Why star delta starter is preferred with induction motor?Star delta starter is preferred with induction motor due to following reasons: Starting current is reduced 3-4 times of the direct current due to which voltage drops and hence it causes less losses. Star delta starter circuit comes in circuit first during starting of motor, which reduces voltage 3 times, that is why current also reduces up to 3 times and hence less motor burning is caused. In addition, starting torque is increased and it prevents the damage of motor winding.State the difference between generator and alternatorGenerator and alternator are two devices, which converts mechanical energy into electrical energy. Both have the same principle of electromagnetic induction, the only difference is that their construction. Generator persists stationary magnetic field and rotating conductor which rolls on the armature with slip rings and brushes riding against each other, hence it converts the induced emf into dc current for external load whereas an alternator has a stationary armature and rotating magnetic field for high voltages but for low voltage output rotating armature and stationary magnetic field is used.Why AC systems are preferred over DC systems?Due to following reasons, AC systems are preferred over DC systems:a. It is easy to maintain and change the voltage of AC electricity for transmission and distribution.b. Plant cost for AC transmission (circuit breakers, transformers etc) is much lower than the equivalent DC transmissionc. From power stations, AC is produced so it is better to use AC then DC instead of converting it.d. When a large fault occurs in a network, it is easier to interrupt in an AC system, as the sine wave current will naturally tend to zero at some point making the current easier to interrupt.How can you relate power engineering with electrical engineering?Power engineering is a sub division of electrical engineering. It deals with generation, transmission and distribution of energy in electrical form. Design of all power equipments also comes under power engineering. Power engineers may work on the design and maintenance of the power grid i.e. called on grid systems and they might work on off grid systems that are not connected to the system.What are the various kind of cables used for transmission?Cables, which are used for transmitting power, can be categorized in three forms: Low-tension cables, which can transmit voltage upto 1000 volts. High-tension cables can transmit voltage upto 23000 volts. Super tension cables can transmit voltage 66 kV to 132 kV.Why back emf used for a dc motor? highlight its significance.The induced emf developed when the rotating conductors of the armature between the poles of magnet, in a DC motor, cut the magnetic flux, opposes the current flowing through the conductor, when the armature rotates, is called back emf. Its value depends upon the speed of rotation of the armature conductors. In starting, the value of back emf is zero.What is slip in an induction motor?Slip can be defined as the difference between the flux speed (Ns) and the rotor speed (N). Speed of the rotor of an induction motor is always less than its synchronous speed. It is usually expressed as a percentage of synchronous speed (Ns) and represented by the symbol S.Explain the application of storage batteries.Storage batteries are used for various purposes, some of the applications are mentioned below: For the operation of protective devices and for emergency lighting at generating stations and substations. For starting, ignition and lighting of automobiles, aircrafts etc. For lighting on steam and diesel railways trains. As a supply power source in telephone exchange, laboratories and broad casting stations. For emergency lighting at hospitals, banks, rural areas where electricity supplies are not possible.9. Explain advantages of storage batteriesFew advantages of storage batteries are mentioned below: Most efficient form of storing energy portably. Stored energy is available immediately because there is no lag of time for delivering the stored energy. Reliable source for supply of energy. The energy can be drawn at a fairly constant rate.10. What are the different methods for the starting of a synchronous motor.Starting methods: Synchronous motor can be started by the following two methods: By means of an auxiliary motor: The rotor of a synchronous motor is rotated by auxiliary motor. Then rotor poles are excited due to which the rotor field is locked with the stator-revolving field and continuous rotation is obtained. By providing damper winding: Here, bar conductors are embedded in the outer periphery of the rotor poles and are short-circuited with the short-circuiting rings at both sides. The machine is started as a squirrel cage induction motor first. When it picks up speed, excitation is given to the rotor and the rotor starts rotating continuously as the rotor field is locked with stator revolving