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.
Electric vehicle interior permanent magnet synchronous motor of present embodiment consists, of a circular stator lamination (100) and rotor lamination (200) separated by an air gap length (300). Other parts and systems such as shaft, enclosure, end covers, mechanical assembly, electrical insulation system, sensors and cooling system are the integral part of interior permanent magnet synchronous motor operation. Plurality of stator lamination (100) and rotor lamination (200) of specific thickness and material class are axially bundled to get particular stack length (400) as per motor output requirement. Stator winding from stator lamination (100) are excluded for the ease of understanding. Present embodiment can vary in radial air gap length (300) and axial stack length (400). Sintered permanent magnet of present invention are from either neodymium, samarium-cobalt, ferrite or alnico material class.
Said stator lamination (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), a stator yoke (105) and plurality of cleating notch (106).
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 and number of pole 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).
Lower split ratio, defined as the ratio between rotor outer diameter (202) and stator outer diameter (102), of present invention maximizes the amount of torque per stator current and torque per rotor volume, furthermore small rotor outer diameter (202) minimizes the mechanical stress on rotor and air friction losses and large stator outer diameter (102) minimizes stator core loss and thermal stress on motor. Larger stator outer diameter (102) than axial stack length (400) of present invention reduces stator winding mean turn length sequentially resulting into curtailed winding resistance, cooper loss and temperature rise.
Ratio of stator outer diameter (102) to stator inner diameter (101) between 1.85:1 and 1.95:1 contributes to develop high torque in constant torque range and optimum power in constant power range.
Ratio of stator outer diameter (102) to axial stack length (400) of embodiment varies between 1.0:1 and 5.0:1 as per motor output demand.
Ratio of stator tooth height (104b) to stator yoke depth (105a) is optimized to 3.0:1 to minimize magnetic saturation in stator yoke (105) and stator tooth (104).
Considering flux density limit and manufacturability, the ratio of stator tooth height (104b) to stator tooth width (104a) is optimized to 4.5:1.
Said rotor lamination (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), salient pole section (207), flux bridge (208), rib (209) 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 (203b), alternately differ and radially directed magnetic orientation of permanent magnet (203) produces N-pole and S-pole on outer circumference of rotor lamination (200). The number of magnet slot (204) of present embodiment corresponds to the number of pole 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.
Magnet slot (204) region near to rotor yoke (205) referred as magnet slot inner surface (204a) and magnet slot (204) region near to rotor outer diameter (202) referred as magnet slot outer surface (204b) are equally broader. Both magnet slot inner surface (204a) and magnet slot outer surface (204b) are flat and the corners that joins magnet slot inner surface (204a) and magnet slot outer surface (204b) to magnet slot side surface (204c, 204d) have small magnet slot corner radius (204e).
On both sides of permanent magnet (203) in the peripheral direction of rotor outer diameter (202), a non-magnetic flux barrier (206) are made inside the magnet slot (204) to prevent flow of magnetic flux between adjacent permanent magnet (203).
Plurality of flux bridge (208) formed over the rotor lamination (200) periphery, separates magnet slot (204) from rotor outer diameter (202) and mechanically strengthens the rotor lamination (200) that allows rotor to operate at high speed without being damaged under centrifugal forces. Flux bridges (208) are made small enough to be saturated by magnetic flux from permanent magnet (203) to restrict the flux leakage over the air gap (300) periphery.
Plurality of parallel sided rib (209) formed between adjacent magnet slot side surfaces (204c, 204d) and rotor yoke (205) are continuous part of assemble providing path to time varying flux.
Smaller permanent magnet (203) dimensions of present invention creates more space inside rotor yoke (205) for weight reducing rotor duct (210a) and mechanical fastening rotor duct (210b).
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 0.50:1 and 0.53:1.
Ratio of pole arc (203a) to pole pitch (203b) between 0.75:1 and 0.80:1 contributes to develop high power-torque density with extended speed range.
As per motor output demand ratio of magnet width (203d) to magnet slot outer surface (204b) of embodiment varies between 0.75:1 and 1:1.
Considering flux density limit and manufacturability, width of rib (209) is optimized to 1.9 millimeter.
Ratio of flux bridge (208) to air gap length (300) of embodiment varies between 0.65:1 and 1.85:1 bearing in mind air gap length (300) varies between 0.4 and 0.8 millimeter.
Stack of rotor lamination (200) along with the embedded permanent magnet (203) are symmetrically step-skewed over its axial length by 15? mechanical angle to reduce cogging torque.
