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Half wave Rectification

BS P-III

Institute of Phsics

Half wave rectification Objects of the experiment To understand the operation of Half wave Rectifier.

Introduction RECTIFIER A rectifier is a circuit that converts pulsating ac into pulsating There are three basic types of rectifier circuits: the half wave, full wave (center tapped) and rectifiers. Of them, bridge rectifier is the most commonly used.

2.1 HALF WAVE RECTIFIER: Half wave rectification is a process, which converts an ac sinusoidal input voltage into a pulsating dc voltage with the output pulse occurring for each input cycle. The half wave rectifier is made up. of a single diode and a resistor (load). The half wave rectifier conducts the current only during the positive half cycle of the a.c input supply. The negative half cycle of a.c supply is suppressed i.e. during the negative half cycle, no current is conducted and hence no voltage appears across the load. Therefore current always flows in one direction (i.e. d.c) through the load after every half cycle. Operation: The a.c voltage is applied across the secondary windings. During the positive half cycle of a.c input voltage point 5 is positive with respect to point 8. This makes the diode D1 forward biased and hence it conducts the current as shown in the upper half cycle of fig1(a). Transformer 5

IN4001

Load

R = L

8

(a)

Oscilloscope

Function generator input

(b) Fig.1 Half Wave Rectifier

During the negative half cycle, point .5 is negative with respect to Under the diode D1 is reverse bias and no current conducts as shown in figure 1 Therefore the current flows through the diode during the positive half cycle. In this the current flows through the load resistor R L always-same direction. Hence d.c output is obtained the R L . The complete output waveform of half wave rectifier of three cycles will look like as shown in figure 2 Vp VDC

0

Figure 2.Half wave rectifications up to three cycles.

1

Half wave Rectification

BS P-III

Institute of Phsics

Ripple Factor (r): Ripple factor is very important criteria for measuring the efficiencies of a rectifier Basically the variations in the output voltage due to charging and discharging is called ripple as shown in figure2-3

Figure 2-3. Ripple waveform. It is formally define as the ratio of the ripple voltage in the output voltage delivered to load and the d.c component of the output voltage is represented by symbol (r).

r=

Vr.m.s Vd.c

Or. alternatively ripple factor can be calculated as r Where

Vr.m.s =

Vp 2

; while

Vavg =

Vr.m.s Vavg

=

2 -1

Vp

Note: Vp denotes the peak value of d.c rectified output.

EQUIPMENT ■ Oscilloscope

1K

■

Function generator COMPONENTS: A bread board

resistor

Diod e (IN40001) A few connecting hard wires

PROCEDURE: 1. Setup the function generator to a suitable frequency and peak voltage. 2. Make the half wave circuit diagram as shown in fig 1(b). 3. Observe the rectified output at diffrent peak to peak voltge values. 4. Calculate the ripple factor in each case. 5. Observe the ripple on the Oscilloscope, using the feature of dc/ac coupling.

OBSERVATION TABLE: S.No.

Vin (p-p)

Vout (peak)

Vavg = Vp/

= Vp

2

REVIEW QUESTIONS: What is rectification? 2. What is half wave Rectification? 1.

3.

What is ripple?

4.

What are the advantages and disadvantages of half wave rectifier?

2

Ripple factor