1. A. Zachas, L. Wu, R.G. Harley & J.R. Mayor
PM Generator Characteristics for Oscillatory Engine Based Portable Power System
A. Zachas, L. Wu, R.G. Harley & J.R. Mayor
Grainger CEME Seminar 5 March 2007
Sponsored by Powerix Technologies under contract to DARPA DSO
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2. Overview Introduction Research Objectives Portable Power System
Oscillatory Motion
Generator Model & Waveform Characteristics
Initial Power Estimate
Influence of Generator Parameters
Experimental Results
Conclusion
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3. Introduction
Need for lightweight portable power system in remote locations
Meso-scaled internal combustion swing engine (MISCE) developed to operate from several fuel sources
Oscillatory motion as opposed to rotational motion
Characteristics of a surface mount PM generator determined for this motion
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4. Research Objectives Understand the oscillatory motion
Model oscillatory motion in FEA package
Determine characteristic waveforms for oscillatory motion
Evaluate effect of generator parameters on the characteristic waveform
Use waveforms to estimate output power from generator
Experimental validation of simulation results
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5. Portable Power System
MICSE Power Generation System technology is a synergy of two novel energy conversion devices, micro-swing engines and swing-optimized PMAC swing-generators
Micro Internal Combustion Swing Engine (MICSE) converts high specific energy liquid fuels to oscillatory mechanical power (chemical-mechanical)
MICSE systems are internal combustion engines with four chambers separated by an oscillating swing arm
Mechanical-to-electrical power conversion via a direct-coupled swing-optimized permanent magnet AC induction generator
MPG systems are adaptable to a wide range of practical fuels, including butane/propane and JP-8
MPGs can be based on two-stroke and four-stroke MICSE designs and enables application-specific tailoring of the power system 1 2 3 4
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6. Initial Swing-engine Testing
In-chamber static combustion testing matched earlier calorimeter testing with cold-start quench losses <40%
Early testing with the swing-engine revealed significant seal failures resulting in chamber-to-chamber leakage
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7. MICSE Summary MTD-1Ex 350W MICSE System Power Level (W) 350
Thermal Efficiency
20%
Quenching Loss
Trapping Efficiency
Burned Mass Fraction
80%
Chemical to Mechanical Efficiency
2.2%
Size (LxWxH)
3.3“ x 4“ x 6"
Total mass (with active valve-train) (g)
1213
Valve-train power draw (W) 20
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8. Oscillatory Motion Harmonic Hz % 1 60 89.7 3 180 7.5 5 300 1.5 7 420
0.7
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9. Generator Model
Modeled with 2D finite element package and used a transient solver to apply motion to the rotor
No load back emf and flux linkage determined by the software
A1+
A1-
A2-
A2+
A3+
A8+
B1+
B8+
B2-
B1-
C7-
C8-
C1+
C8+
SOUTH
NORTH
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10. FEM No Load Results
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11. Initial Power Estimates
Performed FFT analysis on no load back EMF to find dominant harmonics
Estimated winding resistance and winding inductance using machine geometry
Connected no load back EMF as the source to a standard 6-diode bridge rectifier and a resistive load
FFT (Ea)
FFT (Eb)
FFT (Ec)
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12. Initial Power Estimates
Stray Load 5.18 W
Friction & Windage 5.18 W
Copper W
Stator Core W
Armature Reaction W
Loss Breakdown: Case 3 RLoad = 24.5 Ω
Maximum current density of 6 x 106A/m2
% of input power used for additional losses (friction, windage, hysteresis, armature reaction, etc)
Output power of about 417 W
Case
PLoad (W)
VLoad
ILoad
RLoad
Pin (W)
Papp (W)
Iarms
Ibrms
Icrms 1
497.7
108.15
4.602
23.5
537.8
632.35
5.06
5.08
4.81 2
489.2
108.35
4.515
24.0
527.2
622.30
4.98
5.00
4.74 3
481.0
108.56
4.431
24.5
518.0
612.45
4.89
4.92
4.67 4
473.1
108.75
4.350
25.0
508.9
602.80
4.84
4.61
Input Power
518 W
Total Losses
100 W
Average Power
418 W
Efficiency
81%
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13. Generator Parameters Magnet pitch to coil pitch
full pitch to maximize induced back EMF
