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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 is the rating of earth leakage circuit breaker used for welding machines?
yes , it is required so that the leakage current from transformer/electrical windings to metallic enclosure of welding machine does not harm a person/operator & the current is rooted back to earth
bajaj mahesh, asst fire & sec officer
Why does capacitance consume power?
Ideal capacitors and ideal inductors do not dissipate energy, they store energy and release energy like a spring or pendulum. This type of impedance is called reactance as opposed to resistance. Reactance is represented by imaginary numbers, while resistance is represented by real numbers.
Real world capacitors have an Effective Series Resistance (ESR) that consumes a small, usually negligible, amount of energy.
How do you load calculate in building?
Building load is calculated by computing the volume of built masses and multiplying by standard weight. Divide it by the area of the surfaces of the masses which are touching the ground.
In a circuit where is the voltage drop?
In a circuit, the voltage drop is located wherever there is resistance. Ohm's law: voltage = resistance * current; so without resistance there can be no voltage drop, with resistance there is.
How do you build a parallel circuit?
BATTERY
+ -
| |
| |
| ----------------------LED-----------LED---------LED---------LED------------
| | | | | |
| | | | | |
| | | | | |
------------------------------------------------------------------------------------------
No the above is a series circuit it would also need a ballast resistor so not to cook your LED's.
This is a parallel circuit-
+---------- ---- ---- ----
| | | |
LED LED LED LED
| | | |
- ---------- ---- ---- ----
It is best to give each LED its own resistor.(not shown)
For some reason when I click save it removes the spaces, ASCII characters have never been good for representing circuit diagrams.
What are the major load control functions found on a load lift?
Many lifts have the same functions. Thus, the four major load control functions found on a load lift are lift, lower, forward, and backward. Joystick Control Functions. 3-4. Joystick Control Functions (Button Pushed). 3-5. Service Brakes. 3-6 ... major contribution to safety if you, as the equipment users and operators: 1. ... Know that the machine can safety lift each load before attempting to lift. These are ...... Any problems discovered in the steps.
Why ac is used in domestic and industrial purposes?
You should revise your question as it is a very broad stroke of a question that is difficult to answer without being a little more specific. Are you asking why home outlets use AC while appliances use DC? Are you asking why transformers step up AC voltage instead of DC voltage? Vaguely it's due to cost effectiveness, AC travels more readily across cables that have less copper wire and more insulation rather than the opposite for DC voltage/current. I need a more targeted question. Hope this helps.
How is conductivity related to resistance?
It requires a force to propel an object through air, because of the air resistance. Normally, if there were no air resistance and the object were being propelled on the level with no friction, a constant force would accelerate the object steadily. However, it would require a steady force to propel the object through air even without acceleration. And the faster it went the more resistance it would meet.
Ring final circuits in domestic properties usually require a protective device which is rated at?
According to BS7671:2008, Requirements for Electrical Installations, an overcurrent protection device rated at either 30 A or 32 A is required.
Is a neutral considered a current carrying conductor?
No, in a three phase balance load, there should not be any current through Neutral conductor. If it is a 2 wire, single phase system, the Neutral will carry the same current as live conductor if the system has no Earth fault, leak.
What is high voltage circuit breaker?
High voltage the switch blade must be long enough to break the arc
low voltage means a smaller switch
low amperage means smaller wire and contacts
120V 1/2" switch
13,200V 18" switch
vacuum switches can be made smaller since there is no air to ionize
Why does the current lead the voltage across a capacitor by 90 degree rather than lag it?
A: Because a capacitor have to have time to charge to the voltage
In a capacitor, the current depends on the voltage difference across it. On AC, this makes it charge, if the voltage is increasing above zero, and discharge if the voltage is reducing towards zero.
Because a capacitor has almost no internal resistance, and most loads that it is connected to have only very small resistances in series with the capacitor, the charging and discharging currents depend pretty much on the rate at which the voltage is changing. At the zero crossing point of the sine-wave, when the voltage is actually zero, the rate of change of voltage is very high (the sine-wave is at its steepest), so the current is also very high. If the voltage is positive-going, the current is positive, and if the voltage is negative-going, the current is negative.
At the peak of the voltage waveform, the rate of change of voltage is zero or very low (the sine-wave is flat, and not really changing its voltage) so the current is zero, too.
Since the maximum positive current occurs when the voltage is passing through zero, going positive, and the maximum negative current happens when the voltage is passing through zero, going negative, the current peaks happen 90 degrees before the voltage peaks, so the current is said to lead the voltage. This is the same as saying the voltage lags the current by 90 degrees.