field.11. Name the types of motors used in vacuum cleaners, phonographic appliances, vending machines, refrigerators, rolling mills, lathes, power factor improvement and cranes.Following motors are used: - Vacuum cleaners- Universal motor. Phonographic appliances Hysteresis motor. Vending machines Shaded pole motor. Refrigerators Capacitor split phase motors. Rolling mills Cumulative motors. Lathes DC shunt motors. Power factor improvement Synchronous motors.12. State Thevenins Theorem:According to thevenins theorem, the current flowing through a load resistanceConnected across any two terminals of a linear active bilateral network is the ratio open circuit voltage (i.e. the voltage across the two terminals when RL is removed) and sum of load resistance and internal resistance of the network. It is given by Voc / (Ri + RL).13. State Nortons TheoremThe Nortons theorem explains the fact that there are two terminals and they are as follows: One is terminal active network containing voltage sources Another is the resistance that is viewed from the output terminals. The output terminals are equivalent to the constant source of current and it allows giving the parallel resistance.The Nortons theorem also explains about the constant current that is equal to the current of the short circuit placed across the terminals. The parallel resistance of the network can be viewed from the open circuit terminals when all the voltage and current sources are removed and replaced by the internal resistance.14. State Maximum power transfer theoremThe Maximum power transfer theorem explains about the load that a resistance will extract from the network. This includes the maximum power from the network and in this case the load resistance is being is equal to the resistance of the network and it also allows the resistance to be equal to the resistance of the network. This resistance can be viewed by the output terminals and the energy sources can be removed by leaving the internal resistance behind.Explain different losses in a transformer.There are two types of losses occurring in transformer: Constant losses or Iron losses: The losses that occur in the core are known as core losses or iron losses. Two types of iron losses are:o eddy current losso Hysteresis loss.These losses depend upon the supply voltage, frequency, core material and its construction. As long as supply voltage and frequency is constant, these losses remain the same whether the transformer is loaded or not. These are also known as constant losses. Variable losses or copper losses: when the transformer is loaded, current flows in primary and secondary windings, there is loss of electrical energy due to the resistance of the primary winding, and secondary winding and they are called variable losses. These losses depend upon the loading conditions of the transformers. Therefore, these losses are also called as variable losses.16. Explain different types of D.C motors? Give their applicationsDifferent type of DC motors and their applications are as follows:- Shunt motors: It has a constant speed though its starting torque is not very high. Therefore, it is suitable for constant speed drive, where high starting torque is not required such as pumps, blowers, fan, lathe machines, tools, belt or chain conveyor etc. Service motors: It has high starting torque & its speed is inversely proportional to the loading conditions i.e. when lightly loaded, the speed is high and when heavily loaded, it is low. Therefore, motor is used in lifts, cranes, traction work, coal loader and coal cutter in coalmines etc. Compound motors: It also has high starting torque and variable speed. Its advantage is, it can run at NIL loads without any danger. This motor will therefore find its application in loads having high inertia load or requiring high intermittent torque such as elevators, conveyor, rolling mill, planes, presses, shears and punches, coal cutter and winding machines etc.17. Explain the process of commutation in a dc machine. Explain what are inter-poles and why they are required in a dc machine.Commutation: It is phenomenon when an armature coil moves under the influence of one pole- pair; it carries constant current in one direction. As the coil moves into the influence of the next pole- pair, the current in it must reverse. This reversal of current in a coil is called commutation. Several coils undergo commutation simultaneously. The reversal of current is opposed by the static coil emf and therefore must be aided in some fashion for smooth current reversal, which otherwise would result in sparking at the brushes. The aiding emf is dynamically induced into the coils undergoing commutation by means of compoles or interpoles, which are series excited by the armature current. These are located in the interpolar region of the main poles and therefore influence the armature coils only when these undergo commutation.18. Comment on the working principle of operation of a single-phase