EP3583684A1

EP3583684A1 - Electric motor

Info

Publication number: EP3583684A1
Application number: EP18707134.5A
Authority: EP
Inventors: Alexey BIKMUKHAMETOV
Original assignee: Arrival Ltd
Current assignee: Arrival UK Ltd
Priority date: 2017-02-20
Filing date: 2018-02-19
Publication date: 2019-12-25
Also published as: WO2018150198A1

Abstract

An electric motor comprising: a stator comprising a stator electromagnet and an electric bus, the stator electromagnet comprising a plurality of conducting members each being electrically connected to the electric bus; and a rotor rotatably supported in the electric motor, the rotor comprising at least one permanent magnet; wherein a plurality of current paths are formed in the stator when current passes through the stator electromagnet via the electric bus, each of the plurality of current paths corresponding to a different one of the plurality of conducting members.

Description

Electric Motor

Field

This specification relates to an electric motor, particularly but not exclusively to an electric motor which operates without requiring use of rotor position sensors or computer processors.

Background

In part, due to concerns regarding air pollution and instability of petroleum prices, there has been increasing growth in interest in electric vehicles, in particular electric vehicles which adopt advance drive systems and vehicle power systems using induction motors. These electric vehicles require motors which are small in size, lightweight, and low-cost with high efficiency. A number of different types of electric motors have been used to provide the power requirements of the electric vehicles. In currently known electrical motor

configurations, at least one rotor and one stator are provided, wherein the rotor is mounted on a shaft axially relative to the stator. The flux generates a magnetic field in an air gap between the stator and the rotor and induces a voltage which produces current through the rotor bars. The rotor circuit is shorted and current flows in the rotor conductors. The action of the rotating flux and the current produces a force that generates a torque to start the motor.

Summary

In a first aspect, this specification describes an electric motor comprising: a stator comprising a stator electromagnet and an electric bus, the stator electromagnet comprising a plurality of conducting members each being electrically connected to the electric bus; and a rotor rotatably supported in the electric motor, the rotor comprising at least one permanent magnet; wherein a plurality of current paths are formed in the stator when current passes through the stator electromagnet via the electric bus, each of the plurality of current paths corresponding to a different one of the plurality of conducting members.

The electric bus may comprise a first circular disc member and a second circular disc member, and opposite ends of each of the plurality of conducting members of the stator electromagnet may be respectively in direct electrical contact with the first circular disc member and the second circular disc member.

The first circular disc member of the electric bus may be located adjacent to a first side of the rotor, while the second disc member of the electric bus may be located adjacent to a second side of the rotor, the second side being opposite to the first side.

The first circular disc member may be in direct electrical contact with a positive terminal of a power supply, and the second circular disc may be in direct electrical contact with to a negative terminal of the power supply.

The electrical connection between each of the first circular disc and the second circular disc and the power supply may be configured such that resistance along each of the plurality of current paths is the same, such that a uniform magnetic field is generated by the stator to cause the permanent magnet in the rotor to move thereby causing the rotor to rotate.

The plurality of current paths may comprise at least a first current path and a second current path, and the plurality of conducting members may comprise at least a first conducting member and a second conducting member, wherein the first current path corresponds to the first conducting member and the second current path corresponds to the second conducting member, and wherein the second current path may be longer than the first current path. Resistance along the second conducting member may be lower than that along the first conducting member.

The first conducting member may have at least one of a different width and thickness from that of the second conducting member.

At least one of the width or thickness of the second conducting member may be determined such that resistance along the second conducting member offsets a difference in lengths between the first current path and the second current path.

Resistance along each of the plurality of conducting members may be correlated to a length of its corresponding current path, such that uniform magnetic field is generated by the stator to cause the permanent magnet in the rotor to move thereby causing the rotor to rotate.

Each of the plurality of the conducting members of the stator electromagnet may be disposed radially about a central axis of the stator and may be parallel to its adjacent conducting members.

Each of the plurality of the conducting members of the stator electromagnet may form an individual ring, and the stator electromagnet and the electric bus may form a torus shaped coil set.

