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Wednesday, October 5, 2011

HALF WAVE RECTIFIER


HALF – WAVE RECTIFIER

 AIM: - To obtain the load regulation and ripple factor of a half-rectifier.
                            1. with Filter
                             2. without Filter
APPARATUS:-
                                      Experimental Board
                                      Multimeters              –2No’s.
                                      Transformer (6-0-6).
                                       Diode, 1N 4007
                                      Capacitor 100μf.
                                      Resistor     1KΩ.
                                      Connecting wires
THEORY: -
               During positive half-cycle of the input voltage, the diode D1 is in forward bias and conducts through the load resistor R1. Hence the current produces an output voltage across the load resistor R1, which has the same shape as the +ve half cycle of the input voltage.
  During the negative half-cycle of the input voltage, the diode is reverse biased and there is no current through the circuit. i.e, the voltage across R1 is zero. The net result is that only the +ve half cycle of the input voltage appears across the load. The average value of the half wave rectified o/p voltage is the value measured on dc voltmeter.
           For practical circuits, transformer coupling is usually provided for two reasons.
 1. The voltage can be stepped-up or stepped-down, as needed.
 2. The ac source is electrically isolated from the rectifier. Thus preventing shock hazards in the secondary circuit.



CIRCUIT DIAGRAM:-



 PROCEDURE:-
1. Connections are made as per the circuit diagram.
2. Connect the primary side of the transformer to ac mains and the secondary side to the rectifier input.
3. By the multimeter, measure the ac input voltage of the rectifier and, ac and dc voltage at the output of the rectifier.
 4. Find the theoretical of dc voltage by using the formula,

                                            Vdc=Vm/П
                          
Where, Vm=2Vrms, (Vrms=output ac voltage.)
The Ripple factor is calculated by using the formula
                                       r=ac output voltage/dc output voltage.


REGULATION CHARACTERSTICS:-
1.    Connections are made as per the circuit diagram.
2.    By increasing the value of the rheostat, the voltage across the load and current flowing through the load are measured.
3.    The reading is tabulated.
4.    Draw a graph between load voltage (VL and load current ( IL ) taking VL on X-axis and IL on y-axis
5.    From the value of no-load voltages, the %regulation is calculated using the formula,

Theoretical calculations for Ripple factor:-

Without Filter:-
                              Vrms=Vm/2
                              Vm=2Vrms
                              Vdc=Vm/П
                              Ripple factor r=√ (Vrms/ Vdc )2 -1 =1.21
With Filter:-
                           Ripple factor, r=1/ (2√3 f C R)
                                                   Where    f =50Hz
                                                                 C =100µF
                                                                 RL=1KΩ
                                         
PRACTICAL CALCULATIONS:-

                          Vac=
                         Vdc=
                         Ripple factor with out Filter =
                         Ripple factor with Filter =


OBSERVATIONS:-

WITHOUT FILTER

USING DMM
Vac(v)
Vdc(v)
r= Vac/ Vdc





WITH FILTER

USING DMM
Vac(v)
Vdc(v)
r= Vac/ Vdc




WITHOUTFILTER:-
 Vdc=Vm/П,      Vrms=Vm/2,   Vac=√ ( Vrms2- Vdc 2)


USING CRO
Vm(v)
Vac(v)
Vdc(v)
r= Vac/ Vdc





WITHFILTER

USINGCRO
V1(V)
V2(V)
    Vdc= (V1+V2)/2
Vac=
(V1- V2)/2√3
r=
Vac/ Vdc








PRECAUTIONS:

1. The primary and secondary sides of the transformer should be carefully identified.
2. The polarities of the diode should be carefully identified.
3. While determining the % regulation, first Full load should be applied and then it should be decremented in steps.

RESULT:-

1. The Ripple factor for the Half-Wave Rectifier with and without filters is measured.
2. The % regulation of the Half-Wave rectifier is calculated.

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