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WorksheetsELECTRICAL MACHINES-II QUIZ IIEEE-A and B
Total questions: 40
Worksheet time: 32mins
1. In a Double field revolving theory of single phase induction motor, If the slip of the forward
Motor is s, then the slip of backward motor is
2s
s
2-s
s-2
Compared to a resistance split phase motor, a capacitor-start motor has
Low Starting Torque
Low Running Torque
High Running Torque
High Starting Torque
The Rotating Magnetic field in a shaded pole motor is developed by using
Shading Coils
Salient Poles
capacitor
Damper windings
In a split phase motor, the running winding should have
High resistance and low inductance
high resistance as well as high inductance
low resistance as well as low inductance
Low resistance and High Inductance
In a capacitor start and run motors, the function of the running capacitor is to
. increase overload capacity
Improved power factor
to improve torque
reduce fluctuations in torque
Alternators are rated in terms of
KVA
KW
KVAR
NONE
What are the conditions to be satisfied for parallel operation
Voltage
Frequency
Phase sequence
All the above
In synchronous motor minimum armature current corresponds to
lag p.f.
lead p.f.
upf
zero p.f.
Damper winding is provided in synchronous motor
provides starting torque
eliminates hunting effect
both
none
In synchronous motor the inverted V curve represents the relation between
Field current and power factor
field current and Armature current
Armature current and power factor
voltage anf power factor
For synchronous motor where the armature current is minimum corresponding operating power factor is
zero power factor
unit power factor
lagging power factor
leading power factor
which type of synchronous machine can develop more power
salient pole machine
non salient pole machine
both are same
none
In alternator if the load connected is ZPF Lag then the armature reaction is
purely magnetizing
purely demagnetizing
purely cross magnetizing
all the above
Identify the theory for analyzing salient pole synchronous machine
Two reaction theory
one reaction theory
Three reaction Theory
four reaction theory
identify the other name for synchronous impedance method
optimistic method
pessimistic method
A.S.A. Method
All the above
which method is more accurate in analyzing voltage regulation of alternators
EMF method
MMF Method
ZPFC Method
All the above
Synchronous motor is a ------
variable speed motor
constant speed motor
both
none
synchronous motor is a ---
singly excited machine
Doubly excited machine
both
none
If the synchronous motor is over excited then the machine power factor is---
lag
lead
upf
zpf
The primary function of Damper winding in synchronous motor is ----
self start
eliminating hunting
to regulate current
all the above
If the Alternator is designed with 4 number of poles and 50 hertz frequency then at what speed in rpm the machine has to be designed to run ??
1000
2000
1500
3000
what is the maximum operating speed in rpm possible for the induced emf of 50 hz frequeny alternator??
500
1000
2000
3000
The angle between stator field and rotor field in synchronous machine is known as --
power factor angle
impedance angle
load angle
all the above
A synchronous condenser is
An over excited synchronous motor driving a mechanical load
An ordinary capacitor bank
An over excited synchronous motor with no load
An under excited synchronous motor without mechanical load
The motor that is not self-starting is
DC Series Motor
three phase induction motor
synchronous motor
all the above
What are the conditions to be satisfied for parallel operation
voltage
phase sequence
frequency
all the above
In a synchronous motor if excitation is varied with load constant then
Ia cos θ is constant
Ia cos θ is varied
both
none
What is the slip of the synchronous motor
0
1
>1
<1
when a synchronous motor is running at synchronous speed then damping winding produces
damping torque
eddy current torque
no torque
none
In doing parallel operation, what will happen if phase sequence condition is not satisfied
Healthy system
disaster short circuit
runs satisfactorily
all the above
The operating switch used for synchronizing procedure is known as
load switch
voltage switch
current switch
paralleling switch
In experimental setup for determination of Xd and Xq the voltage induced in the field winding is having a frequency of ---
f
sf
[2-s]f
2f
The formula for Xd
Vmax/Imin
Vmin/Imax
Vmax/Imax
Vmin/Imin
The formula for Xq
Vmax/Imax
Vmin/Imin
Vmin/Imax
Imax/Vmin
To pitch factor to eliminate nth Harmonic in the induced emf is ----
cosn α /2
sinn α /2
tann α /2
all the above
The nature of triplen harmonics are
out of phase
co-phasal
both
all the above
The phase sequence of odd harmonics are
positive
negative
can be Both
None
The turbines used in thermal power generation units are known as
water turbines
steam turbines
both
none
what is inherent feature of synchronous motor
power factor can be controlled
speed can be controlled
The inverted V curve is a plot obtained between
armature current and field current
power factor and field current
volatge and armature current
power factor and armature current
