Q:What is inrush current?
A: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.
Q:In a Tap changing transformer where is the tap connected, is it connected in the primary side or secondary side?
A: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.
Q:Why transformer ratings are in kva?
A: 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.
Q: What is difference between fuse and breaker?
A: 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.
Q:What is the difference between delta-delta, delta-star transformer?
A: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.
Q: Capacitor is load free component but why ampere meter shows current when capacitor bank breaker close?
A: 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.
Q: What is difference between fuse and breaker?
A: 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.
Q:What is the difference between delta-delta, delta-star transformer?
A: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.
Q: Capacitor is load free component but why ampere meter shows current when capacitor bank breaker close?
A: 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.
Q:What is
electric traction?
A:Electric traction means using the
electric power for traction system (i.e. for railways,trams, trolleys etc).
Electric traction means use of the electricity for all the above machines. Now
a days, magnetic traction is also used for bullet trains.and basically dc motors
are used for electric traction systems.
Q:How can
you start-up the 40w tube lite with 230v AC/DC without using any choke/Coil?
A:It's possible by means of Electronic
chokes,otherwise it's not possible to ionize the particles in tube light with
normal voltage.
Q:What is
"pu" in electrical engineering?
A:Pu stands for per unit and this will
be used in single line diagram of power distribution and it is like a huge
electrical circuit with no of components (generators, transformers, loads) with
different ratings (in MVA and KV). To bring all the ratings into common
platform we use pu concept in which, in general largest MVA and KV ratings of
the component is considered as base values, then all other component ratings
will get back into this basis.Those values are called as pu values. (p.u=actual
value/base value).
Q:Operation
carried out in Thermal power stations?
A: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.
Q:Why
link is provided in neutral of an ac circuit and fuse in phase of ac circuit?
A: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.
Q: What
is the difference between electronic regulator and ordinary electrical rheostat
regulator for fans?
A:The difference between the
electronic and ordinary electrical regulator is that in electronic regulator
power losses are less because as we decrease the speed the electronic regulator
gives the power needed for that particular speed but in case of ordinary
rheostat type regulator, 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 and it is controlled but in rheostatic ,control
resistance is decreased by steps to achieve speed control.
Q:How
tube light circuit is connected and how it works?
A:A choke is connected in one end of
the tube light and a starter is in series with the circuit. When supply is
provided ,the starter will interrupt the supply cycle of AC. Due to the sudden
change of supply the chock will generate around 1000volts . This volt will
capable of to break the electrons inside the tube to make electron flow. once
the current passes through the tube the starter circuit will be out of part.
now there is no change of supply causes choke voltage normalized and act as
minimize the current.
Q:whats
is MARX CIRCUIT?
A:It is used with generators for
charging a number of capacitor in parallel and discharging them in series.It is
used when voltage required for testing is higher than the available.
Q:What is
encoder, how it function?
A:An encoder is a device used to
change a signal (such as a bitstream) or data into a code. The code may serve
any of a number of purposes such as compressing information for transmission or
storage, encrypting or adding redundancies to the input code, or translating
from one code to another. This is usually done by means of a programmed
algorithm,especially if any part is digital, while most analog encoding is done
with analog circuitry.
Q:What
are the advantages of speed control using thyristor?
A:Advantages :1. Fast Switching
Characterstics than Mosfet, BJT, IGBT 2. Low cost 3. Higher Accurate.
Q:Why
Human body feel Electric shock ?? n in an Electric train during running , We
did nt feel any Shock ? why?
A:Unfortunately our body is a pretty
good conductor of electricity, The golden rule is Current takes the lowest
resistant path if you have insulation to our feet as the circuit is not
complete (wearing rubber footwear which doing some repairs is advisable as our
footwear is a high resistance path not much current flows through our body).The
electric train is well insulated from its electrical system.
Q:what is
the principle of motor?
A:Whenever a current carrying
conductor is placed in an magnetic field it produce turning or twisting movemnt
is called as torque.
Q:Why,
when birds sit on transmission lines or current wires doesn't get shock?
A:Its true that if birds touch the single one line (phase or neutral) they don't get electrical shock... if birds touch 2 lines than the circuit is closed and they get electrical shock.. so if a human touch single one line(phase) then he doesn't get shock if he is in the air (not touching - standing on the ground if he is standing on the ground then touching the line (phase) he will get a shock because the ground on what we standing is like line (ground bed - like neutral)। and in the most of electric lines the neutral is grounded..so that means that human who touch the line closes the circuit between phase and neutral.
Q:what is meant by armature reaction?
A:Its true that if birds touch the single one line (phase or neutral) they don't get electrical shock... if birds touch 2 lines than the circuit is closed and they get electrical shock.. so if a human touch single one line(phase) then he doesn't get shock if he is in the air (not touching - standing on the ground if he is standing on the ground then touching the line (phase) he will get a shock because the ground on what we standing is like line (ground bed - like neutral)। and in the most of electric lines the neutral is grounded..so that means that human who touch the line closes the circuit between phase and neutral.
Q:what is meant by armature reaction?
A:The effect of armature flu to main
flux is called armature reaction. The armature flux may support main flux or
opposes main flux.
Q:what happen if we give 220 volts dc supply to d bulb r tube light?
Q:what happen if we give 220 volts dc supply to d bulb r tube light?
