Capicitor Application Issues
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.
Heat as one of most common cause of motor failure
This slide speaks about that how motor operation fails due to heat. how heat affect motors?
Tuesday, 1 July 2014
Friday, 6 June 2014
.GIF)
Monday, 26 May 2014
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 – Regulation at unit power factor is not affected because IR drop is independent of frequency. Since reactive drop is affected, regulation at low power factor decreases with decrease in frequency and vice versa. For example, the regulation of a 25 Hz transformer when operated at 50 Hz and low power factor is much poorer.
v. Heating – Since total loss is greater at a lower frequency, the temperature is increased with decrease in frequency.
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 – Regulation at unit power factor is not affected because IR drop is independent of frequency. Since reactive drop is affected, regulation at low power factor decreases with decrease in frequency and vice versa. For example, the regulation of a 25 Hz transformer when operated at 50 Hz and low power factor is much poorer.
v. Heating – Since total loss is greater at a lower frequency, the temperature is increased with decrease in frequency.
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 for electric
components used in airplane. Aircraft electrical components operate on many different voltages both AC and DC.
The most of the aircraft systems use
-115 volts (V) AC at 400 hertz (Hz)
- 28 volts DC
DC power is generally provided by “self-exciting”
generators containing electromagnets, where the power is generated by a
commutator which regulates the output voltage of 28 volts DC. AC power,
normally at a phase voltage of 115 V, is
generated by an alternator, generally in a three-phase system and at a
frequency of 400Hz. For emergency purposes turbines called RAM AIR turbines are
used- air driven turbine stowed in aircraft
ventral or nose section. Gen. Sizing varies between 5 and
15kVA.Rat is intended to furnish the crew with sufficient power while attempting to restore primary generators.
Power plants used
in Ships:
Power plants used on ships are generally diesel power
plants. The Power Distributed on board a ship
needs to be supplied efficiently throughout the ship. For this the power
distribution system of the ship is used. Ship Generator consisting of prime
mover and alternator .Main switch board
which is a metal enclosure taking power from the diesel generator and supplying
it to different machinery. Bus Bars which act as a carrier and allow transfer
of load from one point to another. Circuit breakers which act as a switch and
in unsafe condition can be tripped to avoid breakdown and accidents. Fuses as
safety device for machinery. In case of the failure of the main power
generation system on the ship, an emergency power system or a standby system is
also present. The emergency power supply ensures that the essential machinery
and system continues to operate the ship. Emergency power can be supplied by
batteries or an emergency generator or even both systems can be used.
Power Plants used
in commercial enterprises:
Virtually all commercial electric energy
is now produced by generators driven by steam from the burning of fossil fuels
or from nuclear sources or by hydropower. A basic steam-power plant includes a
furnace or reactor for raising the temperature of the water in a boiler, or
steam generator, until it changes into steam, and a turbine, which drives the
generator to produce electric power. The electric power produced is brought
from the generating plant to the user through a network of wires called
transmission and distribution lines.
Majority of enterprises use diesel generators to meet their requirements.
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 and is based on Faraday's
law. It can be
experimented by simply rotating a magnet within closed loop of a conducting
material (e.g. copper wire)
§
Electrochemistry, the direct transformation of chemical energy into electricity, as in a battery, fuel cell or nerve impulse.
§
Photoelectric effect, the transformation of light into
electrical energy, as in solar cells
§
Thermoelectric effect, the direct conversion of temperature
differences to electricity, as in thermocouples, thermopiles, and thermionic
converters.
§
Piezoelectric effect, from the mechanical strain of
electrically anisotropic molecules or crystals. Researchers at
the US Department of Energy's Lawrence Berkeley National Laboratory (Berkeley
Lab) have developed a piezoelectric generator sufficient to operate a liquid crystal
display using thin films of M13 bacteriophage .
§
Nuclear transformation, the creation and acceleration of
charged particles (examples: betavoltaics or alpha particle emission)
§
Ocean Wave Energy Conversion,in this method electrical energy is
produced from floating thing(like ball type shape) over the waves these are
connected to piston,duenwhich piston moves up and down motion and cause
generator to run.
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