Govt. Exams
Entrance Exams
For a boost converter, Vo/Vin = 1/(1-D), where D is duty cycle. 48/24 = 1/(1-D) → 2 = 1/(1-D) → 1-D = 0.5 → D = 0.5 or 50%
Full-bridge phase-shift topology offers high efficiency (>97%), ZVS operation, and high isolation ratio suitable for high-power fast-charging applications.
Active front-end rectifiers use closed-loop current control with PWM modulation to inject harmonics that cancel grid distortion.
Modern VFDs support 0.1Hz to 500Hz+ output, enabling ultra-low speed precision applications and extended-speed motor operation.
In resonant DC-link inverters, the resonant frequency is designed to equal or track the switching frequency for zero-voltage switching.
Matrix converter requires m×n switches where m=output phases and n=input phases. For 3×3: 9 bi-directional switches.
Cycloconverters use back-to-back (antiparallel) thyristor pairs to enable bidirectional power flow for frequency conversion.
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.