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14. Saturation Flux Density
Generator Parameters
Tooth and stator thickness and material
maximize material utilization through FEA studies
minimize core loss effects due to increased oscillation frequency
carried out extensive material study
considering fabrication & availability, fine non-oriented electrical steel (Si Fe) was selected
Material
Saturation Flux Density
Core Loss at 400Hz 1T)
M19 – 26 Gauge (0.47 mm)
1.7 T (17 kG)
24.48 W/kg
Cogent NO 005 (0.12 mm)
1.8 T (18 kG)
11.8 W/kg
Metglas™ 2605C0 (0.023 mm)
1.8 T (14 kG)
6.0 W/kg
Hiperco® 50
2.2 T (22 kG)
17.64 W/kg
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15. Generator Parameters Number of magnet poles
more poles produce “conventional shape at peak speed
60 slot 20 pole rotational
60 slot 20 pole oscillation
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16. Generator Parameters Number of magnet poles
more poles produce “conventional shape at peak speed
18 slot 6 pole oscillation
30 slot 10 pole oscillation
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17. Generator Parameters Magnet thickness
large compared to airgap, yet try not waste material
1mm magnet thickness
2mm magnet thickness
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18. Generator Parameters Magnet thickness
large compared to airgap, yet try not waste material
3mm magnet thickness
3.5mm magnet thickness
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19. Generator Parameters Cogging torque Rotor Starting position
reduce by skewing of the magnets
Stagger magnets to create skew
3 steps of 4o to give 12o skew
Rotor Starting position
found to have little or no effect if the number of poles and swing angle were large
Rotor Speed
increased through use of a 1:4 gearbox by maintaining the same swing frequency but covering a larger swing angle
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20. Swing-optimized PMAC Prototype
Thermo-mechanical design optimization studies resulted in integrated cooling fins and to allow >6A/m2 current densities
Stator windings were potted with thermally conductive epoxy improve winding thermal management
Two 450W PMAC swing-optimized generators were fabricated with different winding configurations for maximum copper fill factor
Stator ring and spider laminates
MTD-1G1
MTD-1G2
Stator outer diameter (mm) 62
Rotor outer diameter (mm)
32.5
Axial length (mm) 40
Rotor Inertia (kg.m2)
2.615 x 10-5
Air Gap (mm)
0.25
Number of stator slots 30
Number of poles 10
Winding AWG
22 bifilar
No. turns per phase
130,130,130
140,130,140
Phase Resistance at 100oC (Ω)
0.681
0.61,0.58
Max. RMS current (A) 5
Mass (kg)
1.4
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21. Experimental Validation 1
Four-bar linkage built to simulate MICSE motion – converts rotational motion to oscillatory motion
Gearing provides 4x increase in speed and amplitude compared to direct drive
Rotation
Oscillation A B C
Front
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22. Simulated Back EMF at 8.4Hz
Experimental Results 1
MTD-1Gx Model Validation
Simulated Back EMF at 8.4Hz
Measured Back EMF at 8.4Hz (MTD-1G1)
Slight differences in model & prototype
Mismatch between simulation & test frequencies
Approximate velocity profile
2D FEA model without skew
Mechanical slip and vibration present in four-bar linkage
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23. Load Oscillatory Performance
Oscillatory Power Testing
Actual power measured at frequencies up to 16Hz
Estimated power at 55Hz is >700W based on FEA simulation
Test
Freq.
Vrms
Power 1
2.15
2.5
3.8 2 4
5.0
15.1 3
8.66
10.3
63.2 16
18.9
213.5 55
~700
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24. Simulated Back EMF at 16Hz
Experimental Results 2
MTD-1Gx Model Validation
No load back EMF
Generator coupled directly to MICSE and operating at approximately 16Hz oscillation frequency
Simulated Back EMF at 16Hz
Measured Back EMF at 16Hz (MTD-1G1)
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25. Conclusion Ultra portable power delivery system has been introduced
Approximate velocity profile for oscillatory motion for use in FEA has been determined
Influence of generator parameters has been evaluated
Characteristic no load waveforms presented
Simulations have been validated with experimental and test data
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26. Questions
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