WO2019102057A1

WO2019102057A1 - Apparatus and method of actuated stator cores for hubless rotors

Info

Publication number: WO2019102057A1
Application number: PCT/FI2017/050800
Authority: WO
Inventors: Ian DENTON; Mikko Kristian GRÖNLUND; Markus Olavi Johannes MERILÄ; Juuso Oskari PÖLLÄNEN; Syed Husnain TANWEER KAZMI; Timo Nyberg
Original assignee: Teraloop Oy
Priority date: 2017-11-21
Filing date: 2017-11-21
Publication date: 2019-05-31

Abstract

A novel apparatus and method of actuated stator cores for hubless rotors (1). The apparatus of stator cores for electric motors or generators comprises an actuator target mounted on a hubless ring shaped rotor (1) having a rotational axis; a series of individually actuated stator module assemblies (3) not connected by a common core, the assemblies thereof facing towards the rotor (1) and distributed around its circumference at fixed distances from each other and having an air gap with the rotor. The method of control of the stator cores for electric motors or generators is characterised in that the stator air-gap diameter is adapted by individually adjusting the respective positions of the individually controlled stator module assemblies (3) so to change the respective air gaps between the individually controlled stator module assemblies (3) and the rotor (1) through drive parameters, which may be pre-defined or controlled with external information such as weather or grid forecasts, combining both production and consumption details.

Description

Title of Invention : Apparatus and method of actuated

stator cores for hubless rotors

[1] Apparatus and method of actuated stator cores for hubless rotors.

Technical Field

[2] The invention relates to motors, generators, and rotating kinetic energy storage devices. Specifically kinetic energy storage devices such as flywheels.

Background Art

[3] Permanent magnet electric motors and generators convert electrical energy into kinetic energy and vice versa. Typically, those include a fixed part, called the stator, and a rotating part called the rotor. Motor cores are located on the stator; those motor cores will interact with the source of the magnetic field emanating from the rotor. In the case of permanent magnet motors and generators, the source of the magnetic field on the rotor consists of permanent magnets, sometimes named motor magnets. When operating as a generator, as the rotor rotates, the source of the magnetic field passes by the conducting motor cores, inducing an electrical current in its windings, thus kinetic energy is converted into electrical energy.

Summary of Invention

[4] The object of the invention is to overcome some of the shortcomings of traditional electric motor and generator designs.

[5] This is achieved with an apparatus of stator cores for electric motors or generators, comprising: an actuator target mounted on a hubless ring shaped rotor having a rotational axis; a series of individually actuated stator module assemblies not connected by a common core, the assemblies thereof(3) facing towards the rotor and distributed around its circumference at fixed distances from each other and having an air gap with the rotor.

[6] The focus of the invention is also a method of control of the stator cores for electric motors or generators, characterised in that the stator air-gap diameter is adapted by individually adjusting the respective positions of the individually controlled stator module assemblies so to change the respective air gaps between the individually controlled stator module assemblies and the rotor through drive parameters which may be pre-defined or controlled with external information such as weather or grid forecasts, combining both production and consumption details.

Brief Description of Drawings

[7] [Fig.1] Illustrates a plan view of the general apparatus arrangement of an example embodiment. In this picture, a ring shaped hubless rotor(1 ) is positioned in an outer position. The stator core(2), in an inner position, is segmented into a series of individually actuated stator module assemblies (3), each facing the hubless rotor(1 ), while being distributed around the rotor’s(1 ) circumference at fixed distances from each other and having an air gap with the rotor(1 ).

[8] [Fig.2] Illustrates a detailed plan view of an example embodiment of a stator module assembly in the same general apparatus arrangement.

In this picture, the stator module assembly(3) includes one linear movement apparatus(7) for controlled stator(2) movement on which the stator core(2) is mounted, a coil(4) is wound around the stator core(2), the stator core comprising slots(6) and teeth(5). In this figure, the stator module assembly(3) is in drive position, keeping a constant air gap as the rotor(1 ) speed increases or decreases, adapting to the rotor(1 ) expansions and deformations. [9] [Fig. 3] illustrates a plan view of the same general apparatus arrangement in a situation where all but three stator module assemblies(3) are pulled back, only three stator module assemblies(3) remains in a drive position. This configuration could be needed per example when the power output required does not require full capacity of the apparatus, or when only certain stator module assemblies are required to stabilize the rotor( 1 ).

