Question

If Vr is the rms value of the inverter output voltage and V1 is the rms value of the fundamental component, then the total harmonic distortion (THD) is given by

(a) Vr/V1

(b) (Vr + V1r

(c) [ (Vr/V1)^2 – 1 ]^1/2

(d) [ (Vr/V1)^1/2 + 1 ]^2

The question was asked in unit test.

I would like to ask this question from Quality of Inverters topic in chapter Inverters of Power Electronics

Answer 1

Correct answer is (c) [ (Vr/V1)^2 – 1 ]^1/2

Explanation: THD is the ratio of rms value of all the harmonic components to the rms value of the fundamental component.

Rms value of all the harmonic components VH = (Vr^2 – V1^2)^1/2

THD = (Vr^2 – V1^2)^1/2/ V1.