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State the need for reduction of harmonics in inverters. Enlist the various methods for reduction of harmonics in inverter output.

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Answer : The main reason for generation of harmonics in a transformer could be saturation of core.

Answer : When a bogie negotiates a curve, reduction in adhesion occurs resulting in sliding. Thus sliding is acute when wheel base of axles is more, degree of curvature is more.

Description : Reduction in core losses and increase in permeability are obtained with transformer employing?

Answer : Reduction in core losses and increase in permeability are obtained with transformer employing core built-up of laminations of cold rolled grain oriented steel.

Description : Purpose of Selective Catalytic Reduction (SCR)

Answer : Purpose of Selective Catalytic Reduction (SCR) : 1. It reduces Nox 75% to 90% 2. Converts it in to molecular nitrogen and water vapor 3. It reduces HC emission up to 80% 4. It reduces PM emission 20 to 25%.

Description : Slot harmonics are reduced in induction motors by using (A) fractional-pitch windings (B) fractional-slot windings (C) integral-slot windings (D) distributed windings

Answer : Slot harmonics are reduced in induction motors by using fractional-slot windings

Answer : Harmonics in transformer result in increased core losses, increased I2R losses, and magnetic interference with communication circuits.

Description : Why harmonics are generated in electrical system?

Description : Explain the effect of Harmonics on the Transformer.

Answer : Effect of Harmonics on the Transformer:  1. Core loss: Harmonic voltage increases the hysteresis and eddy current losses in the lamination. The amount of the core loss depends on ... small core vibrations.  5. Saturation problem: Sometimes additional harmonic voltage causes core saturation.

Description : What is mitigation of harmonics?

Description : What is current harmonics?

Description : What are even and odd harmonics?

Description : What are the main causes of harmonics?

Answer : Harmonic is a non linear load because linear load voltage deviated due to connection of some electrinie device such as converter,inverter

Description : Why do non linear loads cause harmonics?

Description : Explain the pulse width modulation technique for control of AC output voltage.

Description : Why thyristor are not preferred for inverter?

Description : Explain DC coupled drive circuit with unipolar output.

Answer : DC coupled drive circuit with unipolar output: The figure shows the circuit and waveforms

Description : A voltage source inverter will have better performance if its  (1) load inductance is small and source inductance is large.  (2) both load and source inductance are small.  (3) both load and source inductances are large.  (4) load inductance is large and source inductance is small. 

Answer : A voltage source inverter will have better performance if its load inductance is large and source inductance is small. 

Description : A voltage source inverter is normally employed when  (1) source inductance is large and load inductance is small (2) source inductance is small and load inductance is large (3) both source and load inductance are small (4) both source and load inductance are large

Answer : 3

Description : Explain three phase bridge inverter.

Answer : Three phase bridge inverter: Three phase bridge inverter converts DC voltage input to three-phase variable frequency variable voltage output. DC voltage source can be a DC source or output of the rectifier. ... in proper sequence. The switch may be thyristor or IGBT etc.

Description : Give the circuit analysis of current source inverter with resistive load. What are the main difference between voltage source inverter and current source inverter?

Answer : Current source inverter (CSI): In current source inverter, the output current is independent of load. The input current of current source inverter is constant. Current source converter converts DC input current to ... are connected in parallel. In CSI diodes are connected in series.

Description : What is Voltage Source Inverter (VSI) ?

Answer : Voltage Source Inverter (VSI)  Inverter is device which converts Direct Current (DC) to Alternating Current (AC). There are two types of inverters one is Voltage source inverter ... VSI consist of two load terminals and three phase VSI consist of three load terminals.

Description : State the different methods of Power Generation adopted in India. 

Answer : 1. Hydro energy or hydro Electric power plant  2. Nuclear energy or nuclear Power Plant  3. Fossil fuels: i) Thermal energy (by combustion of coal) or Thermal Power Plant ii) Natural gas ... from any organic waste materials. It contains mixture of methane(50-65 % in volume) and carbon dioxide

Description : State the various lighting calculations methods and Describe any one of them.

