Which of the following is not a PWM technique?

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Examoogle · Accepted Answer

Triangular-pulse width modulation

Explanation: Triangular-pulse width modulation is not a standard PWM technique used in power electronics or control systems. PWM techniques are fundamentally defined by how the pulse width is adjusted based on comparison signals, typically involving carrier waves (like triangular waves) and reference waves (like sinusoidal or DC levels). Working Principle: PWM involves comparing a high-frequency carrier signal with a lower-frequency reference modulating signal. The intersection points determine the switching instants of the power semiconductor devices. Techniques like SPWM use a triangular carrier and a sinusoidal reference, whereas Single-pulse PWM uses a simple rectangular pulse variation within each half-cycle. Key Formulas: $d = \frac{T_{on}}{T}$ — Definition of Duty Cycle ($d$); $V_{avg} = d \cdot V_s$ — Average Output Voltage for a Chopper Key Points: SPWM (Sinusoidal PWM) is widely used in VSI (Voltage Source Inverters).; Single-pulse PWM is used for basic control of choppers or inverters where only one pulse per half cycle is sufficient.; Triangular waves are typically used as 'carriers' in PWM, but 'Triangular-pulse width modulation' is not a recognized nomenclature for a modulation technique.; The primary goal of PWM is to minimize harmonics and control the effective output voltage. Advantages: Improved power quality (lower THD); Precise control over voltage/current output Disadvantages: Increased switching losses at high frequencies; EMI (Electromagnetic Interference) generation Applications: Variable Frequency Drives (VFDs); DC-DC Converters (Choppers); UPS Systems Additional Info: Common PWM types include Single-pulse, Multi-pulse, Sinusoidal, and Space Vector PWM.. Option C is invalid because 'Triangular' describes the carrier waveform, not the modulation scheme itself. Answer: C is correct — Triangular-pulse width modulation is not a recognized standard PWM modulation classification. Exam Tip: Always distinguish between the 'Carrier Waveform' (e.g., triangular) and the 'Modulation Technique' (e.g., SPWM). A triangular signal is the tool, not the technique.

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