Most important interview answer and question for EEE Part-2
101. In three pin plug 6 Amp. 220v AC rating. why
earth pin diameter is higher than other two pin?
what its purpose ?
Because Current flow in the conductor is inversely
proportional to the conductor diameter. So if any
short circuits occur in the system first high currents
bypassed in the Earthling terminal.( R=Pl/a area of
the conductor increases resistance value decreases)
102. Difference between megger test equipment
and contact resistance meter test instruments?
Megger test equipment used to measure cable
electric resistance, conductor continuity, phase
identification where as contact resistance meter test
instruments used to measure low resistance like
relays ,contactors.
103. When we connect the large capacitor bank in
series ?
we connect large capacitor bank in series to improve
the voltage power supply at the load end in balanced
transmission line when there is considerable voltage
drop along the balanced transmission line due to
high impedance of the line.So in order to bring the
voltage at the load terminals within its limits (i.e (+
or – %6 )of the rated high terminal voltage )the large
capacitor bank is used in series.
104. What is electrical diversity factor in
electrical installations?
Electrical diversity factor is the ratio of the sum of
the individual maximum demands of the various
subdivisions of a system, or part of a system, to the
maximum demand of the whole system, or part of
the system, under consideration. Electrical diversity
factor is usually more than one.
105. Why field rheostat is kept in minimum
position while armature rheostat at maximum
position?
In motors at the time of starting the armature
resistance is introduced to reduce the high starting
current and the field resistance is kept minimum to
have high starting torque.
106. Why computer humming sound occurred in
HT transmission line?
This computer humming sound is coming due to
ionization (breakdown of air into charged particles)
of air around transmission conductor. This effect is
called as Corona effect, and it is considered as power
loss.
107. What is rated speed?
At the time of motor taking normal current (rated
current)the speed of the motor is called rated speed.
It is a speed at which any system take small current
and give maximum efficiency.
108. What is different between resistance
grounding system and resistance earthing
system?
Resistance grounding system means connecting the
neutral point of the load to the ground to carry the
residual current in case of unbalanced conditions
through the neutral to the ground whereas
resistance earthing system is done in an electric
equipment in order to protect he equipment in
occurrence of fault in the system.
109. Why should be the frequency 50 Hz 60Hz only
why not others like 45, 95 56 or anything , why
should we maintain the frequency constant if so
why it is only 50 Hz 60Hz?
We can have the frequency at any frequency you
like, but than you must also make your own
motors,high voltage transformers or any other
equipment you want to use.We maintain the
frequency at 50hz or 60hz because the world
maintains a standard at 50 /60hz and the equipments
are are made to operate at these frequency.
110. How to determine alternating current
frequency?
Zero crossings of the sine wave to trigger a
monostable (pulse generator) is a way to determine
alternating current frequency. A fixed width pulse is
generated for each cycle. Thus there are “n” pulses
per second, each with with a constant energy. The
more pulses there are per second, the more the
energy. The pulses are integrated (filtered or
averaged) to get a steady DC voltage which is
proportional to frequency. This voltage can then be
displayed on an analogue or digital voltmeter,
indicating frequency. This method is more suitable
than a direct counter, as it can get good accuracy in a
second or so.
111. Why electricity in India is in the multiples of
11 like 11kv, 22kv, 33kv ?
Transformer Induced voltage equation contains 4.44
factor.
E=4.44*f*T*phi
E -Induced emf per phase
T -number of turns
f -frequency
phi -maximum flux per pole
From the equation we see that E is proportional to
4.4 and it is in turn multiple of 11.
So always transmission voltage is multiple of 11
112. Why we use ac system in India why not dc ?
Firstly, the output of power stations comes from a
rotary turbine, which by it’s nature is AC and
therefore requires no power electronics to convert to
DC. Secondly it is much easier to change the voltage
of AC electricity for transmission and distribution.
thirdly the cost of plant associated with AC
transmission (circuit breakers, transformers etc) is
much lower than the equivilant of DC transmission
AC transmission provides a number of technical
advantages. When a fault on the network occurs, a
large fault current occurs. In an AC system this
becomes much easier to interupt, as the sine wave
current will naturally tend to zero at some point
making the current easier to interrupt.