A:Bulbs [devices] for AC are designed
to operate such that it offers high impedance to AC supply. Normally they have
low resistance. When DC supply is applied, due to low resistance, the current
through lamp would be so high that it may damage the bulb element.
Q:Which motor has high Starting Torque and Staring current DC motor, Induction motor or Synchronous motor?
Q:Which motor has high Starting Torque and Staring current DC motor, Induction motor or Synchronous motor?
A:DC Series motor has high starting
torque. We can not start the Induction motor and Synchronous motors on load,
but can not start the DC series motor without load.
Q:what is ACSR cable and where we use it?
Q:what is ACSR cable and where we use it?
A:ACSR means Aluminium conductor steel
reinforced, this conductor is used in transmission & distribution.
Q:What is
vaccum currcuit breaker.define with cause and where be use it Device?
A:A breaker is normally used to break a
ciruit. while breaking the circuit, the contact terminals will be separated. At
the time of seperation an air gap is formed in between the terminals. Due to
existing current flow the air in the gap is ionised and results in the arc.
various mediums are used to quench this arc in respective CB's. but in VCB the
medium is vaccum gas. since the air in the CB is having vaccum pressure the arc
formation is interrupted. VCB's can be used upto 11kv.
Q:What
will happen when power factor is leading in distribution of power?
A:If their is high power factor, i.e
if the power factor is close to one:
1.losses in
form of heat will be reduced,
2.cable
becomes less bulky and easy to carry, and very
cheap to
afford, &
3. it also
reduces over heating of tranformers.
Q:whats
the one main difference between UPS & inverter ? And electrical engineering
& electronics engineering ?
A: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 12v dc with 7 amp. but inverter
is startwith 12v,24,dc to 36v dc and 120amp to 180amp battery with long time
backup.
Q:What is
2 phase motor?
A:A two phase motor is 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.
Q:Advantages
of vvvf drives over non vvvf drives for EOT cranes?
A:1.smooth start and stop.
2.no jerking
of load.
3.exact
posiitoning
4.better
protection for motor.
5.high/low
speed selection.
6.reliability
of break shoe.
7.programmable
break control.
8.easy
circutry
9.reduction
in controls
10.increases
motor life
Q:What is
the significance of vector grouping in Power Transformers?
A:Every power transformer has a vector
group listed by its manufacturer. Fundamentally it tells you the information
about how the windings are connected (delta or wye) and the phace difference
betweent the current and voltage. EG. DYN11 means Delta primary, Wye Secondry
and the current is at 11 o clock reffered to the voltage.
Q:Which
type of A.C motor is used in the fan (ceiling fan, exhaust fan, padestal fan,
bracket fan etc) which are find in the houses ?
A:Its Single Phase induction motor
which mostly squirrel cage rotor and are capacitor start capacitor run.
Q:Give
two basic speed control scheme of DC shunt motor?
A:1. By using flux control method:in
this method a rheostat is connected across the field winding to control the
field current.so by changing the current the flux produced by the field winding
can be changed, and since speed is inversely proportional to flux speed can be
controlled 2.armature control method:in this method a rheostat is connected
across armature winding by varying the resistance the value of resistive
drop(IaRa)can be varied,and since speed is directly proportional to Eb-IaRa the
speed can be controlled.
Q:what is
the principle of motor?
A:Whenever a current carrying
conductor is placed in an magnetic field it produce turning or twisting
movement is called as torque.
Q:what is
meant by armature reaction?
A:The effect of armature flu to main
flux is called armature reaction. The armature flux may support main flux or
opposes main flux.
Q:Give
two basic speed control scheme of DC shunt motor?
A:1. By using flux control method:in
this method a rheostat is connected across the field winding to control the
field current.so by changing the current the flux produced by the field winding
can be changed, and since speed is inversely proportional to flux speed can be
controlled 2.armature control method:in this method a rheostat is connected
across armature wdg.by varying the resistance the value of resistive
drop(IaRa)can be varied,and since speed is directly proportional to Eb-IaRa the
speed can be controlled.
Q:what is
the difference between synchronous generator & asynchronous generator?
A:In simple, synchronous generator
supply's both active and reactive power but asynchronous generator(induction
generator) supply's only active power and observe reactive power for
magnetizing.This type of generators are used in windmills.
Q:What is
the Polarization index value ? (pi value)and simple definition of polarization
index ?
A:Its ratio between insulation
resistance(IR)i.e meggar value
for 10min to
insulation resistance for 1 min. It ranges from 5-7 for new motors &
normally for motor to be in good condition it should be Greater than 2.5 .
:Why syn.
generators r used for the production of electricity?
A:synchronous machines have capability
to work on different power factor(or say
different
imaginary power varying the field emf. Hence syn. generators r used for the
production of electricity.
Q:What is
the difference between synchronous generator & asynchronous generator?
A:In simple, synchronous generator
supply's both active and reactive power but asynchronous generator(induction
generator) supply's only active power and observe reactive power for
magnetizing.This type of generators are used in windmills.
Q:1 ton
is equal to how many watts?
A:1 ton = 12000 BTU/hr and to convert
BTU/hr to horsepower,
12,000 *
0.0003929 = 4.715 hp therefore 1 ton = 4.715*.746 = 3.5 KW.
Q:why
syn. generators r used for the production of electricity?
A:synchronous machines have capability
to work on differentpower factor(or say
different
imaginary pow varying the field emf. Hence syn. generators r used for the
production of electricity.
