Inverter

Toggle between square-wave and sinusoidal PWM switching, choose half-bridge or full-bridge topology, and adjust the DC bus voltage and modulation index. The widget plots the output waveform and computes fundamental voltage and THD in real time — no Fourier tables needed.

V_dc: 200 Vf_out: 50 Hz

H-Bridge State

Fundamental RMS

\small V_{1,rms} = \tfrac{4V_{dc}}{\pi\sqrt{2}} = \tfrac{4\!\times\!200}{\pi\sqrt{2}} = 180.1\;\text{V}

THD

\small THD = \tfrac{\sqrt{V_{rms}^2 - V_1^2}}{V_1} = \tfrac{\sqrt{200.0^2 - 180.1^2}}{180.1} = 48.3\%

$V_{rms}$

200.0 V

$P_{load}$ (R = 50 Ω)

800.0 W

Quick experiments

Full-bridge square wave. Set V_dc = 200 V — the output swings ±200 V with THD around 48%.
PWM clean-up. Switch to PWM and lower the modulation index m_a — watch THD drop as the output approaches a pure sine.
Half vs full-bridge. Compare the two topologies at the same V_dc — the full-bridge doubles the output swing.

DC-AC inverters

A DC-AC inverter converts a battery or DC bus voltage to AC using a bridge of power switches (MOSFETs or IGBTs). The switches are driven with PWM waveforms whose varying duty cycle shapes the output into an approximate or true sine wave.

H-bridge (single-phase) operation

Four switches arranged in an H: diagonal pairs switch alternately at high frequency. PWM duty cycle is varied sinusoidally so the LC output filter reconstructs the fundamental frequency. The switches never conduct simultaneously (dead-time prevents shoot-through).

Output quality — THD

Total Harmonic Distortion (THD) measures how closely the output resembles a pure sine wave. Modified-sine inverters (cheaper, square-wave steps) have THD of 40–45 % — acceptable for resistive loads but can damage motors and sensitive electronics. Pure-sine inverters achieve THD < 3 %.

Learn more → Inverters — Learn