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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 do transmission lines possess inductance?

Transmission lines possess inductance due to the magnetic fields generated by the flow of electric current through the conductors. When current flows, it creates a magnetic field around the conductor, and the changing magnetic field induces an electromotive force (EMF) in the line, which is associated with inductance. Additionally, the physical separation between conductors in a transmission line contributes to the line's overall inductance, as the magnetic field interacts with the surrounding environment. This inductance affects the transmission line's impedance and the propagation of signals along the line.

You have 380 volt electric motor 3 phas 7.5 kw you want to chang it to 240 volt can some one hepl pleas?

That's a powerful motor, and would need a supply greater than 13 amps at 240 volts, also the conversion might be difficult. I have a feeling that you would be better off finding out how powerful a motor you would need for the task you have, then buying a suitable 240 volt motor. You are heading into territory where you should really consult a qualified electrician.

What is the relationship between the length of a co-axial cable and the delay?

Well as length is increased the delay will increase because the signal takes longer to travel to the destination, but i don't know exactly how much delay would be added. Keeping in mind that the RF signal travels at 186,000 miles a second, you will never see or hear a delay.

Why ngt or ngr used in transformer?

Criteria-in order to protect the stator core from damage during internal earth fault it is necessary to limit the stator earth fault current al low as possible.may be upto 10amp for generator.

Basis for selection of ngtr-

if generator is connected to the system through generator transformer then generator can be treated as an isolated system which is not influenced by the distribution earthing system. In this case you can select earth fault current as low as possible, but if we use ngr then in order to limit the low earth fault current size of the ngr will be increased.due to big size of ngr we required more space & also its too costly.

V = ir means if v constant i is inversely proportional to r

exp:-to limit 10amp current , v =11kv/root 3

r = 11/root 3/10*1000=635.10 ohm ( very high value)

for overcome on this, general practice to use a ngtr so that we can limit low earth current without any extra cost.

Exp:- ngtr 11/240v

to limit 10amp current

current reflect on secondary side of ngtr will be

= (11000/root 3/240)*10=264.6 amp.

Resistor value on secondary side r =240/264.6 =0.9 ohm ( approximately) which is much lower than 635.10 ohm.

Basis for selection of ngr-

if generator is directly connected to the system then we can not limit the earth fault current up to 10 amp. We have to select the earth fault current value above the residual capacitive charging current of system.also we need to check the possibility of relay setting operation with ct ratio.

For exmp- if ct ratio is 2000/1amp & earth fault limit current is 100amp relay selected with 10 % setting.

Then that relay will see only 200amp earth fault current it will not see 100amp current.

Also we can not keep generator solidly grounded because of high earth fault current stator can damage same will happen with ht motor if it is connected to this system.

So for this case we need to select the ngr with proper earth fault current

Can you change a dryer from 120 volts to 240 volts It came wired as 120 volts but we do have an outlet for 240 volts Was hoping to speed up dry times and save some?

If the dryer is a clothes dryer then the short answer no. If it is a hair dryer then there might be a voltage switch on the handle that allows you to change voltages. If the manufacturer of the clothes dryer specified that it can be operated on dual voltages then it is just a matter of changing a few terminal connections. Check the instruction manual to see what it states there. This is very unlikely though. In North America all clothes dryers need 120/240 volts to operate. The 120 volts is used for the timer relays and for the drum motor, the 240 volts for the heating elements in the dryer.

By changing to a higher voltage, it will not speed up the speed up the drying time. It is more likely that if you plug the dryer into the 240 volt receptacle it will burn the 120 volt motor out.

What is a monochrome TV?

Do you remember black and white TV? I guess its still around in security monitors.

A 240V to 480V Step up transformer with a load of 85 amps at 480v what amperage will the transformer draw if the primary is 240V?

Since this transformer has a ratio of 1:2 the load current on the 480V side just has to be doubled. 85 x 2 = 170A on the primary. 40.8 KVA transformer. To prove this just find the KVA of both sides and they should be equal.

Why is primary coil in step up transformer thick?

A step up transformer converts low voltage,high amperage current to a high voltage,low amperage current. It requires large diameter wire to carry the high amperage in the primary coil.

