Interview-Questions-with-answers

Induction Generator: Induction Generator is a asynchronous Generator that uses the principle of induction motor to generate electricity. Induction Motor as Induction Generator: The induction motor can be used as Induction Generator by making its speed greater than synchronous speed by using Prime mover Conditions for motor to act as generator: Slip produced should be Negative Prime mover torque should be opposite to electrical torque Working: Induction motor can be used as Induction generator by rotating its rotor more than synchronous speed. This  can be attained by using a Prime mover.  In normal motor, the stator is provided with supply, where it produces stator flux, which produces rotor current. Rotor current produces rotor flux opposite to stator flux. This difference produces a positive slip where the stator flux is greater than rotor flux. In Generator, Prime mover is used to rotate rotor greater than synchronous speed with DC excita...

Synchronous Condensor: In electrical engineering, it is considered as a borderline between a motor and generator with no mechanical load  In other words, it is a DC excited synchronous motor whose shaft is connected to nothing It can compensate either lagging or leading power factor by supplying or absorbing reactive power from the line It is also called as synchronous Condensor or synchronous compensator Working: Kinetic energy stored in motor of machine will help to stable a power system during rapid fluctuations of load  It involves three conditions based on power factor: Under Excitation   Unity or Ideal  Over Excitation  Under excitation: In under excited condition, the machine will operate at lagging power factor  It draws lagging current from the supply line  Lagging power factor can be corrected by supplying reactive power   Reactive power drawn from capacitor bank decreases when grid Voltage decrea...

1. What is Flip Flop?      It is an electronic circuit with two stable states that can be used to store binary data. The stored data can be changes by changing the input. It is also called as latching 2. What is transistor? Transistor is an electronic device used to amplify or switch Signal  It is a three terminal device made up of semiconductor material  These terminals are used to connect with external circuit 3. What is NPN transistor? It consists of one P doped semiconductor material in between two N doped semiconductor materials It passes electrons from emitter to collector so the current flow from collector to emitter  The emitter emits electrons into base which controls number of electrons that emitter emits 4. What is PNP transistor? It consists of  N doped semiconductor material in between two P doped semiconductor layer It emits electrons from collector to emitter so the current flow from emitter to collecto...

1. What is Rectifier?      It is an electrical device which converts Alternating current into Direct current which allows the current to flow in only one direction by using one or more PN junction diode. 2. What is Phase Controlled Rectifier?       Phase Controlled Rectifier converts AC to DC by using thyristor instead of diode. As diode has no control over output, where as SCR can control it's output by adjusting firing angle 3. When Rectifier will acts as an inverter?       When the phase angle alpha becomes greater than 90° rectifier will acts as an inverter 4. What is firing angle?      SCR doesnot turn on until anode Voltage becomes greater than cathode Voltage. To make anode Voltage greater than cathode Voltage pulse Signal are applied to gate of SCR. The angle at which thyristor gate is fired with pulse Signal is called as firing angle 5. What is triggering in SCR?     SCR has two stable s...

Definition: It is defined as the rotating electrical device connected to motor or generator through which an electrical connection can be made  to the load such that it always reverses the current that flows between the motor or generator and the load. In other words, commutator is defined as the splitting device used to keep torque in DC motor from reversing every time, when the coil moves to the plane perpendicular to the magnetic field. Application of commutator:   It is used in : DC motor DC generator Universal motors Use of commutator in motor: In motor, commutator applies the electrical current to the windings, then it reverses these current flow for each half cycle in the rotating windings, thus a steady rotating force called torque is produced to rotate the load Use of commutator in generator :  In generator, commutator picks off the current from the windings and reverses these current for every half cycle such that it converts current fr...

1. What is Power Electronics?     Power Electronics is the branch of electronics which deals with the control and conversion of electric signals. It uses switches, semiconductor devices for control and conversion. 2. What are the Semiconductor Devices? Bipolor Junction Transistor(BJT) Metal Oxide Semiconductor Field Effect Transistor(MOSFET) Power Diode Insulated-Gate Bipolor Transistor (IGBT) Thyristor or Silicon Controlled Rectifier(SCR) 3. What are current controlled power electronic devices? BJT SCR GTO GTR 4. What are voltage controlled power electronics device? MOSFET IGBT MCT IGCT SIT 5 . How BJT is considered as a current control device?     BJT is a current controlled device because its output characteristics are determined by its input characteristics as the base current controls the flow of current between the emitter and collector 6. How FET devices are considered as a voltage controlled device?  ...

Load Condition of synchronous motor: If the synchronous motor is to be loaded, the following conditions need to be satisfied. The conditions are: Motor should be able to run continuously at its synchronous speed even if it is loaded Torque angle  δ should increase with increases in Load Magnitude of excitation voltage Vo and field excitation Ef should remain constant as                           V = Ef + Ia Xs Armature current Ia drawn from the supply should increase Phase angle ϕ should increase in the lagging direction As the load on shaft increases the speed of rotor decreases. After sometime it increases by increasing the power from line and the speed of rotor increases. Such that rotor starts to rotate at Synchronous speed as the rotor slips back in space to increase the torque angle. As the torque angle increases the induced torque increases. Above conditions are derived from the equation: ...

