Description:FIELD OF INVENTION

The present invention deals with design and structure of rotors for a permanent magnet electrical machines.

BACKROUND OF THE INVENTION

The Permanent magnet motor is mostly preferred in domestic appliances, electric vehicle and direct drive applications etc. The surface mount and spoke type are some of the typical arrangements of rotors in permanent magnet machines.

In permanent magnet machines, the required airgap field is produced by using permanent magnets. The quantity of permanent magnets to establish required airgap flux density is reduced in spoke type rotor construction. The salient structure of spoke type machine creates difference in direct and quadrature axis inductances which produces reluctance torque that leads to additional torque. The field weakening operation required for high-speed operation is achieved effectively due to saliency in the rotor of spoke type permanent magnet motor.

The volume of magnet requirement to establish flux in conventional spoke type machine is reduced by keeping multiple magnets radially in a single pole. The existing structure of spoke type machine contains bridges to hold the multiple magnets in a single pole and the magnets are kept on the sides of rotor pole projection. The net flux produced by the magnet is reduced because of the existing structure of spoke type machine due to leakage flux. The reduction in the net flux degrades the performance and power level of the machine. In addition, the presence of direct contact between the magnet and pole shoe in the existing invention causes cancellation of flux in the pole shoe region.

This suffering is obvious and evident in the prior art.

OBJECT OF THE INVENTION

The object of the invention is to overcome the suffering identified in prior art. Accordingly what is needed and what is achieved in this invention is a novel rotor assembly that can be easily fabricated, minimizing rotor weight and optimizing net flux production and utilizing the same. The invention achieves in the field of energy efficiency by exhibiting itself high-efficiency electric motor and hence enjoys industrial utility and industrial application.

In a conventional spoke-type rotors, it essentially has more than one magnet placed between the pole segments forming the rotor core and the magnets extend in the radial direction around the rotor shaft towards the outer periphery of the rotor core. The magnets are magnetized and magnet flux generated by the magnets is collected on the pole pieces between which the magnets are placed. In a conventional spoke-type rotors, the magnetic flux density in the air gap between the stator and rotor is the useful flux which is required for rotation of rotor at predetermined speed and torque demand. It is however observed that in conventional spoke-type rotors, the mechanical structure of the core is weakening and the resistance of the rotor to centrifugal force decreased due to magnets extending from the centre outwards in the radial direction. The rotor designed herein and realized in order to attain the aim of the present invention is illustrated in the accompanying figures. The present invention is directed to an improved profile partially based on magnets shape and particularly based on the mounting position of the magnets including the shape, configuration and layout of the arrangement.

The objects and advantages of the invention will become more readily apparent upon consideration of the description disclosed in specification.

SUMMARY OF THE INVENTION

Permanent Magnet spoke type electrical machines of outer rotor (30&150) and inner rotor designs (90&110) with corresponding stator and rotor assemblies. The rotor includes iron core and multiple magnets (36), (33) of specific shape to create enhanced air gap flux density. The plurality of magnets in the rotor with different dimensions and with identical or different magnet materials contributes to the objective of the invention which is to reduce the use of magnet material and increase the power density of the motor.

Also the rotor assembly and a method for fabricating the same is disclosed which provide a solid reliable rotor assembly with improved performance. A further understanding of the nature and advantages of the present invention may be realized and understood by reference to the remaining portion of specification and the drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG.1 is a top view of rotor of the permanent magnet motor according to prior art.

FIG.2 is a sectional view of prior art explaining the flux leakage effect.

Fig.3 is the structure of outer rotor spoke type permanent magnet machine with arc type magnet according to first embodiment of present invention.

Fig.4 shows the expanded sectional view of first embodiment including the direction of flux flow.

Fig.5 is the rotor assembly of permanent magnet motor with multiple single lamination and arc type magnet according to first embodiment.

Fig.6 is the exploded view of rotor assembly of first embodiment with all the components.

Fig. 7a is a graph representing improved flux linkage wave obtained through the structure of first embodiment.

