Title of Invention

INVERTED SWITCHED RELUCTANCE MOTOR AS HUB DRIVE FOR ELECTRIC VEHICLE

Abstract

The present invention relates to an inverted switched reluctance motor comprising at least three phases. The motor (10) comprises stator (12), rotor (11), where rotor (11) is received by central bore defined by the stator. The rotor circumscribes the stator and comprises plural radially oriented non skewed poles (14) extending inwardly in a predetermined manner. The stator (12) comprises plural non skewed poles (13) radially oriented in a manner to be located in a desired reluctance position. The stator poles comprises phase windings being wound around it to generate suitable torque to rotate the rotor. The invention also relates to a drive system comprising motor (10), converter means (23) and control means (25).

Full Text

FORM2 THE PATENTS ACT, 1970 (39 of 1970) & The Patents Rules, 2003 COMPLETE SPECIFICATION (See section 10; rule 13) 1. Title of the invention. - "INVERTED SWITCHED RELUCTANCE MOTOR ASHUB DRIVE FOR ELECTRIC VEHICLE" 2. Applicant(s) (a) NAME : INDIAN INSTITUTE OF TECHNOLOGY (b) NATIONALITY: Created by an act of Parliament, Institute of Technologies Act, 1961. (c) ADDRESS : Indian Institute of Technology, Bombay, India.. 3. PREAMBLE TO THE DESCRIPTION The following specificati it is to be performed: on particularly describes the invention and the manner in which FIELD OF INVENTION The present invention relates to improvements in wheeled vehicles of the type having an electric powered motor in-wheel drive systems. More particularly, the invention relates to an inverted switched reluctance motor drive system for in wheel vehicle applications adapted to provide improved efficiency, compactness and maintenance free operation in the vehicle system. BACKGROUND AND PRIOR ART Electrically powered vehicles are similar to vehicles powered by an internal combustion engine. The electric vehicle is attractive in that the power unit therefore, in the form of a rechargeable battery pack, is environmentally clean (e.g., does not pollute the air during its operation) and its operation is silent. Switched reluctance motor drives are relatively new entrants in the rapidly developing variable speed drive market. They are inherently variable speed drives featuring simple construction, a wide speed range, good efficiency, and high ratios of torque to inertia. The rotor is simple and requires relatively fewer manufacturing steps; the stator is easy to wind. These make switched reluctance motor a low cost and reliable machine. Because the rotor does not generate significant heat, the motor is relatively easy to cool. Switched reluctance motors thus can be used in high temperature and hostile operating environments, as in vehicles. Switched reluctance motors torque production 2 depends on the stator current magnitude regardless of the direction. This resultant unidirectional flux yields lower core losses. Traditionally inner rotor switched reluctance motor have gained a lot of attention for its simplicity and safe operation. Because of its wide speed range operation, the switched reluctance motor is particularly suitable for vehicle propulsion. US 5111096 mentions about a switched reluctance motor that can not be used as a direct drive as in the present invention. Topology of outer rotor geometry is not found in the prior art. Similarly, US6404095 discloses an assembled type motor outer stator, wherein this stator is of segmented construction, it comprises the conventional winding way for a stator exciting coil and it is inner rotor motor. Topology of outer rotor geometry is not found in the prior art. Thus there is a need to provide an inverted switched reluctance motor drive system for in wheel vehicle applications adapted to provide improved efficiency, compactness and maintenance free operation in the vehicle system. The present inventors have found that by using a outer rotor geometry higher drive efficiency can be achieved due to reduction in transmission loss and better performance can be obtained by controlling each wheel independently. 3 OBJECTS OF INVENTION Accordingly, one object of the present invention is to provide an inverted switched reluctance motor with higher efficiency and compactness. Another object of the present invention is to provide an inverted switched reluctance motor that is wheeled for vehicle application. Another object of the present invention is to provide a windingless, magnetless rotor poles. Another object is to provide appropriate controlling of phase firing in accordance with rotor position. Yet another object is to urge the rotor towards minimum reluctance and maximum inductance position. Another object of the present invention is to provide a drive system comprising inverted switched reluctance motor. SUMMARY OF INVENTION According to one aspect of the present invention there is provided an inverted switched reluctance motor comprising at least three phases, said motor comprising: stator; 4 rotor, said rotor being received by central bore defined by said stator; wherein said rotor circumscribing stator characterized in that said rotor comprising plural radially oriented non skewed poles extending inwardly in a predetermined manner, said stator comprising plural non skewed poles being radially oriented in a manner to be located in a desired reluctance position, said stator poles being characterized by plural phase windings being wound around the stator such that for every stator pole a corresponding pole of opposite polarity is established so as to generate suitable torque thereby rotating the rotor towards a minimum reluctance and maximum