Description:Before explaining the present invention in detail, it is to be understood that the invention is not limited in its application to the details of the construction and arrangement of parts illustrated in the accompanying drawings. The invention is capable of other embodiments, as depicted in different figures as described above and of being practiced or carried out in a variety of ways. It is to be understood that the phraseology and terminology employed herein is for the purpose of description and not of limitation. The numerical values mentioned in embodiment are only approximation, the values higher and/or lower than values mentioned fall within the scope of disclosures.
Spoke type interior permanent magnet synchronous motor of present embodiment consists of a stator (100) and rotor (200) separated by an air gap length (300). Plurality of single piece undivided steel lamination of specific thickness and material class are axially bundled to get particular stack length (400) of stator (100) and rotor (200). Present embodiment can vary in radial air gap length (300) and axial stack length (400) as per motor output requirement. Rotor (200) coupled to shaft (500) collectively rotates about the axis of rotation. Other parts and systems such as enclosure, end covers, mechanical assembly, electrical insulation system, sensors and cooling system are the integral part of interior permanent magnet synchronous motor operation.
Said stator (100) concentrically position between stator inner diameter (101) and stator outer diameter (102), consists of plurality of stator slot (103), plurality of stator tooth (104) and a stator yoke (105). Electrically insulated stator winding housed in plurality of stator slot (103) consists of enameled copper conductors (not shown) coated with thin insulation layer. Plurality of stator slot (103) and stator tooth (104) are equally spaced and radially expanded from stator inner diameter (101) to stator outer diameter (102). Stator slot (103) of present embodiment are determined considering number of phase (600) and number of pole (700) and may vary to keep balance between stator tooth (104) flux density and manufacturability based on stator inner diameter (101) and stator outer diameter (102). Two adjacent sides of plurality of each stator slot (103) are arranged to form parallel sided stator tooth (104). A stator yoke (105) and plurality of stator tooth (104) are continuous part of assemble providing path to time varying flux.
Parallel sided stator tooth (104) of embodiment, shapes stator slot (103) such that stator slot (103) region near to stator yoke (105) referred as slot outer surface (103a) is broader than stator slot (103) region near to stator inner diameter (101) referred as slot inner surface (103b). The slot outer surface (103a) of each stator slot (103) is flat and the corners that joins slot outer surface (103a) to slot side surface (103c) have small slot corner radius (103d). Stator winding coils (not shown) are inserted inside each stator slot (103) through small stator slot opening (103e) made at stator inner diameter (101) periphery and remains inside the stator slot (103) due to slot lip (103f) and slot wedge (103g) section connected to slot inner surface (103b).
Said rotor (200) concentrically position between rotor inner diameter (201) and rotor outer diameter (202), consists of plurality of permanent magnet (203), magnet slot (204), rotor yoke (205), flux barrier (206), pole section (207), rib (209a, 209b) and rotor duct (210a, 210b).
Plurality of magnet slot (204) disposed at equal interval in the peripheral direction of rotor outer diameter (202) houses plurality of permanent magnet (203). Interior mount, equally spaced apart from each other at certain pole pitch (203a), alternately differ and tangentially directed magnetic orientation of permanent magnet (203) produces N-pole and S-pole on outer circumference of rotor (200). The number of magnet slot (204) of present embodiment corresponds to the number of pole (700) of motor. A single flat plate permanent magnet (203) is embedded in each magnet slot (204) however it is also acceptable to embed greater than one permanent magnet (203) in one magnet slot (204) considering balance between magnet cost and overall good performance. Sintered permanent magnet (203) of present invention are from either neodymium, samarium-cobalt, ferrite or alnico material class.
Equally elongated and radially parallel magnet slot (204) region near to pole section (207) referred as magnet slot side surface (204a, 204b), substantially shorter and circumferentially parallel magnet slot (204) region near to rotor yoke (205) referred as magnet slot inner surface (204c) and magnet slot (204) region near to rotor outer diameter (202) referred as magnet slot outer surface (204d) forms rectangular magnet slot (204) shape significantly the same as the shape of permanent magnet (203) to be inserted.