For, the invention described here with respect to the given embodiment, it is appreciated that many variations, modifications and other applications of the invention may be made. However, it is to be expressly understood that such modifications and adaptations are within the scope of the present invention, as set forth in the following claims. , Claims:We claim,
1. An Electric vehicle permanent magnet synchronous motor (PMSM) of present embodiment consisting of a circular stator lamination (100) and rotor lamination (200);
a. wherein stator lamination (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), a stator yoke (105) and plurality of cleating notch (106);
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);
wherein plurality of stator tooth (104) have stator tooth width (104a) and stator tooth height (104b);
ic) wherein stator yoke (105) and plurality of stator tooth (104) are continuous assembly;
I. wherein stator yoke (105) have stator yoke depth (105a);
id) wherein plurality of cleating notch (106) are equally spaced and positioned at stator outer diameter (102) periphery;

b. wherein rotor lamination (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), salient pole section (207), flux bridge (208), rib (209) and rotor duct (210a, 210b);
i. wherein magnet slot (204) region near to rotor yoke (205) referred as magnet slot inner surface (204a) and magnet slot (204) region near to rotor outer diameter (202) referred as magnet slot outer surface (204b) are equally broader;
ia) wherein both magnet slot inner surface (204a) and magnet slot outer surface (204b) are flat and the corners that joins magnet slot inner surface (204a) and magnet slot outer surface (204b) to magnet slot side surface (204c, 204d) have small magnet slot corner radius (204e);
I. wherein plurality of magnet slot (204) are disposed at equal interval in the peripheral direction of rotor outer diameter (202);
ib) wherein plurality of permanent magnet (203) are interior mount in plurality of magnet slot (204);
I. wherein, alternately differ and radially directed magnetic orientation of permanent magnet (203) producing N-pole and S-pole on outer circumference of rotor lamination (200) are equally spaced apart from each other at certain pole pitch (203b);
ic) wherein on both sides of permanent magnet (203) in the peripheral direction of rotor outer diameter (202), a flux barrier (206) are made inside the magnet slot (204);
I. wherein flux barrier (206) are triangular in shape with first side facing rib (209), second side facing flux bridges (208) and third side facing magnet thickness (203c);
id) wherein flux bridges (208), formed over the rotor lamination (200) periphery, separates magnet slot (204) from rotor outer diameter (202);
ie) wherein plurality of parallel sided rib (209) formed between adjacent magnet slot side surfaces (204c, 204d) and rotor yoke (205) are continuous part of assemble providing path to time varying flux
if) wherein plurality of rotor duct rotor duct (210a, 210b) are equally spaced and positioned inside rotor yoke (205);
c. wherein circular stator lamination (100) and rotor lamination (200) are separated by an air gap length (300);
d. wherein plurality of stator lamination (100) and rotor lamination (200) of specific thickness and material class are axially bundled to get particular stack length (400);
2. Electric vehicle permanent magnet synchronous motor (PMSM) as claimed in claim 1, wherein said stator lamination (100) comprises 24 stator slot (103) and rotor lamination (200) comprises 08 magnet slot (204);
a. wherein number of magnet slot (204) corresponds to the number of pole (500) of motor;
b. wherein single or greater than one rectangular flat plate permanent magnet (203) are embedded in each magnet slot (204);
3. Electric vehicle permanent magnet synchronous motor (PMSM) as claimed in claim 1, wherein said stator lamination (100) dimensions such as stator inner diameter (101), stator outer diameter (102), stator slot opening (103e), slot lip (103f), stator tooth width (104a), stator tooth height (104b), stator yoke depth (105a), stack length (400) holds a numerical value;
a. wherein ratio stator outer diameter (102) to stator inner diameter (101) is between 1.85:1 and 1.95:1;
b. wherein ratio of stator outer diameter (102) to axial stack length (400) is between 1.0:1 and 5.0:1;
c. wherein ratio of stator tooth height (104b) to stator yoke depth (105a) is at least 3.0:1;
d. wherein ratio of stator tooth height (104b) to stator tooth width (104a) is 4.5:1
e. wherein ratio of stator slot opening (103e) to slot lip (103f) is between 1.45:1 and 1.65:1;
4. Electric vehicle permanent magnet synchronous motor (PMSM) as claimed in claim 1, wherein said rotor lamination (200) dimensions such rotor inner diameter (201), rotor outer diameter (202), pole arc (203a), pole pitch (203b), magnet slot inner surface (204a), magnet slot outer surface (204b), flux bridge (208), rib (209) holds a numerical value;
a. wherein ratio of rotor outer diameter (202) to stator outer diameter (102) is optimized between 0.50:1 and 0.53:1;
b. wherein ratio of pole arc (203a) to pole pitch (203b) varies between 0.75:1 and 0.80:1;
c. wherein ratio of magnet width (203d) to magnet slot outer surface (204b) varies between 0.75:1 and 1:1;
d. wherein width of rib (209) is optimized to 1.9 millimetre;
e. wherein ratio of flux bridge (208) to air gap length (300) is 0.65:1 and 1.85:1 bearing in mind air gap length (300) varies between 0.4 and 0.8 millimetre;
5. Electric vehicle permanent magnet synchronous motor (PMSM) as claimed in claim 1, wherein said rotor lamination (200) along with the embedded permanent magnet (203) are symmetrically step-skewed over its axial length by 15? mechanical angle;
6. Electric vehicle 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.