inductance position hence increasing the overall efficiency of the system. According to another aspect of the present invention there is provided a drive system comprising: inverted switched reluctance motor comprising at least three phases, said motor including stator; rotor, said rotor being received by central bore defined by said stator; 5 wherein said rotor circumscribing stator characterized in that said rotor comprising plural radially oriented non skewed poles extending inwardly in a predetermined manner, said stator comprising plural non skewed poles being radially oriented in a manner to be located in a desired reluctance position, said stator poles being characterized by plural phase windings being wound around the stator such that for every stator pole a corresponding pole of opposite polarity is established; converter means being operatively connected to said phase windings of the stator such that current flows in a predetermined direction; control means operatively connected to said converter means so as to control phase firing based on rotor position and energizing phases so as to generate suitable torque thereby rotating the rotor towards a minimum reluctance and maximum inductance position hence increasing the overall efficiency of the system. DETAILED DESCRIPTION OF INVENTION In the inverted switched multiple phase reluctance motor of the present invention the principle of making outer rotor geometry is based on the classical switched reluctance motor. 6 In one embodiment of the present invention the motor drive system comprises at least three phases. The system comprises a stator and a rotor. Stator comprises a stack of plate laminations that are formed of a ferromagnetic material. Laminations are stacked face-to-face and suitably adhered to one another by means conventionally known in the art. Stator includes a plurality of like, outwardly extending stator poles having outwardly facing concave stator pole faces. Rotor circumscribing the stator comprises plurality of like, inwardly extending rotor poles having outwardly facing concave rotor pole faces. The stator has at least three poles and the rotor has at least two poles. In the embodiment shown, stator has six stator poles. Stator pole faces define a central bore for receiving rotor. Plural phase windings are wound about the stator poles such that for every stator pole of one polarity there is a corresponding pole of an opposite polarity. In one embodiment of the present invention a drive system comprising inverted motor as described above includes selected windings connected to converter means which is operatively connected to controller means which comprises current pulse generating circuit conventional in the art and is operable to selectively generate pulses of electrical current through windings. The timing of current pulses generated by current pulse generating circuit in the controller is determined by a position sensor. Position sensor may be a Hall effect sensor, a resolver or an encoder. Alternatively, self-inductance of phase windings may be used to indicate the position of the rotor relative 7 to the stator. The position sensor is located on outer body of rotor and provides a signal indicative of the relative position of rotor relative to stator. Position sensor has an output connected to a controller for reporting the angular position of rotor relative to stator. Controller is connected to the converter, for controlling the firing of the respective phases in accordance with the position of rotor relative to stator. In the present case the system is considered to be a three phase system (hereinafter phases being referred to as phase A, phase B and phase C) . At zero degree rotor position the controller provides an excitation in the phase windings to generate a torque on rotor causing rotor to rotate counterclockwise and to align wide rotor pole with the excited phase. At 22.5 degrees rotor position, wide rotor poles and adjacent energized phase A, stator poles are in a minimum reluctance position with respect to each other as a result of a constant gap being formed there between. Stator is disposed within central bore defined by rotor pole faces. Rotor is comprised of a stack of plate laminations that are formed of a ferromagnetic material. Starting from the zero degree rotor position, controller energizes phase A. This excitation produces a torque on rotor causing rotor to rotate counterclockwise and to align wide rotor poles with excited phase. At 22.5 degrees rotor position, wide rotor poles, adjacent energized phase A, and stator poles are in a minimum reluctance position with respect to each other as a result of a constant gap being formed therein. 8 The rotor is advanced through 15 mechanical degrees by the energization of phase B and de-energization of phase A. However, the movement of rotor may extend beyond 15 mechanical degrees by similar energization of phase C. The increasing or decreasing inductance of a phase winding corresponds to the respective decreasing or increasing reluctance in the magnetic flux path associated with the phase winding. In one of the applications in vehicles, the stator is fixed over the hub shaft and rotor is fixed between front and rear disc. These discs are mounted over the hub shaft through bearings. These discs are fixed inside the wheel rim and the tyre covers this rim. A change in inductance with change in angular position (dl/d.theta.) is produced in phase A and windings 16aa, 16ab having a slope that increases and decreases at a rate. At zero degree rotor position, the phase A windings are energized in response, rotor experiences a