[10] [Fig. 4] Illustrates a detailed cut view of an example embodiment of a stator module assembly in the same general apparatus arrangement.

In this picture, the stator module assembly(3) includes one linear movement apparatus(7) for controlled stator(2) movement on which the stator core(2) is mounted, a coil(4) is wound around the stator core(2), the stator core comprising slots(6) and teeth(5). In this figure, the stator module assembly(3) is in drive position, keeping a constant air gap as the rotor(1 ) speed increases or decreases, adapting to the rotor(1 ) expansions and deformations

[11] [Fig. 5] illustrates the same general arrangement in a situation where all the stator module assemblies are retracted(9) to the free-wheeling position. This allows the best efficiency as the losses due to eddy currents are minimized.

Description of Embodiments

[12] The following description is not intended to limit the scope or

applicability of the invention in any way. Rather, the following

description is intended to provide convenient illustrations for implementing various embodiments of the invention. As will become apparent, various changes can be made to the methods, structures, devices, apparatuses, components, and compositions described in these embodiments without departing from the spirit and scope of the invention.

[13] Turning to the drawings wherein like reference characters designate identical or corresponding parts, and more particularly, with reference to Fig. 1 , it is disclosed in this patent An apparatus of stator cores for electric motors or generators, comprising: an actuator target mounted on a hubless ring shaped rotor(1 ) having a rotational axis; a series of individually actuated stator module assemblies(3) not connected by a common core, the assemblies thereof(3) facing towards the rotor(1 ) and distributed around its circumference af fixed distances from each other and having an air gap with the rotor(1 ). The assemblies thereof(3) comprising: at least one linear movement apparatus(7) being actuatable individually in either a radial direction, an axial direction or in any other possible direction, which may allow either the maintaining of a constant air gap or variable air gap between the stator module assemblies(3) and the rotor(1 ), or allow a different air gap between one or any other amount of individually controlled modules(3) and the hubless rotor(1 ); and a motor core comprising at least two spaced radial electromagnetic poles facing the rotor(1 ) and configured to induce electromagnetic flux with the actuator target mounted on the rotor(1 ) and mounted on the linear movement apparatus(7); and at least one motor coil(4) wound around the motor core(2).

[14] A desired effect is the ability to move either one or any other number of individually controlled stator modules either closer or further from the hubless rotor, and consequently control the power output of the device, the management of efficiency and response time, and alternance between charge and discharge phase, and the storage phase.

[15] For the purpose of this invention, in high frequency operations, with regards to stator core materials, soft magnetic composites could sometimes be utilized, while for low frequency operations the utilization of conventional laminated materials could per example be utilized. A known solution to reduce“core losses” compared to traditional silicon iron steels is to use ferrite or soft magnetic composites for the stator core materials. However the advantage of ferrite materials exists only for relatively low flux densities (typically up to B= 0.4T), above which the material becomes saturated. Limiting the flux density increases the machine dimensions for a given torque rating, failing to take advantage of the field strengths provided by modern permanent magnet materials. Soft magnetic composites offer reduced losses compared to traditional silicon-iron steels at comparable flux densities. However the advantage is seen typically above 400 Hz field excitation frequency. Additionally the magnetic permeability of soft magnetic composite material is lower than that of silicon iron (requiring additional conductor turns, or current, for equivalent flux density). The soft magnetic composite materials offer an advantage when complex 3D geometry is required, as these materials are isotropic (unlike laminated silicon iron). Thus although materials exist to reduce losses these do not always offer advantages over conventional silicon steels, particularly for conventional prismatic stator constructions, and the reduction in losses is less than one order of magnitude. Additionally, under “no load rotation” the permanent magnets induces a back electro-motive force in the stator windings (i.e. acting as a generator, converting kinetic energy back to electrical energy). One solution is to make the motor or generator coils“open circuit”. However for large scale machines this can require costly circuit breakers.

