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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 difference between protective current transformer and metering currrent transformer?
Usually nothing. The only difference is what it is connected to and operates. The leads from the current transformer could power a meter for remote indication or a protective relay to trip the system offline.
The turns ratio determines how the transformer transforms the voltage and current applied to the primary winding (I'm labelling as '1'). Here are some equations:
N1 / N2 = turns ratio
V2 = V1 * (N2 / N1)
I2 = I1 * (N1/ N2)
Can you plug a microwave that draws 12.5 amps at 120 volts 60 hz into a regular home outlet?
I'm not sure what "regular home outlet" means to you.
In the US, the plug for a device drawing less than 15 amps should physically fit in a "regular home outlet" as I understand the term. However, the outlet would need to be on a circuit that's rated for at least that amount of current, and the total load on the circuit should never exceed its rating.
At 15 amps, the plug is supposed to be modified so that the blades are perpendicular instead of parallel, and outlets designed for such devices are built to accomodate either perpendicular or parallel blades. These are usually called "20 amp outlets" colloquially, and are NOT the same as 240V outlets, which are also usually capable of handling higher current draws that "regular home outlets" are.
Why are no starting components needed on three-phase motors?
Yes, by using a DOL Starter, which gives a controlled "soft-start" for the motor even though it is always connected in delta configuration.
In this type of starting a 3-phase motor, full voltage is applied to the motor through relays and contactors. Its is the most common type of 3-phase motor starter used.
DOL means Direct On-Line starter.
What size cable a 13 amp supply?
To obtain wire size the voltage has to be known. To run 200 meters and supply 13 amps at the load at 240 volts requires a #4 copper conductor. To run 200 meters and supply 13 amps at the load at 120 volts requires a #2 copper conductor. See View Discussion below. <><><> 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.
What device can be used to increase current in a DC circuit?
Transformer or instrument transformer. It can increase and decrease current output.
How many seconds are there in one cycle as it pertains to 60 cycles?
There is one second in 60 cycles. So 5 cycles is equal to about 0.012 seconds or 12 milliseconds.
AnswerThe periodic time is the reciprocal of frequency. So the answer to your question is 1/60 s or 16.67 ms.
Wiring diagram for 440v three phase plug?
Well that is probably a very complicated circuit. You should just look for a Inverter with 220V single phase input and 415V three phase output. It should be that hard to find.
What is the formula of transmission loss in 132 KV HT line?
The transmission loss is the amount of power lost in the line, mainly in the resistance of the wire used, but also in leakage across the insulators especially in wet weather.
33 kV lines are usually balanced 3-phase 3-wire circuits, using aluminium stranded cables without any insulation covering them. The cables sometimes have steel central conductors for strength. A typical cable size (Lynx) has a 180 mm2 cross-section of aluminium strands and can carry about 450 amps, slightly less in the summer. The resistance is 0.153 ohms per kilometre so the loss per wire with maximum current is 30 kW from the I2R formula. With an average current of half that, the loss goes down by three-quarters.
In three pin switch why earth pin is made bigger in size?
The earth pin is longer in a three pin plug so that when being plugged it it makes contact to ground the equipmemt before the other pins make the equipment live. If the equipment has a fault, the earth circuit is already in place to deal with it.
Why are transformer more efficient that rotating electric machines?
Because the electrical parts of a transformer do not move / rotate.
What is the correct calculation for voltage if the resistance is 3 ohms and the current is 4 amps?
What you are talking about is the electrical potential, or voltage, necessary to produce a current of 4 amps through a material with a resistance of 3 ohms. The typical way to solve such a problem is by using Ohm's Law, stating that the current produced is proportional to the potential across the resistor but inversely proportional to the resistance. In other words, I = V / R, where I is the current in amps, V is the electrical potential in volts, and R is the resistance in ohms. Here we know R and I, so we rearrange this equation to get V by itself: V = I * R. So, to get the answer, multiply your 4-amp current by your 3-ohm resistance, and you will get 12 volts.
A 100 watt 220 volt light bulb (or anything consuming 100 watts on 220 volts) draws 100/220, or .45 Amps. It will also have about 220²/100, or 484 ohms resistance.
A 60 watt 220 volt light bulb (or anything consuming 60 watts on 220 volts) draws 60/220, or .27 Amps. It will also have about 220²/60, or 807 ohms resistance.
Is it possible that primary and secondary windings are interchanged?
By definition, the primary winding is the winding connected to the supply, whereas the secondary winding is the winding connected to the load. If you swap them around, then what was the primary becomes the secondary, and what was the secondary becomes the primary! What you should be asking is whether it is possible to interchange the higher-voltage and lower-voltage windings, to which the answer is yes.
In transformer if frequency are reduce then what happen?
basically a matter of the magnetizing inductive reactance which is inversely proportional to frequency. You want to keep the magnetizing current low to minimize power loss and avoid saturating the core. The higher the frequency, the lower the required inductance for a given inductive reactance and magnetizing current, thus the smaller the required core and/or number of turns on the windings.