Answer : Lighting calculation methods: 1. Lumens or Light flux method 2. Point to point or Inverse Square law method 3. Watts per Square meter method i) Lumens or Light ... is taken according to the illumination desired on an average value considering overall efficiency of the lighting system.

Description : The largest change of input quantity for which there is no output of instrument is called ______ A) Dead time B) Dead input C) Dead output D) Dead zone

Answer : The largest change of input quantity for which there is no output of instrument is called Dead zone

Description : Name two methods for measurement of low, medium and high resistance. Give one advantage and one limitation of V- I method.

Answer : Methods for measurement of low resistance:  1. Ammeter voltmeter method  2. Kelvin's bridge method  3. Ohm meter method  4. Potentiometer method  5. Digital/analog multi-meter ... must be infinity for perfectly accurate measurement which is not possible.  2. Connection errors.

Description : In a battery, the difference between the no-load voltage and the measured voltage output is called ________ A) Internal voltage B) Internal resistance C) External resistance D) All the above

Answer : In a battery, the difference between the no-load voltage and the measured voltage output is called Internal resistance

Description : A 40 W bulb is connected in series with a room heater. If now 40 W bulb is replaced by 100 W bulb, the heater output will?

Answer : A 40 W bulb is connected in series with a room heater. If now 40 W bulb is replaced by 100 W bulb, the heater output will increase.

Description : Analyze the effect of supply voltage on performance of LED as regards current, Lumen output, efficacy and life. 

Answer : 1) Effect on Current:- In LED current depends upon supply voltage, if voltage get changes then current also change but this change in current will be control by resistors which are connected in series.  2) ...   4) Effect on Life:- If supply voltage is not stable then life of LED get reduced. 

Description : With the help of N-channel JFET describe the effect of input voltage VGS on output current ID.

Answer : Working of N channel FET: * When a voltage is applied between the drain and source with a DC supply (VDD), the electrons flows from source to drain through narrow channel ... where the channel gets completely blocked and the drain current becomes zero is called pinch- off voltage. 

Description : Define: i) Input Offset Voltage ii) Input offset Current iii) Input Bias Current iv) Output offset voltage

Answer : Definition of parameters of OPAMP is follows:  i) Input Offset Voltage: Input offset voltage is defined as the voltage that must be applied between the two input terminals of an OPAMP to null or ... to ground) and output voltage is obtained non zero such voltage is output offset voltage of opamp.

Description : A linear network has a current input 4cos(ω t + 20º)A and a voltage output 10 cos(ωt +110º) V. Determine the associated impedance.

Answer : Solution

Description : Explain full wave bridged rectifier with the help of circuit diagram and input output waveform.

Answer : 1. In positive half cycle (0 to Π): The end A of the secondary winding becomes positive and end B negative. This makes diode D1 and D4 forward biased while diode D2 and D3 are reverse biased. These two diodes will ... D2 and D3 when it is conducting is as follows.  B - D2 - RL - D3 - A 

Description : How are nuclear reactors controlled? Explain two different methods in brief.

Answer : Nuclear reactor is controlled using control rods: Control rods are made up of very high neutron absorbing material like boron, cadmium. By adjusting height of control rods on reactor core ... of nuclear reaction will increase. Whereas by pushing control rod towards the core it will reduce.

Description : List any two methods of reactive power measurement in 3 phase circuit.

Answer : Methods of reactive power measurement in 3 phase circuit: (i) Two single phase wattmeter method (ii) One single phase wattmeter method

Description : List the different level measurement methods. 

Answer : Liquid Level Measurement Direct method 1. Hook type 2. Sight glass gype 3. Float type 4. Dip stick Indirect method 1. Hydraustatic pressure type 2. Electrical type a) Capacitance level indicator b) Radiation level detector c) Ultrasonic level gauge 3. Radar type

Description : List different starting methods of three phase synchronous motor. Explain any one of them.

Answer : Different Starting Methods of Three Phase Synchronous Motor: As synchronous motor is not self starting, different methods of starting are as follows: 1) By using an Induction (Pony) motor 2) ... . The rotor gets pulled into synchronism and starts running at constant speed as a synchronous motor. 

