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 Slide 1 of 26

Overview Introduction Research Objectives Portable Power System Oscillatory Motion Generator Model & Waveform Characteristics Initial Power Estimate Influence of Generator Parameters Experimental Results Conclusion Slide 2 of 26

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 Slide 3 of 26

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 Slide 4 of 26

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 Slide 5 of 26

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 Slide 6 of 26

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 Slide 7 of 26

Oscillatory Motion Harmonic Hz % 1 60 89.7 3 180 7.5 5 300 1.5 7 420 0.7 Slide 8 of 26

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 Slide 9 of 26

FEM No Load Results Slide 10 of 26

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) Slide 11 of 26

Initial Power Estimates Stray Load 5.18 W Friction & Windage 5.18 W Copper 37.00 W Stator Core 16.25 W Armature Reaction 36.26 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% Slide 12 of 26

Generator Parameters Magnet pitch to coil pitch full pitch to maximize induced back EMF Slide 13 of 26

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 Slide 14 of 26

Generator Parameters Number of magnet poles more poles produce “conventional shape at peak speed 60 slot 20 pole rotational 60 slot 20 pole oscillation Slide 15 of 26

Generator Parameters Number of magnet poles more poles produce “conventional shape at peak speed 18 slot 6 pole oscillation 30 slot 10 pole oscillation Slide 16 of 26

Generator Parameters Magnet thickness large compared to airgap, yet try not waste material 1mm magnet thickness 2mm magnet thickness Slide 17 of 26

Generator Parameters Magnet thickness large compared to airgap, yet try not waste material 3mm magnet thickness 3.5mm magnet thickness Slide 18 of 26

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 Slide 19 of 26

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 Slide 20 of 26

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 Slide 21 of 26

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 Slide 22 of 26

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 Slide 23 of 26

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) Slide 24 of 26

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 Slide 25 of 26

Questions Slide 26 of 26