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# lecture12 - Stator DC Current Component The expression for...

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(c) Feb 2004 Power Systems I 1 Stator DC Current Component The expression for the stator current for the simplified machine model does not include the effects of the decaying exponential unidirectional current The dc component is a function of the machine’s rotor position, which is indicated by δ when the short-circuit is applied at t = 0 The time constant associated with the decay of the dc component is known as the armature short circuit time constant, τ a Typical time constants range around 0.05 to 0.17 seconds a q d a R X X 2 + =

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(c) Feb 2004 Power Systems I 2 Stator DC Current Component A generator has three windings separated by 120º; each phase will have a different dc component depending on the point of the voltage cycle at which the short circuit occurs Combining the ac and dc components using superpositioning results in () a t d a dc e X E I τ δ ′′ = sin 2 0 a d d t d d t d d t d d ac e X E t X e X X e X X E t i ω + + + + = sin 2 sin 1 1 1 1 1 2 ) ( 0 0
(c) Feb 2004 Power Systems I 3 Determining the Transient Constants The generator transient constants can be estimated by analyzing the current waveforms of a fault applied at the generator terminals The current waveform must not have any dc components - i.e. the fault was applied at a voltage peak Data preparation No-load / open circuit terminal voltage of the generator The current waveform is divided into three periods the subtransient period - first few cycles where the current

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## This note was uploaded on 10/13/2011 for the course EEL 4213 taught by Professor Thomasbaldwin during the Spring '11 term at FSU.

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lecture12 - Stator DC Current Component The expression for...

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