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Electrical Engineering
Electrical engineering is a field of engineering that deals with the study and application of electricity, electronics and electromagnetism.
23,056 Questions
What are the elements of a diesel power plant?
ESSENTIAL ELEMENTS OF DIESEL POWER PLANT
Fuel Supply System
It consists of storage tank, strainers, fuel transfer pump and all day fuel tank. The fuel oil is supplied at the plant site by rail or road. The oil is stored in the storage tank. From the storage tank, oil is pumped to smaller all day tank at daily or short intervals. From this tank, fuel oil is passed through strainers to remove suspended impurities. The clean oil is injected into the engine by fuel injection pump.
Air Intake System
This system supplies necessary air to the engine for fuel combustion. It consists of pipes for the supply of fresh air to the engine manifold. Filters are provided to remove dust particles from air which may act as abrasive in the engine cylinder.
Exhaust System
This system leads the engine exhaust gas outside the building and discharges it into atmosphere. A silencer is usually incorporated in the system to reduce the noise level.
The exhaust system of a diesel engine performs three functions. First, the exhaust system routes the spent combustion gasses away from the engine, where they are diluted by the atmosphere. This keeps the area around the engine habitable. Second, the exhaust system confines and routes the gases to the turbocharger, if used. Third, the exhaust system allows mufflers to be used to reduce the engine noise.
Cooling System
The heat released by the burning of fuel in the engine cylinder is partially converted into work. The remainder part of the heat passes through the cylinder wall, piston, rings etc. and may cause damage to system. In order to keep the temperature of the engine parts within the safe operating limits, cooling is provided. The cooling system consists of a water source, pump and cooling towers. The pump circulates water through cylinder and head jacket. The water takes away heat form the engine and it becomes hot. The hot water is cooled by cooling towers and re circulated for cooling.
Lubricating System
The system minimises the wear of rubbing surfaces of the engine. It comprises of lubricating oil tank, pump, filter and oil cooler. The lubrication oil is drawn from the lubricating oil tank by the pump and is passed through filter to remove impurities .The clean lubrication oil is delivered to the points which require lubrication. The oil coolers incorporated in the system keep the temperature of the oil low.
Engine Starting System
This is an arrangement to rotate the engine initially, while starting, until firing starts and the unit runs with its own power. Small sets are started manually by handles but for larger units, compressed air is used for starting. In the latter case, air at high pressure is admitted to a few of the cylinders, making them to act as reciprocating air motors to turn over the engine shaft. The fuel is admitted to the remaining cylinders which makes the engine to start under its own power.
What is signal distortion in transmission lines?
there are some distortion in transmission line :
copper loss,dielectric loss,skin effect
Why the power factor of semiconverter is better than full converter?
because semi converter has 1ly 2 thyristor where else full converter has 4 thyrister..thn semi converter the rectification is through rectifier and diodes. but in ful converter no diodes is used 1ly 4 thyristers are used
What is the minimum distance allowed between two joints in a high voltage cable of 66 KV?
the minimum distance between two cable joint 2 meter (refer IEC 60052-4)
Can reverse polarity burn a tv set?
If, by 'reverse polarity', you mean the accidental reversal of the line and neutral conductors at the socket outlet or receptacle, then the answer is no.
If there is a situation where power demand exceeds power available, the power company may cut off one area and then another to spread the pain around so that one area won't have to do without power for an extended period.
The voltage is attenuated by the resistance in the media used for transmission. This is regardless of the power factor.
How do you flow current in capacitor through dielectric?
well actually current doesn't exactly pass through the capacitor or dielectric.Current just flows through the wires connected to the capacitor.The reason is that electric charges are only placed onto capacitor plates and they flow in the circuit and it seems to us that current is flowing in the circuit.
Also remember that dielectric only increases the capacitance of a capacitor.
Answer
There are two types of electric current, termed 'conduction current' and 'displacement current', respectively.
A 'conduction current' describes the drift of free electrons in a metal conductor. A 'displacement current' describes the polarisation of atoms in dielectrics.
When an electric field is applied to a dielectric, the elliptical orbits of the electrons around each atom's nucleus become distorted, and stretch, resulting in polarised atoms. The amount of 'stretch' (polarisation) increases with the strength of the electric field. So, as the voltage across the changes so, too, does the amount of polarisation -i.e. so, too, does the displacement current.
