably a baseplate which is the main fixing element of the motor and act as the base of the motor. The baseplate may comprise at least one ball bearing element 602 to rotationally guide the rotor 100 around the stator. The at least one ball bearing element 602 is located between the control electronic board 500 and the stator stack as shown on Fig.15. A ball bearing element greatly improves the rotational guidance of the rotor and therefore reduces the possibilities of collision between the rotor Halbach arrays shown in Fig.4 to Fig.10 and the tip 302b-313b of the stator tooths 302-313 of the stator 300 shown in Fig.12. Additionally, a ball bearing element may act as a hermetic sealing and protect the internal part of the electric motor from the external elements.

The electric motor’s rotor is preferably rotationally guided from the ball bearing element 602 fixed to the baseplate on one end and on the other end by a ball bearing element 604 located on the stator as shown in Fig.15 and Fig.20. The ball bearing element 604 located on the stator is hold in place by an interface ring 600 inserted between the ball bearing element 604 and the stator 300 as shown on Fig.15 and Fig.20 which can be machined with a higher precision compared to the stator itself. The interface ring 600 shown on Fig.15 and Fig.20 can be glued, soldered, press fitted or mechanically fixed to the stator shown on Fig.12.

The stator recesses 300’ as illustrated in Fig.12 can be used to insert round, square, rectangular, triangular or any other shape shaft keys which can be used to rotationally lock the interface ring 600 located at the center of the stator as shown on Fig.15 and Fig.20. The interface ring 600 illustrated in Fig.15 and Fig.20 may be fixed to the gear system 400 by using screws, glue or soldering techniques.

In embodiments, the rotor 100 is connected to the gear system 400 located on the center of the stator by an interface rotor cap to gear system mechanical axis 150 as shown on Fig.20 and which is connected between the rotor cap 4, attached to the rotor 100, and the gear system 400 and passes through the balls bearing 604 hold in place by the interface ring 600 fixed to the stator 300.

In embodiments, the motor 1 combines three key components of any electric powertrain which are the electric motor, the control electronic board as well as the gear system. The combination of those three parts in a single unit drastically reduces the space requirement in the hosting vehicle, increases the power density of the electric motor while reducing the power losses, increases the overall electric motor’s efficiency rate and simplifies the electrical connectivity between the energy pack and the electric motor as only two electrical power connections are required.

The invention is also achieved by an outrunner motor system T, illustrated in Fig.21 , comprising the outrunner motor 1 and an electrical power source 1000 and comprising a control electronic board 500 that is connected via cables 1002, 1002’, 1002” to said electric power source 1000.

In another aspect, the invention is also achieved by a method of fabrication of the motor 1 as described herein. The method comprises the steps (A-D) of:

A. providing a rotor yoke 102 having an inner wall 102b defining a central space being the rotor core 101 defining a virtual central axis 103, the rotor yoke 102 being made, at least partially, of a non-ferromagnetic material;

B. arranging to said rotor yoke 102, to the side of said rotor core 101 , a plurality 200 of magnetic elements consisting in a number N1 of Halbach arrays 202, 202’, each array, comprising Halbach array portions 202a-c, 202’a-c, are arranged to said inner wall 102b, each of said Halbach arrays 202, 202’ providing a single magnetic pole having a magnetic field H1 that is higher to the side of said inner surface 200’ than to the side of said outer surface 200”;

C. arranging a stator 300, having an inner stator surface 300a, in said rotor core 101 ;

D. adapting to said stator a plurality 301 of electrical conducting coils 30-41 so as to provide, in operation of the motor, a number N3 of electrical phases.

The steps A-D are executed so the ratio N2/N1/N3 is not an integer.

In an advantageous embodiment, the stator winding of the outrunner motor of the invention may be realized according to a modular approach. This means that each coil may be produced individually on a separate mandrel, before adapting the coils to the teeth of the stator, which allows to modify the length and width of the coils as well as the section of the wire used. It is therefore possible to easily design stator windings for different motor specifications. In such an embodiment the method comprises the steps (E-G) of:

E. realizing each of said electrical conducting coils 30-41 on a mandrel, separate from stator, so that a predetermined length, width and predetermined cross sections windings of the coils 30-41 are obtained;

F. arranging each of said electrical conducting coils 30-41 to the teeth 302-313 of the stator 300;

G. connecting the coils 30-41 two coil electrical connections 301’ on a control electronic board 500 integrated on the motor’s enclosure.

In an example of execution that is now described, the coils 30-41 are connected to each of the N3 phases of the AC current provided by a control electrical board 500 in a precise order. For example, coils 30, 37 and 36 may be connected in series to the first phase of the AC current source provided by a control electronic board 500. Preferably, control electronic board 500 is part of a system comprising the motor 1 .For example, the first electrical phase may be connected to one of an extremity of a coil 30-41 and exits from the second extremity of that coil 30-41. In operation, said first electrical phase enters one of the two extremity of an adjacent coil 30-41 and exits from the second extremity of adjacent coil 30-41. The electrical connection polarity of each coil, and therefore its generated magnetic field, is not the same for each coil. For the first phase, coil 30 may be configured to provide a first polarity P1 and coil 31 is configured to provide a second polarity P2, and coil 37 is configured to provide a first polarity P1 and coil 36 is configured to provide a second polarity P2. Polarities P1 , P2 are opposite direction polarities. In this example, coils 38, 39, 33 and 32 are connected in series to the second phase of the AC current signal in the same way as for the first phase with polarities P1 for coils 38 and 33 and polarity P2 for coils 39 and 32. In the example, coils 34, 35, 41 and 40 are connected in series to the third AC phase in the same way as for the first and second AC current phase with polarities P1 for coils 34 and 41 and polarity P2 for coils 35 and 40. In the example, the sequence of the polarities provided by the poles are, respectively for the first .second and third: P1-P2- P1-P2. The first .second and third electrical AC current phases are therefore entering, in operation, in the coils 30, 38 and 34 respectively and exiting from coils 36, 32 and 40 respectively. The three AC phase exits are connected together and linked to a neutral wire. The neutral-point coil is the circuit conductor that normally completes the circuit back to the source and that is normally connected to the ground at the main electrical panel.

In a variant the method may also comprise the steps of manufacturing the coils by adapting the length or cross section of the wire in order to achieve a predefined coil electrical resistance. In a variant the method may also comprise the steps of manufacturing the coils by using a multitude of wires instead of a single wire. In a variant the coils 30-41 are realized, before adapting them to the teeth 302-313 of the stator 300, according to a batch process implementing a number of mandrels equal to the number of coils to be produced.