Q:Enlist
types of dc generator?
A:D.C.Generators are classified into
two types 1)separatly exicted d.c.generator 2)self exicted d.c.generator, which
is further classified into;1)series 2)shunt and
3)compound(which
is further classified into cumulative and differential).
Q:What is
Automatic Voltage regulator(AVR)?
A:AVR is an abbreviation for Automatic
Voltage Regulator.It is important part in Synchronous Generators, it controls
theoutput voltage of the generator by controlling its excitation current. Thus
it can control the output Reactive Power of the Generator.
Q:What is an exciter and how does it work?
Q:What is an exciter and how does it work?
A:There are two types of exciters,
static exciter and rotory exciter.purpose of excitor is to supply the
excitation dc voltage to the fixed poles of generator.Rotory excitor is an
additional small generator mounted on the shaft of main generator. if it is dc
generator, it will supply dc to the rotory poles through slip ring and brushes(
conventional alternator). if it is an ac excitor, out put of ac excitor is
rectified by rotating diodes and supply dc to main fixed poles.ac excitor is
the ac generator whose field winding are stationary and armature rotates.
initial voltage is built up by residual magnetism.It gives the starting torque
to the generator.
Q:Difference
between a four point starter and three point starter?
A:The shunt connection in four point
stater is provided separately form the line where as in three point stater it
is connected with line which is the drawback in three point stater
Q:Why use the VCB at High Transmission System ? Why can't use ACB?
Q:Why use the VCB at High Transmission System ? Why can't use ACB?
A:Actually the thing is vacuum has
high arc queching property compare to air because in VCB ,the die electric
strengths equal to 8 times of air . That y always vaccum used as inHT breaker
and air used as in LT .
Q:What is the difference between surge arrestor and lightning arrestor?
Q:What is the difference between surge arrestor and lightning arrestor?
A:LA is installed outside and the
effect of lightning is grounded,where as surge arrestor installed inside panels
comprising of resistors which consumes the energy and nullify the effect of
surge.
Q:What
happens if i connect a capacitor to a generator load?
A:Connecting a capacitor across a
generator always improves powerfactor,but it will help depends up on the engine
capacity of the alternator,other wise the alternator will be over loaded due to
the extra watts consumed due to the improvement on pf. Secondly, don't connect
a capacitor across an alternator while it is picking up or without any other
load.
Q:Why the
capacitors works on ac only?
A:Generally capacitor gives infinite
resistance to dc components(i.e., block the dc components). it allows the ac
components to pass through.
Q:Explain
the working principal of the circuit breaker?
A:Circuit Breaker is one which makes
or breaks the circuit.It has two contacts namely fixed contact & moving
contact.under normal condition the moving contact comes in contact with fixed
contact thereby forming the closed contact for the flow of current. During
abnormal & faulty conditions(when current exceeds the rated value) an arc
is produced between the fixed & moving contacts & thereby it forms the
open circuitArc is extinguished by the Arc Quenching media like air, oil,
vaccum etc.
Q:What is
the difference between Isolator and Circuit Breaker?
A:Isolator is a off load device which
is used for isolating the downstream circuits from upstream circuits for the
reason of any maintenance on downstream circuits. it is manually operated and
does not contain any solenoid unlike circuit breaker. it should not be operated
while it is having load. first the load on it must be made zero and then it can
safely operated. its specification only rated current is given.But circuit
breaker is onload automatic device used for breaking the circuit in case of
abnormal conditions like short circuit, overload etc., it is having three
specification 1 is rated current and 2 is short circuit breaking capacity and 3
is instantaneous tripping current.
Q:what is
boucholz relay and the significance of it in to the transformer?
A:Boucholz relay is a device which is
used for the protection of transformer from its internal faults, it is a gas
based relay. whenever any internal fault occurs in a transformer, the boucholz
relay at once gives a horn for some time, if the transformer is isolated from the
circuit then it stop its sound itself other wise it trips the circuit by its
own tripping mechanism.
Q:What is
SF6 Circuit Breaker?
A:SF6 is Sulpher hexa Flouride gas..
if this gas is used as arc quenching medium in a Circuitbreaker means SF6 CB.
Q:what is
ferrantic effect?
A:Output voltage is greater than the
input voltage or receiving end voltage is greater than the sending end voltage.
Q: what
is meant by insulation voltage in cables? explain it?
A:It is the property of a cable by
virtue of it can withstand the applied voltage without rupturing it is known as
insulation level of the cable.
Q: Why we
do 2 types of earthing on transformer (ie:)body earthing & neutral earthing
, what is function. i am going to install a 5oo kva transformer & 380 kva
DG set what should the earthing value?
A:The two types of earthing are
Familiar as Equipment earthing and system earthing. In Equipment earthing: body
( non conducting part)of the equipment shouldd be earthed to safegaurd the
human beings.system Earthing : In this neutral of the supply source (
Transformer or Generator) should be grounded. With this,in case of unbalanced
loading neutral will not be shifted.so that unbalanced voltages will not arise.
We can protect the equipment also. With size of the equipment( transformer or
alternator)and selection of relying system earthing will be further classified
into directly earthed,Impedance earthing, resistive (NGRs) earthing.
Q:What is
the difference between MCB & MCCB, Where it can be used?