The rotor may be located in an enclosure formed by the torus shaped coil set formed by the stator electromagnet and the electric bus. The rotor may comprise a first permanent magnet and a second permanent magnet, each of the first and second permanent magnet comprising a north magnetic pole and a south magnetic pole, and the first permanent magnet and the second permanent magnet may be arranged in the rotor such that their magnetic pole orientations are rotationally aligned in the rotor.

The rotor may further comprise a rotor shaft, the rotor shaft comprising a cylindrical member positioned in the centre of the rotor having a longitudinal axis about which the rotor can be rotated. Brief Description of the Drawings

For a more complete understanding of the aspects described herein, reference is now made to the following descriptions taken in connection with the accompanying drawings in which: Figure lA is a front cross-sectional view of an electric motor according to a first embodiment;

Figure lB is a side cross-sectional view of the electric motor of Figure lA;

Figure lC is a front view of the electric motor of Figure lA;

Figure 2A is a perspective view of the stator of the electric motor of Figure lA;

Figure 2B is a perspective view of the rotor of the electric motor of Figure lA; Figure 3 is a perspective view of the rotor and the stator of Figures 2A and 2B in an assembled state;

Figure 4 is a schematic diagram of the stator of Figure 2A in an unfolded state;

Figure 5 is a simplified schematic diagram illustrating the interaction between a permanent magnet in the rotor and the stator electromagnet of Figures lA to lC; and Figure 6 is a schematic diagram of a stator of an electric motor according to a second embodiment.

Detailed Description

In known types of synchronous brushless motors, the rotor comprises permanent magnets with magnetic poles arranged to be spaced apart circumferentially such that when current passes through the stator electromagnetic coils, the rotor rotates incrementally from one magnetic pole to another to drive a central motor shaft. These types of known electric motors require the use of a rotor position sensor so as to accurately switch on and off the current in the stator electromagnetic coils as well as a central processing unit (CPU) to control the switching. In addition, it is required in these known types of electric motors to create specific software for the CPU to effectively manage the switching control. The aspects described below provide an improved electric motor in terms of overall electrical and mechanical performance. In particular, these aspects provide an electric motor with increased power efficiency as well as improved dynamic and traction properties, while having a reduced size due to absence of any rotor position sensors (e.g. Hall sensor, resolver, etc.) and computer processors. Moreover, for this reason, the costs for manufacturing the electric motor according to these aspects are reduced.

Figures lA, lB, and lC are respectively a front cross-sectional view, a side cross- sectional view, and a front view of an electric motor 100 according to a first

embodiment. Figure 2A is a perspective individual view of the stator 110 of the electric motor 100, Figure 2B is a perspective individual view of the rotor 120 of the electric motor 100, and Figure 3 is a perspective view of the stator 110 and the rotor 120 in an assembled state.

As illustrated in Figures lA to lC, the electric motor 100 (herein referred to as "the motor") comprises a stator 110 and a rotor 120. The rotor 120 is rotatably supported in the electric motor 100, and comprises a central rotor shaft 126 (herein referred to as "shaft") and a core including a first permanent magnet 122a and a second permanent magnet 122b. Each of the first and second permanent magnets 122a, 122b comprises a north magnetic pole (labelled 'N' in Figure lA) and a south magnetic pole (labelled 'S' in Figure lA). In addition, as shown in

Figure lA, the first permanent magnet 122a and the second permanent magnet 122b are arranged such that their magnetic pole orientations are rotationally aligned in the rotor 120. As such, when the rotor 120 rotates 180 degrees from an initial orientation shown in Figures lA and lC, the north magnetic pole and south magnetic pole of the first permanent magnet 122a would correspond to the north magnetic pole and south magnetic pole of the second permanent magnet 122b in their initial orientation.

