The distortion factor (μ) is the ratio of
(a) total rms output voltage to fundamental rms output voltage
(b) fundamental rms output voltage to fundamental average output voltage
(c) total rms output voltage to rms value of all the harmonic components
(d) fundamental rms output voltage to total rms output voltage
I had been asked this question in final exam.
This key question is from Quality of Inverters topic in division Inverters of Power Electronics