1 Power Electronics Dr.Mohammed Tawfeq Tutorial Sheet No. (3) Controlled rectification 1. The single-phase half-ware controlled rectifier shown in fig.1 is operating at α 1 =90º . The thyristor Th2 is connected across the load and operating with a delay angle α 2 of 45º .Assume the load is highly inductive such that I L is continuous .Plot waveforms of V 2 , I th1 , I th2 ,I L , V th1 and V th1 . Derive an expression for the average load voltage Vdc as a function of α 1 and α 2 (with α 1 < α 2 ). {Ans:Vdc =Vm/2π[cos α 1 +cos α 2 ]} TH1 TH2 VL iL vmsinwt Fig.1 2. The single-phase half-controlled rectifier operating at a delay angle of 45º .Assuming the load is resistive, plot V 2 , I th , I L ,and I D . Express Vdc as a function of α . Calculate Vdc. Fig.2 TH1 V2 D1 Vs= Vmsinwt V1 1:1 R [Ans:Vdc =Vm/2π(cos α +3)] Vdc =0.59v
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Controlled rectification - Philadelphia University TUTORIAL 3.pdf · 3. A single-phase Full-ware fully-controlled bridge rectifier supplying highly inductive load as shown in fig.3.The
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Power Electronics Dr.Mohammed Tawfeq
Tutorial Sheet No. (3)
Controlled rectification 1. The single-phase half-ware controlled rectifier shown in fig.1 is operating at
α1=90º . The thyristor Th2 is connected across the load and operating with a delay
angle α2 of 45º .Assume the load is highly inductive such that IL is continuous
.Plot waveforms of V2, I th1 , I th2 ,I L , V th1 and V th1. Derive an expression for the
average load voltage Vdc as a function of α1 and α2 (with α1< α2).
{Ans:Vdc =Vm/2π[cos α1 +cos α2]}
TH1
TH2 VL
iL
vmsinwt
Fig.1
2. The single-phase half-controlled rectifier operating at a delay angle of 45º
.Assuming the load is resistive, plot V2 , Ith , IL ,and ID. Express Vdc as a function
of α. Calculate Vdc.
Fig.2
TH1
V2 D1
Vs= Vmsinwt
V1
1:1
R
[Ans:Vdc =Vm/2π(cos α +3)] Vdc =0.59v
2
3. A single-phase Full-ware fully-controlled bridge rectifier supplying
highly inductive load as shown in fig.3.The r.m.s value of the a.c. input voltage is
230V.The firing angle is maintained constant at 45 so that the load current is
continuous at a value of 5A.
(a) Calculate the dc output Voltage. [Ans: 146.4V].
(b) Assume that load resistance remains the same; find the current if a
freewheeling diode DF is used at the output. [Ans: 6.03A].
(c) If Th3 is open circuited, find the load voltage and current while
freewheeling diode DF is still connected and α is the same.
[Ans: 88.3V, 3.02A].
TH1 TH3
TH4 TH2
Df
230V r.m.s
S
LOAD
Fig.3
4. A fully-controlled single-phase bridge rectifier is supplied from a 50HZ, 230/100V
transformer .The rectifier supplying a highly inductive load of 10Ω resistance. For a
firing angle of 45º, determine the rectified voltage, the rectified current and the power
factor.
[Ans: 63.7V, 6.37A, 0.637].
5. A single –phase, fully-controlled bridge rectifier supplies a constant current to a
highly inductive load.
Derive an expression for the average d.c. output voltage from the bridge and also the
R.M.S. value of the fundamental component of the alternating line current assuming
(a) that there is no freewheel diode , and (b) that a freewheel diode is used.