Design of Low Speed Axial Flux Permanent
Magnet Generators for Marine Current
Application
Sanjida Moury
Supervised by
Dr. Tariq Iqbal
Faculty of Engineering and Applied Science
Memorial University of Newfoundland
St. John’s, NL, A1B 3X5, Canada
October 16, 2009
1
Presentation at a glance
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Objective
Background
Design challenges
First prototype
•
•
•
•
Minimization of Cogging Torque TORUS Configuration
ƒ
TORUS configuration
ƒ
Alternating Pole Arc
ƒ
Magnet Shifting
ƒ
Fractional Number of Slots Per Pole
Generator design
ƒ
Rotor
ƒ
Stator
ƒ
Stator winding
Prototyped Generator
Test Result
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Mechanical Parameter test
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Electrical parameter test
•
System model
2
Cont….
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Second prototype
•
•
•
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Generator Design
ƒ
Rotor
ƒ
Stator
ƒ
Stator winding
Prototyped Generator
Test Result
ƒ
Mechanical Parameter test
ƒ
Electrical parameter test
•
System model
Comparison between two prototype
Conclusion
Future work
Acknowledgement
3
Objective
† To extract few watts electrical power from the
sea-floor ocean current.
†
To design a generator suitable for under water
application.
†
To design a direct driven generator by
eliminating step-up gearbox.
†
To design permanent magnet generators as a
low speed energy converter.
4
Background
† Permanent Magnet Generator (PMG)
Figure 1(a): Radial Flux PMG
Figure 1(b):Axial Flux PMG
5
Background (Cont….)
† Axial Flux PMG
Figure 2:Different types of AFPMG
6
Background (Cont….)
† AFPM disc-type motor structures
Figure 3: (a) slotless TORUS, (b) slottedTORUS,
(c) slotless AFIR, and (d) slotted AFIR machines.
7
Design Challenges
† No of pole
Tmax
Lm
1
≈
Ls
1
≈
p2
Ls = Lm + Lσ
120 • f
n=
p
† Size
† Material
† Air gap
8
First Prototype
Figure 4: Designed generator
9
Minimization of Cogging Torque
Torque Components
Torque Ripple
Cogging Torque
Pulsating Torque
Minimization technique
Reducing the amplitude of each
portion
2. Shifting the relative phase of the
different components
†
1.
2.
3.
†
1.
10
Minimization of Cogging Torque (Cont….)
† TORUS Configuration
(a)
(b)
Figure 5: TORUS Topology (a) NN type and (b) NS type
11
Minimization of Cogging Torque (Cont….)
† Alternating Pole Arc
Figure 6(a): Same magnet
pole arc
Figure 6(b): Different magnet
Pole arc
12
Minimization of Cogging Torque (Cont….)
† Magnet Shifting
† Fractional Number of Slots Per Pole
Figure 7: Axial view of Rotor
With Shifted magnet
Figure 8: Two dimensional view
of shifted magnet
13
Generator Design
† Rotor
ƒ
Magnetic material- NdFeB
ƒ
Number of pole- 100
Large gap
Large magnet
Steel ring
Small magnet
Small gap
Figure 9: Full and sectional view of Rotor
14
Generator Design (Cont….)
† Stator
ƒ
Slotted stator is build with ferrite E-cores.
(a)
(b)
Figure 10: (a) E-core (b) Stator
15
Generator Design (Cont….)
† Stator Winding
ƒ
Number of turns
E rms =
E max
2
=
2π
Ns
× N × f × ϕ max ×
N ph
2
ϕ max = Amagn ⋅ Bmax
B max
lm
= Br ⋅
(lm + δ )
16
Generator Design (Stator Winding) Cont…
Figure 11: Prototyped stator
17
Generator Design (Stator Winding) Cont…
Figure 12: Stator winding
18
Prototyped Generator
Figure 13: prototyped generator
19
Test result
† Mechanical Parameter test
r
Rotor
mr 2
J =
2
m
F
Figure 14: Initial torque Measurement
20
Test result (cont….)
† Electrical parameter test
Generator
Multimeter
Oscilloscope
Load
Prime mover
Figure 15: Test setup
21
Test result (Electrical parameter test) cont….
Figure 16: Open Circuit voltage characteristic
22
Test result (Electrical parameter test) cont….
Each graph shows the
variation of generated
power with rotational
speed. The different
graphs are for different
load (2-20 ohm).
Figure 17: Output Characteristic
23
Test result (Electrical parameter test) cont….
The graph shows the
variation of load voltage
with load current as load
varies from 0-20 ohm.