A:MCB is miniature circuit breaker
which is thermal operated and use for short circuit protection in small current
rating circuit. MCCB moulded case circuit breaker and is thermal operated for
over load current and magnetic operation for instant trip in short circuit condition.under
voltage and under frequency may be inbuilt. Normally it is used where normal
current is more than 100A.
Q:Where
should the lighting arrestor be placed in distribution lines?
A:Near distribution transformers and
out going feeders of 11kv and incomming feeder of 33kv and near power
transformers in sub-stations.
Q:Define
IDMT relay?
A:It is an inverse definite minimum
time relay.In IDMT relay its operating is inversely proportional and also a
characteristic of minimum time after which this relay operates.It is inverse in
the sense ,the tripping time will decrease as the magnitude of fault current
increase.
Q:What
are the transformer losses?
A:TRANSFORMER LOSSES - Transformer
losses have two sources-copper loss and magnetic loss. Copper losses are caused
by the resistance of the wire (I2R). Magnetic losses are caused by eddy
currents and hysteresis in the core. Copper loss is a constant after the coil
has been wound and therefore a measurable loss. Hysteresis loss is constant for
a particular voltage and current. Eddy-current loss, however, is different for
each frequency passed through the transformer.
Query:What is the count of hvdc
transmission lines in India?
Resolution:At present there are three hvdc transmission lines in india
1)chandrapur to padghe(mumbai)--(1500 MW at ±500 kV DC)
2)rehand to delhi (1500 MW at ±500 kV DC)
3)talchal to kolar (2500 MW)
Query:What is meant by regenerative braking?
Resolution:At present there are three hvdc transmission lines in india
1)chandrapur to padghe(mumbai)--(1500 MW at ±500 kV DC)
2)rehand to delhi (1500 MW at ±500 kV DC)
3)talchal to kolar (2500 MW)
Query:What is meant by regenerative braking?
Resolution:When the supply is cutt off for a running motor, it
still continue running due to inertia. In order to stop it quickly we place a
load(resitor) across the armature winding and the motor should have maintained
continuous field supply. so that back e.m.f voltage is made to apply across the
resistor and due to load the motor stops quickly.This type of breaking is
called as "Regenerative Breaking".
Query:Why is the starting current high in a DC motor?
Resolution:In DC motors, Voltage equation is V=Eb-IaRa (V = Terminal
voltage,Eb = Back emf in Motor,Ia = Armature current,Ra = Aramture
resistance).At starting, Eb is zero. Therefore, V=IaRa, Ia = V/Ra ,where Ra is
very less like 0.01ohm.i.e, Ia will become enormously increased.
Query:What are the advantages of star-delta
starter with induction motor?
Resolution:(1). The main advantage of using the star delta
starter is reduction of current during the starting of the motor.Starting
current is reduced to 3-4 times Of current of Direct online starting.(2). Hence
the starting current is reduced , the voltage drops during the starting of
motor in systems are reduced.
Query:Why Delta Star Transformers are used
for Lighting Loads?
Resolution:For lighting loads, neutral conductor is must and
hence the secondary must be star winding. and this lighting load is always
unbalanced in all three phases. To minimize the current unbalance in the
primary we use delta winding in the primary. So delta / star transformer is
used for lighting loads.
Query:Why in a three pin plug the earth
pin is thicker and longer than the other pins?
Resolution:It depends upon R=rho l/a where area(a) is inversely
proportional to resistance (R), so if (a) increases, R decreases & if R is
less the leakage current will take low resistance path so the earth pin should
be thicker. It is longer because the The First to make the connection and Last
to disconnnect should be earth Pin. This assures Safety for the person who uses
the electrical instrument.
Query:Why series motor cannot be started
on no-load?
Resolution:Series motor cannot be started without load because of
high starting torque. Series motor are used in Trains, Crane etc.
Query:Why ELCB can't work if N input of
ELCB do not connect to ground?
Resolution:ELCB is used to detect earth leakage fault. Once the
phase and neutral are connected in an ELCB, the current will flow through phase
and that much current will have to return neutral so resultant current is zero.
Once there is a ground fault in the load side, current from phase will directly
pass through earth and it will not return through neutral through ELCB. That
means once side current is going and not returning and hence because of this
difference in current ELCB wil trip and it will safe guard the other circuits
from faulty loads. If the neutral is not grounded, fault current will
definitely high and that full fault current will come back through ELCB, and
there will be no difference in current.
Q:How
electrical power is generated by an A.C Generator?
A:For the generation of elect power we
need a prime mover which supplies mechanical power input to the alternator, can
be steam turbines,or hydro turbines .When poles of the rotor moves under the
armature conductors which are placed on the stator ,field flux cut the armature
conductor ,therefore voltage is generated and is of sinusoidal in nature...due
to polarity change of rotor poles(i,e) N-S-N-S.
Q:Why an ac solenoid valve attract the plunger even though we interchanges the terminal? Will the poles changes?
A:Yes because the poles changes for every half-cycle of ac voltage so the polarity of AC voltage is continuously changing for every half cycle. so, interchanging of terminals in ac system does not show any difference. That's why the ac solenoid attract the plunger even though it's terminals are interchanged.
Q:Why an ac solenoid valve attract the plunger even though we interchanges the terminal? Will the poles changes?
A:Yes because the poles changes for every half-cycle of ac voltage so the polarity of AC voltage is continuously changing for every half cycle. so, interchanging of terminals in ac system does not show any difference. That's why the ac solenoid attract the plunger even though it's terminals are interchanged.