Magnet slot opening (204e), extended in radial direction, between rotor outer diameter (202) and magnet slot outer surface (204d), is made for bridging the magnet slot (204) and rotor outer rib (209b) to reduce mechanical stress on rotor (200) and to prevent scattering of permanent magnet (203) during high speed operation.
Rotor yoke (205), a continuous part of rotor (200), formed near to rotor inner periphery, radially extended outward from rotor inner diameter (201), separates magnet slot (204) and flux barrier (206) from rotor inner diameter (201), supports permanent magnet (203) to retain in magnet slot (204), eliminates need of non-magnetic sleeve required to suppress flux leakage from permanent magnet (203) to the shaft (500) and mechanically strengthens the rotor (200) that allows rotor to operate at high speed without being damaged under centrifugal forces.
On both side of permanent magnet (203), near to rotor inner diameter (201) periphery, a non-magnetic flux barrier (206) is made inside each pole section (207) to prevent flux leakage from adjacent permanent magnet (203) to the shaft (500) via rotor yoke (205). Flux barrier (206) region near to rotor yoke (205) referred as flux barrier inner surface (206a) and flux barrier (206) region near to rotor duct (210a) referred as flux barrier outer surface (206b) are substantially parallel to each other. Both flux barrier inner surface (206a) and flux barrier outer surface (206b) are flat and corner that joins flux barrier inner surface (206a) and flux barrier outer surface (206b) to flux barrier side surface (206c, 206d) have small flux barrier corner radius (206e).
Plurality of parallel sided rotor inner rib (209a) formed between magnet slot (204) and flux barrier (206), connects each pole section (207) to rotor yoke (205) and functions as air once saturated.
Plurality of pole section (207), with non-uniform air gap length (300) between rotor pole outer diameter at center (202a) and rotor pole outer diameter at tip (202b), protruding rotor outer rib (209b) in circumferential direction, weight reduction rotor duct (210a) and mechanical fastening rotor duct (210b) in middle portion, forms convex shaped rotor (200) outer periphery to reduce cogging torque.
Smaller permanent magnet width (203d) creates more space inside each pole section (207) for weight reduction rotor duct (210a).
Plurality of circular non-magnetic material bars or rivets (208) inserted into the plurality of rotor duct (210b) provided in each pole section (207), tightly holds the rotor (200) at pole section (207) and offers resistance to the centrifugal and tangential force at high speed.
Considering the tradeoff between magnet volume and mechanical stress on rotor, ratio of rotor outer diameter (202) to stator outer diameter (102) is optimized between 0.57:1 and 0.58:1 bearing in mind stator inner diameter (101) is optimized to 75.0 millimeter.
As per motor output demand ratio of magnet width (203d) to magnet height (203c) of embodiment varies between 0.20:1 and 0.25:1.
Flux barrier outer surface (206b) and flux barrier inner surface (206a) spaced apart from each other to define magnetic flux barrier (206) thickness is not less than 2.4 millimeter and not greater than 2.8 millimeter.
To conquer flux leakage from permanent magnet (203) to the shaft (500), rotor yoke depth (205a) is optimized to 2.0 millimeter.
Considering the limits of demagnetization due to the leakage of stator winding magnetic flux and air gap flux density, width of magnet slot opening (204e) is optimized to 3.0 millimeter.
In view of rotor stiffness and manufacturability, width and thickness of protruding rotor outer rib (209b) in pole section (207) is optimized to 1.0 millimeter.
Ratio of rotor pole outer diameter at tip (202b) to rotor pole outer diameter at center (202a) varies between 0.98:1 and 0.99:1 bearing in mind air gap length (300) varies between 0.4 and 0.8 millimeter.
Allowing flux density limit and manufacturability tolerances, width of parallel sided rotor inner rib (209a) is optimized to 0.5 millimeter.