The rest of the core of the rotor 120 is comprised of intermediate sections 124 made of magnetic material, such as steel, such that a closed magnetic loop can be formed within the core of the rotor 120 by the first permanent magnet 122a and the second permanent magnet 122b. In these Figures, the core is made up of the combination of the first and second permanent magnets 122a, 122b and the intermediate section 124 between the magnets 122a, 122b. The rotor shaft 126 is a hollow cylindrical member positioned in the centre of the rotor 120. The shaft 126 is attached to the rotor 120 and has a longitudinal axis about which the rotor 120 can be rotated. The shaft 126 can be used to drive a component mechanically connected to the shaft 126, such as a vehicle axle. The rotation of the rotor 120 will be explained in more detail below.

In the present embodiment, the stator 110 comprises a stator electromagnet 112 and an electric bus 114 together forming a torus-shaped coil set. The coil set forms an enclosure in which the rotor 120 is located, as shown in Figure 3. The rotor 120 is not in direct contact with the stator 110 so as to minimise friction against rotation of the rotor 120.

The stator electromagnet 112 comprises a plurality of conducting members 116 disposed radially about a central axis of the stator 110 in a parallel manner (i.e. each of the plurality of conducting members 116 is parallel to its adjacent conducting members), each of the plurality of conducting members 116 forming an individual electrically conductive ring and being in electrical connection with the electric bus 114. Therefore, when current passes through the stator electromagnet 112, current in each of the plurality of conducting members 116 flows in the same direction. In detail, when current passes through the stator electromagnet 112, a plurality of current paths are formed in the stator 110, each corresponding to a different one of the conducting members 116.

In addition, when current passes through the stator electromagnet 112, a magnetic field is generated around the stator electromagnet 112, and in particular through the centre of the plurality of rings formed by the plurality of conducting members 116 in the stator electromagnet 112 so as to form a static (i.e. non-rotating) closed magnetic field loop. A permanent magnet positioned in the vicinity of the generated magnetic field would be caused to move under the influence of the magnetic field. In other words, the generated closed magnetic field loop would exert a magnetic force on the first and second permanent magnets 122a, 122b in the rotor 120, thereby causing the rotor 120 to rotate. As a result, due to the attachment between the shaft 126 and the rotor 120, the shaft 126 is caused to rotate. The interaction between the generated magnetic field loop at the stator 110 and the permanent magnets 122 in the rotor will be explained in more detail with reference to Figure 5.

The electric bus 114 is arranged to supply power for the electric motor 100. Specifically, the electric bus 114 provides electrical connection from a main power supply (not shown in the drawing) to the stator electromagnet 112, such that current can pass through the plurality of parallel conducting members 116 of the stator electromagnet 112 so as to generate a magnetic field. As shown in Figure 3, the electric bus 114 comprises two circular disc members, i.e. a first circular disc member and a second circular disc member, to which opposite ends of each of the parallel conducting members 116 of the stator electromagnet 112 are respectively electrically connected. The first circular disc member of the electric bus 114 is located adjacent to a first side of the rotor 120, while the second disc member of the electric bus 114 is located adjacent to a second side of the rotor 120, the second side being opposite to the first side. The first circular disc member 114a as labelled in Figure 3 corresponds to a positive terminal of the main power supply (as denoted by a '+' symbol in Figure 3) while the second circular disc member 114b as labelled in Figure 3 corresponds to a negative terminal of the main power supply. Figure 4 is a schematic diagram of the stator 110 in an unfolded state. Specifically, Figure 4 shows schematically the plurality of current paths through the stator 110 that corresponds to the plurality of conducting members 116 of the stator electromagnet 112. As illustrated in Figure 4, the stator electromagnet 112 in the unfolded state comprises a plurality of conducting members 116 that are parallel to each other. The plurality of parallel conducting members 116 are connected to a DC power supply (not shown in the drawing) via the electric bus 114. The lower horizontal bar shown in Figure 4 labelled 114a corresponds to the first circular disc member of the electric bus 114 (positive terminal '+'), while the upper horizontal bar shown in Figure 4 labelled 114b

corresponds to the second circular disc member of the electric bus (negative terminal '- '). In this particular embodiment, when the stator 110 is in the unfolded state, the positive terminal and the negative terminal of the DC power supply are respectively connected to the diagonally opposite corners of the unfolded stator 110, i.e. the bottom left corner and the top right corner.