Q:What is
derating?, why it is necessary, it is same for all means for drives, motors,and
cables.
A:The current currying of cables will
change depending upon the site temperature (location of site), type of run (it
will run through duct, trench, buried etc.), number of tray, depth of trench,
distance between cables. Considering this condition actual current currying
capacity of cable reduce than current currying capacity (which given to cable
Catalogue) this is called derating.
Q:Why temperature rise is conducted in bus bars and isolators?
Q:Why temperature rise is conducted in bus bars and isolators?
A:Bus bars and isolators are rated for
continuous power flow, that means they carry heavy currents which rises their
temperature. so it is necessary to test this devices for temperature rise.
Q:When voltage increases then current also increases then what is the need of over voltage relay and over current relay? Can we measure over voltage and over current by measuring current only?
A:No.We can't sense the over voltage by just measuring the current only because the current increases not only for over voltages but also for under voltage(As most of the loads are non-linear in nature).So,the over voltage protection & over current protection are completely different. Over voltage relay meant for sensing over voltages & protect the system from insulation break down and firing. Over current relay meant for sensing any internal short circuit, over load condition ,earth fault thereby reducing the system failure & risk of fire.So, for a better protection of the system.It should have both over voltage & over current relay.
Q:If one lamp connects between two phases it will glow or not?
A:If the voltage between the two phase is equal to the lamp voltage then the lamp will glow. When the voltage difference is big it will damage the lamp and when the difference is smaller the lamp will glow depending on the type of lamp.
Q:When voltage increases then current also increases then what is the need of over voltage relay and over current relay? Can we measure over voltage and over current by measuring current only?
A:No.We can't sense the over voltage by just measuring the current only because the current increases not only for over voltages but also for under voltage(As most of the loads are non-linear in nature).So,the over voltage protection & over current protection are completely different. Over voltage relay meant for sensing over voltages & protect the system from insulation break down and firing. Over current relay meant for sensing any internal short circuit, over load condition ,earth fault thereby reducing the system failure & risk of fire.So, for a better protection of the system.It should have both over voltage & over current relay.
Q:If one lamp connects between two phases it will glow or not?
A:If the voltage between the two phase is equal to the lamp voltage then the lamp will glow. When the voltage difference is big it will damage the lamp and when the difference is smaller the lamp will glow depending on the type of lamp.
Q:How do
you select a cable size (Cu & Al) for a particular load?
A:At first calculate the electrical current of the load, after that derate the electrical current considering derating factor(depending on site condition and laying of cable) after choose the cable size from cable catalog considering derating electrical current.After that measure the length of cable required from supply point of load to load poin. Calculate the voltage drop which will max 3% (resistance and reactance of cable found from cable catalog of selecting cable) if voltage drop>3%
then choose next higher size of cable.
Q:What are HRC fuses and where it is used?
A:HRC stand for "high rupturing capacity" fuse and it is used in distribution system for electrical transformers.
Q:Which power plant has high load factor?
A:All base load power plants have a high load factor. If we use high efficiency power plants to supply the base load,we can reduce the cost of generation.Hydel power plants have a higher efficiency than thermal & nuclear power plants.
Q:Mention the methods for starting an induction motor?
A:The different methods of starting an induction motor
DOL:direct online starter
A:At first calculate the electrical current of the load, after that derate the electrical current considering derating factor(depending on site condition and laying of cable) after choose the cable size from cable catalog considering derating electrical current.After that measure the length of cable required from supply point of load to load poin. Calculate the voltage drop which will max 3% (resistance and reactance of cable found from cable catalog of selecting cable) if voltage drop>3%
then choose next higher size of cable.
Q:What are HRC fuses and where it is used?
A:HRC stand for "high rupturing capacity" fuse and it is used in distribution system for electrical transformers.
Q:Which power plant has high load factor?
A:All base load power plants have a high load factor. If we use high efficiency power plants to supply the base load,we can reduce the cost of generation.Hydel power plants have a higher efficiency than thermal & nuclear power plants.
Q:Mention the methods for starting an induction motor?
A:The different methods of starting an induction motor
DOL:direct online starter
Star delta
starter
Auto transformer starter
Resistance starter
Series reactor starter
Q:What is the difference between earth resistance and earth electrode resistance?
A:Only one of the terminals is evident in the earth resistance. In order to find the second terminal we should recourse to its definition: Earth Resistance is the resistance existing between the electrically accessible part of a buried electrode and another point of the earth, which is far away.
The resistance of the electrode has the following components:
(A) the resistance of the metal and that of the connection to it.
(B) the contact resistance of the surrounding earth to the electrode.
Q:What is use of lockout relay in ht voltage?
A: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 and 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.
Q:What is the power factor of an alternator at no load?
A:At no load Synchronous Impedance of the alternator is responsible for creating angle difference. So it should be zero lagging like inductor.
Auto transformer starter
Resistance starter
Series reactor starter
Q:What is the difference between earth resistance and earth electrode resistance?
A:Only one of the terminals is evident in the earth resistance. In order to find the second terminal we should recourse to its definition: Earth Resistance is the resistance existing between the electrically accessible part of a buried electrode and another point of the earth, which is far away.
The resistance of the electrode has the following components:
(A) the resistance of the metal and that of the connection to it.
