KANPUR INSTITUTE OF TECHNOLOGY, KANPURKANPUR INSTITUTE OF
TECHNOLOGY & PHARMACY, KANPURSUBJECT NAME :Electrical Machines
& Controls (NEE-409)PROGRAM :B.Tech.TIME : 3 Hrs
EXAM :PUT-1BRANCH :MEMAX. MARKS : 100
SEMESTER :4FACULTY NAME :Ms. SHWETA GUPTA
SECTION :A/B/C
Note: Attempt all questions.
1. Attempt any two parts: (2 x 10 = 20)
(a) In open circuit test of 1- transformer, why only Iron losses
are measured? Explain this test with suitable circuit and phase
diagram.(b) What is autotransformer? State its merits, demerits and
applications. Derive the expression for copper saving in
autotransformer.(c) A 440 V series motor has a load resistance of
0.8. It takes 110 A to give the rated output at 800 r.p.m.
Determine the resistance of the resistor to be added to obtain
rated torque:(i) At starting (ii) At 600 r.p.m.Assume flux is
proportional to current.
2. Attempt any two parts: (2 x 10 = 20)
(a) What is 2- Servomotor? Explain its torque-speed
characteristics for various control voltages. Also state its
application.(b) Explain the effect of variable excitation on
armature current and power factor in a 3- synchronous motor. Draw
the corresponding curves.(c) A 400 V, 4 pole, 3-, 50 Hz star
connected induction motor has a rotor resistance and reactance per
phase equal to 0.01 and 0.1 respectively. Determine (i) Starting
torque (ii) Slip at which maximum torque will occur (iii) Speed at
which maximum torque will occur (IV) Maximum torque (v) full load
torque if full load slip is 4%. Assume ratio of stator to rotor
turns as 4.
3. Attempt any two parts: (2 x 10 = 20)
(a) (i) Compare the Open Loop & Closed Loop System with
proper examples.(ii) Write the Mathematical expression and draw the
characteristics for standard test signals.(b) (i) What is transfer
function? Write its advantages and disadvantages.(iii) Find the
transfer function V2/V1 for the given network.
(c) (i) Derive the F-V analogy for a linear mechanical
system.(ii) Write the differential equation governing the
mechanical system shown in fig. Draw F-I analogous electrical
systems.
4. Attempt any two parts: (2 x 10 = 20)
(a) The open loop transfer function of a unity feedback control
is given by:
Determine the value of K For which the system is stable Which
will cause the sustained oscillations(b) Sketch the polar plot of
the following transfer function:
Calculate gain margin, phase margin, gain cross-over frequency
and phase cross-over frequency.(c) Explain the transient response
specifications for second order system.
5. Attempt any two parts: (2 x 10 = 20)
(a) Sketch the Bode Plot for a system:
Calculate gain margin, phase margin, gain cross-over frequency
and phase cross-over frequency.(b) The open loop transfer function
of a control system is given as:G(S)= K/[S(S+6)(S2 + 4S +13)]Plot
the root locus for k=0 to .Indicate all points on it and determine
breakaway points, angle of departure from complex poles and
stability condition.(c) Discuss the affect of following controllers
on the second order control system:(i) PI controller(ii) PD
controller(iii) PID controller
2H
1H
2F
1F
V2
I2 = 0
I1
V1