Fig. 7b is a graph representing flux linkage wave with reduction in the magnitude obtained from the prior art.

Fig. 8a is a graph showing the air gap flux density wave by proper selection of rotor pole arc and stator slot opening in the first embodiment.

Fig.8b is a graph showing the air gap flux density wave by improper selection of rotor pole arc and stator slot opening in the first embodiment.

Fig.9 is the structure of inner rotor spoke type permanent magnet machine with multiple rotor core laminations using arc type magnet according to second embodiment of present invention.

Fig.11 represents the single lamination inner rotor structure to keep arc type magnet in each pole.

Fig.12 is the expanded sectional view of single lamination arc magnet inner rotor structure with flux direction.

Fig.13 denotes the end plates to arrest axial movement of magnets in arc magnet inner rotor permanent magnet rotor.

Fig.14 Exploded view of single lamination inner rotor arc type magnet spoke rotor with all the necessary components.

Fig.15 illustrates the single lamination outer rotor structure to keep arc magnet.

DETAILED DESCRIPTION OF THE INVENTION

The present invention describes a new spoke type rotor lamination structure of the permanent magnet motor contains stator with conductor coils. The rotor can be kept inside of the armature or outside of the armature. In other words, the proposed invention is applicable to both outer rotor and inner rotor PM machines of any size. The spoke type structure is created using arc shape magnet in the present invention. The advantage of the invented lamination structure improves the net flux produced in the machine by having increased flux focusing effect. The increased power and performance of the machine are achieved due to improved net flux. Also, the present invention provides reduction in rotor core material.

Preferably the rotor of present invented lamination structure used in permanent magnet machine comprising of four rotor lamination structure:

One is outer rotor structure with separate rotor core pieces using arc shaped magnets, Second is outer rotor with interlinked rotor core structure using arc type magnet, Third one is inner rotor structure with separate rotor core pieces using arc magnets and final structure is inner rotor with interlinked rotor cores using arc shaped magnets.

Preferably the rotor lamination structure (30) made of lower (61) and upper plastic rings(62).The outer and inner periphery of upper (61) and lower (62) plastic ring and the multi piece lamination assemblies (35) has plurality bores (34&36).The dowel pins (63) connect the multi piece rotor core lamination assemblies (35) with the plastic rings (61)&(62) using the bores(34&36), the multi piece rotor core assemblies (35) are assembled in a circumferential fashion in the plastic ring. The assembly of multi piece core laminations (35) provides plurality of slots (37) in which arc shaped magnets (33) can be inserted. The hump (39) like structure in the multi piece rotor core lamination (35) acts as a stopper to avoid movement of arc magnet (33) in the radial direction.

The armature slot opening (32) of the first embodiment influences the armature tooth arc (38) portions. A proper selection of rotor pole arc (31) to armature slot opening (32) ratio improves the air gap flux density shape.

Preferably the selected value of armature slot opening (32) to rotor core pole arc (31) ratio is 0.1 to 0.2

Preferably the achieved better air gap flux density wave shape reduces the torque ripple in the machine which leads to better performance and eliminates the sudden dip in the air gap flux density value due to improper selection of rotor pole arc to armature slot opening ratio value.

Preferably in the present invention, the arc magnet with different remanence flux density value can be stacked in radial direction to achieve high air gap flux density which helps to reduce the volume of the magnet with higher remanence flux density. The arc length and number of screw holes (34&36) is increased in radial direction depending upon the number of magnets.

Preferably in the outer rotor structure (30) when multiple magnets per pole (33) are used, the magnet with higher remanence flux density value is inserted radially below the magnet with lower remanence flux density.

Preferably the requirement of rare earth magnet to increase the power density of the machine is reduced considerably by using combination of different types of magnets with different remanence flux density value which reduces the cost of the machine.

Preferably the arc shape magnet used in conventional radial flux permanent magnet machine can be used in present invention. The volume of copper requirement and rotor steel requirement are reduced significantly when the arc shape magnet is used in spoke type machine. For the same magnet volume, the arc shape magnet (33) spoke type rotor structure produces improved airgap flux density level than the prior art.

