Electric machine
An electric machine comprising a first carrier having an array of electromagnetic elements and a second carrier having electromagnetic elements defining magnetic poles, the second carrier being arranged to move relative to the first carrier. An airgap is provided between the first carrier and the second carrier. The electromagnetic elements of the first carrier include posts, with slots between the posts, one or more electric conductors in each slot, the posts of the first carrier having a post height in mm. The first carrier and the second carrier together define a size of the electric machine. The magnetic poles having a pole pitch in mm. The size of the motor, pole pitch and post height are selected to fall within a region in a space defined by size, pole pitch and post height that provides a benefit in terms of force or torque per weight per excitation level.
1. A rotor for an electric machine, the rotor comprising:
an inner rotor portion comprising outwardly projecting members;
an outer rotor portion comprising inwardly projecting members;
the outer rotor portion being arranged around the inner rotor portion so that the inwardly projecting members and outwardly projecting members are interdigitated; and
permanent magnets arranged between the interdigitated inwardly projecting members and outwardly projecting members so that the inwardly projecting members and outwardly projecting members provide flux paths for the permanent magnets; the permanent magnets being tapered to narrow in a direction towards a stator of the electric machine when the rotor electric machine is assembled, and the interdigitated inwardly and outwardly projecting members defining slots shaped to accommodate the tapered magnets.
2. The rotor of claim 1 in which the inwardly projecting members are regularly spaced and the outwardly projecting members are regularly spaced.
3. The rotor of claim 1 in an electric machine, the electric machine comprising:
a first carrier having an array of electromagnetic elements;
a second carrier having electromagnetic elements defining magnetic poles, the second carrier being arranged to move relative to the first carrier;
an airgap between the first carrier and the second carrier;
the electromagnetic elements of the first carrier including posts, with slots between the posts, one or more electric conductors in each slot, the posts of the first carrier having a post height in mm;
the first carrier and the second carrier together defining a size of the electric machine
the magnetic poles having a pole pitch S in mm;
the size of the machine, pole pitch and post height being selected to fall within a region in a space defined by size, pole pitch and post height, the region being defined by either
1) a first union of:
a) a first surface defined by a first set of inequalities for a first size of electric machine;
b) a second surface defined by a second set of inequalities for a second size of electric machine; and
c) a set defined as containing all points lying on line segments having a first end point on the first surface and a second end point on the second surface;
the first set of inequalities and the second set of inequalities being respectively sets of inequalities A and B, or B and C, or C and D, in which the group of inequalities A is for a size of 25 mm, the group of inequalities B is for a size of 50 mm, the group of inequalities C is for a size of 100 mm, the group of inequalities D is for a size of 200 mm; or
2) a second union of a surface as defined by set of inequalities D and a corresponding set of all points with size greater than the surface but with pole pitch and post height corresponding to points within the surface;
where
A is selected from the group of sets of inequalities consisting of:
Set A1:
Post Height>
−1.070 * S + 2.002
for
0.572 < S < 1.189
1.175 * S + −0.667
for
1.189 < S < 2.269
13.502 * S − 28.637
for
2.269 < S < 2.500
Post Height<
−5.898 * S + 19.863
for
1.970 < S < 2.500
0.229 * S + 7.794
for