113. Which type of motor is used in trains, what is
the rating of supply used explain Working
principal?
Dc series is in the trains to get high starting torque
while starting of the trains and operating voltage is
1500v dc.
114. Battery banks are in connected in series or
parallel and why?
Battery banks are always connected in series in
order to get a multiplied voltage where the AH or
current capacity remaining same. Ex : 24 nos.
2V,200Ah batteries connected in series will give
48V,200Ah output (AH = Ampere hours)
115. What is inrush current?
Inrush current is the current drawn by a piece of
electrically operated equipment when power is first
applied. It can occur with AC or DC powered
equipment, and can happen even with low supply
voltages.
116. In a Tap changing transformer where is the
tap connected, is it connected in the primary side
or secondary side?
Tapings are connected to high voltage winding side,
because of low current. If we connect tapings to low
voltage side, sparks will produce while tap changing
operation due to high current.
117. Why transformer ratings are in kva?
Since the power factor of transformer is dependent
on load we only define VA rating and does not
include power factor .In case of motors, power factor
depend on construction and hence rating of motors
is in KWatts and include power factor.
118. What is difference between fuse and
breaker?
Fuses are burned at the time of over current flows in
the circuit but breakers are just open(not burn) at
the time of over current flow. Fuses are used in only
one time but breakers are used by multiple number
of times.
119. What is the difference between delta-delta,
delta-star transformer?
Delta-delta transformer is used at generating station
or a receiving station for Change of Voltage (i,e)
generally it is used where the Voltage is high &
Current is low.Delta-star is a distribution kind of
transformer where from secondary star neutral is
taken as a return path and this configuration is used
for Step down voltage phenomena.
120. Capacitor is load free component but why
ampere meter shows current when capacitor
bank breaker close?
As we know that Electrical is having two type of load,
Active and Reactive .Capacitor is a reactive load
which is not considering as a load,& its factor is
Isin@ .Meter is design based on Current RMS value
because of it meter is showing the current RMS
value.
121. What’s electric traction?
Traction implies with the electric power for traction
system i. e. for railways, trams, trolleys etc. electric
traction implies use of the electricity for all these.
Now a day, magnetic traction is also utilised for
bullet trains. Essentially dc motors are utilized for
electric traction systems.
122. What is “pu” in EE?
Pu stands for per unit in power system. (pu = actual
value/ base value)
123. Define stepper motor. What is the use of
stepper motor?
The motor which work or act on the applied input
pulse in it, is called as stepper motor.This stepper
motor is under the category of synchronous motor,
which often does not fully depend of complete cycle.
It likes to works in either direction related to steps.
for this purpose it mainly used in automation parts.
124. What is a differential amplifier? Also,
explain CMRR.
Differential Amplifier: The amplifier, which is used
to amplify the voltage difference between two inputlines
neither of which is grounded, is called
differential amplifier. This reduces the amount of
noise which is injected into the amplifier, because
any noise appearing simultaneously on both the
input-terminals as the amplifying circuitry rejects it
being a common mode signal.
CMRR: It can be defined as the ratio of differential
voltage-gain to common made voltage gain. If a
differential amplifier is perfect, CMRR will be infinite
because in that case common mode voltage gain
would be zero.
125. What is use of lockout relay in ht voltage?
A lock-out relay is generally placed in line before or
after the e-stop switch so the power can be shut off at
one central location. This relay is powered by the
same electrical source as the control power which is
operated by a key lock switch. The relay itself may
have up to 24 contact points within the unit itself.
This allows the control power for multiple machines
to be locked out by the turn of a single key switch.
126. How can you start-up the 40w tube lite with
230v AC/DC without using any choke/Coil?
It’s possible with Electronic choke. otherwise it’s not
possible to ionize the particles in tube. light, with
normal voltage.
127. What types domain of Laplace transforms?
What behavior can Laplace transform predict
how the system work?
Types domain of Laplace transforms is s-domain,
Laplace transforms provide a method to find
position, acceleration or voltage the system will
have.