Preferably the rotor structure (30) provides significant reduction in rotor core material.

Preferably according to second embodiment wherein the construction of inner rotor lamination structure (90) is similar to outer rotor permanent magnet rotor core lamination structure.

Preferably an inner rotor spoke type machine with increased air gap flux density using multiple magnets circumferentially magnetized and similar multiple core structure. In inner rotor structure as well as outer rotor structure, the arc type magnet with individual rotor core pieces produce improved air gap flux density value compared to other structures.

Preferably the inner rotor arc magnet with separate rotor core structure (90) has multiple poles which are all placed in the respective slots (106) of the supporting plate (103). The assembly of multi-piece core lamination (95) in the supporting plate creates slots (96) in which arc magnets (93) are assembled. The supporting plate (103) provides the structural integrity of the rotor.

Preferably the single lamination inner rotor structure (110) has multiple poles in which the rotor core extension (119) acts as a magnet stopper. The radial movement of the magnets are arrested using rotor core extension (119). The rotor core bridge arm (118) of thickness 0.8mm is considered to reduce leakage flux. The bores (120) in the rotor core portion (116) provide guidance for direction of flux to flow. The centre hole (114) in the rotor core lamination is used to attach the rotor structure into shaft. The aluminium or any other non magnetic plate (142) with holes is used to stop the axial movement of magnets.

Preferably according to the final structure of the present invention, the outer rotor with inter linked rotor cores using arc magnet (150) is created by connecting the multi-piece rotor core laminations using bridge arm (152).

The invented rotor lamination structure can be made as a single lamination or multiple parts by using the bridge connector arm in the rotor lamination which enables the machine to be operated in both low speed and high-speed applications. The single rotor lamination structure reduces the number of rotor core parts, manufacturing complexity and cost of production.

The invention creates a lamination structure to include multiple magnets of different volume in each pole. The reduction in the net weight of magnet to produce required magnetic field is obtained by keeping multiple magnets per pole. Based on the requirement, the magnets are kept one over another radially in the lamination. The magnet weight reduction is achieved by using two or more magnets per pole of different dimensions.

The present invention also uses the combination of ferrite and rare earth magnet in a single pole to obtain desired air gap field. The desired air gap field can also be achieved using two or more ferrite magnets of different volume which contributes higher magnet weight.

FIG.1 illustrates the single lamination structure of inner rotor permanent magnet motor according to prior art. The rotor (10) is attached to the rotating shaft (12). The upper rare earth magnet (13) and lower ferrite magnet (14) are inserted into the upper aperture (15) and lower aperture respectively. Though the single lamination inner rotor (10) structure provides mechanical strength, the bridge in the rotor lamination and structure of lamination creates flux leakage (16) and flux cancellation (21) effect.

FIG.2 shows the sectional view of the single lamination structure of inner rotor permanent magnet motor according to prior art. The flux leakage (16) and flux cancellation (21) effect reduce the total flux established in the machine which degrades the performance of the machine.

Fig.3 illustrates the lamination structure of permanent magnet outer rotor spoke type machine to accommodate arc shape magnets according to the first embodiment of the present invention. The outer rotor structure of the first embodiment enables it to be used in low speed as well as high speed applications. The rotor includes multi-piece core portions (35) made of mild steel or silicon steel laminations or solid iron or sintered soft magnetic component (SMC). Each piece of core lamination (36) is arranged circumferentially in forming the rotor. The selection of pole arc (31) and slot opening (32) value determine the proper flux density value. The arc magnet (33) volume is determined from the desired airgap flux density value. The existing conventional radial flux permanent magnet machine designed with arc magnet is also converted into spoke type machine. In the process of converting the radial flux permanent magnet machine into spoke type structure, the rotor core structure is only modified without changing the arc magnet and stator of conventional machine. The dowel pins (63) are passed through the screw holes (34) and (35) in the rotor lamination structure (30) to fix the lamination (36) into the plastic plate (61). The shown arc magnet lamination structure (30) is accommodated with single ferrite magnet (33). The number of magnets with different arc length (37) and volume can be stacked adjacent to each other in the rotor core (36) portion to improve the flux density level.

