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
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Sponsored by Powerix Technologies under contract to
DARPA DSO
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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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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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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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
34
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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
1.77 1.78 1.79 1.8 1.81 1.82 1.83
-2
0
2
4
6
8
10
12
14
16
18
Time (sec)
Pre
ssure
(psig
), V
oltage (
V),
or
Positio
n (
deg)
Cham 1Cham 2Cham 3Cham 4Spark 13Spark 24SA position
-10
0
10
20
30
40
50
60
70
80
90
0 0.02 0.04 0.06 0.08 0.1
Time From Spark (sec)
Pre
ssu
re (
psi
g)
MTD Chamber Test 2
MTD Chamber Test 3
Calorimeter Chamber
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MICSE SummaryMTD-1Ex 350W MICSE System
Power Level (W) 350
Thermal Efficiency 20%
Quenching Loss 20%
Trapping Efficiency 20%
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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Oscillatory Motion
Harmonic
Hz %
1 60 89.7
3 180 7.5
5 300 1.5
7 420 0.7
( ) cos(2 )ˆm t ft
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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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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
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V-
V+
V b 4
V c 4
V a 4D 1 D 5D 3
D 6D 2
R lo a d
3 1 5
C d
3 0 0 m
I C = 3 9 3
D 4
L a 0 . 0 1 3 5 8 1 3 6 7
L b 0 . 0 1 3 5 8 1 3 6 7
L c 0 . 0 1 3 5 8 1 3 6 7
V b 1
V a 3
V c 1 R c
4 . 9 1 3 5 9 9 3 0 6
R a
4 . 9 1 3 5 9 9 3 0 6
R b
4 . 9 1 3 5 9 9 3 0 6
V b 2
V c 2
V b 3
V c 3
C 3 5 . 0 9 5 5 u
R 3 1 e 9
C 2 6 . 1 6 5 5 u
R 4 1 e 9
C 1 5 . 0 9 5 5 u
R 5 1 e 9
V a 2 V a 5V a 1
V b 5
V c 5
V a 6 V a 7
V b 6 V b 7
V c 6 V c 7
FFT (Ea)FFT (Eb)FFT (Ec)
Initial Power Estimates
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
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Case
PLoad (W)
VLoad ILoad RLoa
d
Pin (W)
Papp (W)
Iarm
s
Ibrm
s
Icrm
s
1 497.7108.1
54.60
223.5 537.8 632.35
5.06
5.08
4.81
2 489.2108.3
54.51
524.0 527.2 622.30
4.98
5.00
4.74
3 481.0108.56
4.431
24.5
518.0612.4
54.89
4.92
4.67
4 473.1108.7
54.35
025.0 508.9 602.80
4.81
4.84
4.61
Stray Load 5.18 W
Friction & Windage 5.18 W
Copper 37.00 W
Stator Core
16.25 WArmature Reaction 36.26 W
Loss Breakdown: Case 3 RLoad = 24.5 Ω
Input Power 518 W
Total Losses 100 W
Average Power
418 W
Efficiency 81%
Generator Parameters
Magnet pitch to coil pitch• full pitch to maximize induced back EMF
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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
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MaterialSaturation
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
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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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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Generator Parameters
Magnet thickness• large compared to airgap, yet try not waste material
1mm magnet thickness
2mm magnet thickness
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Generator Parameters
Magnet thickness• large compared to airgap, yet try not waste material
3mm magnet thickness
3.5mm magnet thickness
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Generator Parameters
Cogging torque• 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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Swing-optimized PMAC Prototype
MTD-1G1 MTD-1G2Stator outer diameter (mm) 62Rotor outer diameter (mm) 32.5Axial length (mm) 40Rotor Inertia (kg.m2) 2.615 x 10-5
Air Gap (mm) 0.25Number of stator slots 30Number of poles 10Winding AWG 22 bifilarNo. turns per phase 130,130,13
0140,130,140
Phase Resistance at 100oC (Ω)
0.681 0.61,0.58
Max. RMS current (A) 5Mass (kg) 1.4
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
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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
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A
B
C
Front
Rotation
Oscillation
Experimental Results 1
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MTD 1G2: Maxwell 2D Back EMF vs Time
-30
-20
-10
0
10
20
30
0 0.02 0.04 0.06 0.08 0.1 0.12
Time (sec)
Vo
lta
ge
(V
)
Phase A Maxwell
Phase B Maxwell
Phase C Maxwell
MTD-1G1 No-load 8.4Hz
-30
-20
-10
0
10
20
30
0.000 0.020 0.040 0.060 0.080 0.100 0.120
Time (s)
Vo
lta
ge
(V
)
Phase A
Phase B
Phase C
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
Load Oscillatory Performance
Test
Freq.
Vrms
Power
1 2.15 2.5 3.8
2 4 5.0 15.1
3 8.66 10.3 63.2
4 16 18.9 213.5
55 ~700
Oscillatory Power Testing
Actual power measured at frequencies up to 16Hz Estimated power at 55Hz is >700W based on FEA
simulation
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Experimental Results 2
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MTD-1Gx Model Validation
Simulated Back EMF at 16Hz
Measured Back EMF at 16Hz (MTD-1G1)
No load back EMF Generator coupled directly
to MICSE and operating at approximately 16Hz oscillation frequency
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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