So when a capacitor is connected to an external d.c. supply, a varying conduction current drifts around the circuit conductor, while a displacement current occurs within the capacitor's dielectric. When a capacitor is connected to an external a.c. supply, a continuously varying potential difference results in a continuously changing conduction current in the metallic circuit, and a continuously changing displacement current within the capacitor's dielectric.
What is the ampere in terms of coulomb?
As an ampere is an SI base unit, it is NOT defined in terms of the coulomb. In fact, it is defined in terms of the force (in newtons) between two, parallel, current-carrying conductors. The coulomb, being an SI derived unit, is equivalent to an ampere second.
Why a 3 phase fault is more severe than other fault in transmission line?
It isn't necessarily (depending on your perspective). A three phase fault is a severe duty on generators, because all three phases are shorted. In solidly grounded systems a phase to ground fault could result in higher magnitude currents, which would be more difficult for a breaker to interrupt (so from the breaker's perspective, this would be more severe).
Why copper is used in electrical transmission line?
Copper is a good conductor and is fairly strong. It generally is not used in power transmission lines due to cost - generally aluminimum is used.
What is the difference between external and internal characteristics of dc shunt generator?
everything
What is the difference between Y or Wye and Delta 3 phase power?
The transformer connection. Transformers can be connected in Wye (One side of each winding connected to the phase wire and the other connected to neutral or ground) or Delta (the polarity of each winding connected to the nonpolarity of another winding to form a triangle).
There are different problems that arise as a result of being connected wye vs. delta or vice versa, and multiple fixes or partial fixes to address these.
Alternative Answer'Wye' (also known as 'star') and 'delta' (also known as 'mesh') are two methods (there are others!) of connecting the three phase windings of alternators, transformers, and loads such as motors). A wye connection is generally a four-wire system, comprising three line conductors and a neutral conductor, whereas a deltaconnection is a three-wire system, comprising three line conductors. For a perfectly-balanced load (e.g. a three-phase motor), a wye-connected system can dispense with the neutral conductor. In wye-connected systems, the line voltage (line-to-line) is 1.732 times larger than the phase voltage (line-to-neutral). In a delta-connected system the line voltage is exactly the same as the phase voltage (line-to-line in both cases).
(This is what my teacher said, I wrote this down in my notes) The answer is, Step-up transformers are used to increase the voltage of an electric current before it is sent out over transmission lines from the electric company. Step-down transformers are used to reduce the voltage of current from high-voltage transmission lines before it enters homes and businesses. Some devices, such as televisions, contain step-up transformers that increase the voltage once again.
Does the ohmmeter need to be parallel to the load when measuring resistance?
It does not matter, since the ohmmeter needs to be connected to the device in isolated mode. Series or parallel; they are both the same, in this case.
0.1M ohms
How will insulation resistance change with rise in temperature?
Insulation resistance is temperature-sensitive. When temperature increases, insulation resistance decreases, and vice versa. A common rule of thumb is insulation resistance changes by a factor of two for each 10 DegrC change. So, to compare new readings with previous ones, you'll have to correct your readings to some base temperature. For example, suppose you measured 100 megohms with an insulation temperature of 30 DegrC. A corrected measurement at 20 DegrC would be 200 megohms (100 megohms times two).
What are the different types of soft starters for large motors?
Parameter FCMA Starter WWE LRS Remarks
Starting current 1.Fixed
2.Goes upto 5 times Ie
(Rated current) 1.Adjustible, programmable at site2.Limited to 3.5 times Ie (Rated current)
1.Flexibility
2.Ensures less stress on motor coils & hence, longer coil life
Starting Voltage dip
1.Higher than 5%.
2.Power Factor drops during start, hence further Voltage dip
3.Voltage drop fixed, cannot be adjusted; hence not possible to add new equipment in the plant if the power supply is not adequate.
1.Can be limited to less than 3%.
2.No affect on Power Factor
3.Voltage drop adjustable at site, so new equipment can be added easily on the same power supply.
1.Lower Voltage dip ensures smooth functioning of other equipment in the plant.
2.Programmable voltage drop ensures that further equipment can be added to the system as & when required with the existing power supply.
Starting results
Possible to predict the starting results like starting current, starting time & starting voltage drop
Helps to predict & confirm the starting of the motor. Rating
Max. rating supplied less than 10000 KW
Max rating supplied 25000 KW. Can go upto 40 MW.
Contains lot of copper metal & hence, heavy.
Weight is comparatively less
Involves costly copper metal, hence expensive & price fluctuating
Lesser price.
