Question

In the full-bridge converter circuit as shown in figure, $V_d=300V,$ and the fundamental frequency is 47 Hz. Suppose a PWM with unipolar switching is used with $m_f=38.m_a$ of first dominant harmonic is 0.314. RMS voltage and frequency of first dominant harmonic in the output voltage is

• A. 66.61 V, 3550 Hz
• B. 66.61 V, 3525 Hz
• C. 60.61 V, 3525 Hz
• D. 94.2 V, 3550 Hz

Answer 1

The correct option is B 66.61 V, 3525 Hz

For unipolar switching
Harmonic order, $h=j\left(2m_f\right)\pm k$
$h=2m_f-1=2\times 38-1=75$
$f_{75}=75\times 47=3525Hz$
$V_{D\left(75\right)}=\frac{V_d}{\sqrt{2}}\times m_a$
$=\frac{300}{\sqrt{2}}\times 0.314=66.61V$