transformer.Working principle of operation of a single-phase transformer can be explained asAn AC supply passes through the primary winding, a current will start flowing in the primary winding. As a result, the flux is set. This flux is linked with primary and secondary windings. Hence, voltage is induced in both the windings. Now, when the load is connected to the secondary side, the current will start flowing in the load in the secondary winding, resulting in the flow of additional current in the secondary winding. Hence, according to Faradays laws of electromagnetic induction, emf will be induced in both the windings. The voltage induced in the primary winding is due to its self inductance and known as self induced emf and according to Lenzes law it will oppose the cause i.e. supply voltage hence called as back emf. The voltage induced in secondary coil is known as mutually induced voltage. Hence, transformer works on the principle of electromagnetic induction.19. Define the following terms:- Reliability, Maximum demand, Reserve-generating capacity, Availability (operational).Reliability: It is the capacity of the power system to serve all power demands without failure over long periods.Maximum Demand: It is maximum load demand required in a power station during a given period.Reserve generating capacity: Extra generation capacity installed to meet the need of scheduled downtimes for preventive maintenance is called reserve-generating capacity.Availability: As the percentage of the time a unit is available to produce power whether needed by the system or not.20. Mention the disadvantages of low power factor? How can it be improved?Disadvantages of low power factor: Line losses are 1.57 times unity power factor. Larger generators and transformers are required. Low lagging power factor causes a large voltage drop, hence extra regulation equipment is required to keep voltage drop within prescribed limits. Greater conductor size: To transmit or distribute a fixed amount of power at fixed voltage, the conductors will have to carry more current at low power factor. This requires a large conductor size.State the methods of improving power factor?Methods of improving power factor: By connecting static capacitors in parallel with the load operating at lagging power factor. A synchronous motor takes a leading current when over excited and therefore behaves like a capacitor. By using phase advancers to improve the power factor of induction motors. It provides exciting ampere turns to the rotor circuit of the motor. By providing more ampere-turns than required, the induction motor can be made to operate on leading power factor like an overexcited synchronous motor.22. State the factors, for the choice of electrical system for an aero turbine.The choice of electrical system for an aero turbine is guided by three factors: Type of electrical output: dc, variable- frequency ac, and constant- frequency ac. Aero turbine rotational speed: constant speed with variable blade pitch, nearly constant speed with simpler pitch- changing mechanism or variable speed with fixed pitch blades. Utilization of electrical energy output: in conjunction with battery or other form of storage, or interconnection with power grid.23. What are the advantages of VSCF wind electrical system?Advantages of VSCF wind electrical system are: No complex pitch changing mechanism is needed. Aero turbine always operates at maximum efficiency point. Extra energy in the high wind speed region of the speed duration curve can be extracted Significant reduction in aerodynamic stresses, which are associated with constant speed operation.24. Explain the terms real power, apparent power and reactive power for ac circuits and also the units used. Real Power: It is the product of voltage, current and power factor i.e. P = V I cos j and basic unit of real power is watt. i.e. Expressed as W or kW. Apparent power: It is the product of voltage and current. Apparent power = V I and basic unit of apparent power is volt- ampere. Expressed as VA or KVA. Reactive Power: It is the product of voltage, current and sine of angle between the voltage and current i.e. Reactive power = voltage X current X sinj or Reactive power = V I sin j and has no other unit but expressed in VAR or KVAR.25. Define the following: Average demand, Maximum demand, Demand factor, Load factor. Average Demand: the average power requirement during some specified period of time of considerable duration is called the average demand of installation. Maximum Demand: The maximum demand of an installation is defined as the greatest of all the demand, which have occurred during a given period. It is measured accordingly to specifications, over a prescribed time interval during a certain period. Demand Factor: It is defined as the ratio of actual maximum demand made by the load to the rating of the connected load. Load Factor: It is defined as the ratio of the average power to the maximum demand.