A top end of each of the plurality of parallel conducting members 116 is in direct electrical contact with the upper bar corresponding to the second circular disc member of the electric bus 114, while a bottom end of each of the plurality of parallel conducting members 116 is in direct electrical contact with the lower bar corresponding to the first circular disc member of the electric bus 114.

When power is supplied to the stator 110 through the electric bus 114, a plurality of current paths are formed within the stator 110, each of the current path corresponding to a different respective parallel conducting member 116. In the embodiment shown in Figure 4, the stator electromagnet 112 comprises k parallel conducting members 116. Starting from the left of the schematic diagram in Figure 4, a first current path l_t flows through a first parallel conducting member, a second current path I₂ flows through a second parallel conducting member, a third current path I₃ flows through a third parallel conducting member, a fourth current path I₄ flows through a fourth parallel conducting member, a fifth current path I₄ flows through a fifth parallel conducting member, etc., and a k* current path Ik flows through a k* parallel conducting member. All of the current paths Ii to Ik start from the bottom left corner of the unfolded stator 110 which corresponds to the positive terminal of the power supply, along a

corresponding conducting member 116, and ends at the top right corner of the unfolded stator 110 which corresponds to the negative terminal of the power supply. Since the plurality of conducting members 116 have the same length as illustrated in Figure 4, all the plurality of current paths have the same length along the stator 110. The current paths are indicated by dotted lines in Figure 4. The resistances along each of the current paths are denoted as Ri to Rk in Figure 4. In order to achieve a uniform magnetic field in the stator 110, the resistance along each of the plurality of current paths should be kept the same. In the present embodiment, as shown in Figure 2A and Figure 3, constant resistance along each of the plurality of current paths is ensured by using conducting members 116 that have the same width, thickness and length.

Figure 5 is a simplified schematic diagram illustrating the interaction between a permanent magnet 122 in the rotor 120 and the stator electromagnet 112 of Figures lA to lC.

Figure 5 shows a section of the stator 110, i.e. the stator electromagnet 112 and the electric bus 114, as a simplified circuit diagram, and either the first permanent magnet 122a or the second permanent magnet 122b is represented as a permanent magnet 122 positioned along the centres of the rings formed by each of the parallel conducting members 116 of the stator electromagnet 112.

As explained above, a plurality of current paths are established in the stator 110 when current passes through. The direction of the first current path l_t in the first parallel conducting member is indicated by an arrow. The other current paths also follow the same direction in respective conducting members 116, i.e. a clockwise direction in

Figure 5. Accordingly, the magnetic field generated at the stator electromagnet 112 has a direction of pointing into the plane of the page. Hence, the permanent magnet 112 placed within a section of the coil set formed by the stator 110 as illustrated in Figure 5 would be caused to move into the plane of the page. As Figure 5 illustrates only a section of the stator electromagnet 112 which is part of a circular coil set, it will be appreciated that, when applied to the embodiment as illustrated in Figure 3, the permanent magnets will be caused to rotate within the stator 110 thereby causing the rotor 120 to rotate. A sequence of the operation of the electric motor 100 according to the first embodiment is described below: Current is passed through the stator electromagnet 112 through the electric bus 114 from a main DC power supply (not shown in the drawing), thereby forming a plurality of current paths in the stator 110, each of the plurality of current paths corresponding to a different conducting member 116 in the stator electromagnet 112. In other words, each of the plurality of current paths passes through a part of the electric bus 114 and one of the conducting members 116 of the stator electromagnet 112, as shown in Figure 4. Due to the configuration of the electric bus 114, particularly the connection of the negative terminal and the positive terminal of the power supply at the electric bus 114, each of the plurality of current paths in the first embodiment has the same length, also as shown in Figure 4. Since the resistance along each of the plurality of current paths is the same due to the conducting members 116 having the same dimensions (i.e. length, width, and thickness), a uniform magnetic field along the centres of each of the ring formed by each of the plurality of conducting members 116 is generated.