[16] For the purpose of this invention, the individually controlled modules (3) may be alternatively situated inside, outside, above or below the hubless rotor (1 ) or in any combination of the aforementioned configurations, so long as they are facing the hubless rotor. The desired effect of not limiting the position of the stator as an outer stator, and to choose instead for exemplary purposes an inner stator is to allow the deployment of machines of smaller diameter, requiring less land use and resulting in a smaller environmental footprint for the deployment of a device.

[17] For the purpose of the invention the linear movement apparatus(7) associated with each individually controlled stator module assemblies(3) have some means of movement. As examples shift arms, lead screw, hydraulic cylinder, pneumatic cylinder, linear direct drives, linear motors or any other means of moments. Other solutions involving rotary movement apparatuses could be utilized. The desired effect is the ability of moving the stator modules either towards or away from the source of the magnetic field on the hubless rotor, while limiting the hoop diameter of the device.

[18] For the purpose of the invention, the movements of the individually controlled stator module assemblies(3) are controlled with drive parameters which may be pre-defined or controlled with external information such as weather or grid forecasts, combining both production and consumption details. Depending on the usage scenario, such as collocation with renewable source of energy arrays, machine behavior could be optimized so that the stator modules are moved closer to the stator when weather forecasts indicate an upcoming large energy production by the renewable array, or further so to reduce electromagnetic losses, thus improving efficiency, when no production is expected in the near future. Further, the power output of the device can be adjusted to the expected charge or discharge need of the device. [19] The use of modular and individually movable stator module assemblies goes beyond the state of the art by first allowing the management of the apparatus response time and the efficiency to the specific usage scenario of the flywheel and the apparatus in which it is deployed. The number of stator module assemblies engaged at one time can be varied as a means of optimising the power rating at a given time. The movements of the individually controlled stator module assemblies are then controlled with drive parameters that can be pre-defined or controlled with external information such as weather or electric grid forecasts. This results in higher efficiency and good response times, as the stator module assemblies can be pre-emptively positioned closer to the rotor when a charge or discharge event is expected, or displaced further from the rotor in the opposite scenario.

[20] Further, the use of modular and individually movable stator module assemblies goes beyond the state of the art by allowing the stator to adapt to the expansions or deformations of the hubless rotor during charge and discharge events. Especially for ring shaped hubless rotors, hoop expansions or deformations are major contributors to the changing air gap between the hubless rotor and the stator cores.

Moving the stator cores allows better control of the airgap and by extension better control and drive quality of the hubless rotor.

[21] The disclosed apparatus and method further reduces the required rate of heat dissipation. This reduces the required capacity of the cooling apparatuses, and has the potential to allow natural dissipation of heat. This is particularly relevant to kinetic energy storage devices with a hubless rotor design where it can be difficult to provide adequate cooling of the hubless rotor. It further reduces back electromagnetic force induced in the hubless rotor windings, potentially removing the requirement for costly circuit breakers. Industrial Applicability

[22] The use of individually and dynamically controlled stator module

assemblies has advantages for the deployment of hubless larger scale electric motor or generators such as flywheel energy storage devices : when the diameter of the device reaches tens of meters, the hubless rotor becomes subject to expansions and deformations which may reach amplitudes sufficient to affect the efficiency of the device.

Especially in scenarios where the hubless rotor is not stabilized by its positioning on a shaft, the utilization of a individually controlled stator module assemblies can play a key role in keeping a constant air gap with the hubless rotor through its expansions or deformations in charge and discharge events. It further opens the opportunity of adapting the rated power of the device to the grid needs.

Patent Literature

[23] US 1153076 A (John O Heinze Jr), 7 Sep. 1915.

[24] US 2892144 A (Kober William), 23 Jun. 1959.

[25] US 3250976 A (Mcentire Eldon T), 19 May 1966.

[26] US 5627419 A (United Technologies Corporation), 6 May 1997.

[27] US 6194802 B1 (Dantam K. Rao) 27 Sep. 2001.

[28] US 20040160141 A1 (Jean-Yves Dube), 19 Aug. 2004.

