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Department of Electrical Engineering and Computer Science
6.334 Power Electronics Practice Exam 1
Problem 1
qt Ty
Eo _——
+
Fig. 1
The buck/boost converter of Pig. 1 contains a very large inductor, L, with 2 winding resistance,
R, = 0.19. The circuit is operating under the following conditions:
D=0%
=10A
vy, =40V
Determine 13.
Problem 2
is Vp
é
a gts
+ xy y reek -
uC N at
al
Fig. 2
The network N of Fig. 2 is supplied by a sinusoidal voltage soarce, », = Voinwt, and draws a
current i, as shown in the figure. What is the power factor of the network N at terminal pair « -
a?
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
Department of Electrical Engineering and Compater Science
6.334 Power Electronics Practice Exam 1
Problem 3
Figure 20.2 shows an inductor made of a three-legged core with a winding of N tums on
the center leg. The two outer legs have cross-sectional areas different from that of the center
leg. What is the inductance of the winding?
a)
Figure Magn . The
etic structure with one winding of N turns and three legs.
m2 a outer legs have cross-sectional area A). and the inner leg has area
A,. The core material has permeability 4,
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
Department of Electrical Engineering and Computer Science
6.334 Power Electronics Practice Exam 4
Problem | A ferrite core, shown in Fig. 1, has a mean core length /. of 10 em and a cross-
sectional area of 2 em’. Its sz
turation flux density is 0.3 T, and the permeability of the core is
1250, (where x, = 4 *107 Him),
a. 1f10 turns of wire are placed on the core, how much current can the
saturating the core?
without
b. What is the minimum number of tums on the core necessary so that the core will not
saturate when a 120 VW (rms !}, 6 Hz sinusoidal voltage is applied across the coil?
Depth: 2 cm
w= 1250H9
Figure 1
: Beat = 0.3T
faire
Problem 2
(a) What is the minimum value of V, needed to permit the circuit of Fig. 2 to operate at D = 0.27
(b) Sketch and dimension i,,%,, and vs for D= 0.2.
Fig. 2
a
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