The 3-phase modulating waveforms (vₐ(t), v_b(t) and v_c(t)), used in sinusoidal PWM in a V Voltage Source Inverter (V SI) are

vₐ(t) = 0.8 sin(ωt) V

v_b(t) = 0.8 sin(ωt − 2π/3) V

v_c(t) = 0.8 sin(ωt + 2π/3) V

where ω = 2π × 40 rad/s is the fundamental frequency. The modulating waveforms

Question

The 3-phase modulating waveforms (vₐ(t), v_b(t) and v_c(t)), used in sinusoidal PWM in a V Voltage Source Inverter (V SI) are

vₐ(t) = 0.8 sin(ωt) V

v_b(t) = 0.8 sin(ωt − 2π/3) V

v_c(t) = 0.8 sin(ωt + 2π/3) V

where ω = 2π × 40 rad/s is the fundamental frequency. The modulating waveforms are compared with a 10 kHz triangular carrier whose magnitude varies between +1 and −1. The VSI has a DC link voltage of 600 V and feeds a star connected motor. The per phase fundamental RMS motor voltage, in volts, is closest to

Accepted Answer

169.71. In linear sinusoidal PWM the per-phase fundamental peak = ma x Vdc/2 = 0.8 x 300 = 240 V. RMS = 240/sqrt(2) = 169.71 V. Stored 212.13 V is incorrect.

Solution

Related GATE Technical questions