Description : List various transistor biasing methods.

Answer : Types of biasing methods: i. Base bias (or fixed bias) ii. Base bias with emitter feedback. iii. Base bias with collector feedback iv. Voltage divider bias (or self bias) v. Emitter bias. 

Description : Describe the following energy conservation methods of lighting system. i) By replacing lamp sources ii) Using light control gears.

Answer : Energy conservation methods of lighting system:  i) By replacing lamp sources:  Installation of energy efficient fluorescent lamps in place of Conventional fluorescent lamps. Installation of ... (HF) electronic ballasts in place of conventional ballasts which saves energy up to 35%.

Description : Describe the following energy conservation methods of electrical motor. i) By motor survey ii) By matching loads with motor rating

Answer : Energy conservation methods of electrical motor:  1) By Motor Survey: Large industries have a massive population of LT motors. Load survey of LT motors can be taken-up methodically to ... -speed motors, eddy-current couplings, fluid couplings, and solid-state electronic variable speed drives.

Description : List the different methods to produce damping torque.

Answer : Methods of providing damping torque in indicating type instruments: 1) Air friction damping. 2) Fluid friction damping. 3) Eddy current damping.

Description : Identify the correct combination of respective Electric arc welding and Electric resistance welding methods :  (A) Butt welding and Seam welding  (B) Hydrogen shielding and Projection welding  (C) Seam welding and Coated electrode welding  (D) Coated electrode welding and Hydrogen shielding

Answer : Identify the correct combination of respective Electric arc welding and Electric resistance welding methods :  (A) Butt welding and Seam welding  (B) Hydrogen shielding and Projection welding  ... Seam welding and Coated electrode welding  (D) Coated electrode welding and Hydrogen shielding

Description : What are the speed control methods of dc motor?

Answer : Field control of DC motor Armature control of DC motor

Description : A 3-phase voltage source inverter operates in 180° conduction mode with a star connected resistive load. If input dc voltage is 100 V, then the peak to peak output line voltage is :

Answer : A 3-phase voltage source inverter operates in 180° conduction mode with a star connected resistive load. If input dc voltage is 100 V, then the peak to peak output line voltage is : 200 V

Description : In a self-controlled synchronous motor fed from a variable frequency inverter  (1) the rotor poles invariably have damper windings  (2) there are stability problems  (3) the speed of the rotor decides stator frequency  (4) the frequency of the stator decides the rotor speed

Answer : In a self-controlled synchronous motor fed from a variable frequency inverter the frequency of the stator decides the rotor speed

Answer : Igbt alone cant convert dc to ac. igbt half bridge or full bridge or three phase topology could be used to convert dc to ac. also igbt gates should be driven by microcontroller or pwm/spwm gate driving signals ... e4(-) and g4 c2e1 and c4e3 pins are AC output pins. its name is igbt inverter.

Description : What is means inverter topology and  name different inverter typologies?

Answer : Topology is the circuit arrangement. Generally 6 IGBT's for an inverter, all switching at high frequency to chop DC into AC. Most often used as a power supply or to control a motor but also as the power converter in a solar system as mentioned already.

Description : Draw CMOS inverter characteristic and explain it.

Answer : Characteristics: The characteristics of CMOS inverter depend on the charging and discharging of the load capacitance CL through the PMOS and NMOS transistors respectively. The finite time taken for this charging ... pass from input to output High-to-low delay (tdf) Low-to-high delay (tdr)

Description : The direction of rotation of an inverter fed 3-phase ac motor is reversed by (A) a mechanical reversing switch (B) reversing the input dc link voltage (C) operating the inverter as a rectifier (D) changing the sequence of switching

Answer : The direction of rotation of an inverter fed 3-phase ac motor is reversed by changing the sequence of switching

Description : What is an inverter gate?

Answer : Not gate is known as inverter gate as it inverts the I/P

Description : what is inverter ?

Answer : Inverter is a device which converts DC into AC. For example, inverter are used in ups systems where the DC power stored in the battery is converted to AC when required.

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