NORPIE 2004

14-16 June, Trondheim, Norway

Analysis of a PM Machine with Concentrated Fractional Pitch Windings

Freddy Magnussen, Dmitry Svechkarenko, Peter Thelin, Chandur Sadarangani

Layout of presentationLayout of presentation

IntroductioIntroductionn

Torque ripple computation resultsTorque ripple computation results

Presentation of Presentation of machine designmachine design

Parasitic effects (noise and losses)Parasitic effects (noise and losses)

ConclusionsConclusions

Laboratory prototype and measurementsLaboratory prototype and measurements

Thermal computation resultsThermal computation results

Machine design: 14 poles and 15 slotsMachine design: 14 poles and 15 slots

+A

-A

+B

-B

+C

-C

Iron

PM

Air

q=0,36 q=0,36 (number of slots per pole per phase; normally 0,5)(number of slots per pole per phase; normally 0,5)

kkw1w1=0,95=0,95 (fundamental winding factor; normally 0,87)(fundamental winding factor; normally 0,87)

Grain-oriented iron teeth, non-oriented iron yokeGrain-oriented iron teeth, non-oriented iron yoke

Rectangular copper conductors, cRectangular copper conductors, cff=0,74=0,74

-120

-80

-40

0

40

80

120

0 0,0005 0,001 0,0015 0,002 0,0025 0,003 0,0035 0,004

Time [s]

Pha

se E

MF

[V

]Electromotive forceElectromotive force

FEM-computed torque rippleFEM-computed torque ripple

Pure sinusoidal q-current Pure sinusoidal q-current no inverter influence no inverter influence

Current loadings: Current loadings: 00, , 103103, , 207207, , 413413 and and 827827 A/cm (RMS) A/cm (RMS)

-100

102030405060708090

100110120130140150160170180

0 5 10 15 20 25 30 35 40 45 50

Rotor position [o]

To

rqu

e [

Nm

]

Air gap flux densityAir gap flux density

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

0 30 60 90 120 150 180 210 240 270 300 330 360

Angular position [o]

Flu

x d

ensi

ty [

T]

Armature reaction for the current loading 827 A/cm (RMS)Armature reaction for the current loading 827 A/cm (RMS)

No-load flux densityNo-load flux density

-0,10,00,10,20,30,40,50,60,70,80,91,01,11,21,31,41,5

0 0,5 1 1,5 2 2,5 3 3,5 4

Time [ms]

Flu

x d

en

sity

[T]

Flux density in rotor back (Machine C)Flux density in rotor back (Machine C)

Current loadings: Current loadings: 00, , 103103, , 207207, , 413413 and and 827827 A/cm (RMS) A/cm (RMS)

Tangential flux density component at 2000 rpmTangential flux density component at 2000 rpm

0

100

200

300

400

500

600

700

0 30 60 90 120 150 180 210 240 270 300 330 360

Angular position [o]

Rad

ial m

agne

tic s

tres

s [k

N/m

2]

Radial magnetic stress in air gapRadial magnetic stress in air gap Unbalanced radial forces Unbalanced radial forces noise noise

Some radial vibration mode shapesSome radial vibration mode shapes

Mode 0 Mode 1

Mode 2 Mode 3

Prototype statorPrototype stator

Parameter Unit

Torque [Nm] 2,0 35,0 34,0 31,5

Speed [rpm] 4000 560 1000 2000

Mechanical power [W] 838 2053 3560 6597

Phase voltage (RMS) [V] 132,4 12,3 24,1 35,4

Phase current (RMS) [A] 0 49,3 44,6 57,1

Electrical power [W] 0 1786 3228 5850

Losses [W] 838 267 332 747

Water flow [dm3/min] 2,5 3,2 3,3 3,1

Temperatures

End-winding [oC] 35 47 43 84

Tooth [oC] 36 36 35 71

Yoke [oC] 35 35 34 68

Rotor iron [oC] 29 32 37 87

Cooling cylinder [oC] 15 13 14 31

Inlet water [oC] 9 9 9 23

Temperature rise [K] 26 38 34 61

Value Parameter Unit Value

Torque [Nm] 30,7 59,8 81,7

Speed [rpm] 341 344 346

Mechanical power [W] 1096 2154 2960

Fund. phase voltage (RMS) [V] 14,1 17,9 21,7

Phase current (RMS) [A] 36,8 71,5 104,1

Electrical power [W] 1151 2469 3898

Losses [W] 55 315 938

Water flow [dm3/min] 2,9 2,9 2,9

Temperatures

End-winding [oC] 31 73 168

Tooth [oC] 26 52 112

Yoke [oC] 22 52 115

Rotor iron [oC] 25 49 93

Cooling cylinder [oC] 18 27 40

Inlet water [oC] 22 20 25

Temperature rise [K] 9 53 143

Measurement resultsMeasurement results

Low speed high torque : copper loss thermal influenceLow speed high torque : copper loss thermal influence

Generator testsGenerator tests Motor testsMotor tests

High speed low torque : iron loss thermal influenceHigh speed low torque : iron loss thermal influence

Thermal computations (I)Thermal computations (I)

Aluminium frame

Cooling duct

Velocity profile

Water-cooling cylinderWater-cooling cylinder

Thermal computations (II)Thermal computations (II)

Max139ºC

Max86ºC

Max157ºC

Max98ºC

0

10

20

30

40

50

60

70

80

90

100

0 2 000 4 000 6 000

Speed [rpm]

Tor

que

[Nm

]

[K]Inlet water:

22ºC

Speed Torque Power Winding losses Iron losses[rpm] [Nm] [kW] [W] [W]

1 95 0 708 02000 95 20 708 2704000 48 20 228 3906000 32 20 255 500

ConclusionsConclusions

HHigh torque density (5,0 Nm/kg)igh torque density (5,0 Nm/kg)

Low torque rippleLow torque ripple

Concentrated winding machines with an odd Concentrated winding machines with an odd number of slots and an almost equal number of number of slots and an almost equal number of poles (e.g 8/9, 14/15, 20/21) are sensitive to poles (e.g 8/9, 14/15, 20/21) are sensitive to these these parasitic effects:parasitic effects:

Unbalanced radial forces Unbalanced radial forces noise noise Alternating magnetic fields in the rotor Alternating magnetic fields in the rotor losses losses

Cost effective manufacturing processCost effective manufacturing process

Thank you!Thank you!