torque in a counterclockwise direction that results in minimum reluctance in the rotor, maximum inductance position with respect to stator. BRIEF DESCRIPTION OF ACCOMPANYING FIGURES Figure 1 illustrates a switched reluctance motor with six stator poles and four rotor poles. Figure 2 illustrates sectional view of an inverted switched reluctance motor with six stator poles, eight rotor poles, 9 converter 23, controller 25, power supply 24, sensor input 26, phase windings 16aa, 16ca, 16ba, 16ab, 16cb, 16bb, stator 11, and rotor 10. Figures 3 and 4 illustrate magnetic flux patterns in under-aligned and just-unaligned conditions under the excitation of a phase of the motor shown in figure 1. Figure 5 illustrates sectional view of the assembly of switched reluctance motor and the respective vehicle wheel. Figure 6 illustrates an inductance profile of a phase with respect to the rotation of the rotor relative to the stator. DETAILED DESCRIPTION OF ACCOMPANYING FIGURES FIG. 2 shows a 6/8 motor 10, i.e., a motor having a inner stator with six stator poles and a rotor with eight rotor poles. During each phase energization, two of the six-stator poles are energized. Energization of a particular phase causes the rotor to rotate in a step manner but due to synchronization of rotor position and phase excitation, rotor is made to rotate continuously. Motor 10 is comprised of a stator 12 and a rotor 11. Stator 12 includes a plurality of like, outwardly extending stator poles 13 having outwardly facing concave stator pole faces. Rotor 11 includes a plurality of like, inwardly extending rotor poles 14 having outwardly facing concave rotor pole faces. In the embodiment shown, stator 12 has six stator poles. Stator pole faces define a central bore for receiving rotor 10 11. Phase windings 16aa, 16ab are wound about one of the stator pole 13Aa, 13Ab other stator poles 13Ba, 13Bb, 13Ca, and 13Cb are wound such that for every stator pole 13 of one polarity there is a corresponding pole of an opposite polarity. As schematically illustrated in FIG. 2, windings 16aaf 16ab are connected to a converter 23 in Leg A. A controller 25 has a pulse generating logic based on rotor position feedback from sensor circuit 26. Windings 16aa and 16ab are connected to Leg A of converter 23, windings 16ba and 16bb are connected to Leg B of converter 23 and windings 16ca and 16cb are connected to Leg C of converter 23, as shown in FIG. 2 As illustrated in FIG. 2, phase A windings 16aa and 16ab are series connected such that current flows through the phase winding only in one direction. It is to be appreciated, however, that the phase windings could be parallel connected, or combination series-parallel connected, to their respective sources of switched current. The current pulse generating circuit in controller 25 is conventional in the art and is operable to selectively generate pulses of electrical current through windings 16aa, 16ab, 16ba, 16bb, 16ca and 16cb. The timing of current pulses generated by current pulse generating circuit in controller 25 is determined by a position sensor 26. Position sensor 26 may be a Hall effect sensor, a resolver or an encoder. Alternatively, self-inductance of phase windings 16aa, 16ab, 16ba, 16bb, 16ca and 16cb may be used to indicate the position of the rotor relative to the stator. Position sensor 26 is located on outer body of rotor llmotor 10 and provides a signal indicative of the 11 relative position of rotor 11 relative to stator 12. Position sensor 26 has an output connected to a controller 25 for reporting the angular position of rotor 11 relative to stator 12. Controller 26 is connected to converter 23, for controlling the firing of the respective phases in accordance with the position of rotor 11 relative to stator 12. In the embodiment shown in FIGS. 1-5, motor 10 is a unidirectional motor in which rotor 11 rotates in a counterclockwise (CCW) direction with respect to stator 12. It will of course be appreciated that the motor could be designed for clockwise (CW) rotation and that the direction of rotation is not to be construed as limiting the invention. Referring now to stator 12, in the embodiment shown, stator 12 is disposed within central bore defined by rotor 11 pole faces. Like stator 12, rotor 11 is comprised of a stack of plate laminations that are formed of a ferromagnetic material. Starting from the zero degree rotor position shown in FIG. 3, controller 25 energizes phase A This excitation produces a torque on rotor 11 causing rotor 11 to rotate counterclockwise and to align wide rotor poles with excited phase. In FIG. 3, at 22.5 degrees rotor position, wide rotor poles 54 and adjacent energized phase A, stator poles are in a minimum reluctance position with respect to each other as a result of a constant gap being formed there between. FIG. 3 show magnetic flux patterns corresponding to the position of rotor 11 and energizations of phase A in just aligned case. FIG. 4 shows magnetic flux patterns corresponding to the position of rotor 11 and energizations of phase C in aligned case. 12 Referring now to FIG. 5, stator 12 is fixed over the hub shaft 38 and rotor 11 is fixed between front and rear disc 32. These disc 32 are mounted over the hub shaft 38 through bearings 37. These discs 32 are fixed inside the wheel rim 40 and the tyre 31 covers this rim 40. It is to be appreciated that FIG. 5 illustrates the assembly of the motor 10 inside the wheel. It is to be appreciated that FIG. 6 is for illustration purposes and is not to be construed as limiting the invention. At zero degree rotor position, the phase A windings are energized in response, rotor 11 