[29] US 8803354 B2 (Unimodal Systems Lie) 12 Aug. 2014.

[30] EP 2782215 A1 (For Optimal Renewable Energy Systems S.L.), 24

Sep. 2014.

Claims

[Claim 1] An apparatus of stator cores for electric motors or generators, comprising: an actuator target mounted on a hubless ring shaped rotor(1 ) having a rotational axis; a series of individually actuated stator module assemblies(3) not connected by a common core, the assemblies thereof(3) facing towards the rotor(1 ) and distributed around its circumference at fixed distances from each other and having an air gap with the rotor(1 ), the assemblies thereof(3) comprising: at least one linear movement apparatus(7) being actuatable individually in either a radial direction, an axial direction or in any other possible direction, which may allow either the maintaining of a constant air gap or variable air gap between the stator module assemblies(3) and the rotor(1 ), or allow a different air gap between one or any other amount of individually controlled modules(3) and the hubless rotor(1 ); and a motor core comprising at least two spaced radial electromagnetic poles facing the rotor(1 ) and configured to induce electromagnetic flux with the actuator target mounted on the rotor(1 ) and mounted on the linear movement apparatus(7); and at least one motor coil(4) wound around the motor core(2).

[Claim 2] An apparatus according to the preceding claim, wherein the individually controlled stator module assemblies(3) may be alternatively situated inside, outside, above or below the rotor(1 ) or in any combination of the aforementioned configurations, so long as they are facing the rotor(1 ).

[Claim 3] An apparatus according to any of the preceding claims, wherein the linear movement apparatus(7) associated with each individually controlled modules(3) have some means of movement.

[Claim 4] An apparatus according to any of the preceding claims, wherein the movements of the individually controlled modules(3) may be controlled with drive parameters which may be pre-defined or controlled with external information such as weather or grid forecasts, combining both production and consumption details.

[Claim 5] A method of control of the stator cores for electric motors or

generators, characterised in that the stator(2) air-gap diameter is adapted by individually adjusting the respective positions of the individually controlled stator module assemblies(3) so to change the respective air gaps between the individually controlled stator module assemblies(3) and the rotor(1 ) through drive parameters which may be pre-defined or controlled with external information such as weather or grid forecasts, combining both production and consumption details.

[Claim 6] A method according to the preceding claim, wherein the individually controlled stator module assemblies’(3) respective positions are adapted to the expansion or deformation of the rotor(1 ) so to maintain constant or variable air gaps between the individually controlled stator module assemblies(3) and the rotor(1 ).

[Claim 7] A method according to claims 6 and 7, wherein one or any other

amount of individually controlled stator module assemblies’(3) respective positions can be adapted so to adjust the power rating of the device to the weather or grid forecasts, combining both production and consumption details.

[Claim 8] A method according to claims 6 to 8, wherein one or any other amount of the individually controlled stator module assemblies(3) are

positioned away from the rotor(1 ), increasing the air gap space between the stator(2) and the rotor(1 ).

[Claim 9] A method according to claims 6 to 9, wherein one or any other amount of the individually controlled stator module assemblies(3) are

positioned near to the hubless rotor(1 ), reducing the air gap space between the stator (2) and the hubless rotor (1 ).

[Claim 10] A method according to claims 6 to 10, wherein the individually

controlled stator module assemblies(3) are moved depending on the load, by means of the linear movement apparatus(7) and their associated means of movement, varying the air gap spaces between the individually controlled modules (3) and the hubless rotor(1 ).

[Claim 11] Use of individually and dynamically controlled modular stator cores for hubless electric motors or generators, as described in the preceding claims, in electric motors or generators where the hubless rotor may be subject to expansions or deformations of a magnitude sufficient to impact the efficiency of the device.

[Claim 12] Use of individually and dynamically controlled modular stator cores for hubless electric motors or generators according to claim 12, in which the electric motor or generator is used to transfer kinetic energy from or towards a flywheel.

[Claim 13] Use of individually and dynamically controlled modular stator cores for hubless electric motors or generators according to claim 12, in which the electric motor or generator forms part of an electric vehicle.