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Unformatted text preview: Page 1 Fundamentals of Power Systems Lecture 12 1 SM No-Load Characteristic A E k IZ Characteristic of the iron (stator and rotor) Rotor field current Rotor flux magnitude Induced stator voltage magnitude Rotor field current Effect of saturation: for large field currents the no-load armature voltage magnitude scales sub-proportionally with I F and the voltage waveform becomes non sinusoidal (distorted). Fundamentals of Power Systems Lecture 12 2 SM Armature Reaction I z Unloaded generator at arbitrary rotor position z Phase-A induced voltage can be represented by a space vector E A which aligns with rotor field vector B R The time evolution of phase-A voltage and current is the projection of the respective space vector onto the y-axis Phase A x y Rotor field axis E A Page 2 Fundamentals of Power Systems Lecture 12 3 SM Armature Reaction II z Generator with lagging load current (balanced) z Phase-A current space vector I A is rotated (in space) out of the rotor B R axis by the load phase...
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