ELEG3201 Lab 2
1155047511 Li Man Hin
1155047506 Chow Yun Hing
Part 1 - Rectifier and Transformer
1. What type of rectifier circuit configuration is Figure 2(a): is it a half or
full-wave circuit?
Half-wave circuit.
2. Is the voltage across the load positive or negative (with respect to the
common terminal)?
Positive.
3. How can a negative supply be obtained?
Reverse the diode so that current only flows in opposite direction.
Table I
Figure 2 Full-wave Half-wave Positive
(a)
◦
◦
(b)
◦
◦
(c)
◦
Y2
(d)
◦
◦
(e)
◦
Y1
1
Negative
Y1
Y2
Part 2 - Measurement of Voltages
Table II
VpL
Vpa
Vpa − VpL
VpL
Vpa
Vdc
Vpa : Vrms
Vdc
Vrms
Half-wave Full-wave
7.6
8.2
8.95
9.25
1.35
1.05
0.849
0.886
2.68
√
2:1
5.79
√
2:1
0.423
0.885
4. Why is VpL less than Vpa ?
There is voltage drop across the diode.
5. Why is Vdc so much less than Vrms ?
For the half-wave circuit, no more than half cycle of the ac voltage can be consumed
by the load.
For the full-wave circuit, although the ac voltage is fully rectified into the load, the
current passes through two diode which may consume a large amount of voltage,
especially the ac voltage is comparable to the voltage drop of diode.
6. How would you expect the values of Vdc to compare in the full-wave and
half-wave cases?
Since half-wave circuit rectifies much less proportion of the ac voltage into the load,
Vdc in half-wave circuit must be much lower than that in full-wave circuit.
Vdc in half-wave circuit = 2.68
Vdc in full-wave circuit = 5.79
7. How does the power in the load compare in the full-wave and half-wave
cases?
Vdc2
R
Power in full-wave circuit is about 4.67 times than in half-wave circuit.
PL =
8. What is the required rating of reverse voltage for the diodes in each
circuit?
√
Vrms = 6V ⇒ Vpk = 6 2 = 8.49 ≈ 8.5 V
To prevent breakdown, each diode should have a 8.5 V of reverse voltage rating.
2
Part 3 - Capacitor Filters
Part 3-a) Voltage and Current Waveforms with and without Reservoir Capacitor
Table III
Vm (V)
Ipk (mA)
W/ reservoir capacitor W/o reservoir capacitor
15.0
17.7
555
181
VL (V)
IL (mA)
Diode ’on’ period (ms)
13.49
62.83
5
5.45
25.41
10
9. Are the voltage VL and current IL read from the multimeter, rms, average
or peak values?
RMS.
10. Will VL and IL increase or decrease when a reservoir capacitor is connected across the load?
Increase.
Part 3-b) Factors affecting Ripple Voltage
11. How will the ripple voltage be affected if the resistance of the load is
halved?
It will have greater peak-to-peak voltage. It fluctuates more.
12. How will the ripple voltage be affected if the reservoir capacitor is doubled?
It will have smaller peak-to-peak voltage. It fluctuates less.
13. If the supply frequency were doubled, how would the amount of ripple
be affected?
It will have smaller fluctuation because the capacitor is ”recharged” more frequently.
Table IV
Capacitor
RL
Vm (V)
Vr (V)
VL (V)
IL (mA)
Vr (V)
Ripple (%)
470 µF
200Ω
15.0
3.2
13.48
63.51
2.70
20.04
3
470 µF
100Ω
13.8
4.7
11.35
100.01
4.25
37.49
940 µF
200Ω
14.7
2.4
13.60
63.40
1.34
9.92