# Chapter 11 - SJTU 1 Chapter 11 AC power analysis SJTU 2 rms...

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Unformatted text preview: SJTU 1 Chapter 11 AC power analysis SJTU 2 rms value The rms value of a periodic function is defined as the square root of the mean value of the squared function. effective value or DC-equivalent value The RMS value is the effective value of a varying voltage or current. It is the equivalent steady DC (constant) value which gives the same effect. ∫ = T rms dt t v T V 2 ) ( 1 SJTU 3 If the periodic function is a sinusoid, then What do AC meters show, is it the RMS or peak voltage? AC voltmeters and ammeters show the RMS value of the voltage or current. What does '6V AC' really mean, is it the RMS or peak voltage? If the peak value is meant it should be clearly stated, otherwise assume it is the RMS value . m m T m rms V V t V T V 707 . 2 1 ) ( cos 1 2 2 = = + = ∫ φ ϖ SJTU 4 AC power analysis Instantaneous Power v(t) i(t) N ) cos( 2 ) ( cos 2 ) ( φ ϖ ϖ- = = t I t i t V t v rms rms Suppose: ) 2 cos( cos ) cos( 2 cos 2 φ ϖ φ φ ϖ ϖ- + =- × = = t I V I V t I t V vi p rms rms rms rms rms rms Invariable part Sinusoidal part SJTU 5 E page415 figure 10.2 SJTU...
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Chapter 11 - SJTU 1 Chapter 11 AC power analysis SJTU 2 rms...

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