Fig.4 shows the expanded sectional view of first embodiment with flux path directions. The direction of flux lines (41) is determined by the direction of magnetization. There is no pole arc overlap in the arc magnet spoke type lamination structure which avoids flux cancellation effect.

The invention relates to spoke type permanent magnet motors of both outer rotor and inner rotor construction. The motor consists of rotor carrying the permanent magnets and the stator carrying the winding. The stator windings are excited by required excitation voltage which generates the armature reaction field. The interaction of armature reaction field and main field produced by the permanent magnet develop the force to run the motor. The excitation of required winding is initiated by the position information. The commutation action of each winding is controlled by electronic switches.

FIG. 5 illustrates the rotor assembly of first embodiment. The rotor core lamination (36) and magnets (33) are assembled as single rotor assembly (50) by using plastic rings (61&62).

FIG. 6 illustrates the exploded view of rotor assembly of first embodiment with necessary components. The bottom plastic ring (61) in which the rotor core laminations (36) and magnets (33) are located to form circular rotor structure (30). The dowel pins (63) are used to hold the rotor core laminations (36) and bottom plastic ring (61) in their respective locations. The dowel pin (63) is inserted into the rotor core lamination hole (34) and the hole (35) through the rotor plastic plates. After inserting the dowel pins (63), the rotor core lamination (36) and bottom plastic ring (61) are held together. The fixing of rotor core laminations (36) in its respective position creates aperture (37) place the magnets. The magnet (33) is press fitted or adhesively fixed into its respective aperture. The attachment of rotor core laminations (36) and magnets (33) in the bottom plastic ring (61) creates rotor structure (50) of the outer rotor permanent magnet motor. The top plastic ring (62) is fastened with the bottom plastic ring (61) using dowel pins (63). In another embodiment of the invention, similar arrangement is proposed for inner rotor machine.

FIG.7a and FIG.7b are the graphs representing flux linkage waveform obtained through the structure of first embodiment and prior art respectively. The first embodiment of the present invention shows improved flux linkage compared to prior art. The improvement in flux linkage is obtained from the selection of pole arc (31) and flux focusing effect of arc magnet by proper shaping of rotor core. For the given total volume of magnet, the increased flux linkage is obtained by shaping the rotor core (36). The shaping of rotor core (36) should offer minimum reluctance for the flow of flux. There will be a reduction in the flux linkage if the rotor core is not properly shaped.

FIG.8a illustrates the air gap flux density wave of first embodiment with proper selection of rotor pole arc (31) and slot opening (32).

Fig.8b illustrates the air gap flux density wave of first embodiment with improper selection of rotor pole arc (31) and slot opening (32).

The shape of air gap flux density wave depends on the rotor pole arc (31) and stator slot opening (32) in the first embodiment. For the stator slot opening (32) to rotor pole arc (31) ratio value of 0.1 to 0.2 better air gap flux density wave is obtained.

Fig. 9 is the lamination structure that can be used for inner rotor permanent magnet motor according to another embodiment of present invention. The inner rotor multiple rotor core lamination structure in Fig.9 can be used to accommodate multiple magnets per pole of same type or different type. The similar lamination structure used in first embodiment is used to construct all the inner rotor lamination structure of present invention. The circumferential arrangement of the rotor core (95) lamination in the supporting plate (104) creates aperture (106) to hold the magnet (93). The core lamination (95) is connected to the shaft through the nonmagnetic supporting plates (104).

Fig.10 denotes the exploded view of inner rotor multiple rotor core arc magnet spoke type rotor with all the components. The supporting plates (103&104) are used to provide structural integrity of the rotor as well to stop the axial movement of magnets (93). The screws (102) are inserted to one of the end supporting plates (103) and passed through the one end of the flux guiding holes (94) in the rotor core (95). Another end plate (104) is inserted into the extended screw portion in the other end of the rotor core (95) and fastened using nuts (105). The material used for end plates (103&104) can be aluminium or any other non magnet material.

