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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
Why short circuiting rings are used in squirrel cage motor?
Squirrel Cage motor is a kind of Induction Motor. The reason an induction motor sometimes refered to a rotating transformer is because the stator (Primary windings in a transformer), which is powered to set up a magnetic field induces a current in the armature coils (secondar coils in a transformer). However, instead of giving an electrical power output, the coil is short circuited to produce mechanical output (torque in this case)
I am assuming that its a 240 Volt AC circuit supplying an inductive load with a fault loop impedance of 1.9 ohms at the time of the short circuit. The power factor is assumed to be 0.8
The instantaneous earth fault current value would be;
Current = (Voltage x Power Factor) / Impedance
(240 x 0.8) / 1.9
192 / 1.9
= 101 Amps.
However this may be a trick question as it doesn't ask for an instantaneous value, the fuse will limit the fault current to 15 amps and should disconnect the circuit within 0.4 seconds.
Why the rotor of an alternator at rated power dissipates more heat at a low power factor load?
In an alternator, the load current is supplied by the stator and the excitation is applied to the rotor. When the power factor is low (lagging), more excitation is required to maintain rated output voltage at rated current. More excitation is also required to maintain rated output voltage with increased output current. Increased excitation current means increased rotor losses that must be dissipated as heat.
(akash)
What are potential transformer?
potential transformer is that which transforms one range of voltage (potential difference ) to another range without changing frequency.
AnswerA 'potential transformer' is the North American term for what, elsewhere, is called a 'voltage transformer'. It, together with a current transformer, belongs to a class of transformers known as 'instrument transformers'.
Potential transformers are used to (1) reduce the value of a high-voltage supply to a lower value (often 120 V) so that it may be read by ordinary voltmeters, and (2) to electrically-isolate the voltmeter from the high-voltage source for the purpose of safety.
In electricity substations, potential transformers are also used to provide an input to certain types of protective relay.
How Paper presentation in IEEE format on data mining?
hi sir actually i'm preparing first time for taking participant for paper presentation so,i want help about the topics data mining.plz help......
The GE website says the following regarding 3-way lamps:
"GE does make CFL bulbs for use in 3-way lamps. Check the package for this application. If a regular CFL is use in a 3-way switch, it will work on the middle (medium) setting and it should not damage the bulb. The 3-way switch does not alter the performance of the bulb."
There don't appear to be 2-way CFLs in existence, so I don't know what this means for a 2-way lamp. Will it damage the bulb (ballast?) to be using a regular CFL in a 2-way? How would it actually work in that situation? I don't know because I don't understand the mechanics of a CFL and how these 2-brightness lights work. Hopefully someone else can shed some light! (ha)
What is the electrical symbol for a receptacle with an Ethernet port?
The symbol will look like it can fit in your Ethernet cable. It will have an opening just big enough for it.
What is making capacity of a circuit breaker?
Hard to define... A four year old child has the strength to physically "make" a typical household circuit breaker, while a teen would be able to "make" a typical industrial circuit breaker. (The latter breaker being physically much larger than the former.) Circuit breakers have their "breaking capacity" rated in AMPS. A typical household breaker is rated at 20, 30 or 50 Amps. Industrial breakers might be rated at 500 amps or a thousand or even more. Hope this helps but if it didn't answer your question, please rephrase it and ask again.
It is a device that measures the differential pressure between two inputs.
Example:
You have a pressure container where you connect the H-side (high) of the DP-cell. The L-side (low) you leave in the atmosphere (open air). The DP-cell will tell you the pressure in the pressure container relative to atmosphere pressure. Depending on what class the DP-cell is, it will give you feedback with a current signal. Normal in Europe is 4-20 mA, where 4 is lowest and 20 is highest.
The work to be done to bring a unit positive charge from infinity to a point in an electric field exists which is having a magnitude unity and direction opposite to the movement of the unit charge.
Reluctance is the opposition offered by a magnetic circuit to the formation of magnetic flux. It is equivalent to resistance in an electric circuit.
Reluctance is the ratio of a magnetic circuit's magnetomotive force (measured in amperes) to its magnetic flux(measured in webers, pronounced 'vay-bers'). So, reluctance is measured in amperes per weber (which is often 'spoken' as 'ampere-turns per weber'). This is equivalent, in an electric circuit, to the ratio: electomotive force to electric current.
If you don't know how to test and fix fault conditions as you have described you should not be doing what you are doing. Any work on a circuit carrying 480 Volts is potentially very dangerous. Unless you are a licensed electrician don't even attempt it!
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As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.
Before you do any work yourself,
on electrical circuits, equipment or appliances,
always use a test meter to ensure the circuit is, in fact, de-energized.
IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB
SAFELY AND COMPETENTLY
REFER THIS WORK TO QUALIFIED PROFESSIONALS.
It's the property of the material which allow only certain bandwidth of wavelength. Materials that exhibit this property is known as photonic crystal. In order to exhibit this property the material has to have a periodic arrangement of dielectric structures with periodicity of the order of wavelength.
0.5 lead PF or Power Factor means that the signal is ahead of the input voltage by a factor of 90 degrees. The lagging PF means it falls behind the input signal. In sinusoidal signals 0.5 lead or lag will be the same.