128. In the magnetic fluxes, what is the role of
armature reaction?
The armature flux has an important role for the
running condition. This armature flux can oppose
the main flux or it may support the main flux for
better running condition. This effect of supporting
and opposing of main flux to armature flux is called
armature reaction.
129. Explain thin film resistors and wire-wound
resistors
Thin film resistors- It is constructed as a thin film of
resistive material is deposited on an insulating
substrate.
Desired results are obtained by either trimming the
layer thickness or by cutting helical grooves of
suitable pitch along its length. During this process,
the value of the resistance is monitored closely and
cutting of grooves is stopped as soon as the desired
value of resistance is obtained.
Wire wound resistors – length of wire wound around
an insulating cylindrical core are known as wire
wound resistors. These wires are made of materials
such as Constantan and Manganin because of their
high resistivity, and low temperature coefficients.
The complete wire wound resistor is coated with an
insulating material such as baked enamel
130. whats the one main difference between UPS
& inverter ? And electrical engineering &
electronics engineering ?
uninterrupt power supply is mainly use for short
time . means according to ups VA it gives backup. ups
is also two types : on line and offline . online ups
having high volt and amp for long time backup with
with high dc voltage.but ups start with v dc with 7
amp. but inverter is startwith v,24,dc to 36v dc and
0amp to 180amp battery with long time backup.
131. What are the operation carried out in
Thermal power station?
The water is obtained in the boiler and the coal is
burnt so that steam is obtained this steam is allowed
to hit the turbine, the turbine which is coupled with
the generator generates the electricity
132. What is the difference between Electronic
regulator and ordinary rheostat regulator for
fans?
The difference between the electronic and ordinary
regulator is the fact that in electronic reg. power
losses tend to be less because as we minimize the
speed the electronic reg. give the power necessary
for that particular speed but in case of ordinary
rheostat type reg. the power wastage is same for
every speed and no power is saved. In electronic
regulator triac is employed for speed control. by
varying the firing angle speed is controlled but in
rheostatic control resistance is decreased by steps to
achievespeed control.
133. What is 2 phase motor?
A two phase motor is often a motor with the the
starting winding and the running winding have a
phase split.
e.g; ac servo motor. where the auxiliary winding and
the control winding have a phase split of 90 degree.
134. What does quality factor depend on in
resonance?
Quality factor q depends on frequency and
bandwidth.
135. What are the types of power in electrical
power?
There are normally three types of power are counted
in electrical power. They are,
• Apparent power
• Active power
• Reactive power
136. What are the advantages of VSCF wind
electrical system?
Advantages of VSCF wind electrical system are:
• No complex pitch changing mechanism is needed.
• Aero turbine always keeps going at maximum
efficiency point.
• Extra energy in the high wind speed region of the
speed – duration curve can be extracted
• Significant reduction in aerodynamic stresses,
which are associated with constant – speed
operation.
137. What is slip in an induction motor?
Slip can be defined as the distinction between the
flux speed (Ns) and the rotor speed (N). Speed of the
rotor of
an induction motor is always less than its
synchronous speed. It is usually expressed as a
percentage of
synchronous speed (Ns) and represented by the
symbol ‘S’.
138. Why link is provided in neutral of an ac
circuit and fuse in phase of ac circuit?
Link is provided at a Neutral common point in the
circuit from which various connection are taken for
the individual control circuit and so it is given in a
link form to withstand high Amps. But in the case of
Fuse in the Phase of AC circuit it is designed such
that the fuse rating is calculated for the particular
circuit (i.e load) only.So if any malfunction happen
the fuse connected in the particular control circuit
alone will blow off.
139. State the difference between generator and
alternator?
Generator and alternator are two devices, which
converts mechanical energy into electrical energy.
Both have the same principle of electromagnetic
induction, the only difference is that their
construction. Generator persists stationary magnetic
field and rotating conductor which rolls on the
armature with slip rings and brushes riding against
each other, hence it converts the induced emf into dc
current for external load whereas an alternator has
a stationary armature and rotating magnetic field for
high voltages but for low voltage output rotating
armature and stationary magnetic field is used.
earth pin diameter is higher than other two pin?
what its purpose ?