Is it possible to have the full load terminal voltage greater than the no load terminal voltage?

Not normally because the supply has a small resistance and very little reactance. Therefore the application of a load causes a voltage drop in the equivalent series resistance of the supply, so its voltage becomes slightly less.

A typical supply resistance can be taken from my home, which has a 240 v 60 amp supply, and the resistance is 0.1 ohms, so that a 10 amp load gives a drop of 1 volt.

What two things are needed to make a current flow in a circuit?

For the circuit to be connected all the way round because if there are breaks in the circuit the electricity will not flow back round. and number 2 a battery or a power source because without power where is the electricity coming from to be honest.

Hope it helped. Thanks. xx

How can you get a v line?

To achieve a V-line, focus on reducing body fat through a combination of a healthy diet and regular exercise. Incorporate strength training exercises that target the core, such as planks and leg raises, alongside cardio workouts to boost fat loss. Additionally, maintaining a calorie deficit by eating nutritious foods can help reveal muscle definition. Consistency and patience are key to seeing results.

What is the transformer turns ratio in terms of inductance of primary and secondary coil?

Turns-Ratio (TR) = Npri/Nsec Inductance-Ratio (LR) = (Npri/Nsec)^2 = (TR)^2 Turns ratio (TR) = (Npri/Nsec) Inductance ratio (LR) = (Lpri/Lsec) = (Npri/Nsec)^2 = TR^2 TR = SQRT[ Lpri/Lsec ]

What would happen if you combine a dilithium crystal with a flux capacitor?

The anti-matter tachyons would reverse their polarity, creating a physi-babble field of strength 20.3 kilo-cochrans. It would be pretty impressive, I think you agree.

But that's not the only thing that would happen. To be completely correct about it,

anything could happen that you want to happen. You've already made up dilithium

crystals and flux capacitors, so why stop there ? Go ahead and write the rest of

the story. Complete the fantasy, and tell the rest of us what happens next.

Caution: in experiment with such arrangements it MUST be kept in mind that dilithium crystals have a maximum power dispersal rate of only 11269 KWatts and there come a point where they just 'can't take anymore'.

What is the maximum allowable resistance of a 680ohms resistor?

This depends on the tolerance rating of the resistor. There's 1, 2, 5, 10% tolerances. For tighter tolerances, you pay a premium - you can get tolerances as close as .1%. This is defined by one of the bands on the resistor. For a 10% tolerance, the maximum resistance of a 680 ohm resistor could be 748 ohms.

What is the advantage of the capacitor-start induction-run motor over the resistance-start induction-run motor?

A capacitor-start system will limit the current drawn by an induction machine by correcting the devices poor power factor during the start up. This limits the current needed to start the device without using any real power.

A resistance-start system will limit the starting current by drawing current unto the resistor instead of the induction machine. The real power used by the resistor is turned into heat and lost.

A capacitive-start system will use no real power and will not create excess heat, it will be more expensive to initially purchase.

Working of MHD generator?

Quiero saber que capacidad es este equipo porque me lo vendieron y no se como se usa

What current is drawn from a 230 V supply by a 8 KW shower?

Since this is basically a pure resistance load, the DC formula for power will be awfully darn close.

That formula says that current times voltage equals watts. Therefore 230 V times unknown amps equals 8000 watts. Or, 8000 divided by 230 equals amps. 8000/230= 34.78 amps, or 35 Amps.

This formula doesn't work if there is a reactive load ( a load that involves either coils or capacitors). A heating element involves neither, it is pure resistance.

70 amperes at 12 volts through 2000 ohms of restance equals?

If you had 12 volts across 2000 ohms, you would get 6 milliamperes, not 70 amperes. Ohm's Law: Voltage = Current times resistance.

This situation is impossible per ohms law: E = I x R In order to push 70A through a 2000 ohm reisistor requires 140,000 Volts! In order to get 70A from a 12V supply a 0.171 ohm (171 milli-ohm) resistor is required.

70A @ 12 V is 840 Watts

70A through 2000 ohms is 9.8 Megawatts!! (P = I^2 x R)</P>

Basic operation of phase angle regulator?

to synchronize the angel in degrees from source to load