Download Tutorial 2 Rectifier

EC301 Electronics Devices & Circuits-1
TUTORIAL: 2
RECTIFIER CIRCUITS
1. A half wave rectifier circuit feed a resistive load of 10kΩ through a power
transformer having a step down turns ratio of 8:1 and operated from 230V,50Hz
AC mains supply. Assume forward resistance of diode to be 40Ω and transformer
secondary winding resistance as 12Ω. Calculate
(i)
Maximum, RMS and Average value of current
(ii)
DC output voltage and power
(iii) Efficiency
(iv)
Ripple Factor.
[Ans:
Im=4.045mA,Irms=2.024mA,Idc=1.2875mA,Vdc=12.875V,Pdc=16.58mW,
Pac=41.179mW,n=40.26%,r=1.21].
ANS:
V2/V1 = N2/N1 so V2rms= 230/8
And V2=Vmax=Vm= --Im= maximum voltage=Vm/rf+Rs+RL
Irms= Im/2
Idc=Im/pi
Pdc=Idc2.RL
Pac=Irms2(Rf+Rs+RL)
n=efficiency=pdc/pacΧ100%
ripple factor = √(Irms/Idc)2-1 = 1.21
2. A full wave rectifier is fed from a transformer having a center-tapped secondary
winding. The rms voltage from either end of secondary to center tap is 20V. if the
diode forward resistance is 3Ω and that of the half secondary is 5Ω, for a load of
1kΩ, calculate
(i)
Power Delivered to load
(ii)
Efficiency.[Ans: Pdc=0.3191W,n=0.8041]
ANS:
V2rms=20V
Vm=20.√2
Pdc=Idc2.RL
Pac and then efficiency
3. The four semiconductor diodes used in a bridge rectifier circuit, each having a
forward resistance of 0.05 Ω and infinite reverse resistance, feed a mean current of
10A to a resistive load from a 30V rms input. Determine the resistance of load and
efficiency of circuit.[Ans: RL=2 Ω, n=78%].
ANS:
Mean=average current= Idc= 2Im/pi
Where Im= Vm/rf+RL
Find RL.
Efficiency n= 8/pi2 .RL/RL+2RF Χ 100%
4. Analyze operation of circuit as shown in figure 2.1 and determine the output
waveform and calculate the output dc level and the required PIV of each
diode.[V0=3.18V,PIV=10V]
Figure 2.1
ANS:
For positive half cycle,
vo=+5V
For negative half cycle,
v0=+5V
So Vm=5V and VDc=2Vm/pi
PIV= 5V
5. A 1mA dc meter whose resistance is 10Ω is calibrated to read rms volts when used
in a bridge circuit with semiconductor diodes. The effective resistance of each
element may be considered to be zero in the forward direction and infinite in reverse
direction. The sinusoidal input voltage is applied in series with a 5K resistance. By
applying concept of bridge rectifier circuits, what is a full scale reading of this
meter? Also state application of this circuit. [Ans:5.56V]
ANS: Application: Rectifier meter
Idc = 1mA = Vm/Rmeter + RL
6. Analyze each block of Figure 2.2 with suitable circuit diagram with following
specifications. Dc power supply for 12V with ripple factor of 5%. The maximum
load
current
is
10mA.
The
input
ac
supply
220V,50Hz.[Ans:n=25.92,C=192uf,PIV of diode=24V,Cv=12V,RL=1.2K]
Figure 2.2
ANS:
is
RL= vdc/IDC
220.√2/N = Vdc..find turns ratio N
Ripple factor = VPP/√3.Vdc (because rms of triangular wave is VPP/√3)
Find Vpp=____
Ripple voltage Vpp= Vp.T/RL.C
Find C=______
Voltage rating of C>12V
PIV of Diode=24V