Because Current flow in the conductor is inversely
proportional to the conductor diameter. So if any
short circuits occur in the system first high currents
bypassed in the Earthling terminal.( R=Pl/a area of
the conductor increases resistance value decreases)
102. Difference between megger test equipment
and contact resistance meter test instruments?
Megger test equipment used to measure cable
electric resistance, conductor continuity, phase
identification where as contact resistance meter test
instruments used to measure low resistance like
relays ,contactors.
103. When we connect the large capacitor bank in
series ?
we connect large capacitor bank in series to improve
the voltage power supply at the load end in balanced
transmission line when there is considerable voltage
drop along the balanced transmission line due to
high impedance of the line.So in order to bring the
voltage at the load terminals within its limits (i.e (+
or – %6 )of the rated high terminal voltage )the large
capacitor bank is used in series.
104. What is electrical diversity factor in
electrical installations?
Electrical diversity factor is the ratio of the sum of
the individual maximum demands of the various
subdivisions of a system, or part of a system, to the
maximum demand of the whole system, or part of
the system, under consideration. Electrical diversity
factor is usually more than one.
105. Why field rheostat is kept in minimum
position while armature rheostat at maximum
position?
In motors at the time of starting the armature
resistance is introduced to reduce the high starting
current and the field resistance is kept minimum to
have high starting torque.
106. Why computer humming sound occurred in
HT transmission line?
This computer humming sound is coming due to
ionization (breakdown of air into charged particles)
of air around transmission conductor. This effect is
called as Corona effect, and it is considered as power
loss.
107. What is rated speed?
At the time of motor taking normal current (rated
current)the speed of the motor is called rated speed.
It is a speed at which any system take small current
and give maximum efficiency.
108. What is different between resistance
grounding system and resistance earthing
system?
Resistance grounding system means connecting the
neutral point of the load to the ground to carry the
residual current in case of unbalanced conditions
through the neutral to the ground whereas
resistance earthing system is done in an electric
equipment in order to protect he equipment in
occurrence of fault in the system.
109. Why should be the frequency 50 Hz 60Hz only
why not others like 45, 95 56 or anything , why
should we maintain the frequency constant if so
why it is only 50 Hz 60Hz?
We can have the frequency at any frequency you
like, but than you must also make your own
motors,high voltage transformers or any other
equipment you want to use.We maintain the
frequency at 50hz or 60hz because the world
maintains a standard at 50 /60hz and the equipments
are are made to operate at these frequency.
110. How to determine alternating current
frequency?
Zero crossings of the sine wave to trigger a
monostable (pulse generator) is a way to determine
alternating current frequency. A fixed width pulse is
generated for each cycle. Thus there are “n” pulses
per second, each with with a constant energy. The
more pulses there are per second, the more the
energy. The pulses are integrated (filtered or
averaged) to get a steady DC voltage which is
proportional to frequency. This voltage can then be
displayed on an analogue or digital voltmeter,
indicating frequency. This method is more suitable
than a direct counter, as it can get good accuracy in a
second or so.
111. Why electricity in India is in the multiples of
11 like 11kv, 22kv, 33kv ?
Transformer Induced voltage equation contains 4.44
factor.
E=4.44*f*T*phi
E -Induced emf per phase
T -number of turns
f -frequency
phi -maximum flux per pole
From the equation we see that E is proportional to
4.4 and it is in turn multiple of 11.
So always transmission voltage is multiple of 11
112. Why we use ac system in India why not dc ?
Firstly, the output of power stations comes from a
rotary turbine, which by it’s nature is AC and
therefore requires no power electronics to convert to
DC. Secondly it is much easier to change the voltage
of AC electricity for transmission and distribution.
thirdly the cost of plant associated with AC
transmission (circuit breakers, transformers etc) is
much lower than the equivilant of DC transmission
AC transmission provides a number of technical
advantages. When a fault on the network occurs, a
large fault current occurs. In an AC system this
becomes much easier to interupt, as the sine wave
current will naturally tend to zero at some point
making the current easier to interrupt.