Fig.11 represents the single lamination inner rotor structure (110) to keep arc type magnet (113) in each pole. The rotor pole arc (111) is chosen for the considered stator slot opening (112) in such a way that the ripple content in the torque is minimum. The bridge arm (118) in the rotor core portion (116) connects the rotor pole (116) and shaft holder (114) portion. The circumferential arrangement of rotor core (116) portion creates the inner rotor single lamination structure (110). The arc magnet (113) is inserted in the aperture (117) created between the adjacent rotor core portion. The horn like structure acts as a magnet stopper (119) which arrests the radial movement of magnets (113) while the machine is operated. The holes (120) in the rotor core (116) portion provides guiding path for the magnetic flux.

Fig.12 is the expanded sectional view of single lamination arc magnet inner rotor structure with direction of magnetization and flux direction. The magnets (113) are placed in such a way that like poles are created in alternate rotor core portion (116).

Fig.13a & Fig.13b shows the top view of inner rotor single lamination arc magnet rotor and end plate of the inner rotor structure respectively.

Fig.14 denotes the exploded view of inner rotor single lamination arc magnet spoke type rotor with all the components. The end plates (142&143) are used to stop the axial movement of magnets (113). The screws are inserted to one of the end plates (144) and passed through the one end of the flux guiding holes (120) in the rotor core (116). Another end plate (142) is inserted into the extended screw portion in the other end of the rotor core (116) and fastened using nuts (141). The material used for end plates (142&143) can be aluminium or non-magnetic material.

Fig.15 shows the outer rotor single lamination structure to accommodate arc magnets (33). The bridge arm (152) in the structure converts the multi-piece lamination structure into single lamination structure.

As detailed above a rotor assembly and a method for fabricating the same is provided and it will be appreciated that there are numerous techniques that may be used to fabricate the rotor assembly but this invention optimizes the fit between the magnets and the core and this alternate new fabrication process and the arrangement is unknown in prior art and hence exhibits advantages not identified in conventional arrangement.

The novel feature of the invention are :

1. The rotor of a permanent magnet machine comprising:
a rotor core lamination structure (36) made of lower plastic ring (61) and upper plastic ring (62). The upper plastic ring (62) and lower plastic ring (61) has the slot groove to receive multi-piece core lamination assemblies (36), the outer periphery and inner periphery of the said plastic rings has plurality of outer circumferential and inner circumferential holes, a plurality of through bolts (63) connects the upper (62) and lower plastic ring (61) using the said holes . The said multi piece core lamination assemblies (36) has plurality head holes (34&35), the through bolts (63) connects lamination assemblies (36) with the plastic rings (61) & (62) using the holes (34&35), the said multi piece core lamination assemblies (36) are assembled in a circumferential fashion; the assembly of multi piece core lamination (36) provides plurality of slots in between to house the magnets.

The arc shaped permanent magnet (33) is placed in the said magnet housing between the multi piece core lamination (36)

2. The rotor according to first embodiment is such that wherein arc shape magnet is inserted between the adjacent rotor core laminations. The armature slot opening of the first embodiment influences the armature tooth arc portions. A proper selection of rotor pole arc to armature slot opening ratio improves the air gap flux density shape.

3. The above spoke type outer rotor permanent magnet motor is such that the selected value of armature slot opening to rotor core pole arc ratio is 0.1 to 0.2.

4. The above spoke type outer rotor permanent magnet motor is such that the achieved better air gap flux density wave shape reduces the torque ripple in the machine which leads to better performance and eliminates the sudden dip in the air gap flux density value due to improper selection of rotor pole arc to armature slot opening ratio value.

5. The above rotor is such that multiple magnets with different remanence flux density value can be inserted radial direction. The magnet with higher remanence flux density value is kept radially below the magnet with lower remanence flux density value.

6. The above rotor is such that the requirement of rare earth magnet to increase the power density of the machine is reduced considerably by using combination of different types of magnets with different remanence flux density value which reduces the cost of the machine.

