Govt. Exams
Entrance Exams
Power factor = cos(α) = cos(60°) = 0.5 for fully controlled single-phase rectifier. For 3-phase, it's slightly higher at approximately 0.67 considering the waveform.
Liquid cooling provides superior heat transfer coefficient (500-5000 W/m²K) compared to forced air (50-500 W/m²K), essential for high-power applications with stringent thermal requirements.
For buck converter: L = (Vi × D × (1-D))/(f × ΔI) = (24 × 0.5 × 0.5)/(100×10³ × 2) = 120 μH
Space Vector Modulation provides superior harmonic performance with THD approximately 30% lower than SPWM and enables higher DC utilization (15.5% improvement in voltage utilization).
Peak phase voltage = (Ma × Vdc)/2 × √3 for three-phase. Vpeak = 0.8 × 400 / 2 × √3/√3 ≈ 184.8V (considering line-to-neutral relationship)
IGBTs contain a parasitic thyristor structure. When collector current becomes too high, this thyristor can turn on, causing the device to latch and potentially causing permanent damage.
Resonant converters inherently provide soft-switching conditions through LC resonance, reducing switching losses and EMI compared to hard-switching topologies.
In a boost converter, voltage stress on switch = Vo = 80V. The diode experiences stress of (Vo - Vi) = 32V.
For a 3-phase fully controlled rectifier: Vavg = (3√2/π) × Vline × cos(α) = 1.654 × 415 × cos(60°) = 280.7V
ZCS occurs when the device current reduces to zero before switching, eliminating switching losses due to current commutation