A permanent magnet positioned in the vicinity of the generated magnetic field would be caused to move under the influence of the magnetic field. As the rotor 120 in the illustrated embodiment is located inside the enclosure formed by the stator 110, the first permanent magnet 122a and the second permanent magnet 122b, which are rotationally aligned in the rotor 120, would be caused to move under the influence of the generated magnetic field loop. Due to the constancy of magnetic force exerted by the generated magnetic field loop throughout the stator 110, a stable and smooth rotation of the rotor 120 can be achieved. If it is desired to change the direction of rotation of the rotor 120, the direction of the current in the stator electromagnet 112 has to be reversed by reversing the terminals of the main power supply.

Since current passing through the stator electromagnet 112 does not have to be controlled or regulated depending on orientation or position of the rotor 120, there is no need for any rotor position sensor, any processor, or any special software for controlling the current passing through the stator electromagnet 112.

Figure 6 is a schematic diagram of a stator of an electric motor according to a second embodiment. Similar to the first embodiment described above, in the second embodiment the electric motor comprises a stator and a rotor, the stator comprising a stator electromagnet and an electric bus, and the rotor being located within an enclosure formed by the stator and comprising a core which includes a first permanent magnet and a second permanent magnet. In addition, the electric bus in the second embodiment also comprises a first circular disc member and a second circular disc member. In the second embodiment, however, the stator 130 has a different configuration from that of the first embodiment, as will be explained with reference to the schematic diagram of Figure 6.

As illustrated in Figure 6, the stator electromagnet 132 of the stator 130 in the unfolded state comprises a plurality of conducting members 136 that are parallel to each other. The plurality of parallel conducting members 136 are connected to a DC power supply (not shown in the drawing) via the electric bus 134. The upper horizontal bar shown in Figure 6 labelled 134a corresponds to the first circular disc member of the electric bus 134 (negative terminal '-'), while the lower horizontal bar shown in Figure 6 labelled 134b corresponds to the second circular disc member of the electric bus (positive terminal '+'). In the second embodiment, when the stator 130 is in the unfolded state, the positive terminal and the negative terminal of the DC power supply are respectively connected to the opposite corners on the same end of the unfolded stator 130, i.e. the bottom left corner and the top left corner.

A top end of each of the plurality of parallel conducting members 136 is in direct electrical contact with the upper bar corresponding to the first circular disc member of the electric bus 134, while a bottom end of each of the plurality of parallel conducting members 136 is in direct electrical contact with the lower bar corresponding to the second circular disc member of the electric bus 134.

When power is supplied to the stator 130 through the electric bus 134, a plurality of current paths are formed within the stator 130, each of the current paths corresponding to a different parallel conducting member 136. In the second embodiment as shown in Figure 6, the stator electromagnet 132 comprises M parallel conducting members 136. Starting from the left of the schematic diagram in Figure 6, a first current path I_u flows through a first parallel conducting member, a second current path I₁₂ flows through a second parallel conducting member, a third current path I₁₃ flows through a third parallel conducting member, a fourth current path I₁₄ flows through a fourth parallel conducting member, etc., and a M^th current path I_M flows through an M^th parallel conducting member. All of the current paths In, Ii₂,... to IM start from the bottom left corner of the unfolded stator 130 which corresponds to the positive terminal of the power supply, along a corresponding conducting member 136, and end at the top left corner of the unfolded stator 130 which corresponds to the negative terminal of the power supply. As explained, the starting point and ending point of the plurality of current paths are on the same end of the stator 130 and the plurality of parallel conducting members 136 are arranged increasingly further away from that end of the stator 130. Therefore, the further away a conducting member 136 is from a

starting/ending point of current paths, the longer a current path corresponding to the conducting member 136 is. The current paths are indicated by dotted lines in Figure 6.