What is tranformer turn ratio?
Transformer turn ratio is the ratio between the turns on the primary side and the number of turns on the secondary side. For instance if you have a turn ration of 100:200 the primary side has 100 turns and the secondary side has 200 turns. This will be a step up transformer. 10 volts AC into the primary side will result in 20 volts on the secondary side. There will be a decrease in current but the voltage will increase. The total power into and out of the transformer will be the same minus some losses for resistance in the windings.
Scroll down to related links and look at "6 different resistors - Wikipedia".
How do you convert electrical energy into gravitational potential energy?
You could for example drive an electric train up a mountain track, or you could raise a heavy weight using an electric crane.
An ammeter consists of a coil with very low resistance. when electric current flows through the coil, the coil induces a magnetic field which turns the needle.
What makes an electric arc furnace electrode break?
Electrode are some times broken due to: -
1) Electrodes making contact with a none metallic object as they are being hard pressed and ultimately broken. Electronic instruments are available to find this condition and take corrective measures to avert breakage of electrodes.
2) Scrap falling against the electrode(also known as scrap cave-in or collapse)
Above conditions are applicable for EAF
3) Electrode breaking at joints due to incorrect jointing (Not having the correct torque applied to the sections being jointed)
4) Rough handling prior to being used (While being moved or stored)
5) If thermosetting thead lock are missing due to some reason or other,the same mishap may happen.
6) Thread may have some entrapped external material which in turn damage the thread while torquing.
7) If phase sequence is not correct, electrode will be loosened from the joint and may fall in the molten metal.
vipin@vaibhavfurnaces.com
What is the derivation of Torque and power equation of induction motor?
Torque is the cross product of radius and force .Torque is a twisting effect. Torque is the cross product of radius and force .Torque is a twisting effect.
What is a studio-transmitter link?
A studio-transmitter link (STL) is just that. It is the link between the studio and the transmitter. Let's look at one in action. KWIZ radio is a hip FM station with studios on the top floor of the insurance building downtown. They got a good deal on the space, and they like being downtown 'cause it makes them (and their listeners) feel more connected. Their transmitter is located on top of Mount Fritz, some 20 miles away. The transmitter is up there because real estate is a bit cheaper there, and from that spot it can hit (reach) a lot of territory. And the tower doesn't have to be super tall, either. Besides, there isn't any place downtown to put up an FM broadcast antenna. If the antenna was downtown, it would have to be super tall. And it couldn't get the kind of coverage KWIZ can get with a transmitter located up on a big hill. They want lots of area where their signal can reach out to and arrive at receivers. That translates into lots of listeners and lots of opportunities to sell radio ads and get lots of money for them because the station has lots of coverage/listeners. Dusty Rhodes and Sandy Beach share the mic on the morning show. They draw music from the tracks stored in the memory of the station's music computer. (Who still uses CD's?) When they play a tune, the signal is routed to the input of a microwave transmitter on the roof of the insurance building. The microwave transmitter takes that signal and uses it to modulate the microwave carrier, and then the modulated carrier is sent through amplifiers and finally to a microwave power amplifier. From there, it is sent into a waveguide (or, more probably, a length of heliax cable) and routed to the little microwave dish on that short mast on the roof. The dish is a parabolic reflector, and it may be anything from a foot or two across to half a dozen feet across, depending on the system used and the distance it needs to cover. (A meter in diameter would not be uncommon for something like this.) The microwave signal is then radiated from the feedhorn into the dish. From there it is reflected off the dish and goes where the dish is pointed. The transmitter's dish is pointed at a similar receiver dish up on Mount Fritz. That receiver dish (which is pointed at the transmitter dish) is often mounted on the tower that the FM broadcast antenna sits on. The microwave signal is collected on that second dish and reflected to the focal point to be gathered up by a horn positioned appropriately. There may be a low noise amplifier built right into the horn at the focal point of the receiver's dish. The microwave signal is then demodulated and music track recovered. Then that signal can then be used to modulate the FM transmitter, which is right there. The amplified signal goes out of the FM transmitter and into the transmission line which connects the transmitter to the antenna. The signal is being routed point to point from the studio to the transmitter. And that's the studio-transmitter link (STL) that is common today. AM and FM radio stations and also the TV stations use the links commonly.
Electric power is defined as the rate at which electrical energy is transferred by an electric circuit.
Power is energy over time. For example electrical energy is watts and watts are usually measured by the hour by the utility company and the unit of power is a kilowatt hour
AnswerThere is really no such thing as 'electric power', despite the term being widely used in everyday life. Power is simply a rate, the rate of doing work, or the rate of heat transfer. Work is done whenever one form of energy is converted into another form, so power applies to the all forms of energy conversion, as well as to heat transfer.
The above answer is completely incorrect to say that electrical 'energy' is expressed in watts, and that 'watts are measured by the hour'. The watt is the unit of power, while energy is expressed in joules. The answer is also incorrect to say that the unit of power is the kilowatt hour, as this is used by electricity utilities to measure energy consumption, not power! In other words, the kilowatt hour is an alternative unit for energy.
What are the advantages of skewed slots in the rotor of a squirrel cage rotor?
It helps to put on a little more traction. The rotor will stay on better because it is not as slippery.