(B) the contact resistance of the surrounding earth to the electrode.
Q:What is use of lockout relay in ht voltage?
A: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 and 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.
Q:What is the power factor of an alternator at no load?
A:At no load Synchronous Impedance of the alternator is responsible for creating angle difference. So it should be zero lagging like inductor.
Query:How to determine capacitor tolerance
codes?
Resolution:In electronic circuits, the capacitor tolerance can be determined by a code that appears on the casing. The code is a letter that often follows a three-digit number (such as 130Z).The first two are the 1st and 2nd significant digits and the third is a multiplier code. Most of the time the last digit tells you how many zeros to write after the first two digits and these are read as Pico-Farads.
Query:Why most of analog o/p devices having o/p range 4 to 20 mA and not 0 to 20 mA?
Resolution:In electronic circuits, the capacitor tolerance can be determined by a code that appears on the casing. The code is a letter that often follows a three-digit number (such as 130Z).The first two are the 1st and 2nd significant digits and the third is a multiplier code. Most of the time the last digit tells you how many zeros to write after the first two digits and these are read as Pico-Farads.
Query:Why most of analog o/p devices having o/p range 4 to 20 mA and not 0 to 20 mA?
Resolution:4-20 mA is a standard range used to indicate measured
values for any process. The reason that 4ma is chosen instead of 0 mA is for
fail safe operation .For example- a pressure instrument gives output 4mA to
indicate 0 psi, up to 20 mA to indicate 100 psi, or full scale. Due to any problem
in instrument (i.e) broken wire, its output reduces to 0 mA. So if range is
0-20 mA then we can differentiate whether it is due to broken wire or due to 0
psi.
Query:Two bulbs of 100w and 40w respectively connected in series across a 230v supply which bulb will glow bright and why?
Query:Two bulbs of 100w and 40w respectively connected in series across a 230v supply which bulb will glow bright and why?
Resolution:Since two bulbs are in series they will get equal
amount of electrical current but as the supply voltage is constant across the
bulb(P=V^2/R).So the resistance of 40W bulb is greater and voltage across 40W
is more (V=IR) so 40W bulb will glow brighter.
Query:What is meant by knee point voltage?
Resolution:Knee point voltage is calculated for electrical
Current transformers and is very important factor to choose a CT. It is the
voltage at which a CT gets saturated.(CT-current transformer).
Query:What is reverse power relay?
Resolution:Reverse Power flow relay are used in generating
stations's protection. A generating stations is supposed to fed power to the
grid and in case generating units are off,there is no generation in the plant
then plant may take power from grid. To stop the flow of power from grid to
generator we use reverse power relay.
Query:What will happen if DC supply is given on the primary of a transformer?
Resolution:Mainly transformer has high inductance and low resistance.In case of DC supply there is no inductance ,only resistance will act in the electrical circuit. So high electrical current will flow through primary side of the transformer.So for this reason coil and insulation will burn out.
Query:What is the difference between isolators and electrical circuit breakers? What is bus-bar?
Resolution:Isolators are mainly for switching purpose under normal conditions but they cannot operate in fault conditions .Actually they used for isolating the CBs for maintenance. Whereas CB gets activated under fault conditions according to the fault detected.Bus bar is nothing but a junction where the power is getting distributed for independent loads.
Query:What will happen if DC supply is given on the primary of a transformer?
Resolution:Mainly transformer has high inductance and low resistance.In case of DC supply there is no inductance ,only resistance will act in the electrical circuit. So high electrical current will flow through primary side of the transformer.So for this reason coil and insulation will burn out.
Query:What is the difference between isolators and electrical circuit breakers? What is bus-bar?
Resolution:Isolators are mainly for switching purpose under normal conditions but they cannot operate in fault conditions .Actually they used for isolating the CBs for maintenance. Whereas CB gets activated under fault conditions according to the fault detected.Bus bar is nothing but a junction where the power is getting distributed for independent loads.
Query:What are the advantage of free wheeling diode in a Full Wave rectifier?
Resolution:It reduces the harmonics and it also reduces sparking and arching across the mechanical switch so that it reduces the voltage spike seen in a inductive load
Query:What is the function of interposing
current transformer?
Resolution:The main function of an interposing current transformer is to balance the currents supplied to the relay where there would otherwise be an imbalance due to the ratios of the main current transformers. Interposing current transformer are equipped with a wide range of taps that can be selected by the user to achieve the balance required.
Query:What are Motor Generator Sets and explain the different ways the motor generator set can be used ?
Resolution:The main function of an interposing current transformer is to balance the currents supplied to the relay where there would otherwise be an imbalance due to the ratios of the main current transformers. Interposing current transformer are equipped with a wide range of taps that can be selected by the user to achieve the balance required.
Query:What are Motor Generator Sets and explain the different ways the motor generator set can be used ?
Resolution:Motor Generator Sets are a
combination of an electrical generator and an engine mounted together to form a
single piece of equipment. Motor generator set is also referred to as a genset,
or more commonly, a generatorThe motor generator set can used in the following
different ways:
1.Alternating
current (AC) to direct current (DC)
2.DC to AC
3.DC at one voltage to DC at another voltage
4.AC at one frequency to AC at another harmonically-related frequency
Query:What is power quality meter ?