Mechanical angle (203b) between center of pole section (207) and center of magnet slot (204) is optimized to 22.5°.
, Claims:We claim,
1. Spoke type Interior Permanent Magnet Synchronous Motor (PMSM) of present embodiment mainly consists of a circular stator (100) and rotor (200);
a. wherein stator (100) concentrically position between stator inner diameter (101) and stator outer diameter (102), consists of plurality of stator slot (103), plurality of stator tooth (104) and stator yoke (105);
i. wherein plurality of stator slot (103) and stator tooth (104) are equally spaced and radially expanded from stator inner diameter (101) to stator outer diameter (102);
ia) wherein stator slot (103) region near to stator yoke (105) referred as slot outer surface (103a) is broader than stator slot (103) region near to stator inner diameter (101) referred as slot inner surface (103b);
I. wherein slot outer surface (103a) of each stator slot (103) is flat and the corners that joins slot outer surface (103a) to slot side surface (103c) have small slot corner radius (103d);
II. wherein small stator slot opening (103e) is made at stator inner diameter (101) periphery;
III. wherein slot lip (103f) section connects slot wedge (103g) section and slot inner surface (103b);
ib) wherein two adjacent sides of plurality of each stator slot (103) forms parallel sided stator tooth (104);
ic) wherein stator yoke (105) and plurality of stator tooth (104) are continuous assembly;

b. wherein rotor (200) concentrically position between rotor inner diameter (201) and rotor outer diameter (202), consists of plurality of permanent magnet (203), magnet slot (204), rotor yoke (205), flux barrier (206), pole section (207), rib (209a, 209b) and rotor duct (210a, 210b);
i. wherein plurality of magnet slot (204) are disposed at equal interval in the peripheral direction of rotor outer diameter (202);
ia) wherein magnet slot (204) region near to pole section (207) referred as magnet slot side surface (204a, 204b) are flat, equally elongated and radially parallel;
ib) wherein magnet slot (204) region near to rotor yoke (205) referred as magnet slot inner surface (204c) and magnet slot (204) region near to rotor outer diameter (202) referred as magnet slot outer surface (204d) are flat, substantially shorter and circumferentially parallel;
ic) wherein magnet slot side surface (204a, 204b), magnet slot inner surface (204c) and magnet slot outer surface (204d) jointly forms rectangular magnet slot (204) shape significantly the same as the shape of permanent magnet (203) to be inserted;
id) wherein radially extended magnet slot opening (204e) made between rotor outer diameter (202) and magnet slot outer surface (204d), bridges magnet slot (204) and rotor outer rib (209b);
ii. wherein plurality of permanent magnet (203) are interior mount in plurality of magnet slot (204);
ia) wherein alternately differ and tangentially directed magnetic orientation of permanent magnet (203) producing N-pole and S-pole on outer circumference of rotor (200) are equally spaced apart from each other at certain pole pitch (203a);
iii. wherein rotor yoke (205), formed near to rotor inner periphery, is a continuous part of rotor (200);
ia) wherein rotor yoke depth (205a) , radially extended outward from rotor inner diameter (201), separates magnet slot (204) and flux barrier (206) from rotor inner diameter (201);
iv. wherein plurality of non-magnetic flux barrier (206) made inside each pole section (207), on both side of permanent magnet (203), near to rotor inner diameter (201) periphery are trapezoidal in shape;
ia) wherein flux barrier (206) region near to rotor yoke (205) referred as flux barrier inner surface (206a) and flux barrier (206) region near to rotor duct (210a) referred as flux barrier outer surface (206b) are flat and substantially parallel to each other;
ib) wherein corner that joins flux barrier inner surface (206a) and flux barrier outer surface (206b) to flux barrier side surface (206c, 206d) have small flux barrier corner radius (206e);
ic) wherein plurality of parallel sided rotor inner rib (209a) formed between magnet slot (204) and flux barrier (206), connects each pole section (207) to rotor yoke (205);