Basic Electrical & Electronics Engineering and Technology Interview Questions & Answers1. Why we cant store AC in Batteries instead of DC?2. Why Motor rated in kW instead of kVA?3. Why Battery rated in Ah (Ampere hour) and not in VA.4. Three Phase Induction Motors (MCQs with Explanatory Answers)5. The Main Difference between Active and passive Components (Very Easy Explanation with Examples)6. Batteries. (MCQs with Explanatory Answers)7. How to find The value of Burnt Resistor ( By three handy Methods )8. Capacitors (MCQs with Explanatory Answers)9. How to Calculate/Find the value of Ceramic / Non-Polarized Capacitors?10. Why Power is Zero (0), in Pure Inductive, Pure Capacitive or a circuit in which Current and Voltage are 90 Degree out of phase?11. Basic Concepts (MCQs With Explanatory Answers)12. DC Circuits (MCQs with Explanatory Answers.)13. Alternator / Generator ( MCQs with Explanatory Answers)14. Transformer (MCQs With Explanatory Answers)15. A (50/60 Hz) Transformer. Which one will give more Output? (When operates on 50 or 60 Hz frequency)16. Why the circuit Current (I) decrease, when Inductance (L) or inductive reactance (XL) increases in inductive circuit?17. Why the Circuit Power factor (Cos ) Decreases, when Inductance (L) or inductive reactance (XL) increases, In inductive circuit?18. Single Phase AC Circuits. MCQs ( With Explanatory Answers)19. In inductive circuit, Why Current increases, when frequency Decreases?20. Three Phase AC Circuits (MCQs With Explanatory Answers)21. What is Main Difference b/w Electrical and Electronics Engineering? ( Very Simple)22. Easy Charging Time and Charging Current Formula for Batteries. ( with Example of 120Ah Battery).23. How To remember the direction of PNP and NPN Transistor. One of the Easiest way.24. What is the Rule of Capacitor in AC and DC Circuit?25. Batteries Configuration. These Batteries have Connected in series or parallel? Clear Your Concept.26. A Bulb is Connected in this strange way with Ammeter as shown in fig. then what will be the current in Amp-Meter? (Clear Your Concept)27. Clear Your Concept. What will be the Current In ampere-meter which connected in Short path in This Basic Circuit.?28. Clear Your Concept. What will be the Current In ampere-meter in This Basic Circuit.?29. Ampere meter is connected in series with load. if there is also a short path, then what will be the current in Amp-Meter? (As shown Below)30. What is the normal or average life expectancy of a Transformer ?31. Why Flux in Primary and Secondary Winding of the Transformer is Same? With a Simple Explanation and Example.32. According to Ohms Law, Current increases, when Voltage increases,(I=V/R), But Current decreases, when Voltage increases according to (P=VI). Explain?33. What is the difference between a battery and a capacitor?34. Why A.C needs more insulation than D.C at same voltage level?35. What is The Difference between a VOLTAMETER and a VOLTMETER?36. What is the objection to have lamps in a house-lighting circuit connected in series?37. How To Find/Calculate the Number of Fluorescent Lamps in a Sub Circuit?38. How to Determine the Number of Lamps in Final Sub Circuit?39. How much Watts Solar Panel We need for our Home Electrical appliances?40. Will a D.C Shunt Motor operate on an A.C Supply?41. Why the reactance of a system under fault condition is low and faults currents may raise dangerously high value. ? (With simple example)42. Explain the statement that induction motor is fundamentally a Transformer?43. What is the difference between Power Transformers and Distribution Transformers?44. What is the purpose of ground wires in over-Head Transmission lines?45. What is the difference between real ground and virtual ground?46. How To Calculate Your Electricity Bill. Easy and simple Explanation.47. Under what condition is D.C supply applied safely to the primary of a transformer?48. A step up transformer which has 110/220 turns. Can we replace it with 10/20 turns? Turns ratio is same shall its rating be same? Give appropriate reason?49. What are the fundamental differences between E.M.F (Electro motive force) and P.d (Potential difference)?50. Why alternator rated in kVA. Not in kW?51. Can we operate a 60HZ Transformer on 50Hz Supply Source and Vice Versa?52. What would happen if a power transformer designed for operation on 50 Hz (frequency) were connected to a 5 Hz (frequency) source of the same voltage?53. What would happen if a power transformer designed for operation on 50 Hz (frequency) were connected to a 500 Hz (frequency) source of the same voltage?54. What will happen if the primary of a transformer is connected to D.C supply?55. Why Transformer Rating In kVA, Not in KW?56. Main Difference between contactor and Starter.57. Why We Need to Install a Starter with a Motor?58. Why XL (Inductive Reactance) In DC Supply Is Zero (0)?59. What is motor starter?60. How to calculate the value of resistor for LEDs (with different types of LEDs circuits)61. How to Calculate/Find the Rating of Transformer in kVA (Single Phase and Three Phase)?62. How to Check a Capacitor with Digital (Multi meter) and Analog (AVO Meter). By Four (4) Methods with pictorial View.63. What