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Electrical engineering interview questions and answers 
 
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<tr height="30px" width="50%"><td position="relative" style="padding: 6px 15px 5px 20px; vertical-align: top;"><a href="http://qexampre.com/engineering/electrical-engineering/electrical-engineering-online-test1/" style="background-color: inherit; background-image: url(data:image/png; background-position: 0% 50%; background-repeat: no-repeat no-repeat; color: #3366cc; padding-left: 20px; text-decoration: none;">Electrical Engineering Online Test1</a></td></tr>
<tr height="30px" width="50%"><td position="relative" style="padding: 6px 15px 5px 20px; vertical-align: top;"><a href="http://qexampre.com/engineering/electrical-engineering/electrical-engineering-online-test/" style="background-color: inherit; background-image: url(data:image/png; background-position: 0% 50%; background-repeat: no-repeat no-repeat; color: #3366cc; padding-left: 20px; text-decoration: none;">Electrical Engineering Online Test</a></td></tr>
<tr height="30px" width="50%"><td position="relative" style="padding: 6px 15px 5px 20px; vertical-align: top;"><a href="http://qexampre.com/engineering/electrical-engineering/ac-fundamentals/" style="background-color: inherit; background-image: url(data:image/png; background-position: 0% 50%; background-repeat: no-repeat no-repeat; color: #3366cc; padding-left: 20px; text-decoration: none;">AC Fundamentals</a></td></tr>
<tr height="30px" width="50%"><td position="relative" style="padding: 6px 15px 5px 20px; vertical-align: top;"><a href="http://qexampre.com/engineering/electrical-engineering/power-electronics/" style="background-color: inherit; background-image: url(data:image/png; background-position: 0% 50%; background-repeat: no-repeat no-repeat; color: #3366cc; padding-left: 20px; text-decoration: none;">Power Electronics</a></td></tr>
<tr height="30px" width="50%"><td position="relative" style="padding: 6px 15px 5px 20px; vertical-align: top;"><a href="http://qexampre.com/engineering/electrical-engineering/electrostatics/" style="background-color: inherit; background-image: url(data:image/png; background-position: 0% 50%; background-repeat: no-repeat no-repeat; color: #3366cc; padding-left: 20px; text-decoration: none;">Electrostatics</a></td></tr>
<tr height="30px" width="50%"><td position="relative" style="padding: 6px 15px 5px 20px; vertical-align: top;"><a href="http://qexampre.com/engineering/electrical-engineering/control-systems/" style="background-color: inherit; background-image: url(data:image/png; background-position: 0% 50%; background-repeat: no-repeat no-repeat; color: #3366cc; padding-left: 20px; text-decoration: none;">Control Systems</a></td></tr>
<tr height="30px" width="50%"><td position="relative" style="padding: 6px 15px 5px 20px; vertical-align: top;"><a href="http://qexampre.com/engineering/electrical-engineering/circuit-theory/" style="background-color: inherit; background-image: url(data:image/png; background-position: 0% 50%; background-repeat: no-repeat no-repeat; color: #3366cc; padding-left: 20px; text-decoration: none;">Circuit Theory</a></td></tr>
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<tr height="30px" width="50%"><td position="relative" style="padding: 6px 15px 5px 20px; vertical-align: top;"><a href="http://qexampre.com/engineering/electrical-engineering/alternating-current-fundamentals/" style="background-color: inherit; background-image: url(data:image/png; background-position: 0% 50%; background-repeat: no-repeat no-repeat; color: #3366cc; padding-left: 20px; text-decoration: none;">Alternating Current Fundamentals</a></td></tr>
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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: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)</div>
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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. 
 
 
Practice More Questions At :- http://qexampre.com 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.</div>
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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. 
 
Practice More Questions At :- http://qexampre.com 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 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)</div>
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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: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. 
 
Practice More Questions At :- http://qexampre.com 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.</div>
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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: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? 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. 
 
Practice More Questions At :- http://qexampre.com 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</div>
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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 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.</div>
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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. 
 
 
Practice More Questions At :- http://qexampre.com 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?  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.</div>
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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: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. 
 
Practice More Questions At :- http://qexampre.com 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.</div>
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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.</div>
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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. 
 
Practice More Questions At :- http://qexampre.com 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. 
 
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<tr height="30px" width="50%"><td position="relative" style="padding: 6px 15px 5px 20px; vertical-align: top;"><a href="http://qexampre.com/engineering/electrical-engineering/electrical-engineering-online-test1/" style="background-color: inherit; background-image: url(data:image/png; background-position: 0% 50%; background-repeat: no-repeat no-repeat; color: #3366cc; padding-left: 20px; text-decoration: none;">Electrical Engineering Online Test1</a></td></tr>
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