experiences a torque in a counterclockwise direction that urges rotor 11 towards a minimum reluctance, maximum inductance position with respect to stator 12. Application : The motor of the present invention can be applied in midrange motorcycles, any four wheelers and the like. The foregoing description discloses preferred embodiments of the invention. The embodiments are described for the purpose of illustration only. It will be appreciated that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the present invention. Moreover, the embodiments show an inner stator and outer rotor switched reluctance motor. Similar motors having an inner stator and outer rotor having different combinations of radially oriented stator poles with different shapes in order to 13 balance the torque production and minimization of vibrations are contemplated by the present invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or equivalents thereof. 14 WE CLAIM 1. An inverted switched reluctance motor comprising at least three phases, said motor comprising: stator; rotor, said rotor being received by central bore defined by said stator; wherein said rotor circumscribing stator characterized in that said rotor comprising plural radially oriented non skewed poles extending inwardly in a predetermined manner, said stator comprising plural non skewed poles being radially oriented in a manner to be located in a desired reluctance position, said stator poles being characterized by plural phase windings being wound around the stator such that for every stator pole a corresponding pole of opposite polarity is established so as to generate suitable torque thereby rotating the rotor towards a minimum reluctance and maximum inductance position hence increasing the overall efficiency of the system. 2. Motor as claimed in claim 1, wherein the stator poles comprise outwardly facing concave stator pole faces. 15 Motor as claimed in claims 1 and 2, wherein the stator poles comprises ferromagnetic lamination stack. Motor as claimed in claims 1 to 3, wherein the stator comprises at least three poles. Motor as claimed in claim 1, wherein the rotor poles comprise outwardly facing concave rotor pole faces. Motor as claimed in claim 4, wherein the rotor poles comprises ferromagnetic lamination stack. Motor as claimed in claims 5 and 6, wherein the rotor comprises at least two poles. Motor as claimed in any preceding claims wherein the rotor is bi-directional. A drive system comprising: inverted switched reluctance motor comprising at least three phases, said motor including stator; rotor, said rotor being received by central bore defined by said stator; wherein said rotor circumscribing stator characterized in that 16 said rotor comprising plural radially oriented non skewed poles extending inwardly in a predetermined manner, said stator comprising plural non skewed poles being radially oriented in a manner to be located in a desired reluctance position, said stator poles being characterized by plural phase windings being wound around the stator such that for every stator pole a corresponding pole of opposite polarity is established; converter means being operatively connected to said phase windings of the stator such that current flows in a predetermined direction; control means operatively connected to said converter means so as to control phase firing based on rotor position and energizing phases so as to generate suitable torque thereby rotating the rotor towards a minimum reluctance and maximum inductance position hence increasing the overall efficiency of the system. 10. System as claimed in claim 9, wherein the control means is adapted to energize phase A starting from zero degree position thereby producing torque on the rotor so as to align rotor poles with the excited phase. 17 11. System as claimed in claims 9 and 10, wherein the control means being adapted to energize phase A such that rotor poles are placed adjacent to energized phase A at 22.5 degree rotor position in a manner that the stator poles are in a minimum reluctance position with respect to each other. 12. System as claimed in claims 9 to 11 further comprising position sensor, selectively a hall effect sensor, a resolver or an encoder adapted to identify angular position of the rotor. 13. System as claimed in any preceding claims adapted to produce a change in inductance in phase A and windings 16aa, 16ab with change in angular position of the rotor. 14. Motor and system as claimed in any preceding claims is used for improved performance in midrange motorcycles, four wheelers and the like. 15. An inverted switched reluctance motor and drive system as herein substantially described and illustrated with reference to the accompanying figures. Dated this the 26th day of February 2007 Ashwini Sandu Of S. Majumdar & Co. Applicant's Agent 18 ABSTRACT TITLE : INVERTED SWITCHED RELUCTANCE MOTOR AS HUB DRIVE FOR ELECTRIC VEHICLE The present invention relates to an inverted switched reluctance motor comprising at least three phases. The motor (10) comprises stator (12), rotor (11), where rotor (11) is received by central bore defined by the stator. The rotor circumscribes the stator and comprises plural radially oriented non skewed poles (14) extending inwardly in a predetermined manner. The stator (12) comprises plural non skewed poles (13) radially oriented in a manner to be located in a desired reluctance position. The stator poles comprises phase windings being wound around it to generate suitable torque to rotate the rotor. The invention also relates to a drive system comprising motor (10), converter means (23) and control means (25). Figure 2