1.349 < S < 1.970
7.607 * S − 2.160
for
0.723 < S < 1.349
11.430 * S − 4.924
for
0.572 < S < 0.723
Set A2:
Post Height>
−1.340 * S + 2.305
for
0.619 < S < 1.120
1.100 * S − 0.429
for
1.120 < S < 2.074
3.830 * S − 6.082
for
2.074 < S < 2.269
Post Height<
−69.510 * S + 160.318
for
2.222 < S < 2.269
−3.430 * S + 13.492
for
1.667 < S < 2.222
2.830 * S + 3.056
for
1.133 < S < 1.667
8.650 * S − 3.545
for
0.619 < S < 1.133
Set A3:
Post Height>
−4.160 * S + 5.032
for
0.723 < S < 0.967
0.839 * S + 0.198
for
0.967 < S < 1.692
2.713 * S − 2.973
for
1.692 < S < 1.939
Post Height<
−53.233 * S + 105.506
for
1.879 < S < 1.939
−1.406 * S + 8.122
for
1.465 < S < 1.879
3.898 * S + 0.353
for
1.035 < S < 1.465
7.535 * S − 3.412
for
0.723 < S < 1.035
B is selected from the group of sets of inequalities consisting of:
Set B1:
Post Height>
0.254 * S + 0.462
for
0.319 < S < 3.667
2.665 * S + −8.380
for
3.667 < S < 5.000
Post Height<
−18.282 * S + 96.357
for
4.500 < S < 5.000
−4.663 * S + 35.071
for
2.738 < S < 4.500
2.585 * S + 15.227
for
1.447 < S < 2.738
16.013 * S − 4.204
for
0.319 < S < 1.447
Set B2:
Post Height>
0.269 * S + 0.456
for
0.380 < S < 3.016
3.051 * S − 7.936
for
3.016 < S < 4.167
Post Height<
−14.766 * S + 66.309
for
3.667 < S < 4.167
−3.952 * S + 26.654
for
2.315 < S < 3.667
3.108 * S + 10.310
for
1.278 < S < 2.315
14.542 * S − 4.303
for
0.389 < S < 1.278
88.444 * S − 33.051
for
0.380 < S < 0.389
Set B3:
Post Height>
0.191 * S + 0.626
for
0.472 < S < 2.181
2.135 * S − 3.613
for
2.181 < S < 3.095
53.475 * S − 162.511
for
3.095 < S < 3.175
Post Height<
−5.095 * S + 23.450
for
2.222 < S < 3.175
0.805 * S + 10.339
for
1.381 < S < 2.222
10.251 * S − 2.706
for
0.572 < S < 1.381
24.420 * S − 10.810
for
0.472 < S < 0.572
C is selected from the group of sets of inequalities consisting of:
Set C1:
Post Height>
0.322 * S + 0.359
for
0.233 < S < 6.667
2.202 * S − 12.179
for
6.667 < S < 8.333
Post Height<
−25.555 * S + 219.122
for
7.778 < S < 8.333
−5.585 * S + 63.794
for
4.000 < S < 7.778
3.214 * S + 28.600
for
1.793 < S < 4.000
21.749 * S − 4.633
for
0.233 < S < 1.793
Set C2:
Post Height>
0.277 * S + 0.593
for
0.250 < S < 5.182
2.342 * S − 10.111
for
5.182 < S < 7.222
Post Height<
−13.149 * S + 101.763
for
6.111 < S < 7.222
−4.885 * S + 51.265
for
3.333 < S < 6.111
4.291 * S + 20.680
for
1.520 < S < 3.333
20.788 * S − 4.395
for
0.251 < S < 1.520
161.000 * S − 39.588
for
0.250 < S < 0.251
Set C3:
Post Height>
0.277 * S + 0.591
for
0.278 < S < 4.425
1.916 * S − 6.663
for
4.425 < S < 6.111
Post Height<
−21.337 * S + 135.438
for
5.556 < S < 6.111
−4.985 * S + 44.588
for
3.175 < S < 5.556
2.749 * S + 20.031
for
1.560 < S < 3.175
18.321 * S − 4.260
for
0.278 < S < 1.560
and
D is selected from the group of sets of inequalities consisting of:
Set D1:
Post Height>
0.257 * S + 0.327
for
0.208 < S < 7.778
1.977 * S − 13.044
for
7.778 < S < 9.444
Post Height<
−36.195 * S + 347.445
for
8.889 < S < 9.444
−5.777 * S + 77.062
for
4.833 < S < 8.889
1.950 * S + 39.718
for
2.222 < S < 4.833
20.301 * S + −1.058
for
0.389 < S < 2.222
34.481 * S + −6.574
for
0.208 < S < 0.389
Set D2:
Post Height>
0.322 * S + 0.359
for
0.233 < S < 6.667
2.202 * S + −12.179
for
6.667 < S < 8.333
Post Height<
−25.555 * S + 219.122
for
7.778 < S < 8.333
−5.585 * S + 63.794
for
4.000 < S < 7.778
3.214 * S + 28.600
for
1.793 < S < 4.000
21.749 * S + −4.633
for
0.233 < S < 1.793
Set D3:
Post Height>
0.212 * S + 0.600
for
0.264 < S < 4.833
3.017 * S + −12.960
for
4.833 < S < 6.667
Post Height<
−12.356 * S + 89.531
for
5.556 < S < 6.667
−4.551 * S + 46.170
for
3.175 < S < 5.556
3.850 * S + 19.496
for
1.502 < S < 3.175
19.751 * S + −4.387
for
0.264 < S < 1.502.
4. The rotor of claim 1 in which the inner rotor portion and outer rotor portion are integrally connected at the inwardly projecting members or outwardly projecting members or both by tabs smaller in cross section than the inwardly projecting members and the outwardly projecting members and small enough in cross section to be saturated by flux from the permanent magnets.