Synchronous motor vs Induction motor: In AC motor there are two types: Synchronous motor Asynchronous motor or Induction motor Lets see the main difference between synchronous and Asynchronous motor: 1. In construction wise : Synchronous motor has stator wounded on winding for specific number of poles and a salient pole rotor which is energized by DC supplysimilar to that of synchronous motor but the rotor may be short circuited squirrel cage or changing slip ring 2. In Speed wise : As we know Synchronous motor always runs at Synchronous speed where as Induction motor runs at speed less than\n synchronous speed Synchronous speed: N =Ns Induction motor speed: N<Ns   3. In working principle wise : Synchronous motor principle is magnetic locking , where as Induction motor principle is Relative Magnetic Field (RMF) as it is based on Lenz law 4. In power factor wise : Synchronous motor has the ability to operate in leading, lagging and unity where as Induct...

The Resistor is covered with plastic coat with different color coated is called as color coding. Each and every color coated on the resistor insists the range of resistance in it. Resistance with color coding Lets us see the value for each color on the resistor: The plastic coat of the resistor may consists of Black Brown Red Orange Yellow Green Blue Violet Grey White Gold Silver Resistor Color Values In this color starting from Black to White will available in 1st to 3rd digit and it implies the numerical value where as Gold and Silver will always appear as tolerance. The colors with their ranges are given in Resistor Color values. There are different number of band available in resistor. It starts from 3 band to 5 band. How to Calculate Resistance: The calculation of resistance starts from right to left. The first and second digit of color will take numerical values. Where as third digit will take multiplier and fourth digit will take tole...

Definition:  It is a two terminal passive electrical Component that resists the flow of current in circuit Resistor  How it Works: It converts electrical energy into heart which will dissipated into Air Uses of Resistor: Reduce Current Flow Adjust Signal levels Divide Voltage Bias Active Element Unit of Measurement:      Unit of Resistor is Ohm which is name after the scientist George Simon Ohm Types of Resistor: There are two main types of Resistor: Linear Resistor  Non-Linear Resistor  Linear Resistor: Linear Resistor is a resistor those Value changes with change in temperature and current  Types of Linear Resistor: Fixed Resistor  Variable Resistor  Fixed Resistor:  In this the Value of Resistor is fixed it doesnot change with changes with temperature and Current  Types of Fixed Resistor: Carbon Film Resistor  Wire wound Resistor  Thin Film Resist...

1. What is Power System? It is a branch of electrical engineering which deals with the study of generation, transmission, distribution and utilization of electrical energy 2. What is Power Factor? The cosine of angle between voltage and the current in an AC circuit is known as power factor 3. How should be power factor for the good working system? Power Factor should be less than 1 for the good working system 4. What is one line diagram? One line diagram is a single line representation of  three phase power system It consists of symbol representation of  bus bar, Generator, Alternator, e.t.c [caption id="attachment_91" align="alignnone" width="624"]                                                                one line diagram 5. W...

1.  Why AC current is used for transmission?  AC current is used for transmission because it can be step up for transmission purpose and step down  for distribution The output of rotating turbine is AC hence there is no necessary for convert into DC The losses and maintenance cost are high for DC then for AC 2. Why AC is stepped up before transmission ? To reduce the volume of conductor used To reduce the voltage drop and percentage line drop To reduce the loss and increase losses 3. What are the types of transmission lines? Balanced two wire Co-axial Cable Wave guide Micro strip Fiber optic 4. What is Balanced two wire system? Two wires are separated by insulators 5. What is Co-axial cable? This consists of inner conducting copper wire surrounded by polyethylene. The outer surface is surrounded by plastic layer to prevent damage. 6. What is difference between co-axial and Balanced two wire system? In co-axial cable the outer surface is ground...

1. What is transformer?     A transformer is a static electrical device that transfers electrical energy between two or more circuits through electromagnetic induction without any electrical connection between the circuits. 2. What is the principle of transformer?       Mutual inductance 3. What is mutual inductance?       Mutual induction is defined as the current flowing in one coil that induces a voltage in an adjacent coil. 4. What are the types of transformer based on the voltage levels? Step up transformer Step down transformer 5. What are the types of transformer based on the core medium used? Air core transformer Iron core transformer 6. What are the types of transformer based on the core arrangement? Core type Shell type 7. What are the other common  types of transformer? Auto transformer Variable frequency transformer Resonant transformer Power ...

Here are some of the basic questions asked in interviews for EEE students 1. what is the principle of motor?       The electric motor is based on the principle that whenever a current carrying conductor is placed in an magnetic field it experiences a mechanical force i.e turning or twisting movement is called as torque. 2. what is the principle of generator?   The electric generator is based on the principle of faraday's law of electromagnetic induction. Such that whenever a current carrying conductor is placed in an varying magnetic field it induces an emf in it. 3. what are the types of DC motor? Series motor Shunt motor Compound motor Permanent magnet DC motor 4. What are the types of AC motor? Synchronous motor Asynchronous motor 5. What is Synchronous motor?       Synchronous motor is a kind of AC motor where the rotation of the shaft is synchronized with the frequency of the supply current at steady ...