v. wherein plurality of pole section (207) with non-uniform air gap length (300) between rotor pole outer diameter at center (202a) and rotor pole outer diameter at tip (202b) forms convex shaped rotor (200) outer periphery;
ia) wherein protruding rotor outer rib (209b) are formed on circumference of pole section (207);
ib) wherein weight reduction rotor duct (210a) and mechanical fastening rotor duct (210b) are made in middle portion of each pole section (207);
I. wherein plurality of circular non-magnetic material bars or rivets (208) inserted into the plurality of rotor duct (210b), tightly holds the rotor (200) at pole section (207);
c. wherein shaft (500) coupled to rotor (200) collectively rotates rotor (200) about the axis of rotation;
i. wherein rotor inner diameter (201) and shaft outer diameter (501) are overlapped;
d. wherein circular stator (100) and rotor (200) are separated by an air gap length (300);
e. wherein plurality of single piece undivided stator (100) and rotor (200) of specific thickness and material class are axially bundled to get particular stack length (400);
2. Spoke type Interior Permanent Magnet Synchronous Motor (PMSM) as claimed in claim 1, wherein said stator (100) comprises thirty six stator slot (103) and rotor (200) comprises eight magnet slot (204);
a. wherein number of magnet slot (204) corresponds to the number of pole (700) of motor;
b. wherein single or greater than one rectangular flat plate permanent magnet (203) are embedded in each magnet slot (204);
c. wherein greatest common divisor (GCD) for thirty six stator slot (103) and eight number of pole (700) of present embodiment is four. In other embodiment GCD can be different number, preferably greater than or equal to four;
3. Spoke type Interior Permanent Magnet Synchronous Motor (PMSM) as claimed in claim 1, wherein said stator inner diameter (101), stator outer diameter (102), rotor outer diameter (202), rotor pole outer diameter at center (202a), rotor pole outer diameter at tip (202b), mechanical angle (203b), magnet height (203c), magnet width (203d), magnet slot opening (204e), rotor yoke depth (205a), flux barrier inner surface (206a), flux barrier outer surface (206b), rotor inner rib (209a), rotor outer rib (209b), air gap length (300) holds a numerical values;
a. wherein ratio of rotor outer diameter (202) to stator outer diameter (102) is between 0.57:1 and 0.58:1 bearing in mind stator inner diameter (101) is optimized to 75.0 millimeter;
b. wherein ratio of magnet width (203d) to magnet height (203c) is between 0.20:1 and 0.25:1;
c. wherein flux barrier outer surface (206b) and flux barrier inner surface (206a) spaced apart from each other defining magnetic flux barrier (206) thickness is not less than 2.4 millimeter and not greater than 2.8 millimeter;
d. wherein rotor yoke depth (205a) is optimized to 2.0 millimeter;
e. wherein width of magnet slot opening (204e) is optimized to 3.0 millimeter;
f. wherein width and thickness of protruding rotor outer rib (209b) is optimized to 1.0 millimeter;
g. wherein ratio of rotor pole outer diameter at tip (202b) to rotor pole outer diameter at center (202a) is between 0.98:1 and 0.99:1 bearing in mind air gap length (300) varies between 0.4 and 0.8 millimeter;
h. wherein width of parallel sided rotor inner rib (209a) is optimized to 0.5 millimeter;
i. wherein mechanical angle (203b) between center of pole section (207) and center of magnet slot (204) is optimized to 22.5°;
4. Spoke type Interior Permanent Magnet Synchronous Motor (PMSM) as claimed in claim 1, wherein said rotor (200) along with the embedded permanent magnet (203) are symmetrically step-skewed over its axial length by 5° mechanical angle.;
5. Spoke type Interior Permanent Magnet Synchronous Motor (PMSM) as claimed in claim 1, wherein said plurality of permanent magnet (203) are from either neodymium, samarium cobalt, ferrite or alnico material class;
6. Spoke type Interior Permanent Magnet Synchronous Motor (PMSM) as claimed in claim 1, wherein said shaft (500) is from either mild steel or alloy steel material class.