Exam text content

 

Tampere University of Technology 15.12.2015
Electrical Engineering DEE-34016 Modeling and Control of Electric Drives

Jenni Rekola

Programmable calculator allowed 5 guestions/ ä 6 p
Answers in English or in Finnish allowed

1. Propositions

Answer, if the following propositions are true or not true. Correct answer 1p, wrong answer -1p.

a) PMSM machine is usually modeled in rotor flux reference frame.

b) Stator resistance value has a major effect to the accuracy of the speed estimation

c) Space vector theory is not possible to use if the three-phase voltages are asymmetrical.
d) Common mode voltage can be reduced by using multilevel converter topology.

€) The switching freguency of the IGBTS in the converter is constant when DTC is used
£) Rotor resistance of a slip-ring machine can be changed

2.DC machine

a)
b)

o)
K)

Draw the eguivalent circuit of a separately exited DC machine

Draw the control block diagram of separately exited DC machine with position control and
shortly explain the figure.

What means electrical time constant of DC machine, how it is defined?

The load torgue of the uncontrolled separately excited machine is decreased step-wisely
from its nominal value to 0,5*nominal torgue in the nominal operating point. How the
rotationa! speed, armature current and magnetizing current change? Why?

The magnetizing voltage of the uncontrolled separately excited DC machine decrease step-
wisely from its nominal value to 0,5*nominal voltage when the motor rotates at its nominal
speed without the load. How the rotational speed, armature current and magnetizing current
change? Why?

How does the rotationa] speed, armature current and magnetizing current of the uncontrolled

separately excited DC machine behave when the supply voltage decreases to be
0,9*nominal?

3. Permanent magnet synchronous machine

a) What is the difference in the mechanical structure of salient and ona PMSM machines?

b) How the torgue production of these two machines differs from each other?

c) How the control method of these two machines differs from each other?

d) What is the benefit/benefits of PMSM compared to induction machine?

e) Whatis the drawback/drawbacks of PMSM compared to induction machine?

f) The torgue reference of the controlled, non-salient PMSM is decreased step-wisely from its
nominal value to 0,1 *nominal torgue in the nominal operating point. How the rotational speed
and stator current (d- and g-component) change? Why?

4. Reluctance machine

a)
b)
c)
d)
e)
n

Describe shortly the operation principle of reluctance machine

How torgue is produced in reluctance machine?

How torgue is controlled?

What is the benefit/benefits of reluctance machine?

What is the drawback/drawbacks of reluctance machine?

Why the magnetized assisted reluctance machine is used in electric vehicles instead of
conventional reluctance machine?

1(2)
 

 

Tampere University of Technology 15.12.2015
Electrical Engineering DEE-34016 Modeling and Control of Electric Drives

Jenni Rekola Programmable calculator allowed 5 guestions/ ä 6 p
Answers in English or in Finnish allowed

5. Induction machine

a) Draw the control block diagram of direct vector control (field oriented control) of an induction
machine and explain it shortly. (2p)

b) Why the flux model is needed in the control system?

c) The measured speed and speed reference of an induction machine are shown in Fig. 1. Are the
speed control parameters good according to the figure? Why?

d) How the discretization of the control system might affect to the control?

e) What are the most important un-idealities which might affect to the operation of the real-world
motor drive control system, but which are not usually taken into account in the ideal simulation
models?

 
 
 
      

Rotational spood [rpm]
> 1

268 27 272 274 276 278 28 282 284 286 288
Time [s]

Fig. 1. Measured speed ans speed reference

Markus ia Cstu JI 14.6

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