What does the inside of a 3 phase transformer look like?
A three phase transformer has three primary coils and three secondary coils wound on a laminated iron core shaped like the capital letter 'E'. Each pair of primary and secondary coils are wound concentrically onto each leg of the 'E'. There is a straight , laminated core segment, that connects across all three legs of the 'E', forming a circuit path for the magnetic flux.
The primary and secondary coils can be arranged as an autotransformer, with the primary and secondary coils connected end-to-end, with a common conductor tapped at the interconnection, or as separate coils with two separate connections for each coil.
Horsepower is a rating of power, and power is equivalent to voltage times current.
AnswerThe horsepower is the Imperial unit for power, whereas the volt is the SI unit for potential difference. These are two different quantities, so your question makes no sense. It's like asking how many miles per hour there are in 10 metres!
87 amps three phase means 87 amps on each phase.
Additional Answer
It's only 87 A per phase for a wye (star) connected load; for a delta connected load, the current per phase will be 50 A, while each line current will be 87 A. That's assuming a balanced load, of course. Line currents pass through the supply conductors to the load, whereas phase currents pass through the loads themselves.
Next answer: No, 87 amps three-phase means 87 amps on each phase wire, so you can put an ammeter in each wire and it registers 87 amps.
It doesn't matter whether the load is connected delta or star :) But the amount of power is different because the line-to-line voltage is sqrt(3) times as much as the line-to neutral voltage. It isn't the current that is different, it's the voltage.
Another AnswerThis question is rather confusing as we don't really know what the original '87' A is referring to. Is it a line current or a phase current? But it's important that we use the correct terminology if we are to sort it out.
First of all, the 'hot' conductors that connect the generator to its load are called line conductors (or, simply, 'lines'), and the voltages between any pair of line conductors are termed 'line voltages', while the currents flowing through each of them are termed a 'line currents'. (Confusion exists when people call these three interconnecting conductors 'phases', which is common but completely incorrect! Remember, 'line' voltages and currents are so-called because they refer to 'lines', not phases!)
Next, the three windings within the generator, which may be connected either in delta or in star (wye) represent the machine's 'phases'. So the voltage appearing across any one of these internal windings is called a 'phase voltage', while the current through any one of these windings is termed a 'phase current'.
Generally speaking, while its very easy to place a voltmeter and ammeter to measure line voltages and line currents, it's usually very much more difficult to place these instruments so that they can measure phase voltages and currents, This is because the phases are inaccessible, because they are enclosed insidethe generator.
So, in practise, whenever we work with a generator (and the same goes for a motor), we usually measure line values notphase values.
So, returning to the question, if we assume the '87 A' quoted by the questioner is a phase current (that is, as measured in any winding inside the generator) then, for a balanced load, the value of the line current (as measured in any one of the external line conductors) will depend on whether the windings are connected in delta or in star. If the windings are connected in star, then the line currents (i.e. outside the generator) will have exactly the same magnitude as the winding (phase) currents -i.e. they will also be 87 A. If, on the other hand, the windings (phases) are connected in delta, then each line current will be 1.732 times the phase current -that is, about 151 A.
On the other hand, if the '87 A' quoted is a line current (that is, as measured outside the generator) then, for a delta-connected generator, the winding (phase) current will be 0.577 times the line current: i.e. about 50 Awhereas, for a star-connected generator, the winding (phase) current will be exactly the same as the line current, i.e. 87 A.
Next Answer: the longer it gets, the more confusing it gets :) However the wires carrying the three-phase supply can correctly be called 'lines'. Then you can have a 'line-to-line' voltage and a 'line-to-neutral' voltage and those terms are unambiguous. At the generator or load, if it's star-connected, the line current equals the generator or load current. When the generator or load are delta-connected, the line current splits two ways and the generator/load current is 1/sqrt(3) times as much as the line current.
The confusion is based in calling one condition 'line' and the other 'phase'.
All this assumes a perfectly balanced system.
What happen to the current and voltage of a battery if it in connected in series and parallel?
assuming the batteries are the same:
if you connect + to + and - to - the line out will be the same volts as one battery (parallel)
if you connect + to - and - to + (series) the line out will be the sum of all the batteries in series Do not connect batteries together in either configuration unless they are the same size and rating Observe all safety precausions when handling batteries
Operation of two cavity klystron amplifier?
The power gain of a two cavity klystron amplifier is about 30 dB.
