EGH448 – Quiz 2
1. The diode (D) in the circuit shown in Fig. 1 has a leakage current of 50 mA at 200 V,
the thyristor (TH) has the latching current of 80 mA, and the initial current of the
inductor L is 0 A. For this circuit:
a) Determine the minimum duration of the gate pulse for a successful turn on of the
thyristor.
b) Sketch the current waveform 𝑖TH for two different gate pulses with the durations
of 1μs and 2 μs in a time window of 5 μs. s
(Please, use the diagrams provided at the bottom of the page).
200 V
5
Fig. 1
(a)
(b)
iTH
iTH
Gate Pulse
Gate Pulse
IL = 80 mA
t (µs)
IL = 80 mA
t (µs)
1
2
1
2. The single half-wave diode rectifier shown in Fig. 2 powered by 230 V AC 50Hz
mains produces 100 V (average voltage) across an inductive load. Determine the
conduction angle and the duration at which there is no current (load current zero
duration per fundamental cycle).
Also complete the v0 and i0 waveforms below.
io
+ v d
R
+
vo
VS
L
-
Fig. 2.
Mathematical Calculations:
Graphs:
vs
wt
p
2p
io
wt
p
2p
vo
wt
p
2
2p
3. In the circuit of Fig.3, the source voltage 𝑣 = 220√2 sin 𝜔𝑡 𝑉 , 𝑅 = 5𝛺, and the load-circuit emf
𝑉𝑐 = 200𝑉. If switch SW is closed during the negative half cycle of the source voltage. Calculate:
(a)
(b)
(c)
(d)
Fig.3
The angle α at which diode D starts to conduct.
The conduction angle .
The average value of the current 𝑖
Draw waveforms for 𝑣, 𝑣0 , 𝑖
Mathematical Calculations:
Graphs:
v
wt
p
2p
Vo
wt
p
2p
i
wt
p
3
2p