What will happen to the operation of Transformer if the frequency of operation is changed?

Change in frequency affects the operation of a transformer in the following ways: i. Iron Loss – Increases with a decrease in frequency. A 60 Hz transformer will have nearly 11% higher losses, when worked on 50 Hz instead of 60 Hz. However, when a 25 Hz transformer is worked on 60Hz, iron losses are reduced by 25%. ii. Cu Loss – In distribution transformer, it is independent of frequency. iii. Efficiency- Since Cu loss is unaffected by change in frequency, a given transformer efficiency is less at a low frequency than at a higher one. iv. Regulation...

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DC Machines

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Discus the types and works of power plants used in ships, Airplanes, industries and commercial enterprises

Power Plants used in Industries:  Power plants used in industries are known as captive power plants these are used only for industry demand. Type of power plant installed in industries depends upon the fuel feasibility for industry. Most of the industries use gas and diesel power plants. However nowadays industries are prone towards renewable sources of energy i.e. Solar and wind.    Power Plants used in Airplanes: Engine driven generators are used in airplane due to accessibility of air. Both AC and DC generators are used...

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What are direct energy conversion methods for producing electric power?

: There are seven fundamental methods of directly transforming other forms of energy into electrical energy: §  Static electricity, from the physical separation and transport of charge (examples: triboelectric effect and lightning) §  Electromagnetic Induction, where an  electrical generator, dynamo or alternator transforms             generator kinetic energy (energy of motion) into electricity. This is the most used form for generating electricity...

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List out all energy worldwide available natural energy resources for electrical power generation.

Ans.      Energy resources are categorized in two groups conventional and non conventional. Available      resources worldwide for electrical power generation  are enlisted below:     Conventional Sources: ü  Coal Energy. ü  Hydel Energy. ü  Diesel Energy. ü  Gas Energy.   Non-Conventional Sources: ü  Solar Energy. ü  Wind Energy. ü  Biomass Energy. ü  Ocean Energy. ü  Nuclear Energy. ü  GeoThermal Energy. Some ...

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What is Turbine's Critical Frequency and why a turbine should not be operated at its critical frequency?

Answer: Turbine shaft material has its own natural frequency, when turbine rotates on such a speed that frequency of shaft become close to its natural frequency, machine causes noise & high vibrations because of resonance due to matching of frequency. Running of Steam "TURBINE" on this speed is avoided & this is called Critical speed. A turbine may have more then one critical speed, which may depend upon number of couplings.  A second critical speed is when the Turbine blade tips approach the speed of sound. This effectively limits...

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Why efficiency in Thermal Power Plant is Low?

Almost 50% of the heat generated is lost at the condenser as heat rejection. It is unavoidable as with out heat rejection it is not possible to convert heat energy into mechanical energy and drive the turbine without drop in temperature. Therefore majority of the loss takes place in the condenser. Thus efficiency of the thermal power plant is between 30-35%. On What Cycle does Thermal Power Plant operate? Thermal Power plant works on the principle of Rankine cycle Why Generation Voltage in Thermal Power Plant is between 11kV to 33kV? The current...

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Electronics Fundametals Chapter 8

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Discuss the criterion for choice of voltage for transmission and distribution

Criterion For Choice Of Voltage For Transmission And Distribution. We know that the power W =VI , so for the same power if voltage is increased then current will decrease. If suppose power required is 500 W and voltage is 250 V then current I will be equal to 500/250 =2A. Now if voltage is increased from 250V to 500V and the power required is same then I = 500/500 =1 A Now, if the voltage is still increased to say 1000V for the same power then I = 500/1000 =0.5 A From the above examples, we see that if the voltage is doubled, the current...

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What are the advantages of high voltage transmission? Give its limitations also.

Ans: High voltage transmission is subdivided into HVAC and HVDC transmission systems. (i) HVAC transmission: Advantages of HVAC transmission are as follows: As the voltage is increased, the current carried by the conductors decreases. The i2R losses correspondingly get reduced. However the cost of transmission towers, transformers, switches and circuit breakers rapidly increases with increase in voltage, in the upper ranges of a.c. transmission voltages. (ii) HVDC transmission: Advantages They (HVDC lines) are economical for bulk power...

