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Types of Rectification

There are two types of Rectification:

Half Wave Rectification Full Wave Rectification

Half Wave Rectification:

In half wave rectification of a single-phase supply, either the

positive or negative half of the AC wave is passed, while the other half is blocked. Because onlyone half of the input waveform reaches the output, mean voltage is lower. Half-wave

rectification requires a single diode in a single-phase supply, or three in a three-phase supply.

The Half-wave Rectifier:

The half-wave rectifier is the simplest type of rectifier since it only uses one diode as shown.

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When the AC input is positive, the diode is forward-biased and lets the current through. When

the AC input is negative, the diode is reverse-biased and the diode does not let any currentthrough, meaning the output is 0V.

The output DC voltage of an ideal half wave rectifier is:

Full Wave Rectification:A full-wave rectifier converts the whole of the input waveform to one

of constant polarity (positive or negative) at its output. Full-wave rectification converts both

polarities of the input waveform to DC (direct current), and yields a higher mean output voltage.

The Full-wave Rectifier:In full wave rectifier four diodes are arranged so that both the

positive and negative parts of the AC waveform are converted to DC.

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When the AC input is positive, diodes A and B are forward-biased, while diodes C and D are

reverse-biased. When the AC input is negative, the opposite is true - diodes C and D areforward-biased, while diodes A and B are reverse-biased.

Capacitor:

A capacitor is an electrical device for storing charge. In general, capacitors are

made from two or more plates of conducting material separated by a layer or layers of insulators.

The capacitor can store energy to be given to a circuit when needed.

Symbol of Capacitor CapacitorFor a capacitor of capacitance C connected in circuit with a battery of voltage V:

So Q = CV

Where:

Q is the stored charge

C is capacitance of Capacitor

V is the potential difference

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Oscilloscope:

An oscilloscope is a laboratory instrument commonly used to display and

analyze the waveform of electronic signals. In effect, the device draws a graph of the

instantaneous signal voltage as a function of time.

A typical oscilloscope can display alternating current (AC) or pulsating direct current (DC)

waveforms having a frequency as low as approximately 1 hertz (Hz) or as high as several

megahertz (MHz). High-end oscilloscopes can display signals having frequencies up to severalhundred gigahertzes (GHz).

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Experiment # 02

Objective:

To demonstrate the use of Diode as a half wave rectifier.

Equipment:

Oscilloscope Resistor of 1k Transformer Analogue and Digital Multi meter Connecting wires Diode IN4007 Bread Board Capacitor of 100F

Circuit:

Procedure:1. Connect the circuit as shown in figure:2. Measure the AC voltage across the output terminals of voltage transformer.3. Observe the input and output waveform of the circuit with the help of an oscilloscope.4. Measure the RMS, average and peak value of input and output voltage with the help of

Multi meter and Oscilloscope.

5. Calculate PIV (peak inverse voltage).

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6. Calculate the of half wave rectifier by:

Efficiency (H.W) = Pdc/ Pac

Pdc = VdcIdc

Pac = Vrms Irms = ( Vrms )2 / RL

7. Now connect a capacitor of 100 F as shown below and calculate Vrms and average of ripple.

It shows when capacitor is added then there occur ripple in output waveform and

VR(P-P) = VP(rect) / RL f C

Vrms = VR(P-P) / 2 2

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Observation and Calculation

Resistor: 1K

Input:Vp = 10 V

Vp-p = 20 V

Vav = 0 V

Vrms = 6.4 V

Output:

Vp (Vp-p) = 17 V

Vav

= 1.72 VVrms = 4.1 V

Efficiency:

= 7.2

When Capacitor is added:

Vp(Vp-p) = 8 V

Vav = 9.04 V

Vrms = 18.7 V

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Experiment # 03

Objective:

To demonstrate the use of Diode as a full wave rectifier.

Equipment:

Oscilloscope Transformer Resistor of 1k Analogue and Digital Multi meter Connecting wires Diode IN4007 Bread Board Capacitor of 100F

Circuit:

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Procedure:

1. Connect the circuit as shown in figure:2. Measure the AC voltage Vac across the output terminals of voltage transformer.3. Observe the input and output waveform of the circuit with the help of an oscilloscope and

calculate their frequency as well.

4. Measure the RMS, average and peak value of input and output voltage with the help ofMulti meter and Oscilloscope and also record the waveform.

5. Measure current across load resistor.6. Connect probe of the oscilloscope across the diodes. Draw the waveforms and measure

peak values. These are the PIV values across the diodes compare it with reading of half

wave rectifier and full wave circuit of previous circuit.

7. Calculate theof full wave rectifier.8. Now connect a capacitor of 100 F as shown below then ripple also occur in outputwaveform of full wave rectifier.

Observation and Calculation

Resistor: 1K

Input:

Vp = 18.5 V

Vp-p = 37 V

Vav = 0 V

Vrms = 14.9 V

Output:

Vp (Vp-p) = 16.5 V

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Vav = 12.46 V

Vrms = 26.8 V

Efficiency:

= 70

Conclusion:

In half wave rectifier, half of the AC signal is converted into DC.In full wave rectifier, both the halves of ac signal are converted into dc. So efficiency in full wave rectifier is more than that of half wave rectifier. When capacitor is added in circuit ripple occurs in waveform.The experiment was not done efficeintly