The resistances along each of the current paths are denoted as Ru to RM in Figure 6. In order to achieve a uniform magnetic field in the stator 130, the resistance along each of the plurality of current paths should be kept the same. In this particular embodiment, since the length of the plurality of current paths increases the further away a corresponding conducting member 136 is from the starting/ ending point of the current paths, the resistances along each of the plurality of conducting members 136 should be varied accordingly so as to offset the differences in lengths of the plurality of current paths. In the second embodiment, resistance along the plurality of current paths is varied by increasing at least one of the width and the thickness of the corresponding conducting member 136 the further it is away from the starting/ ending point of the plurality of current paths. For example, as shown in Figure 6, the width of each of the conducting member 136 increases starting from the left. In other words, the longer a current path is, the lower the resistance along the conducting member corresponding to that current path is, and the amount of resistance along the conducting member is determined based on a difference in length between the current path and the shortest current path (i.e. the current path closest to the starting/ending points).

A sequence of the operation of the electric motor according to the second embodiment is described below:

Current is passed through the stator electromagnet 132 through the electric bus 134 from a main DC power supply (not shown in the drawing), thereby forming a plurality of current paths in the stator 130, each of the plurality of current paths corresponding to a different conducting member 136 in the stator electromagnet 132. In other words, each of the plurality of current paths passes through a part of the electric bus 134 and one of the conducting members 136 of the stator electromagnet 132, as shown in Figure 6. Due to the configuration of the electric bus 134, particularly the connection of the positive terminal and the negative terminal of the power supply at the electric bus 134, each of the plurality of current paths in the second embodiment has a different length, also as shown in Figure 6. The stator 130 of the second embodiment is configured such that resistance along each of the plurality of current paths is correlated to the length of a corresponding current path, by means of varying at least one of the width and the thickness of the conducting member 136. Hence, a uniform magnetic field along the centres of each of the rings formed by each of the plurality of conducting members 136 is generated.

A permanent magnet positioned in the vicinity of the generated magnetic field would be caused to move under the influence of the magnetic field. As the rotor in the

embodiment is located inside the enclosure formed by the stator 130, the first permanent magnet and the second permanent magnet, which are rotationally aligned in the rotor, would be caused to move under the influence of the generated magnetic field loop. Due to the constancy of magnetic force exerted by the generated magnetic field loop throughout the stator 130, a stable and smooth rotation of the rotor can be achieved. Although it is described above that the intermediate sections of the rotor core are made of magnetic material, in alternative embodiments, the intermediate sections of the rotor core may be made of non-magnetic material or may be hollow. Although it is described above that the rotor shaft is a hollow cylindrical member, in alternative embodiments the rotor shaft may be a solid cylindrical member.

Although it is described above that the rotor comprises a first permanent magnet and a second permanent magnet, in alternative embodiments the rotor may comprise only one permanent magnet. Moreover, in other alternative embodiments, the rotor may comprise more than two permanent magnets. In these alternative embodiments, the plurality of permanent magnets may be arranged within the rotor such that the magnetic pole orientations of the plurality of permanent magnets are rotationally aligned in the rotor. In addition, in these alternative embodiments, the plurality of permanent magnets may be spaced evenly within the core of the rotor. Although it is described above that the conducting members of the stator electromagnet are arranged in a parallel manner, in alternative embodiments the plurality of conducting members may have a different arrangement in the stator electromagnet. In these alternative embodiments, the conducting members may have different dimensions from what is described above and/or from each other.

In alternative embodiments, dimensions of the permanent magnets in the rotor may be different from what is illustrated in the drawings.

Although it is described above that the rotor is located within an enclosure formed by the stator electromagnet and the electric bus, thereby forming an "internal rotor" configuration, in alternative embodiments the rotor may be located external to the stator, i.e. the stator electromagnet and the electric bus.

In alternative embodiments, the stator electromagnet may comprise a plurality of layers, wherein each of the layers in the stator electromagnet may comprise a plurality of conducting members electrically connected to the electric bus.

Although it is described in the embodiments above that resistance along each of the plurality of current paths is the same, such that a uniform magnetic field is generated by the stator, in alternative embodiments, the stator electromagnet may be configured such that resistance along each of the plurality of current paths may not be the same. For example, in some alternative embodiments, the stator electromagnet of the electric motor may be configured such that the resistances along certain current paths corresponding to certain conducting members are higher and the resistances along other current paths corresponding to other conducting members are lower.

