MASSACHUSETTS INSTITUTE OF TECHNOLOGY
Department of Electrical Engineering and Computer Science
6.334 Power Electronics
Problem Set 2
Issued: February 14, 2003
Due: February 21, 2003
Reading: KSV Chapter 4 through 4.1, Chapter 6 Problem 2.1
Consider the rectifier shown in KSV Fig. 4.3, with the following parameters: Vs = 170 V, ω =
377 rad/sec. Also, assume that L/R >> 2π/ω, so iD ≈ ID.
a.
Please compute the power factor kp, the distortion factor kd, the displacement factor kθ for
this system.
b.
Calculate the total harmonic distortion (THD) in the line current of this system. Is the
THD better, worse, or the same as that of a half-wave rectifier (e.g., KSV Fig. 3.6)?
c.
What is the maximum power that could be drawn from the ac source without exceeding a
20 ARMS limit on the line current? How much power could be drawn with a purely
resistive load (no rectifier) with the same current limit?
d.
Would addition of a power factor compensation capacitor or inductor allow more power
to be drawn without increasing the rms line current? Why or why not?
Problem 2.2
0.2 Ohms
L
+
5V
12 V
D
5 Ohms
-
Figure 1 A boost converter operating from a source with output resistance.
Figure 1 shows a boost (up) converter supplying 12 V to a load of 5 Ω from a 5 V source having
an internal resistance of 0.2 Ω. Determine the duty ratio D at which the converter operates. (You
may neglect semiconductor device drops in your calculations.)
Problem 2.3 KSV Problem 6.4
Problem 2.4 KSV Problem 6.8 (How would your answer change for fsw = 200 kHz?)
Problem 2.5
Derive the current conversion ratio I2/I1 of the converter in KSV Fig. 6.15. Which direction(s)
can power flow in this converter?