is the Q Factor in Electrical and Electronics Engineering64. How to Get Connection from Solar Panel. Back Side of The Solar Panel Junction Box and The Function of Diodes in it.65. Power Factor improvement Methods with Their advantages & Disadvantages66. Causes of Low power Factor67. Advantages of Power factor improvement and Correction:68. How to Calculate the Suitable Capacitor Size in Farads & kVAR for Power factor Improvement (Easiest way ever)69. How to Convert Capacitor Farads into kVAR and Vice Versa (For Power factor improvement)70. Why Power Plant Capacity Rated in MW and not in MVA?71. Working and Construction of Electric Phase or Line Tester72. How to find Diversity Factor in Electrical Wiring Installation73. Series, Parallel and Series-Parallel Configuration of Batteries74. How to Connect a Portable Generator to Home Supply System (Three Methods)75. Nortons Theorem. Easy Step by Step Procedure with Example (Pictorial Views)76. Thevenins Theorem. Easy Step by Step Procedure with Example (Pictorial Views)77. Difference between Unilateral and Bi-Lateral Circuits & Elements78. How to determine the number of Nodes, Branches, Loops and Meshes in a Circuit?79. What is The Main Difference between Linear and Nonlinear Circuit80. A Voltmeter, an ammeter (Ampere meter) and a battery cell are connected in series. It is observed that ammeter practically shows No Deflection. Why?81. How to calculate or Find the value of SMD Resistors82. How to determine the suitable size of cable for Electrical Wiring Installation with Solved Examples (in both British and Si System)83. What is the difference between AC and DC Resistance & How to calculate it?84. Electric circuits / Networks and important terms related to it you must know

What is the Scope of Electrical Engineering?[ This question is mostly asked to check your communication. Speak casually. Tell the importance of electrical and electronics engineering course, what are the topics to be covered in the course, what are the job prospects etc.]

Answer:Electrical Engineering has a very broad scope with the science and technology which involves electricity, electronics, and electromagnetism in order to design, construct, and maintain products, services, and information systems.Electrical Engineering is a branch that deals with the field associated with power transmission and motor control.Electrical engineering is one of the core fields of engineering, so it is always evergreen in terms of job prospects.Electrical Engineering is the heart of whole engineering discipline.Nowadays, we see Electronics playing an important role in the implementation and control of Electrical Machines. Keeping this fact file in mind the course have transformed from core electrical Engineering into a Fusion of Electronics and Electrical and has been renamed as Electronics and Electrical engineering.Electricity has become the basic need for survival, globally. From household to industrial plants, communication and satellite navigation system, electronic equipment, computers etc., all require electricity.Electrical engineering thus deals with study and applicationof electrical systems for use in these different environments. It equips you with the knowledge of transmission and generation of electrical power, electrical circuit design,electronics, instrumentation, control system, understanding electrical and electronic networks etc.The course also covers the study of electronic devicesand circuits involved in measurement, instrumentation, control and protection of electrical equipments and conversion systems. Concept of computer and recent applications of computer based systems in design, analysis and efficient operation of power system, maintaining quality and security, also included in the course.

What does '230V AC Supply' really mean? Is it the RMSor peak voltage?If the peak value is meant it should be clearlystated, otherwise assume it is theRMS value.The supply is 230V AC means 230V RMS,so the peak voltage of the mains is about 320V.

What does the multimeter in volt meter mode show? Is it the RMS orpeak voltage?If the multimeter is in voltmeter mode and when it connects to AC circuits it shows theRMSvalueof the voltage or current. When it connects to varying DC signals it will show RMS value only.

How does Induction Motor work?Induction motors are also known as rotating transformer.( Primary winding is stator and secondary winding is rotor).When the 3 phase stator windings are fed by 3 phase supply a magnetic flux of constant magnitude, rotating at synchronous speed is generated. These flux passes through the air gap, sweeps past the rotor surface, cuts stationary rotor conductors.According to Faraday's laws of electro-magnetic induction, an emf is induced in the rotor. This emf frequency is same as supply frequency.As rotor conductors form a closed circuit, the induced emf produces a current. It's direction will oppose the cause producing it ( according to lenz's law).In this case, the cause is relative velocity between the rotating flux of the stator and stationary rotor conductors. So to reduce the relative speed, the rotor starts to run in the same direction of the stator flux.