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