FULL WAVE RECTIFIER (Centre Tapped)
AIM: - To study full wave rectifier (C.T).
APPARATUS: - Full wave centre tapped circuit, a CRO and digital multimeter.
INTRODUCTION:- The circuit employs two diodes D1 and D2 as shown in figure a centre tapped secondary winding ‘AB’ is used with two diode is connected so that each uses one half cycle of input A.C voltage. In other words, diodes given utilizes the A.C voltage appearing across the upper half (OA) of secondary winding for rectification while diode ‘D2’ used the lower half winding ‘OB’.
During the positive half cycle of secondary voltage, the end ‘A’ of the secondary winding becomes positive and end ‘B’ negative. This makes the diode ‘D1’ forward bias and diode ‘D2’ reverse bias. Therefore, diode ‘D1’ conducts while diode ‘D2’ does not. The conventional current flow is through diode ‘D1’, load resistor RL and the upper half of secondary winding as shown by the dotted arrows. During the negative half – cycle, end ‘A’ of the secondary winding becomes negative and end ‘B’ positive. Therefore, diode ‘D2’ load resistor RL and lower half winding at shown by solid arrows. Referring to figure. It may be seen that current in the load RL is in the same direction for both half cycles of input A.C voltage. Therefore D.C obtained across the load resistor RL .Also the polarities of the D.C output across the load should be noted.
PROCEDURE:-
Vdc = 2Vm/π
Compare this value with the practically measured value of the output D.C voltage.
Ripple factor = Output A.C voltage / Output D.C voltage = 0.482.
OBSERVATION:-
Quantity Theoretical Value Practical Value
1. Output D.C voltage Vdc=2 Vm/π
2. Ripple factor 0.482
RESULTS:-
APPARATUS: - Full wave centre tapped circuit, a CRO and digital multimeter.
INTRODUCTION:- The circuit employs two diodes D1 and D2 as shown in figure a centre tapped secondary winding ‘AB’ is used with two diode is connected so that each uses one half cycle of input A.C voltage. In other words, diodes given utilizes the A.C voltage appearing across the upper half (OA) of secondary winding for rectification while diode ‘D2’ used the lower half winding ‘OB’.
During the positive half cycle of secondary voltage, the end ‘A’ of the secondary winding becomes positive and end ‘B’ negative. This makes the diode ‘D1’ forward bias and diode ‘D2’ reverse bias. Therefore, diode ‘D1’ conducts while diode ‘D2’ does not. The conventional current flow is through diode ‘D1’, load resistor RL and the upper half of secondary winding as shown by the dotted arrows. During the negative half – cycle, end ‘A’ of the secondary winding becomes negative and end ‘B’ positive. Therefore, diode ‘D2’ load resistor RL and lower half winding at shown by solid arrows. Referring to figure. It may be seen that current in the load RL is in the same direction for both half cycles of input A.C voltage. Therefore D.C obtained across the load resistor RL .Also the polarities of the D.C output across the load should be noted.
PROCEDURE:-
- Connect the given circuit to mains
- Now connect the C.R.O to the output of the rectifier i.e. across RL.
- Observe the output waveform on C.R.O and draw it in your note book.
- Connect the C.R.O to the secondary of the transformer observe the A.C waveform and draw it in your note book.
- Now use a multimeter to measure the A.C voltage at the secondary terminals of the transformer .this gives R.M.S value. Also measure the A.C voltage and D.C voltage at the output point. Multiply this R.M.S value by two to get the peak value .Calculate the theoretical value of D.C voltage using in formula
Vdc = 2Vm/π
Compare this value with the practically measured value of the output D.C voltage.
- Using the measured value of D.C and A.C output voltages calculate the ripple factor. This value should be about 0.482.
Ripple factor = Output A.C voltage / Output D.C voltage = 0.482.
OBSERVATION:-
- D.C voltage at the output=……..V.
- A.C voltage at the output=……..V.
Quantity Theoretical Value Practical Value
1. Output D.C voltage Vdc=2 Vm/π
2. Ripple factor 0.482
RESULTS:-
- The wave shape at input and output are observed on the C.R.O and they are plotted.
- The output D.C voltage is a little less than the theoretical value.
- There is a little difference between the theoretical value and measure value of ripple factor.