Although various aspects of the present disclosure are set out in the independent claims, other aspects of the present disclosure comprise other combinations of features from the describe embodiments and/or the dependent claims with the features of the independent claims, and not solely the combinations explicitly set out in the claims.

It is also noted herein that while the above described various examples, these descriptions should not be viewed in a limiting sense. Rather, there are several variations and modifications which may be made without departing from the scope of the claims. Particular embodiments have been illustrated and described. For technical experts it will be evident that several modifications or changes can be made without exceeding the scope of the disclosure. The attached claims intend to cover the aforementioned information so that all the changes and modifications are within the scope of the claims.

Claims

1. An electric motor comprising:

a stator comprising a stator electromagnet and an electric bus, the stator electromagnet comprising a plurality of conducting members each being electrically connected to the electric bus; and

a rotor rotatably supported in the electric motor, the rotor comprising at least one permanent magnet;

wherein a plurality of current paths are formed in the stator when current passes through the stator electromagnet via the electric bus, each of the plurality of current paths corresponding to a different one of the plurality of conducting members.

2. The electric motor according to claim l, wherein the electric bus comprises a first circular disc member and a second circular disc member, wherein opposite ends of each of the plurality of conducting members of the stator electromagnet are respectively in direct electrical contact with the first circular disc member and the second circular disc member.

3. The electric motor according to claim 2, wherein the first circular disc member of the electric bus is located adjacent to a first side of the rotor, while the second disc member of the electric bus is located adjacent to a second side of the rotor, the second side being opposite to the first side.

4. The electric motor according to claim 2 or claim 3, wherein the first circular disc member is in direct electrical contact with a positive terminal of a power supply, and the second circular disc is in direct electrical contact with to a negative terminal of the power supply.

5. The electric motor according to claim 4, wherein the electrical connection between each of the first circular disc and the second circular disc and the power supply is configured such that resistance along each of the plurality of current paths is the same, such that a uniform magnetic field is generated by the stator to cause the permanent magnet in the rotor to move thereby causing the rotor to rotate.

6. The electric motor according to any of the preceding claims, wherein the plurality of current paths comprises at least a first current path and a second current path, and the plurality of conducting members comprises at least a first conducting member and a second conducting member, wherein the first current path corresponds to the first conducting member and the second current path corresponds to the second conducting member, and wherein the second current path is longer than the first current path.

7. The electric motor according to 6, wherein resistance along the second conducting member is lower than that along the first conducting member.

8. The electric motor according to 7, wherein the first conducting member has at least one of a different width and thickness from that of the second conducting member.

9. The electric motor according to claim 8, wherein at least one of the width or thickness of the second conducting member is determined such that resistance along the second conducting member offsets a difference in lengths between the first current path and the second current path.

10. The electric motor according to claim 4, wherein resistance along each of the plurality of conducting members is correlated to a length of its corresponding current path, such that uniform magnetic field is generated by the stator to cause the permanent magnet in the rotor to move thereby causing the rotor to rotate.

11. The electric motor according to any of the preceding claims wherein each of the plurality of the conducting members of the stator electromagnet is disposed radially about a central axis of the stator and is parallel to its adjacent conducting members.

12. The electric motor according to claim 11, wherein each of the plurality of the conducting members of the stator electromagnet forms an individual ring, and wherein the stator electromagnet and the electric bus form a torus shaped coil set.

13. The electric motor according to claim 12, wherein the rotor is located in an enclosure formed by the torus shaped coil set formed by the stator electromagnet and the electric bus.

14. The electric motor according to any of the preceding claims, wherein the rotor comprises a first permanent magnet and a second permanent magnet, each of the first and second permanent magnet comprising a north magnetic pole and a south magnetic pole, and the first permanent magnet and the second permanent magnet are arranged in the rotor such that their magnetic pole orientations are rotationally aligned in the rotor.

15. The electric motor according to any of the preceding claims, wherein the rotor further comprises a rotor shaft, the rotor shaft comprising a cylindrical member positioned in the centre of the rotor having a longitudinal axis about which the rotor can be rotated.