The different graphs are
for different frequencies.
Figure 18:Load current and voltage characteristic
24
Test result (Electrical parameter test) cont….
Each graph shows the
variation of generated
power with load. The
different graphs are for
different frequencies.
Figure 19: Load characteristic
25
Test result (Electrical parameter test) cont….
The voltage wave form for
the both sides of the stator
Resultant wave form after
connecting the both sides
of the stator in series
Figure 20: Voltage wave form
26
System model
Internal resistance, Rg, [ohm]
1.8
Internal inductance, Lg [µH]
216.7
Machine constant, λm
0.071
No load loss. Rnull [ohm]
Figure 21: System model
0.003f2+0.0116f-0.1458
Inertia, Jm [Kg-m2]
o.96
Initial torque, To [N-m]
14.5
Open Circuit voltage at 72 rpm [volt]
5.18
Load for maximum power point
[ohm]
1.8
27
Conclusion
† Output Power is 3.5 watt at 72 rpm.
† Open circuit voltage is 5.2 volt at
designed speed.
† Generating current is high due to
thicker wire.
† Cogging torque is minimized.
† Large in size
† More frictional loss
28
Second Prototype
Figure 22: Designed generator
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Generator design
PCB stator
Figure 23: Designed topology of second prototype
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Generator design (cont….)
† Rotor
Figure 24: Rotor
31
Generator design (Rotor )cont….
Figure 24: Rotor
32
Generator design (cont….)
† Stator
Figure 25: 4 layer PCB Stator
33
Generator design (cont….)
† Stator Winding
Figure 26: Stator Winding Pattern
Figure 27: Stator winding
34
Generator design (Stator winding) cont….
Figure 28: A single winding with dimension (in Inches)
35
Prototyped generator
Figure 29: Prototyped Generator
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Test Result
† Stress and strain test
Figure 30: Stress strain test result
37
Test Result (Cont…)
† Mechanical parameter test
N1= No (1-e
–t1/BJ
)
Figure 31: Friction loss test result
38
Test Result (Cont…)
† Electrical parameter test
Figure 32: Test setup
39
Test Result (Electrical parameter test) Cont….
Figure 33: Open Circuit voltage characteristic
40
Test Result (Electrical parameter test) Cont….
Each graph shows the
variation of generated
power with rotational
speed. The different
graphs are for different
load (2-20 ohm).
Figure 34: Output Characteristic
41
Test Result (Electrical parameter test) Cont….
The graph shows the
variation of load voltage
with load current as load
varies from 0-20 ohm.
The different graphs are
for different frequencies.
Figure 35:Load current and voltage characteristic
42
Test Result (Electrical parameter test) Cont….
Each graph shows the
variation of generated
power with load. The
different graphs are for
different frequencies
Figure 36: Load characteristic
43
Test Result (Electrical parameter test) Cont….
Figure 37: Voltage wave form
44
System parameter
Internal resistance, Rg, [ohm]
4.4
Internal inductance, Lg [µH]
66.2
Machine constant, λm
0.078
No load loss. Rnull [ohm]
Inertia, Jm [Kg-m2]
Friction, Bm
Initial torque, To [N-m]
0.0003f2+0.0066f-0.1107
0.213
0.3
0
Open Circuit voltage at 72 rpm [volt]
5.6
Load for maximum power point [ohm]
4.5
45
Conclusion
†
†
†
†
†
†
Small in size
No cogging
Less friction
Zero initial torque
Higher voltage, 5.6 volt at 72 rpm.
Less current and power (1.8 watt)
46
Comparison between two prototype
† Size
† Output
† Torque
† Manufacturing process
47
Conclusion
†
Two prototypes are built and tested.
†
First Prototype
ƒ
ƒ
ƒ
ƒ
ƒ
†
New cogging torque minimization technique
More power
Larger size
Higher current
Lower voltage
Second prototype
ƒ
ƒ
ƒ
ƒ
PCB stator
Smaller size
Higher voltage
Lower current and power
48
Future Work
† Air gap reduction
† Material choice
† Smaller E-core
† More layer PCB
† Optimization
49
Acknowledgement
† Dr. Tariq Iqbal
† Seaformatics group
† Atlantic Innovation Funds
(www.acoa.ca)
† Memorial University of Newfoundland
† All of my friends and family
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THANKS
Questions
?
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Magnet properties
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RENSHAPE 440 material properties
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Properties of AWG 20
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Rotor Yoke (mild steel C-1020) data
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FR-4 data
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Generator design parameters
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Generator design parameters
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