Recifiers Questions and Answers for Viva

Answer-1: The process of converting A.C. voltage into D.C. voltage which is in only one direction, a process known as rectification is called rectification and it is done by rectifier.

Answer-2: Rectifiers have many uses including as components of power supplies and as detectors of radio signals. Rectifiers may be made of solid state diodes, vacuum tube diodes, mercury arc valves, and other components. Rectifiers also find a use in detection of amplitude modulated radio signals.

Answer-3: There are two type of rectifier: Half wave rectifier and Full wave rectifier. Full wave rectifier is further classified into center tape full wave rectifier and bridge full wave rectifier.

Answer-4: The ripple factor of the rectifier is as follow: For Half wave recitifer, ripple factor is 1.21, for Center tape wave rectifier, ripple factor is 0.48 and for Bridge full wave rectifier, ripple factor is 0.48.

Answer-5: The PIV of rectifier: - Half wave rectifier=Vm, Center tape wave rectifier=2Vm, Bridge full wave=Vm

Answer-6: In a half wave rectifier only one half cycle of ac voltage is taking. The circuit is given. Here only one diode is using. During the positive half cycle of ac voltage the diode conducts. So current flows through load. During the negative half cycle, the diode is reverse biased .So no current flows through the diode. Half-wave rectification can be achieved with a single diode in a one-phase supply, or with three diodes in a three-phase supply.

Answer-7: Full wave bridge rectifier: In full wave bridge rectifiers 4 diodes are using. During positive half cycle, D1 and D4 are in forward biased condition. In the negative half cycle of ac D3 and D2 are in forward biased condition. So in both the half cycles current through the load is in single direction. This circuit does not need a centre tap rectifier. But it requires more number of diodes than centre tap and half wave rectifiers.

Answer-8: In this method only two diodes are using. But it requires a center tap transformer. During the positive half cycle diode D1 conducts. In the negative half cycle diode D2 conducts. So in both half cycles current flowing through load in same direction. Full-wave rectification converts both polarities of the input waveform to DC (direct current), and is more efficient.

Answer-9: While half-wave and full-wave rectification suffice to deliver a form of DC output, neither produces constant-voltage DC. In order to produce steady DC from a rectified AC supply, a smoothing circuit or filter is required. In its simplest form this can be just a reservoir capacitor or smoothing capacitor, placed at the DC output of the rectifier. There will still remain an amount of AC ripple voltage where the voltage is not completely smoothed.

Answer-10: The efficiency of half wave rectifier is not as good as that of full wave rectifier because only one half of the input waveform reaches the output, it is very inefficient if used for power transfer. The ripples are maximum in the single phase half-wave rectifier and being reduced in the full-wave rectifier and being reduced further with the increase in the number of phases.