Lab # 002 - Best lab report PDF

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01/10/2019

Lab Title :To analyse the waveform at the output of half wave rectifier with and without capacitor.

Objective :    

Understand the Circuit behaviour the Half wave Rectifier Construct the Halfwave Rectifier with the required equipment Plot output waveform of a Halfwave rectifier. Evaluate the Ripple factor for the Halfwave Rectifier Evaluate the efficiency for a Halfwave Rectifier.

Introduction Of Theory:Rectifiers: A rectifier is an electrical device that converts alternating current (AC) to direct current (DC), a process known as rectification. 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.

Half-wave rectification In half wave rectification, either the positive or negative half of the AC wave is passed, while the other half is blocked. Because only one half of the input waveform reaches the output, it is very inefficient if used for power transfer. Half-wave rectification can be achieved with a single diode in a one-phase supply, or with three diodes in a three-phase supply.

Working of Half Wave Rectifier: If In Half wave Rectifier, we remove the negative Half Cycle of AC wave by using one diode, while in Full Wave Rectifier we convert the negative half cycle of AC into positive cycle using 4 diodes. Let us now consider an AC voltage with lower amplitude of 15Vrms and rectify it into dc voltage using a single diode. The diode conducts only during positive half cycle. But, the output will be discontinuous pulsed positive DC voltage. It has to be further filtered to make it a pure DC with lesser ripple. Point to be kept in mind is all the voltage, current that we measure through DMM is rms in nature. Hence the same is considered in simulation also

Fig # 01

The output waveform above is as expected, a discontinuous pulsed DC waveform. In order to smoothen the waveform or to make it continuous we add a capacitor filter in the output. The working of parallel capacitor is to maintain a constant voltage at the output. It decides the amount of ripple present in the output. 1|Pa ge

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Operation with capacitor: During the positive half cycle, the diode is forward biased and the capacitor gets charged as well as the load gets supply. During negative half cycle the diode gets reverse biased and the circuit is open during which the capacitor supplies the stored energy in it. The more the energy storage capacity the lesser the ripple in the output waveform. The ripple factor can be calculated theoretically by,

The efficiency is the major problem in half wave rectifier which is lesser than full wave rectifier. Generally the efficiency(ƞ) = 40%.

Advantages of Half wave Rectifier    

Cheap Simple Easy to use Low number of components

Disadvantages of Half wave Rectifier    

More amount of ripple content Transformer utilization factor is very low Rectification efficiency is low Generates harmonics

Circuit Diagram :-

Fig # 02

Practical Work :Equipment :    2|Pa ge

Resistor Diode Connecting Wires Breadboard 26961

Capacitor Oscilloscope Signal generator

  

Procedure :1. Connect the circuit as shown in the circuit diagram. 2. Connect the primary side of the transformer to AC mains and the secondary side to rectifier input. 3. Using a CRO, measure the maximum voltage Vm of the AC input voltage (at the anode) of the rectifier and AC voltage (at the cathode) at the output of the rectifier. 4. Using a DC voltmeter, measure the DC voltage at the load resistance. 5. Observe the Waveforms at the secondary windings of transformer and across load resistance for a load of 10K . 6. Calculate the ripple factor ( ).

Formula & Theoretical Calculation:Ripple factor

= Vr/Vdc.

Vr

= Vm/2fRC. V

=

I*R

Some common values are: Frequency = f = 50 Hz

Resister = r = 10 Kohm

Period

Diod

Vin

=

20 ms

= Vpp = 20 v

=

1N4007

Capacitor = C = 10 µF

Half Wave Rectifier (without filter): Vpp = VAC =

9.40 v

VDC = Vmax =

9.60 v

V rms = 4.60 v By using above formulas find I : IDC = 0.96 mA

Half Wave Rectifier (with filter): Vpp = VAC =

1.60 v

VDC = Vmax =

9.20 v

V rms =

8.40 v

By using above formulas to find the following given bellow: IDC Vr Ripple factor

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=

0.92 mA

=

0.92 v =

0.1 v

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Graphical Data :Half Wave Rectifier (without filter):

Graph # 01

Half Wave Rectifier (with filter):

Graph # 02

Discussion of Results :A practical half wave rectifier with a resistive load is shown in the circuit diagram. During the positive half cycle of the input the diode conducts and all the input voltage is dropped across RL. During the negative half cycle the diode is reverse biased and is in FF state and so the output voltage is zero. The filter is simply a capacitor connected from the rectifier output to ground. The capacitor quickly charges at the beginning of a cycle and slowly discharges through RL after the positive peak of the input voltage. The variation in the capacitor voltage due to charging and discharging is called ripple voltage. Generally, ripple is undesirable, thus the smaller the ripple, the better the filtering action. The ripple factor can be lowered by increasing the value of the filter capacitor or increasing the load capacitance. 4|Pa ge

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Conclusion :The waveform with the diode and after it by using capacitor is observed clearly.  A rectifier converts AC voltage to DC voltage.  Half wave Rectifier only passes current through load during the positive half cycle of sinusoidal.  The output of half wave rectifier is pulsating DC voltage, to convert it to a steady state, a filter is used.  The effectiveness of the filter can be measured by the ripple factor.

References :   

https://studentboxoffice.in/jntuh/notes/electronic-devices-and-circuits-lab/half-waverectifier-with-and-without-filters/4 http://vlab.amrita.edu/?sub=3&brch=60&sim=1112&cnt=2147 https://www.elprocus.com/half-wave-rectifier-circuit-working-principle-and-characteristics2/ https://electric-shocks.com/half-wave-rectifier-with-capacitor-in-filter-and-ripple-factorcalculation/

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