Resolution:Power Quality meters are common in many industrial environment. Small units are now available for home use as well. They give operators the ability to monitor the both perturbations on the power supply, as well as power used within a building, or by a single machine or appliance. In some situations, equipment function and operation is monitored and controlled from a remote location where communication is via modem, or high-speed communication lines.So we can understand the importance of power measurement through power quality meters.
Query:What is the different between digital phase converter and ordinary phase converter?
Resolution:Digital phase converter are a recent development in phase converter technology that utilizes proprietary software in a powerful microprocessor to control solid state power switching components. This microprocessor, called a digital signal processor (DSP), monitors the phase conversion process, continually adjusting the input and output modules of the converter to maintain perfectly balanced three-phase power under all load conditions.
Query:Explain the operation of variable frequency transformer?
Resolution:A variable frequency transformer is used to transmit electricity between two asynchronous alternating current domains. A variable frequency transformer is a doubly-fed electric machine resembling a vertical shaft hydroelectric generator with a three-phase wound rotor, connected by slip rings to one external ac power circuit. A direct-current torque motor is mounted on the same shaft. Changing the direction of torque applied to the shaft changes the direction of power flow; with no applied torque, the shaft rotates due to the difference in frequency between the networks connected to the rotor and stator.The variable frequency transformer behaves as a continuously adjustable phase-shifting transformer. It allows control of the power flow between two networks .
Query:What is the main use of rotary phase converter ?
Resolution:Rotary phase converter will be converting single phase power into true balanced 3 phase power,so it is often called as single phase to three phase converter .Often the advantages of 3 phase motors, and other 3 phase equipment, make it worthwhile to convert single phase to 3 phase so that small and large consumers need not want to pay for the extra cost of a 3 phase service but may still wish to use 3 phase equipment.
2.DC to AC
3.DC at one voltage to DC at another voltage
4.AC at one frequency to AC at another harmonically-related frequency
Query:What is power quality meter ?
Resolution:Power Quality meters are common in many industrial environment. Small units are now available for home use as well. They give operators the ability to monitor the both perturbations on the power supply, as well as power used within a building, or by a single machine or appliance. In some situations, equipment function and operation is monitored and controlled from a remote location where communication is via modem, or high-speed communication lines.So we can understand the importance of power measurement through power quality meters.
Query:What is the different between digital phase converter and ordinary phase converter?
Resolution:Digital phase converter are a recent development in phase converter technology that utilizes proprietary software in a powerful microprocessor to control solid state power switching components. This microprocessor, called a digital signal processor (DSP), monitors the phase conversion process, continually adjusting the input and output modules of the converter to maintain perfectly balanced three-phase power under all load conditions.
Query:Explain the operation of variable frequency transformer?
Resolution:A variable frequency transformer is used to transmit electricity between two asynchronous alternating current domains. A variable frequency transformer is a doubly-fed electric machine resembling a vertical shaft hydroelectric generator with a three-phase wound rotor, connected by slip rings to one external ac power circuit. A direct-current torque motor is mounted on the same shaft. Changing the direction of torque applied to the shaft changes the direction of power flow; with no applied torque, the shaft rotates due to the difference in frequency between the networks connected to the rotor and stator.The variable frequency transformer behaves as a continuously adjustable phase-shifting transformer. It allows control of the power flow between two networks .
Query:What is the main use of rotary phase converter ?
Resolution:Rotary phase converter will be converting single phase power into true balanced 3 phase power,so it is often called as single phase to three phase converter .Often the advantages of 3 phase motors, and other 3 phase equipment, make it worthwhile to convert single phase to 3 phase so that small and large consumers need not want to pay for the extra cost of a 3 phase service but may still wish to use 3 phase equipment.
Query:Use of switch mode power converter
in real-time basis?
Resolution:Switch mode power converter can be used in the following 5 different ways
1) step down an unregulated dc input voltage to produce a regulated dc output voltage using a circuit known as Buck Converter or Step-Down SMPS,
2)step up an unregulated dc input voltage to produce a regulated dc output voltage using a circuit known as Boost Converter or Step-Up SMPS,
3)step up or step down an unregulated dc input voltage to produce a regulated dc output voltage,
4)invert the input dc voltage using usually a circuit such as the Cuk converter, and
5)produce multiple dc outputs using a circuit such as the fly-back converter.
Query:Which type of oil is used as a transformer oil?
Resolution:Switch mode power converter can be used in the following 5 different ways
1) step down an unregulated dc input voltage to produce a regulated dc output voltage using a circuit known as Buck Converter or Step-Down SMPS,
2)step up an unregulated dc input voltage to produce a regulated dc output voltage using a circuit known as Boost Converter or Step-Up SMPS,
3)step up or step down an unregulated dc input voltage to produce a regulated dc output voltage,
4)invert the input dc voltage using usually a circuit such as the Cuk converter, and
5)produce multiple dc outputs using a circuit such as the fly-back converter.
Query:Which type of oil is used as a transformer oil?
Resolution:Transformer oil, or insulating oil, is usually a
highly-refined mineral oil that is stable at high temperatures and has
excellent electrical insulating properties. It is used in oil filled
transformers, some types of high voltage capacitors, fluorescent lamp ballasts,
and some types of high voltage switches and circuit breakers. Its functions are
to insulate, suppress corona and arcing, and to serve as a coolant.
Well into the 1970s, polychlorinated biphenyls (PCB)s were often used as a dielectric fluid since they are not flammable. They are toxic, and under incomplete combustion, can form highly toxic products such as furan. Starting in the early 1970s, concerns about the toxicity of PCBs have led to their banning in many countries.
