Waveform quality vs. operating frequency in a series inverter In a thyristorized series inverter, what happens to the distortion of the output voltage waveform when the operating frequency is lower than the natural (damped) resonant frequency of the series RLC path?

Introduction / Context:
Series inverters exploit resonance to shape current and, via the load impedance, the output voltage. Matching or exceeding the natural frequency improves sinusoidality; driving well below resonance alters the charge/discharge intervals and increases distortion.

Given Data / Assumptions:

• Series RLC branch sets a damped resonant frequency f_d.
• Inverter switches at an operating frequency f_o.
• Comparing cases where f_o < f_d.

Concept / Approach:
When f_o is less than f_d, the resonant current fully decays before the next switching event. The resulting piecewise waveform has pronounced dead intervals and sharp transitions, increasing harmonic content and thus distortion of the load voltage.

Step-by-Step Solution:
At f_o ≈ f_d, current waveforms are close to sinusoidal.Decrease f_o below f_d → extended decay and gaps between pulses.Voltage across the load reflects these discontinuities → higher THD and visible distortion.

Verification / Alternative check:
Fourier analysis of the pulsed, nonuniform conduction intervals shows stronger low-order harmonics when the inverter is driven significantly below resonance.

Why Other Options Are Wrong:
Low distortion claim: Opposite to behavior below resonance.
‘‘May be high or low’’: While load affects exact THD, the general tendency below resonance is increased distortion compared to near-resonant operation.

Common Pitfalls:
Assuming lower frequency automatically eases filtering; in resonant inverters, operation away from resonance can deteriorate waveform quality.

Final Answer:
the distortion of output voltage waveform is high