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The stator core of a synchronous machine is built of laminations of
stainless steel
silicon steel
cast steel
cast iron

The maximum possible speed at which an alternator can be driven to generate an emf of 50 Hz is
1500 rpm
3000 rpm
3600 rpm
4000 rpm

A 4 - pole, 1500 rpm alternator will generate an emf at a frequency of
60 Hz
50 Hz
40 Hz
25 Hz

The frequency of emf induced by an alternator depends upon the alternator speed N( rpm ). and number of poles on the alternator P, and is given by
(PN)/60
(60N)/P
(P N)/120
(120 N)/P

The salient pole type rotors have
smaller diameter
larger diameter
smaller axial length
both (2) & (3)

The field winding of an alternator is excited by
dc
ac
both dc & ac

For full-pitch coil, the pitch factor kp is
1
greater than 1
less than 1

The number of cycles generated in a 6-pole alternator in one revolution is
3
6
50

A 4-pole, 1200-rpm alternator generates emf at a frequency of
25 Hz
40 Hz
50 Hz
60 Hz

The rated voltage of alternators used in power stations is usually
440 kV
220 kV
110 kV
11 kV

A salient-pole field alternator is used for alternator having
low and medium speed
large speed
very large speed

The number of cycles generated in a 4-pole alternator per revolution is
4
2
50
100

When an alternator is loaded, its terminal voltage
increases
decreases
does not change

In a three-phase induction motor,
three-phase supply is connected to the stator winding and a dc supply is connected to the rotor winding
three-phase supply is connected to both the stator and rotor windings
three-phase supply is connected to rotor winding only
three-phase supply is connected to stator winding only

The speed of a 50 Hz, three phase induction motor under full-load condition is 720 rpm. The number of pole in the motor is
4
6
8
12

An induction motor works with
dc only
ac only
both ac and dc

The number of poles in a 3-phase induction motor is determined by
supply frequency
motor speed
supply voltage
both (1) & (2)

The rotor of a 3-phase induction motor rotates in the same direction as that of stator rotating field. This can be explained by
Lenz's law
Newton's laws of motion
Fleming's right hand rule

The rotor circuit of a three-phase induction motor under running condition
is always closed
is always open
is sometimes closed and sometimes open
is neither completely closed nor completely open

If Ns is synchronous speed and 's' is the slip, then the actual running speed of an induction motor will be
Ns
s Ns
(1-s) Ns
(Ns-1) s

When an induction motor is standstiill, its slip is
zero
0.5
1
infinity

The synchronous speed of an induction motor can be increased by
reducing mechanical friction
increasing supply voltage
increasing number of poles
increasing frequency of supply

If an induction motor is made to run at synchronous speed, then
the rotor emf would be zero
the rotor current would be zero
torque developed would be zero
all of the above

A 4 pole, 50 Hz induction motor runs at a speed of 1440 rpm. The frequency of the rotor induced emf is
3 Hz
2.5 Hz
2 Hz
1 Hz

0.03
0.1
0.3
zero

A three -phase, 440-V, 50-Hz induction motor has 4% slip. The frequency of rotor emf is
200 Hz
50 Hz
2 Hz
0.2 Hz

When a three-phase supply is given to the stator of a three-phase induction motor, a ______ field is produced.
stationary
alternating
rotating

The air gap between the stator and the rotor of a 3-? induction motor ranges from
2 cm to 4 cm
0.4 mm to 4 mm
1 cm to 2 cm
4 cm to 6 cm

In a dc machine, ohmic or copper losses occur in the
armature winding only
field winding only
brush contact only
interpole winding only
all of the above

The overall efficiency of a well designed dc machine may be expected to be around
99%
92%
75%
50%

Efficiency of a dc machine is maximum when the variable losses are equal to
constant losses
square of the constant losses
square root of the constant losses

The test that can be used for determination of no-load losses in a large dc shunt machine is
brake test
field test
Hopkinson's test
Swinburne's test

Two dc shunt machines 200 kW each are tested by Hopkinson's test. The power input would be of the order of
200 kW
100 kW
35 kW
10 kW

The retardation test for dc shunt machines is employed for determination of
stray losses
windage and friction losses
magnetic or core losses
copper losses

Core loss in a dc machine occurs in
armature only
pole shoe only
yoke only
all of above

The function of a starter in a dc motor is to
control its speed
increase its starting torque
limit the starting current to a safer value
reduce armature reaction effect

A 3 point starter is considered suitable for dc _____ motors.
series
shunt
compound
shunt as well as compound
series as well as compound

The current drawn by a dc motor at starting is
zero
very low
normal
very high

The speed of a cumulatively compounded dc motor can be controlled by varying
armature voltage
armature resistance
shunt field resistance
any of the above

The function of the field regulator in a dc compound motor is to
limit the armature current
vary the armature resistance
control the field current

The speed of a dc motor depends upon
flux per pole
applied voltage to armature
voltage drop in armature circuit resistance
all of the above

The dc motor most suitable for applications requiring high starting torque is
shunt
series
cumulative compound
differential compound

A dc series motor is best suited for driving
line shafting, blowers and fans
machine tools
shear and punches
cranes and hoists

DC series motor is best suited for electric traction as
it develops high starting torque
it runs at very high speed at light load
it is cheaper in cost
it consumes less power

The dc motor, which can provide zero speed regulation at full load without any controller is
series
shunt
cumulative compound
differential compound

For parallel operation, the dc generators normally preferred are
shunt
series
over-compound
under compound
both shunt and under compound

The ____ generator has the poorest voltage regulation
shunt
over compounded
under compounded
differential compounded

The speed of a dc shunt motor ___________ from no load to full load
falls slightly
improves slightly
remains unchanged
falls rapidly

An ideal dc generator has a regulation of ______ percent
zero
10
25
100

The armature MMF waveform of a dc machine is
pulsating
rectangular
triangular
sinusoidal

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