In order to achieve higher overall gain, one way is to connect several two-cavity tubes in cascade, feeding the output to each of the tubes to the input of the following one. Besides using the multistage techniques, the tube manufacturers have designed and produced multi cavity klystron to sere the high-gain requirement.
In a multi cavity klystron each of the intermediate cavities, placed at a distance of the bunching parameter X of 1.841 away from the previous cavity, acts as a buncher with the passing electron beam inducing a more enhanced RF voltage than the previous cavity, which in turn sets up an increased velocity modulation.
Why three phase motor has the better performance when compare to single phase motor?
If you are asking what is the advantage of a motor wound for a Y or Delta configuration over a motor wound for a single phase configuration, then the advantage of the Y or Delta motor is more efficient operation. And in a motor, or in any power application, efficiency is all important.
Which type of winding use in power transformer?
The transformation ration for a transformer is (Vs/Vp) = (Ns/Np).
Which means, Voltage ∞ No. of turns.
So, we can say if we have to increase voltage, then we have to increase the no. of turns, and as the no. of turns increase the space between the core and the winding reduce.
So, from above we can say that the HV windings are closer to the core than the LV windings.
AnswerThere are two configurations for windings in transformers.
The first is called 'concentric' or 'tubular', in which the low-voltage windings are placed innermost (i.e. closest to the core) with the high-voltage windings outermost.
The second is called 'sandwich', in which the windings are arranged in ring bundles, with alternate rings of high- and low-voltage windings placed one above the other.
The first configuration is used with 'core' type cores, with half the LV/HV windings placed around one limb of the core, and the other half of the windings placed around the second limb. The second configuration is used with 'shell' type cores, with the ring bundles placed around the centre limb.
How do you convert single phase kva to three phase kva?
Va=volts x amps. The K stands for one thousand. So 1 Kva is one thousand watts. So 415v times 120a= 49,800 what's. You divide that by a thousand and you get 49.8. So it would be 49.8 Kva.
What happens if there is too much current in the circuit?
It causes the disruption of the fuse, switching off the disjunctor, or set on fire the conductors if there isn'ta circuit protector and therefore burns the parts of the electric device. The cause of too much current in a ciucuit is always a resistance that has a low value. To check the cause of the excess of current in a circuit is necessary to measure all the components.
Power dissipation of a resistor or any load is the amount of power (in watts) that is converted to heat, light, or other form of energy. In a resistor, power dissipation is defined by Ohm's law P = I^2 * R Power dissipated equals current through the resistor squared times the resistance in ohms. Since the power is converted to heat, a resistor has a maximum dissipation rating set by the manufacturer, above which the resistor will be damaged.
Can a 3 phase motor be wired to run in your house?
The physical internal windings between single phase and three phase motors makes this an impossibility That being said money can make anything happen. Depending on the amount of money you want to spend to make this happen there is a device on the market called a VFD ( Variable Frequency Drive). On the three phase input terminals you apply your single phase voltage. On the output terminals you connect your three phase motor. When run in this configuration there is an internal switch that has to be changed to let the VFD know that it should be looking for only two lines on the input to be hot. Otherwise the VFD thinks that there is a line loss on the three phase input terminals and the unit will not start. <<>> You can make a phase converter with a couple extra motors. Wire up a 120V single phase motor and couple it to a 3 phase motor. This turns the 3 phase motor into a generator for you to run to whatever equipment the 3 phase motor is. Although if you had a single phase motor you probable don't need a 3 phase motor. == == <<>> yes! you will have to buy a phase converter. <<>> yes, it is possible to this with a rotary phase converter . one manufacturer is "phase master" (as an example only, not wishing to promote any brand). these are not cheap units and it may be more cost effective to purchase a single phase (220V.) replacement motor . the overall efficiency (operational costs) would be better too . a rotary phase converter is usually the "last choice on the list" .
What are the importance of electrical splice and joints?
Totally important!
The connections must be well made and the wires tightly joined to prevent a loss of voltage to the device powered. In high current situations a poor connection causes heat at the connection and oxididaion of the wires and no more or intermittent connections.
Most problems in electrical is not a short but: an open connection.
Additional AnswerIn the case of high-voltage underground cables, the restoration of the insulation is critically important, as is restoring the cable's waterproof integrity. The skills required are such that cable jointers serve a full apprenticeship in that particular trade.
What is the Single phase voltage in India?
The single phase voltage in India is 230v when we check with the phase and the nutral single line