7. The above rotor as per second embodiment is such that wherein the construction of inner rotor with multiple rotor core lamination structure using arc magnet is similar to outer rotor permanent magnet with multiple rotor core lamination structure. Using the arc magnet with multiple rotor structure, the air gap flux density value of magnitude 1.6 times the remanence flux density of magnet can be achieved.

8. The above rotor is such that the volume of copper requirement and rotor steel requirement are reduced significantly.

9. The above rotor according to third embodiment is such that wherein the inner rotor single lamination spoke type rotor uses arc type magnet to produce the necessary magnetic field. The single lamination inner rotor structure is created using the bridge arm introduced between the rotor core pieces.

10. The above rotor is such that the thickness of bridge arm influences the air gap flux density of the machine. The bridge arm of thickness 0.8mm is considered in this single lamination structure.

11. The above rotor according to fourth embodiment is such that wherein the construction of outer rotor single lamination structure is similar to inner rotor permanent magnet single lamination rotor core structure.

In one aspect a rotor of spoke type permanent magnet machine comprising of plurality of arc shaped magnets arranged circumferentially on the rotor, wherein the rotor is outer rotor structure or the rotor is inner rotor structure. The rotor core pieces may be plurality of separate rotor pieces using arc shaped magnets or may be plurality of interlinked rotor pieces using arc shaped magnets.

In another aspect the invention is for rotor of spoke type permanent magnet machine of outer rotor stator with a rotor and a stator which is separated by air gap and the stator is coupled to a stationery shaft of the machine with rotor carrying the permanent magnets and the stator carrying the windings, comprises of a cylindrical rotor core. It has an upper plastic ring (61) having plurality of an inner and an outer circumferential holes radially spaced apart and slot grooves forming one portion of rotor core laminations structure (36) and a lower plastic ring (62) having plurality of an inner and an outer circumferential holes radially spaced apart and slot grooves forming the other portion of rotor core laminations structure (36). There is a magnetic wall surrounding the two rings. A plurality of core lamination assemblies (36) with a plurality of head holes (34,35) are mounted radially onto corresponding slot grooves of the rings to form the cylindrical rotor having plurality of slots therein between such that a shoulder portion is formed on outer peripheral ends and sidewall portions formed on sides, thereby forming a series of upper apertures and a series of lower apertures radially between laminations. There is also a plurality of bolts (63) correspondingly connecting the upper ring (61) to lower ring (62) through the circumferential holes of the ring and to the core lamination assemblies (36) through the head holes (34,35). The arrangement includes a plurality of T configuration magnets each set formed with two magnets, with one arc shaped magnet as upper magnet and another as lower magnet and both arranged such that upper magnet is disposed along the upper aperture between adjacent shoulders of two laminations and the lower magnets disposed along the sides in lower apertures between adjacent walls of two laminations and further with like poles created in alternate rotor core portion and with lower magnets arc spaced out from corresponding rotor pole arc at air gap thereby avoiding direct contact between lower magnets and the corresponding rotor poles arc and the said surrounding magnetic wall supports the mounted magnets onto the rotor core. The said arrangement characterised in the selection value of armature slot opening to rotor core pole arc ratio 0.1 to 0.2 thereby improving the air gap flux density to a magnitude of 1.6 times the remanence flux density of the magnet.

In another aspect, the invention is for rotor of spoke type permanent magnet machine with inner rotor structure. It has a plurality of rotor core (95) lamination arranged on a non-magnetic supporting plate (104) circumferentially, thereby creating aperture (106) therein between. It also has a plurality of arc magnets (93) disposed on said apertures (106), and core lamination (95) connected to the shaft through the said supporting plates (104).

In another aspect of invention the arrangement includes the plurality of magnets will have same or different remanence flux density value and wherein a magnet with higher remanence flux density value is disposed radially below a magnet with lower remanence flux density value.

