Midterm Examination
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EELE-4258 Electric Machines II
October 20, 2021
This is an open-book exam
No zoom meeting. All questions have been double checked and please write the exam based on your
understanding.
Start time: 5:30 pm
• End Time: 7:00pm + X (X is the extra time for students who requested academic accommodation). It is
the students’ responsibility to calculate the extra time X according to the approved request. Extra 15
minutes have been included considering the time on downloading, submission, PDF format conversion.
Where to submit your midterm answers: D2L, EELE4258, Assignments, Midterm
Format to be submitted: pdf.
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Midterm Examination
EELE-4258 Electric Machines II
October 20, 2021
Question 1 (6)
Voltage V is given as below. Find the polarities of induced voltage across terminals AB, CD, and EF. The number
of turns is same as the one drawn in the figure.
V
t
0
E
F
A
C
B
D
V
Question 2 (10)
Four coils are wound on one magnetic core as shown below, in which a, b, and c are not connected yet. To ensure
a flux density of the core is B = 2.094 T, give TWO designs for N4. Assuming the flux is confined within the core.
12cm
6cm
I=10A
N1=100
a
N4
N2=200
b
N3=100
Cross-section = 3 cm x 3 cm
2
μr = 1000
c
Midterm Examination
EELE-4258 Electric Machines II
October 20, 2021
Question 3 (14)
A single-phase 60-Hz 10-kVA 100/1000-V-rms transformer has an infinite permeability of the core, and the
generated flux is confined to the core. Under open circuit test, wattmeter = 100 W, and under short circuit test,
wattmeter = 100 W.
1) Draw the finalized equivalent circuit of the transformer (3')
2) Determine the parameters of the transformer when referred to the low-voltage side (4')
3) Determine the power factors under open circuit test and short-circuit test, respectively (3')
4) Assuming you are using a 60-Hz programmable voltage source supply that has a maximum rms voltage of 120
V and a maximum rms current of 8 A to re-test this transformer, determine Voc and Isc. (4')
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