Documents:

365-MUM-2007-ABSTRACT(26-2-2007).pdf

365-MUM-2007-ABSTRACT(29-6-2009).pdf

365-MUM-2007-ABSTRACT(GRANTED)-(30-7-2010).pdf

365-mum-2007-abstract.doc

365-mum-2007-abstract.pdf

365-MUM-2007-CANCELLED PAGES(25-3-2010).pdf

365-MUM-2007-CLAIMS(26-2-2007).pdf

365-MUM-2007-CLAIMS(29-6-2009).pdf

365-MUM-2007-CLAIMS(AMENDED)-(25-3-2010).pdf

365-MUM-2007-CLAIMS(GRANTED)-(30-7-2010).pdf

365-mum-2007-claims.doc

365-mum-2007-claims.pdf

365-mum-2007-correspondance-received.pdf

365-MUM-2007-CORRESPONDENCE(01-12-2009).pdf

365-MUM-2007-CORRESPONDENCE(12-5-2008).pdf

365-MUM-2007-CORRESPONDENCE(29-6-2009).pdf

365-MUM-2007-CORRESPONDENCE(29-9-2008).pdf

365-MUM-2007-CORRESPONDENCE(3-4-2009).pdf

365-MUM-2007-CORRESPONDENCE(IPO)-(9-8-2010).pdf

365-mum-2007-correspondence-received.pdf

365-mum-2007-description (complete).pdf

365-MUM-2007-DESCRIPTION(COMPLETE)-(26-2-2007).pdf

365-MUM-2007-DESCRIPTION(COMPLETE)-(29-6-2009).pdf

365-MUM-2007-DESCRIPTION(GRANTED)-(30-7-2010).pdf

365-MUM-2007-DRAWING(26-2-2007).pdf

365-MUM-2007-DRAWING(GRANTED)-(30-7-2010).pdf

365-mum-2007-drawings.pdf

365-MUM-2007-FORM 1(26-2-2007).pdf

365-MUM-2007-FORM 1(29-6-2009).pdf

365-MUM-2007-FORM 18(8-3-2007).pdf

365-mum-2007-form 2(29-6-2009).pdf

365-MUM-2007-FORM 2(COMPLETE)-(26-2-2007).pdf

365-MUM-2007-FORM 2(GRANTED)-(30-7-2010).pdf

365-MUM-2007-FORM 2(TITLE PAGE)-(26-2-2007).pdf

365-MUM-2007-FORM 2(TITLE PAGE)-(29-6-2009).pdf

365-MUM-2007-FORM 2(TITLE PAGE)-(GRANTED)-(30-7-2010).pdf

365-mum-2007-form-1.pdf

365-mum-2007-form-2.doc

365-mum-2007-form-2.pdf

365-mum-2007-form-3.pdf

365-MUM-2007-POWER OF ATTORNEY(16-4-2007).pdf

365-MUM-2007-REPLY TO EXAMINATION REPORT(25-3-2010).pdf

365-MUM-2007-SPECIFICATION(AMENDED)-(25-3-2010).pdf

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