Half-bridge single-phase inverter: If a DC battery of voltage V feeds an ideal half-bridge that produces a two-level square wave of +V/2 and −V/2 at the output, what is the rms value of the fundamental component of the output voltage (express your choice in terms of V)?
Electronics and Communication Engineering
Power Electronics
Difficulty: Medium
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Answer
Correct Answer: (√2/π) * V (≈ 0.450 V)
Explanation
Introduction / Context:Fourier analysis of inverter waveforms is central to designing filters and estimating fundamental RMS values. In a half-bridge, the output toggles between +V/2 and −V/2, producing a square wave whose fundamental must be extracted for RMS calculations.Given Data / Assumptions:
- Ideal half-bridge with amplitude levels ±V/2.
- Pure square wave, 50% duty, no dead-time or device drop.
- We seek RMS of the fundamental component only (not total RMS).
- 2V: Dimensionally incorrect for RMS of a component.
- V/√2: That is the RMS of a sinusoid with peak V, not applicable here.
- V/2: Not the fundamental RMS; it is just the DC magnitude half, irrelevant here.
- (2/π) * V ≈ 0.637V: That is the average of a ±V square wave magnitude, not the fundamental RMS.
- Confusing total RMS of square wave with fundamental RMS.
- Dropping the factor of 1/2 for half-bridge amplitude.