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5715ch12 - 12 Linear Motion Alternators(LMAs 12.1 12.2 12.3...

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© 2006 by Taylor & Francis Group, LLC 12 -1 12 Linear Motion Alternators (LMAs) 12.1 Introduction ................................................................... 12 -1 12.2 LMA Principle of Operation ......................................... 12 -2 The Motion Equation 12.3 PM-LMA with Coil Mover ............................................ 12 -6 12.4 Multipole LMA with Coil Plus Iron Mover ................. 12 -7 12.5 PM-Mover LMAs ......................................................... 12 -13 12.6 The Tubular Homopolar PM Mover Single-Coil LMA .......................................................... 12 -16 12.7 The Flux Reversal LMA with Mover PM Flux Concentration ............................................... 12 -20 12.8 PM-LMAs with Iron Mover ........................................ 12 -27 12.9 The Flux Reversal PM-LMA Tubular Configuration ............................................................... 12 -27 The Analytical Model 12.10 Control of PM-LMAs .................................................. 12 -32 Electrical Control The Spark-Ignited Gasoline Linear Engine Model Note on Stirling Engine LMA Stability 12.11 Progressive-Motion LMAs for Maglevs with Active Guideway .................................................. 12 -35 Note on Magnetohydrodynamic (MHD) Linear Generators 12.12 Summary ....................................................................... 12 -39 References .................................................................................. 12 -40 12.1 Introduction This chapter deals mainly with linear oscillatory motion electric generators. The linear excursion is within a few centimeters. As prime movers, free piston Stirling engines (SEs), linear internal combustion single- piston engines, and direct wave energy engines (with meter range excursions) are proposed. So far, the Stirling engine [1] has been used for spacecraft and for residential electric energy generation electric vehicles. While rotary motion electric generators are multiphase machines, in general, the linear motion alter- nators (LMAs) tend to be single-phase machines, because the linear oscillatory motion imposes a change of phase sequence for change in the direction of motion. A three-phase LMA may be built of three single- phase LMAs. ( Figure 12.1 ) [1]. The linear internal combustion engine (ICE) was recently proposed for series hybrid
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© 2006 by Taylor & Francis Group, LLC 12 -2 Variable Speed Generators Though at first LMAs with electromagnetic excitation were proposed as single-phase synchronous generators (SGs), more recently, permanent magnet (PM) excitation took over, and most competitive LMAs now rely on PMs. A brief classification into three categories may be useful: With coil mover (and stator PMs) With PM mover With iron mover (and stator PMs) One configuration in each category is treated separately in terms of principle and performance equations. The dynamics and control will be treated once for all configurations. A special kind of linear motion generator with progressive motion to provide on-board energy on maglev (magnetically levitated) vehi- cles with active guideway is also briefly discussed. 12.2 LMA Principle of Operation PM-LMAs with oscillatory motion are, generally, single-phase machines with harmonic motion: (12.1) The electromagnetic force (emf) is, in general, (12.2) where is the PM flux linkage in the phase coils. With Equation 12.1 in Equation 12.2, (12.3) To obtain a sinusoidal emf waveform, Equation 12.3 yields the following: (12.4) FIGURE 12.1 Stirling engine — linear alternator.
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