Download AKTU (Dr. A.P.J. Abdul Kalam Technical University (AKTU), formerly Uttar Pradesh Technical University (UPTU) B-Tech 6th Semester (Sixth Semester) 2015-2016 EEC 604 Introduction To Electric Drives Question Paper
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PaperID:131604 RollN0.| I I I I I | | | |
B.TECH.
Theory Examination (Semester?VI) 2015-16
INTRODUCTION TO ELECTRIC DRIVES
T ime : 3 Hours Max. Marks : 100
Section-A
1. Attempt all parts of the following : (2X10=20)
(a) What are VDWM and VDRM?
(b) De?ne latching and holding currents as applicable to
SCR.
(0) A 3-(1) induction motor having 4 poles is fed With 3-4),
50Hz supply. Find the slip when the motor is running at
1600 rpm.
((1) Why chopper based DC drives give better performance
than recti?es controlled drives?
(e) Give two different of two quadrant and four quadrant
drives.
(D What is slip power recovery system?
(1) P.T.O.
(g)
(h)
(i)
(i)
What is time ratio control in do choppers?
A 3-pulse cycloconverter feeds a single - phase load at
200 V. Estimate the value of the supply voltage.
What is the need for controlling the voltage at the output
terminals of the inverter?
De?ne the phase angle control.
Section-B
Attempt any ?ve questions from this section. (5X10=50)
(a)
(b)
(C)
(d)
Describe the resistance ?ring circuit used for triggering
SCRs. Is it possible to get a ?ring angle greater than 90?
With resistance ?ring? Illustrate your answer with appro-
priate wave form.
De?ne di/dt and dV/dt protection of SCRs. What are the
components used to protect SCR ?om dV/dt and di/dt
in large values.
Describe the working of a single phase full converter in
the recti?er mode with RLE load. Derive an expression
for the average output voltage in terms of source voltage
and ?ring angle.
Explan the concept of step down cycloconverter. Enu-
merate the advantages and applications of cycloconverter.
(2)
(e)
(f)
(g)
(h)
A dc chopper feeds power to an RLE load with R=ZQ,
L = lOmH and E = 6V. If this chopper is operating at
a chopping frequency of lKHz and With duty cycle of
10% from a 220 V dc source, compute the maximum
and minimum currents taken by the load.
Describe the working of single phase parallel inverter
With relevant circuit and wave forms.
Describe stator voltage control technique for the speed
control of a 3-phase induction motor.
In static rotor-resistance control of a 3-phase SRIM,
each diods in the rotor circuit conducts for 120?.
Assuming ripple free rotor currents derive expressions
for rms value ofrotor current referred to stator, ?mda?
mental component ofrotor current and its value referred
to stator.
Section-C
Note : Attempt any two questions from this section. (2X15=30)
3.
(a)
(?3)
Draw a wuitable diagram & explain working of slip power
recovery system using commutator?less kramer drive.
Explain With the associated wave farm, how power
factor can be improved With symmetrical angle control
scheme.
(3) P.T.O.
(a)
(b)
(a)
(b)
A 3-4), 460V, 60Hz, 6 pole, star connected cylindrical
rotor synchronous motor has synchronous reactance of
X5 = 2.59 per pole and the armature resistance is neg-
ligible. The load tarque Which is propartional t0 the speed
squared is IL = 400 N?m to 1200 rpm. The power
factor is maintained at unity by constant at the rated
value. If the inverter frequency is 36 Hz. and the motor
speed is 720 rpm determine the following :
(i) The input voltage Ea
(ii) The armature current 13.
Enumerate the variable frequency control of an induction
motor.
Draw & explain the tarque - speed characteristics of a
separately excited dc motor at different ?ring angles for
a ?ll converter feeding.
The speed of a seperately excited dc motor is controlled
through 1 half wave controlled converter ?om 230V
mains. The motor armature resistance is 0.5W and motor
constant is K = 0.4 V?s/rod, for load tarque 0f 20Nm
at 1500 rpm and for constant armature current.
Calculate.
(i) r.m.s. value of thyristor current
(i1) ?ling angle of convertors
(iil) I/P power factor of the motor
(4)
This post was last modified on 29 January 2020