Đề thi và đáp án môn Truyền Động Điện ( Electric Drives)

HCMC UNIVERSITY OF
TECHNOLOGY AND EDUCATION
Faculty for High Quality Training
Program name: Mechatronics

FINAL EXAMINATION
SEMESTER 2 – ACADEMIC YEAR 2018-2019
Course name: Electric drives
Course ID: ETDR336429E
Exam code: 01 Number of pages: 01
Duration: 60 minutes.
Open-book.

Question 1: (6/10)
A separately excited DC motor has the following data P=20.5kW (rated power); Va=440V
(rated voltage); Ia=55A (rated current); n=1000 rpm (rated speed), the load torque is 90%
rated torque
a. Determine the original responses? Determine the artifical responses when the
armature voltage is reduced to 90% rated voltage?
b. The armature voltage is reduced to 270V. Draw the artifical responses and
determine the rotor speed at that time. Explain the process of braking in this case.
c. To stop the DC motor, the armature voltage is reversed and the resistance of 1.75Ω
is added to armature circuit. Calculate the rotor speed and the torque at the first
time of braking?
a)

The original responses
.0d
The artifical responses when the armature voltage is reduced to 90% rated voltage
.0d
b)

.0d

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the artifical responses
Regenerative Braking AB D A’.
Regenerative Braking: BD .0d
c)

the torque at the first time of braking
(Nm)

.0d

.0d

Question 2: (4/10)
A 208-V, six pole, 60 Hz, Y-connected induction motor, R1=0.6Ω; R2’=0.4; Xeq=5Ω.
a. Calculate the motor speed if the load torque is 30 Nm?
b. Calculate the smallest voltage source so that the motor could handle the load
torque 25 Nm?
c. Calculate the starting current, starting torque, maximum torque,
d. Calculate the resistance should be added to rotor circuit to reduce starting current a
half.
e. Calculate the resistance should be added to rotor circuit to keep the starting torque
equal to the maximum torque.

a)

the motor speed when the load torque is 30 Nm
.0d

b.
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c. the starting current, starting torque, maximum torque
Ist=23.551A0.5d
Tst=5.297Nm0.5d
Tmax=30.546Nm0.5d

d.
Ist’=11.776A
Radd=7.888�0.5d
e.
smax=1
Radd=4.636�0.5d
Note: Proctors are not allowed to give any unauthorised explaination.
Learning outcome mapping
[LO 1.1]: Describe structure of electric motors; symbols
and roles of electric motors in mechatronic systems
[LO 2.1]: Create mathematic models of electricalmechanical responses of typical electric motors
[LO 2.2]: Describe structure and working principles of
typical electric motors

Assessed in
Question 1

Question 2

20/05/2019
Approved by program chair

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