5715ch4 - 4 Self-Excited Induction Generators 4.1 4.2 4.3...

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4 -1 4 Self-Excited Induction Generators 4.1 Introduction . ...................................................................... 4 -1 4.2 The Cage Rotor Induction Machine Principle. ................ 4 -2 4.3 Self-Excitation: A Qualitative View. .................................. 4 -4 4.4 Steady-State Performance of Three-Phase SEIGs. ........... 4 -6 Second-Order Slip Equation Methods SEIGs with Series Capacitance Compensation 4.5 Performance Sensitivity Analysis . ................................... 4 -12 For Constant Speed For Unregulated Prime Movers 4.6 Pole Changing SEIGs for Variable Speed Operation. .... 4 -14 4.7 Unbalanced Operation of Three-Phase SEIGs. .............. 4 -17 4.8 One Phase Open at Power Grid. ..................................... 4 -19 4.9 Three-Phase SEIG with Single-Phase Output. ............... 4 -22 4.10 Two-Phase SEIGs with Single-Phase Output. ................ 4 -26 4.11 Three-Phase SEIG Transients. ......................................... 4 -30 4.12 Parallel Connection of SEIGs. ......................................... 4 -33 4.13 Connection Transients in Cage Rotor Induction Generators at Power Grid. ............................................... 4 -35 4.14 More on Power Grid Disturbance Transients in Cage Rotor Induction Generators. ........................................... 4 -41 4 . 15 Summary. .......................................................................... 4 -45 References. ................................................................................... 4 -47 4.1 Introduction By self-excited induction generators (SEIGs), we mean cage rotor induction machines with shunt (and series) capacitors connected at their terminals for self-excitation. The shunt capacitors may be constant or may be varied through power electronics (or step-wise). SEIGs may be built with single-phase or three-phase output and may supply alternating current (AC) loads or AC rectified (direct current [DC]) autonomous loads. We also include here SEIGs connected to the power grid through soft-starters or resistors and having capacitors at their terminals for power factor compensation (or voltage stabilization). Note that power electronics controlled cage rotor induction generators (IGs) for constant voltage and This chapter will introduce the main schemes for SEIGs and their steady-state and transient perfor- mance, with sample results for applications such as wind machines, small hydrogenerators, or generator © 2006 by Taylor & Francis Group, LLC frequency output at variable speed, for autonomous and power grid operation, will be treated in Chapter 5 .
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4 -2 Variable Speed Generators sets. Both power grid and stand-alone operation and three-phase and single-phase output SEIGs are treated in this chapter. 4.2 The Cage Rotor Induction Machine Principle The cage rotor induction machine is the most built and most used electric machine, mainly as a motor, but, recently, as a generator, too. The cage rotor induction machine contains cylindrical stator and rotor cores with uniform slots separated by a small airgap (0.3 to 2 mm in general). The stator slots host a three-phase or a two-phase AC winding meant to produce a traveling magne- tomotive force (mmf). The windings are similar to those described for synchronous generators (SGs) in this book. This traveling mmf produces a traveling flux density in the airgap, B g 10 : (4.1) (for three phases) (4.2) where q r is the rotor position p 1 equals the pole pairs The cage rotor contains aluminum (or copper, or brass) bars in slots. They are short-circuited by end- rings with resistances that are smaller than those of bars (Figure 4.1).
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5715ch4 - 4 Self-Excited Induction Generators 4.1 4.2 4.3...

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