Power Electronics Assignment (15-20%)
1.
The data sheets of a switching device specify the following switching times corresponding to
the linearized characteristics shown in Fig. b for clamped-inductive switching’s:
tri = 100 ns tfv = 50 ns trv = 100 ns tfi; = 200 ns Calculate and plot the switching power loss
as a function of frequency in a range of 25-100 kHz, assuming Vd = 300 V and 10 = 4A in
the circuit of Fig. a.
Submission Date: 24/1/14 @ 4 local time
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Power Electronics Assignment (15-20%)
2. Consider the resistive-switching circuit shown in Fig. below. Vd = 300 V, fs = 100 kHz and R
= 75 Ω, so that the on-state current is the same as in Problem-1. Assume the switch turn-on
time to be the sum of tri; and tfv in Problem-1. Similarly, assume the tum-off time to be the
sum of trv and tfi;
Assuming linear voltage- and current-switching characteristics, plot the switch voltage and
current and the switching power loss as a function of time. Compare the average power loss
with that in Problem-1
3. In the three-phase. Four-wire system of Fig. below, all single-phase rectifier loads are
identical and the conditions are such that each line current flows for less than 60° during each
half-cycle of the line-to-neutral voltage. Show that in terms of their rms values In = √3 Iline.
4. Consider the single-phase, half-controlled converter shown in Fig. P6-5, where Vs is
sinusoidal.
Submission Date: 24/1/14 @ 4 local time
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Power Electronics Assignment (15-20%)
A.
Draw Vs, is. and Vd waveforms and identify the devices conducting for various intervals
for the following values of α: 45°, 90°, and 135°.
B. Calculate DPF, PF, and %THD for Vd = ~1/2VdO' where Vdo is the dc output at α= O.
C. Repeat part (b) for a full-bridge converter.
D. Compare results in parts (b) and (c).
5. As a consequence of the harmonics in the inverter output voltage, the ripple in the output
current does not depend on the level of power transfer at the fundamental frequency; instead
the ripple depends inversely on the load inductance, which is more effective at higher
frequencies.
Submission Date: 24/1/14 @ 4 local time
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