Sinusoidal PWM (SPWM) for inverters – pulse widths In sinusoidal PWM control of voltage-source inverters, are the widths of the individual gating pulses within a half cycle all equal?

Introduction / Context:
Sinusoidal PWM (SPWM) shapes the fundamental output and controls harmonics by comparing a high-frequency triangular carrier with a low-frequency sinusoidal modulating signal. The resulting pulse widths convey the sinusoidal information to the load after filtering.

Given Data / Assumptions:

• Voltage-source inverter using carrier-based SPWM.
• Constant switching frequency carrier (triangular wave).
• Sinusoidal reference for desired fundamental.

Concept / Approach:

Where the sinusoidal reference exceeds the carrier, the switch turns on; where it is lower, it turns off. Because the sinusoid varies over the half-cycle, the intersections occur at non-uniform points, creating pulses whose widths increase near the sine peak and decrease toward the zero crossings.

Step-by-Step Solution:

Verification / Alternative check:

SPWM spectra show a controllable fundamental with sidebands around multiples of the carrier; equal pulse width would correspond to square-wave or uniform PWM, not sinusoidal PWM.

Why Other Options Are Wrong:

• “True” would imply uniform pulse width, which is not how SPWM encodes the sinusoid.

Common Pitfalls:

Confusing SPWM with fixed-width, variable-position schemes, or with selective harmonic elimination where a few notches are placed deliberately.

Final Answer:

False