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Understanding Electric Utilities and De-Reguration 2ed - Lor

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Electronics Fundametals Slides 7

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Electronics Fundamentals Slides 6

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Electronics FUndamentals Slides 5

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Electronics Fundamentals Slides 4

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Electronics Fundamental slides Chapter 3

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Electronics Fundamental Slides chapter 2

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Electronics Fundamentals Chapter 1

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Home Made Power Plant

There is one disturbing fact that people are slowly beginning to realize. We can't depend on fossil fuels for our energy forever. Oil prices are skyrocketing around the world. People are fighting and dying over oil reserves. The damage to our planet and our climate is irreversible and is becoming more and more apparent by the day. Put shortly, chances are that if we don't do something about our energy situation now, our kids and their kids are...

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Electrical Engineering MCQs

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Understanding Electric Power Systems

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Electrical Engineering MCQs

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How do the synchronizing lamps indicate the correctness of phase sequence between existing and incoming Alternators?

The correctness of the phase sequence can be checked by looking at the three sets of lamps connected across the 3-pole of the synchronizing switch. If the lamps grow bright and dark in unison it is an indication of the correctness of the phase sequence. If on the other hand, they become bright and dark one after the other, connections to any two machine terminals have to be interchanged after shutting down the machi...

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State the condition to be satisfied before connecting two alternators in parallel

The following are the three conditions to be satisfied by synchronizing the additional Alternator with the existing one or the common bus-bars. The terminal voltage magnitude of the incoming Alternator must be made equal to the existing Alternator or the bus-bar voltage magnitude.  The phase sequence of the incoming Alternator voltage The phase sequence of the incoming Alternator voltage must be similar to the bus-bar voltage.  The frequency of the incoming Alternator voltage must be the same as the bus-bar voltage.&...

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What are the causes of changes in voltage in Alternators when loaded?

Variations in terminal voltage in Alternators on load condition are due to the following three causes: Voltage variation due to the resistance of the winding, R Voltage variation due to the leakage reactance of the winding, Xt Voltage variation due to the armature reaction effect, X...

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How does electrical degree differ from mechanical degree?

Mechanical degree is the unit for accounting the angle between two points based on their mechanical or physical placement. Electrical degree is used to account the angle between two points in rotating electrical machines. Since all electrical machines operate with the help of magnetic fields, the electrical degree is accounted with reference to the magnetic field. 180 electrical degree is accounted as the angle between adjacent North and South pol...

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Why are Alternators rated in kVA and not in kW?

The continuous power rating of any machine is generally defined as the power the machine or apparatus can deliver for a continuous period so that the losses incurred in the machine gives rise to a steady temperature rise not exceeding the limit prescribed by the insulation class. Apart from the constant loss incurred in Alternators is the copper loss, occurring in the 3 –phase winding which depends on I2R, the square of the current delivered by the generator. As the current is directly related to apparent – power delivered by the generator...

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Which type of Synchronous generators are used in Hydro-electric plants and why?

As the speed of operation is low for hydro turbines use din Hydro-electric plants, salient pole type Synchronous generators are used. These allow better ventilation and also have other advantages over smooth cylindrical type rot...

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Why do cylindrical Alternators operate with steam turbines?

Steam turbines are found to operate at fairly good efficiency only at high speeds. The high speed operation of rotors tends to increase mechanical losses and so the rotors should have a smooth external surface. Hence, smooth cylindrical type rotors with less diameter and large axial length are used for Synchronous generators driven by steam turbines with either 2 or 4 pole...

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Why almost all large size Synchronous machines are constructed with rotating field system type?

The following are the principal advantages of the rotating field system type construction of Synchronous machines: · The relatively small amount of power, about 2%, required for field system via slip-rings and brushes. · For the same air gap dimensions, which is normally decided by the kVA rating, more space is available in the stator part of the machine for providing more insulation to the system of conductors, especially for machines rated for 11kV or above. · Insulation to stationary system of conductors is not subjected to mechanical stresses...

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SF6 or Vacuum MV Circuit Breaker?

SF6 or vacuum? Approximately 35 years ago, in the mid 1960s, two new breaker technologies, one using SF6 gas and the other vacuum as its arc quenching medium, were introduced to the market. Research and development work on both technologies has continued unabated since then, and today it can be said that, together, they have all but replaced the older types of switchgear. Instead of an objective selection based on real-world characteristics,...

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Capacitor Application Issues

Capacitor Ratings Capacitors must be built to tolerate voltages and currents in excess of their ratings according to standards. The applicable standard for power capacitors is IEEE Std 18-2002, IEEE Standard for Shunt Power Capacitors. Additional information is given in IEEE Std 1036-1992, IEEE Guide for Application of Shunt Power Capacitors. IEEE Std 18-2002 gives the following continuous overload limits. These...

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