Investigatory Project on Bridge Rectifier
INVESTIGATORY PROJECT ON THE BRIDGE RECTIFIER
Aim: To construct a bridge rectifier
using four identical diodes and to calculate its ripple factor with and without
filtering.
Materials
and Apparatus
(i) Four
identical diodes
(ii) An
electrolytic condenser 500µF or 1000 µF, a condenser
0.1 µF
(iii)
Resistance 1000Ω
(iv) A step down
transformer with 220 to 240 V primary and 6.3 V, 100mA secondary
(v) ac and dc
voltmeters or a multimeter etc.
(vi) CRO
Working
During the
positive half cycles of the secondary voltage in the circuit, the diodes D2 and D4
would conduct current and the diodes D1 and D3 would not conduct.
Therefore, the current flows through the secondary winding of the transformer to the diode D2, then Load resistor RL and through the diode D4. During the negative half
cycles in the circuit, the diodes D1 and D3 would conduct and the diodes D2
and D4 would not conduct. Therefore, current flows through the
secondary winding of the transformer to the diode D3, then load resistor RL and through the diode D1.
In both cases, the current passes through the RL in the same direction.
Procedure
1. Wire the
Bridge rectifier circuit without capacitor after testing all the components.
2. Switch
ON the mains supply to generate current. Observe the Secondary Voltage waveform from the transformer and and also the output
voltage waveform across RL, simultaneously on CRO Screen. Note down peak
values.
3.
Calculate the ripple factor using the expression.
4. Connect
the capacitor filter and observe the waveforms. Calculate the ripple factor
using the expression.
5. Connections
are made as shown in the figure. D1, D2, D3
and D4 are four identical diodes, C is a 500 µF or 1000 µF electrolytic condenser, C’ is a
0.1µF condenser. RL is 1kΩ resistor. The rectified output is obtained across RL.
(a) To find the ripple
factor (r) with filter circuit
Specification
of the diodes (from data book)
Type number
of the diode: ............
Maximum
forward current rating = ............mA
PIV rating
= .........V
The ac
output voltage Vac is measured by an ac voltmeter or by a multimeter
across the points T3 and T4. The dc output voltage Vdc
is measured between the point T1 and T2. The ripple
factor is calculated by the equation,
r = Vac/Vdc
ac output
voltage = Vac = ........V
dc output
voltage = Vdc = ........V
Ripple
Factor, r = Vac/Vdc = .........
(b) To find
the ripple factor (r) without the filter circuit
The filter
circuit is removed by disconnecting the condenser C from the above figure. The
ripple factor is determined as explained above.
ac output voltage = Vac = ........V
dc output
voltage = Vdc = ........V
Ripple
Factor, r = Vac/Vdc = .........
Result:
The ripple
factor of the bridge rectifier:
(a) with
the filter circuit = ......
(b) without
the filter circuit = ......
Note:
Ripple factor r may be calculated for different loads RL; and a
graph with r and RL may be drawn.
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