5. A rotor for an electric machine, the rotor comprising:
an inner rotor portion comprising outwardly projecting members;
an outer rotor portion comprising inwardly projecting members;
the outer rotor portion being arranged around the inner rotor portion so that the inwardly projecting members and outwardly projecting members are interdigitated;
permanent magnets arranged between the interdigitated inwardly projecting members and outwardly projecting members so that the inwardly projecting members and outwardly projecting members provide flux paths for the permanent magnets; and
in which the inner rotor portion and outer rotor portion are integrally connected at the inwardly projecting members or outwardly projecting members or both by tabs smaller in cross section than the inwardly projecting members and the outwardly projecting members and small enough in cross section to be saturated by flux from the permanent magnets.
6. The rotor of claim 5 in which the inwardly projecting members are regularly spaced and the outwardly projecting members are regularly spaced.
7. The rotor of claim 5 in which the tabs include outer tabs connecting the inner rotor portion and the outer rotor portion at tips of the outwardly projecting members.
8. The rotor of claim 5 in which the tabs include inner tabs connecting the inner rotor portion and the outer rotor portion at tips of the inwardly projecting members.
9. The rotor of claim 5 in which the tabs include cross tabs connecting between the outwardly projecting members and the inwardly projecting members.
10. A rotor in an electric machine, the rotor comprising:
an inner rotor portion comprising outwardly projecting members;
an outer rotor portion comprising inwardly projecting members;
the outer rotor portion being arranged around the inner rotor portion so that the inwardly projecting members and outwardly projecting members are interdigitated; and
permanent magnets arranged between the interdigitated inwardly projecting members and outwardly projecting members so that the inwardly projecting members and outwardly projecting members provide flux paths for the permanent magnets;
the electric machine comprising:
a first carrier having an array of electromagnetic elements;
a second carrier having electromagnetic elements defining magnetic poles, the second carrier being arranged to move relative to the first carrier;
an airgap between the first carrier and the second carrier;
the electromagnetic elements of the first carrier including posts, with slots between the posts, one or more electric conductors in each slot, the posts of the first carrier having a post height in mm;
the first carrier and the second carrier together defining a size of the electric machine
the magnetic poles having a pole pitch S in mm;
the size of the machine, pole pitch and post height being selected to fall within a region in a space defined by size, pole pitch and post height, the region being defined by either
1) a first union of:
a) a first surface defined by a first set of inequalities for a first size of electric machine;
b) a second surface defined by a second set of inequalities for a second size of electric machine; and
c) a set defined as containing all points lying on line segments having a first end point on the first surface and a second end point on the second surface;
the first set of inequalities and the second set of inequalities being respectively sets of inequalities A and B, or B and C, or C and D, in which the group of inequalities A is for a size of 25 mm, the group of inequalities B is for a size of 50 mm, the group of inequalities C is for a size of 100 mm, the group of inequalities D is for a size of 200 mm; or
2) a second union of a surface as defined by set of inequalities D and a corresponding set of all points with size greater than the surface but with pole pitch and post height corresponding to points within the surface;
where
A is selected from the group of sets of inequalities consisting of:
Set A1:
Post Height>
−1.070 * S + 2.002
for
0.572 < S< 1.189
1.175 * S + −0.667
for
1.189 < S < 2.269
13.502 * S −28.6337
for
2.269 < S < 2.500
Post Height<
−5.898 *S + 19.863
for