113. Which type of motor is used in trains, what is
the rating of supply used explain Working
principal?
Dc series is in the trains to get high starting torque
while starting of the trains and operating voltage is
1500v dc.
114. Battery banks are in connected in series or
parallel and why?
Battery banks are always connected in series in
order to get a multiplied voltage where the AH or
current capacity remaining same. Ex : 24 nos.
2V,200Ah batteries connected in series will give
48V,200Ah output (AH = Ampere hours)
115. What is inrush current?
Inrush current is the current drawn by a piece of
electrically operated equipment when power is first
applied. It can occur with AC or DC powered
equipment, and can happen even with low supply
voltages.
116. In a Tap changing transformer where is the
tap connected, is it connected in the primary side
or secondary side?
Tapings are connected to high voltage winding side,
because of low current. If we connect tapings to low
voltage side, sparks will produce while tap changing
operation due to high current.
117. Why transformer ratings are in kva?
Since the power factor of transformer is dependent
on load we only define VA rating and does not
include power factor .In case of motors, power factor
depend on construction and hence rating of motors
is in KWatts and include power factor.
118. What is difference between fuse and
breaker?
Fuses are burned at the time of over current flows in
the circuit but breakers are just open(not burn) at
the time of over current flow. Fuses are used in only
one time but breakers are used by multiple number
of times.
119. What is the difference between delta-delta,
delta-star transformer?
Delta-delta transformer is used at generating station
or a receiving station for Change of Voltage (i,e)
generally it is used where the Voltage is high &
Current is low.Delta-star is a distribution kind of
transformer where from secondary star neutral is
taken as a return path and this configuration is used
for Step down voltage phenomena.
120. Capacitor is load free component but why
ampere meter shows current when capacitor
bank breaker close?
As we know that Electrical is having two type of load,
Active and Reactive .Capacitor is a reactive load
which is not considering as a load,& its factor is
Isin@ .Meter is design based on Current RMS value
because of it meter is showing the current RMS
value.
121. What’s electric traction?
Traction implies with the electric power for traction
system i. e. for railways, trams, trolleys etc. electric
traction implies use of the electricity for all these.
Now a day, magnetic traction is also utilised for
bullet trains. Essentially dc motors are utilized for
electric traction systems.
122. What is “pu” in EE?
Pu stands for per unit in power system. (pu = actual
value/ base value)
123. Define stepper motor. What is the use of
stepper motor?
The motor which work or act on the applied input
pulse in it, is called as stepper motor.This stepper
motor is under the category of synchronous motor,
which often does not fully depend of complete cycle.
It likes to works in either direction related to steps.
for this purpose it mainly used in automation parts.
124. What is a differential amplifier? Also,
explain CMRR.
Differential Amplifier: The amplifier, which is used
to amplify the voltage difference between two inputlines
neither of which is grounded, is called
differential amplifier. This reduces the amount of
noise which is injected into the amplifier, because
any noise appearing simultaneously on both the
input-terminals as the amplifying circuitry rejects it
being a common mode signal.
CMRR: It can be defined as the ratio of differential
voltage-gain to common made voltage gain. If a
differential amplifier is perfect, CMRR will be infinite
because in that case common mode voltage gain
would be zero.
125. What is use of lockout relay in ht voltage?
A lock-out relay is generally placed in line before or
after the e-stop switch so the power can be shut off at
one central location. This relay is powered by the
same electrical source as the control power which is
operated by a key lock switch. The relay itself may
have up to 24 contact points within the unit itself.
This allows the control power for multiple machines
to be locked out by the turn of a single key switch.
126. How can you start-up the 40w tube lite with
230v AC/DC without using any choke/Coil?
It’s possible with Electronic choke. otherwise it’s not
possible to ionize the particles in tube. light, with
normal voltage.
127. What types domain of Laplace transforms?
What behavior can Laplace transform predict
how the system work?
Types domain of Laplace transforms is s-domain,
Laplace transforms provide a method to find
position, acceleration or voltage the system will
have.