Today, non-toxic, stable silicon-based or fluoridated hydrocarbons are used, where the added expense of a fire-resistant liquid offsets additional building cost for a transformer vault. Combustion-resistant vegetable oil-based dielectric coolants and synthetic pentaerythritol tetra fatty acid (C7, C8) esters are also becoming increasingly common as alternatives to naphthenic mineral oil. Esters are non-toxic to aquatic life, readily biodegradable, and have a lower volatility and higher flash points than mineral oil.
Query: If we give 2334 A, 540V on Primary side of 1.125 MVA step up transformer, then what will be the Secondary Current, If Secondary Voltage=11 KV?
Resolution:As we know the Voltage & current relation for transformer-V1/V2 = I2/I1
We Know, VI= 540 V; V2=11KV or 11000 V; I1= 2334 Amps.
By putting these value on Relation-
540/11000= I2/2334
So,I2 = 114.5 Amps
Well into the 1970s, polychlorinated biphenyls (PCB)s were often used as a dielectric fluid since they are not flammable. They are toxic, and under incomplete combustion, can form highly toxic products such as furan. Starting in the early 1970s, concerns about the toxicity of PCBs have led to their banning in many countries.
Today, non-toxic, stable silicon-based or fluoridated hydrocarbons are used, where the added expense of a fire-resistant liquid offsets additional building cost for a transformer vault. Combustion-resistant vegetable oil-based dielectric coolants and synthetic pentaerythritol tetra fatty acid (C7, C8) esters are also becoming increasingly common as alternatives to naphthenic mineral oil. Esters are non-toxic to aquatic life, readily biodegradable, and have a lower volatility and higher flash points than mineral oil.
Query: If we give 2334 A, 540V on Primary side of 1.125 MVA step up transformer, then what will be the Secondary Current, If Secondary Voltage=11 KV?
Resolution:As we know the Voltage & current relation for transformer-V1/V2 = I2/I1
We Know, VI= 540 V; V2=11KV or 11000 V; I1= 2334 Amps.
By putting these value on Relation-
540/11000= I2/2334
So,I2 = 114.5 Amps
Query:what are the points to be consider for MCB(miniature circuit breaker selection?
Resolution:I(L)*1.25=I(MAX) maximum current. Mcb specification are done on maximum current flow in circuit.
Query:what is the full form of KVAR?
Resolution:We know there are three types of power in Electrical
as Active, apparent & reactive. So KVAR is stand for ``Kilo Volt Amps with
Reactive component.
Query:What is excitation?
Resolution:Excitation is applying an external voltage to DC shunt coil
in DC motors.
Query:In three pin plug 6 Amp. 220v AC rating. why earth pin diameter is higher than other two pin? what its purpose ?
Resolution: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)
value decreases)
Query:Difference between megger test
equipment and contact resistance meter test instruments?
Resolution: 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.
Query:When we connect the large capacitor bank in series ?
Resolution :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.
Query:What is electrical diversity factor in electrical installations?
Resolution :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.
Query:Why field rheostat is kept in minimum position while armature rheostat at maximum position?
Resolution :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.
Query:Why computer humming sound occurred in HT transmission line?
Resolution :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.
Query:What is rated speed?
Resolution :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.
Query:What is different between resistance grounding system and resistance earthing system?
Resolution :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.
Query: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?
Resolution :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.
Resolution: 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.
Query:When we connect the large capacitor bank in series ?
Resolution :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.
Query:What is electrical diversity factor in electrical installations?
Resolution :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.
Query:Why field rheostat is kept in minimum position while armature rheostat at maximum position?
Resolution :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.
Query:Why computer humming sound occurred in HT transmission line?
Resolution :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.
Query:What is rated speed?
Resolution :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.
Query:What is different between resistance grounding system and resistance earthing system?
Resolution :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.
Query: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?
Resolution :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.
Q:How to determine alternating current
frequency?
A: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.
Q:Why electricity in India is in the multiples of 11 like 11kv, 22kv, 33kv ?
A: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.
Q:Why electricity in India is in the multiples of 11 like 11kv, 22kv, 33kv ?
A: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
Q:Why we use ac system in India why
not dc ?
A: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.
Q:Which type of motor is used in
trains, what is the rating of supply used explain Working principal?
A:Dc series is in the trains to get high starting torque
while starting of the trains and operating voltage is 1500v dc.
Q:Battery banks are in connected in
series or parallel and why?
A: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)
Q:What is inrush current?
A: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.
Q:In a Tap changing transformer where is the tap connected, is it connected in the primary side or secondary side?
A: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.
Q:Why transformer ratings are in kva?
A: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.
Q:In a Tap changing transformer where is the tap connected, is it connected in the primary side or secondary side?
A: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.
Q:Why transformer ratings are in kva?
A: 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.
Q: What is difference between fuse and breaker?
A: 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.
Q:What is the difference between delta-delta, delta-star transformer?
A: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.
Q: Capacitor is load free component but why ampere meter shows current when capacitor bank breaker close?
A: 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.
Q: What is difference between fuse and breaker?
A: 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.
Q:What is the difference between delta-delta, delta-star transformer?
A: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.
Q: Capacitor is load free component but why ampere meter shows current when capacitor bank breaker close?
A: 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.
