RectifiersShubhanshi tiwari
0601ee121051 7th sem
ContentsIntroductionClassificationSingle phase half wave rectifierSingle phase full wave rectifierThree phase half wave rectifierThree phase full wave rectifierAdvantages and Disadvantages
INTRODUCTIONRectifiers take a number of forms, including
vacuum tube diodes, mercury-arc valves, copper and selenium oxide rectifiers , semiconductor rectifiers , silicon-controlled rectifiers and other silicon-based semiconductor switches.
rectifier is an electrical device that converts alternating current (AC) to direct current (DC).
The process is called Rectification.A Rectifiers employing diodes is called an
uncontrolled rectifier.
RECTIFIER CICUITS Single phase rectifiers
Half-wave rectificationFull-wave rectification
Three phase rectifiersThree phase half-wave rectification Three phase full-wave rectification
Half Wave Rectifier
Operation of Half Wave Rectifier
Waveform of Half Wave Rectifier
Average DC current
Average (DC) Voltage
RMS Load Current (Irms)
RMS Load Voltage
Rectifier Efficiency (η)
Working of full wave Bridge Rectifier
Waveforms of Bridge Rectifier
Three phase Half Wave Rectifierconsists of a three
phase transformera star connected
secondary three phase transformer with three diodes connected to the three phases
the neutral point ‘NTRL’ of the secondary is considered as the earth for the circuit and is given as the negative terminal for the load
Three phase Half Wave Rectifier
For each one-third of the cycle, each diode conducts.
At the instant when one diode out of three is conducting, the other two are left inactive, at that instant their cathodes becomes positive with respect to the anodes.
Then the process repeats for each of the three diodes.
: Three phase Full Wave Rectifier
also called as a six wave half wave rectifier
in the figure below the diodes D1 to D6 will conduct only for ⅙ th of the period, with a period of pi/3.
Six diodes are used
Three phase Full Wave Rectifier
the fluctuation of dc voltage is less in a three phase circuit
the variation lies between the maximum alternation voltage and 86.6% of this, with the average value being 0.955 times the maximum value
Disadvantage of Half wave Rectifiers
•The ripple factor of half wave rectifier is 1.21, which is quite high.•The output contains lot of ripples •The maximum theoretical efficiency is 40%. •The practical value will be quite less than this.•This indicates that HWR is quite inefficient.
Advantages of Full Wave Rectifier
Efficiency is higher. The large dc power outputThe ripple factor is less
Disadvantages of Full Wave Rectifier
• PIV rating of diode is higher. • Higher PIV diodes are larger in size
and costlier.• The cost of center tap transformer is
high.
Thank you
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