128. In the magnetic fluxes, what is the role of
armature reaction?
The armature flux has an important role for the
running condition. This armature flux can oppose
the main flux or it may support the main flux for
better running condition. This effect of supporting
and opposing of main flux to armature flux is called
armature reaction.
129. Explain thin film resistors and wire-wound
resistors
Thin film resistors- It is constructed as a thin film of
resistive material is deposited on an insulating
substrate.
Desired results are obtained by either trimming the
layer thickness or by cutting helical grooves of
suitable pitch along its length. During this process,
the value of the resistance is monitored closely and
cutting of grooves is stopped as soon as the desired
value of resistance is obtained.
Wire wound resistors – length of wire wound around
an insulating cylindrical core are known as wire
wound resistors. These wires are made of materials
such as Constantan and Manganin because of their
high resistivity, and low temperature coefficients.
The complete wire wound resistor is coated with an
insulating material such as baked enamel
130. whats the one main difference between UPS
& inverter ? And electrical engineering &
electronics engineering ?
uninterrupt power supply is mainly use for short
time . means according to ups VA it gives backup. ups
is also two types : on line and offline . online ups
having high volt and amp for long time backup with
with high dc voltage.but ups start with v dc with 7
amp. but inverter is startwith v,24,dc to 36v dc and
0amp to 180amp battery with long time backup.
131. What are the operation carried out in
Thermal power station?
The water is obtained in the boiler and the coal is
burnt so that steam is obtained this steam is allowed
to hit the turbine, the turbine which is coupled with
the generator generates the electricity
132. What is the difference between Electronic
regulator and ordinary rheostat regulator for
fans?
The difference between the electronic and ordinary
regulator is the fact that in electronic reg. power
losses tend to be less because as we minimize the
speed the electronic reg. give the power necessary
for that particular speed but in case of ordinary
rheostat type reg. the power wastage is same for
every speed and no power is saved. In electronic
regulator triac is employed for speed control. by
varying the firing angle speed is controlled but in
rheostatic control resistance is decreased by steps to
achievespeed control.
133. What is 2 phase motor?
A two phase motor is often a motor with the the
starting winding and the running winding have a
phase split.
e.g; ac servo motor. where the auxiliary winding and
the control winding have a phase split of 90 degree.
134. What does quality factor depend on in
resonance?
Quality factor q depends on frequency and
bandwidth.
135. What are the types of power in electrical
power?
There are normally three types of power are counted
in electrical power. They are,
• Apparent power
• Active power
• Reactive power
136. What are the advantages of VSCF wind
electrical system?
Advantages of VSCF wind electrical system are:
• No complex pitch changing mechanism is needed.
• Aero turbine always keeps going at maximum
efficiency point.
• Extra energy in the high wind speed region of the
speed – duration curve can be extracted
• Significant reduction in aerodynamic stresses,
which are associated with constant – speed
operation.
137. What is slip in an induction motor?
Slip can be defined as the distinction between the
flux speed (Ns) and the rotor speed (N). Speed of the
rotor of
an induction motor is always less than its
synchronous speed. It is usually expressed as a
percentage of
synchronous speed (Ns) and represented by the
symbol ‘S’.
138. Why link is provided in neutral of an ac
circuit and fuse in phase of ac circuit?
Link is provided at a Neutral common point in the
circuit from which various connection are taken for
the individual control circuit and so it is given in a
link form to withstand high Amps. But in the case of
Fuse in the Phase of AC circuit it is designed such
that the fuse rating is calculated for the particular
circuit (i.e load) only.So if any malfunction happen
the fuse connected in the particular control circuit
alone will blow off.
139. State the difference between generator and
alternator?
Generator and alternator are two devices, which
converts mechanical energy into electrical energy.
Both have the same principle of electromagnetic
induction, the only difference is that their
construction. Generator persists stationary magnetic
field and rotating conductor which rolls on the
armature with slip rings and brushes riding against
each other, hence it converts the induced emf into dc
current for external load whereas an alternator has
a stationary armature and rotating magnetic field for
high voltages but for low voltage output rotating
armature and stationary magnetic field is used.
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