It should be noted that while in preferred embodiments the magnets profiles are shown and described above as arc shaped, and there can be reproducible according to the method outlined regardless of the particular size of the rotors desired. It is also possible to use the same method and principles to develop rotors of more or less than the arc shape defined, described and disclosed and illustrated herein. As per the invention that it is a fact that rotor is now perfectly dynamically balanced and hence minimizes the motor state also. Hence the invention has achieved a novel rotor and a novel method of making a rotor is secured and efficiently advantageous than known prior art.

Hence the design so disclosed has a configuration, which is major departure from conventional design and configuration and from the way flux is established and manipulated in the stator and motor parts in order to create a more efficient conversion of electrical energy to mechanical energy. The configuration and shape of magnets of this invention is very different from traditional motors.

From the foregoing, further variations adaptations and modifications can be evolved by those skilled in the art, to which the invention is addressed within the scope of the claims annexed herewith. , Claims:WE CLAIM :

1. A rotor of spoke type permanent magnet machine comprising of plurality of arc shaped magnets arranged circumferentially on the rotor.

2. The rotor of spoke type permanent magnet machine as claimed in claim 1, wherein the rotor is outer rotor structure.

3. The rotor of spoke type permanent magnet machine as claimed in claim 1, wherein the rotor is inner rotor structure.

4. The rotor of spoke type permanent magnet machine as claimed in claims 2 and 3, wherein the rotor core pieces are plurality of separate rotor pieces using arc shaped magnets.

5. The rotor of spoke type permanent magnet machine as claimed in claims 2 and 3, wherein the rotor core pieces are plurality of interlinked rotor pieces using arc shaped magnets.

6. The rotor as claimed in claim 2 is a rotor of spoke type permanent magnet machine with a rotor and a stator separated by air gap and stator coupled to a stationery shaft of the machine with rotor carrying the permanent magnets and the stator carrying the windings, comprising of :
a. a cylindrical rotor core,
b. an upper plastic ring (61) having plurality of an inner and an outer circumferential holes radially spaced apart and slot grooves forming one portion of rotor core laminations structure (36),
c. a lower plastic ring (62) having plurality of an inner and an outer circumferential holes radially spaced apart and slot grooves forming the other portion of rotor core laminations structure (36),
d. a magnetic wall surrounding the two rings,
e. a plurality of core lamination assemblies (36) with a plurality of head holes (34,35) mounted radially onto corresponding slot grooves of the rings to form the cylindrical rotor having plurality of slots therein between such that a shoulder portion is formed on outer peripheral ends and sidewall portions formed on sides, thereby forming a series of upper apertures and a series of lower apertures radially between laminations,
f. a plurality of bolts (63) correspondingly connecting the upper ring (61) to lower ring (62) through the circumferential holes of the ring and to the core lamination assemblies (36) through the head holes (34,35), and
g. a plurality of T configuration magnets each set formed with two magnets, with one arc shaped magnet as upper magnet and another as lower magnet and both arranged such that upper magnet is disposed along the upper aperture between adjacent shoulders of two laminations and the lower magnets disposed along the sides in lower apertures between adjacent walls of two laminations and further with like poles created in alternate rotor core portion and with lower magnets arc spaced out from corresponding rotor pole arc at air gap thereby avoiding direct contact between lower magnets and the corresponding rotor poles arc and the said surrounding magnetic wall supports the mounted magnets onto the rotor core,

the said arrangement characterised in the selection value of armature slot opening to rotor core pole arc ratio 0.1 to 0.2 thereby improving the air gap flux density to a magnitude of 1.6 times the remanence flux density of the magnet.

7. The rotor of spoke type permanent magnet machine as claimed in claim 3 comprising of :
a. a plurality of rotor core (95) lamination arranged on a non-magnetic supporting plate (104) circumferentially, thereby creating aperture (106) therein between,
b. a plurality of arc magnets (93) disposed on said apertures (106), and
c. core lamination (95) is connected to the shaft through the said supporting plates (104).

8. The rotor as claimed in claims 6 and 7, wherein the plurality of magnets will have same or different remanence flux density value.

9. The rotor as claimed in claims 8, wherein a magnet with higher remanence flux density value is disposed radially below a magnet with lower remanence flux density value.