Govt. Exams
Entrance Exams
Full-bridge phase-shift topology offers high efficiency (>97%), ZVS operation, and high isolation ratio suitable for high-power fast-charging applications.
In resonant DC-link inverters, the resonant frequency is designed to equal or track the switching frequency for zero-voltage switching.
For AC controller: Vo/Vi = √[(π-α+sin(2α)/2)/π] with α=45°≈0.785rad gives ≈0.642.
In a five-level inverter, maximum voltage across each switch is Vdc/4, compared to Vdc/2 in a two-level inverter, reducing stress by half.
ΔIL = (Vin × D × (1-D))/(L × f). Assuming standard inductor ~10μH: ΔIL ≈ (48 × 0.7 × 0.3)/(10e-6 × 500e3) ≈ 2.4A.
MMC offers scalability, modularity, and superior voltage quality for utility-scale applications, making it the industry standard for >100kW systems.
Conduction loss = I²rms × RDS(on). With 50A average current (≈35.4A RMS) and 0.5Ω: Loss ≈ (35.4)² × 0.5 ≈ 625W. At high frequency, peak current factor increases loss to ~1250W.
ZVS eliminates capacitive discharge losses during switching, significantly reducing switching losses and high-frequency EMI emissions.
For AC voltage controller: PF = (1/π)√(π² - 4α²) × sin(2α)/(2α) where α = 30° = π/6. This yields PF ≈ 0.87 with leading reactive current.
Minimum OFF-time must account for semiconductor recovery characteristics: tOFF(min) = ts + tf, allowing complete device turn-off before the next cycle.
