Question

In the single-pulse width modulation method, the Fourier coefficient bn is given by

(a) (Vs/π) [ sin(nπ/2) sin(nd) ].

(b) 0

(c) (4Vs/nπ) [sin(nπ/2) sin(nd)].

(d) (2Vs/nπ) [sin(nπ/2) sin(nd)].

I got this question in my homework.

I'd like to ask this question from PWM Inverters-1 in chapter Inverters of Power Electronics

Answer 1

Right choice is (c) (4Vs/nπ) [sin(nπ/2) sin(nd)].

For explanation: The Fourier analysis is as under:

bn = (2/π) ∫ Vs sin⁡ nωt .d(ωt)  , Where the integration would run from (π/2 + d) to (π/2 –  d)

2d is the width of the pulse.