1.970 < S < 2.500
0.229 * S + 7.794
for
1.349 < S < 1.970
7.607 * S −2.160
for
0.723 < S < 1.349
11.430 * S −4.924
for
0.572 < S < 0.723
Set A2:
Post Height>
−1.340 * S + 2.305
for
0.619 < S < 1.120
1.100 * S −0.429
for
1.120 < S < 2.074
3.830 * S −6.082
for
2.074 < S < 2.269
Post Height<
−69.510 * S + 160.318
for
2.222 < S < 2.269
−3.430 * S + 13.492
for
1.667 < S < 2.222
2.830 * S + 3.056
for
1.133 < S < 1.667
8.650 * S −3.545
for
0.619 < S < 1.133
Set A3:
Post Height>
−4.160 * S + 5.032
for
0.723 < S < 0.967
0.839 * S + 0.198
for
0.967 < S < 1.692
2.713 * S −2.973
for
1.692 < S < 1.93
Post Height<
−53.233 * S + 105.506
for
1.879 < S < 1.939
−1.406 * S + 8.122
for
1.465 < S < 1.879
3.898 * S + 0.353
for
1.035 < S < 1.465
7.535 *S −3.412
for
0.723 < S < 1.035
B is selected from the group of sets of inequalities consisting of:
Set B1:
Post Height>
0.254 * S + 0.462
for
0.319 < S < 3.667
2.665 * S + −8.380
for
3.667 < S < 5.000
Post Height<
−18.282 * S + 96.357
for
4.500 < S < 5.000
−4.663 * S + 35.071
for
2.738 < S < 4.500
2.585 * S + 15.227
for
1.447 < S < 2.738
16.013 * S −4.204
for
0.319 < S < 1.447
Set B2:
Post Height>
0.269 * S + 0.456
for
0.380 < S < 3.016
3.051 * S −7.936
for
3.016 < S < 4.167
PostHeight<
−14.766 * S + 66.309
for
3.667 < S < 4.167
−3.952 * S + 26.654
for
2.315 < S < 3.667
3.108 * S + 10.310
for
1.278 < S < 2.315
14.542 * S −4.303
for
0.389 < S < 1.278
88.444 * S −33.051
for
0.380 < S < 0.389
Set B3:
Post Height>
0.191 * S + 0.626
for
0.472 < S < 2.181
2.135 * S −3.613
for
2.181 < S < 3.095
53.475 * S −162.511
for
3.095 < S < 3.175
PostHeight<
−5.095 * S + 23.450
for
2.222 < S < 3.175
0.805 * S + 10.339
for
1.381 < S < 2.222
10.251 * S −2.706
for
0.572 < S < 1.381
24.420 * S −10.810
for
0.472 < S < 0.572
C is selected from the group of sets of inequalities consisting of:
Set C1:
Post Height>
0.322 * S + 0.359
for
0.233 < S < 6.667
2.202 * S −12.179
for
6.667 < S < 8.333
Post Height<
−25.555 * S + 219.122
for
7.778 < S < 8.333
−5.585 * S + 63.794
for
4.000 < S < 7.778
3.214 * S + 28.600
for
1.793 < S < 4.000
21.749 * S −4.633
for
0.233 < S < 1.793
Set C2:
Post Height>
0.277 * S + 0.593
for
0.250 < S < 5.182
2.342 * S −10.111
for
5.182 < S < 7.222
Post Height<
−13.149 * S + 101.763
for
6.111 < S < 7.222
−4.885 * S + 51.265
for
3.333 < S < 6.111
4.291 * S + 20.680
for
1.520 < S < 3.333
20.788 * S −4.395
for
0.251 < S < 1.520
161.000 * S −39.588
for
0.250 < S < 0.251
Set C3:
Post Height>
0.277 * S + 0.591
for
0.278 < S < 4.425
1.916 * S −6.663
for
4.425 < S < 6.111
Post Height<
−21.337 * S + 135.438
for
5.556 < S < 6.111
−4.985 * S + 44.588
for
3.175 < S < 5.556
2.749 * S + 20.031
for
1.560 < S < 3.175
18.321 * S −4.260
for
0.278 < S < 1.560
and
D is selected from the group of sets of inequalities consisting of:
Post Height>
0.257 * S + 0.327
for
0.208 < S < 7.778
1.977 * S −13.044
for
7.778 < S < 9.444
Post Height<
−36.195 * S + 347.445
for
8.889 < S < 9.444
−5.777 * S + 77.062
for
4.833 < S < 8.889
1.950 * S + 39.718
for
2.222 < S < 4.833
20.301 * S + −1.058
for
0.389 < S < 2.222
3 4.481 * S + −6.574
for
0.208 < S < 0.389
Set D1:
Set D2:
Post Height>
0.322 * S + 0.359
for
0.233 < S < 6.667
2.202 * S + −12.179
for
6.667 < S < 8.333
Post Height<
−25.555 * S + 219.122
for
7.778 < S < 8.333
−5.585 * S + 63.794
for
4.000 < S < 7.778
3.214 * S + 28.600
for
1.793 < S < 4.000
21.749 * S + −4.633
for
0.233 < S < 1.793
Set D3:
Post Height>
0.212 * S + 0.600
for
0.264 < S < 4.833
3.017 * S + −12.960
for
4.833 < S < 6.667
Post Height<
−12.356 * S + 89.531
for
5.556 < S < 6.667
−4.551 * S + 46.170
for
3.175 < S < 5.556
3.850 * S + 19.496
for
1.502 < S < 3.175
19.751 * S + −4.387
for
0.264 < S < 1.502.
11. The rotor of claim 10 in which the inwardly projecting members are regularly spaced and the outwardly projecting members are regularly spaced.
12. The rotor of claim 10 in which the inner rotor portion and outer rotor portion are integrally connected at the inwardly projecting members or outwardly projecting members or both by tabs smaller in cross section than the inwardly projecting members and the outwardly projecting members and small enough in cross section to be saturated by flux from the permanent magnets.