Magnetizing current is a normal parasitic byproduct of the transformer inductance and the applied voltage level and frequency. The amount of power that can be transferred through a transformer is usually limited by the transformer winding resistances and is unrelated to the magnetizing current. Thus core size goes up at higher power levels due to larger required wire size, not due to any core limitations.
Why using electrolytic capacitor for dc voltage?
Electrolytic Capacitors can only be used with DC supplies because they cannot cope with AC; they are polarised and AC will cause them to blow, whether that's internal or external; in which case you've some cleaning-up to do!
About 24 volts. Take 18 and divide by 0.707, then subtract about 1.4 to compensate for the two diodes that will always be in series with the load.
Of course, any load will cause ripple, so the 24 volts is with nearly no load.
What are the basic principles of ohms law?
Not all circuits obey Ohm's Law; in fact, most don't!
Ohm's Law is a law of constant proportionality, and states that 'the current flowing through a conductor is directly-proportional to the potential difference across the ends of that conductor providing physical conditions, such as temperature, remain constant'. Expressed another way, the ratio of voltage to current must be a constant for variations in voltage, for Ohm's Law to apply.
Ohm's Law only applies to linear ('ohmic') materials which includes metals, providing their temperatures are constant. Electrolytes, gases, semiconductors, however are non-linear ('non-ohmic'), and Ohm's Law doesn't apply to these.
The ratio of voltage to current is resistance, and this applies to all circuits, whether linear or non-linear. But it only tells us what the resistance happens to be at that particular ratio. But for Ohm's Law to apply, the resistance must remain constant for changes in voltage. Put simply, if the resistance of a circuit changes when the applied voltage varies, then it is not obeying Ohm's Law.
What is diff between vcb and sf6?
SF6 (Sulfur Hexaflouride) is the god of gaseous dielectrics. It is a VERY poor conductor, and when it does decompose in an arc, it re-assembles itself in short order. It is also dense, so that it sinks to the floor, and pools in the lowest spot it can get to. This also makes it great in breaking arcs, because it makes it highly thermally conductive, stealing the heat from the arc & diffusing it. SF6 breakers are generally smaller than other types (of the same handling capacity), and therefore lighter. There's nothing we've found better with high voltage.
Vacuum is decent. It has fair dielectric strength, can break an arc pretty well. It has one massive advantage over SF6: It is environmentally benign. SF6 is pretty destructive, and has a 3200 year life in the atmosphere. That's tenacity !
So, it has been suggested that if your application is below 36kv or so, you should stick with the VCBs, but you can't beat the handling of SF6 as you go higher.
Why it is useful to use rms notation for alternating current and voltage?
AC waveform is sinusoidal waveform it has both positives and negative cycles so we dont have a standard constant value to do Measurements so instead of using AC quantities we use ROOT mean square values which is obtained by dividing Vpp(peak to peak voltage) by 1.414
AnswerThe rms-value of an AC current is the same as as the value of DC current that will do the same amount of work. For example, 10 A (rms) AC will do exactly the same amount of work as 10 A DC.What would be a parallel circuit in your house?
== == A Parallel circuit is one where the current flows in several circuits (or 'branches') at the same time.
In the house, the Main Breaker box (or fuse panel) is connected to the city's power lines. The current flows through the main circuit breaker and is then split into 2 or more circuits each of which is protected by its own circuit breaker.
Envision a water pipe that is mounted horizontally in the attic. The pipe has 10 one inch holes cut into it, into these holes are fitted 10 one inch pipes that let water flow through each one as required (such as when the toilet is flushed, or the kitchen sink faucet is turned on).
So, coming out of the Main Breaker box are several cables (each protected by its own smaller breaker), each going to a separate room, or area (outdoor patio, or detached garage).
The reason for parallel electrical circuits is to limit the amount of current in each cable. If there was only one cable for the entire house, all of the current for every electrical device in the house would have to flow through the same cable, as opposed to each room (or area) having its own cable and only using as much current as is required for that room.
I hope this helps, if so, please 'Recommend Contributor', and reply to this answer for more info, or a more detailed explanation.
Why the pins in the three pin plug are split up to the middle?
In the UK, we use three pin plugs. Neutral (blue cable), Positive (brown cable), Earth (green and yellow striped cable). Positive is also known as the Live cable. The Earth cable is an important safety feature that directs electricity safely to earth should a short-circuit cause the device's metal body (a toaster, for instance) to become live and a dangerous shock is possible to any one touching the device's metal body. Before the modern standard colouring was introduced, black was the neutral, red the positive, and green the earth. This old colouring can still be found in buildings built before the change-over.
What are the disadvantages of a three phase induction motor?
The primary disadvantage of the three phase induction motor is that speed control is a challenge. But new technology in the form of VFDs (variable speed drives) is now rectifying this situation very effectively. Another disadvantage is that single phase power is common while three phase power is less commonly available.
What is the color assigned to the high leg conductor of a 4-wire delta secondary three phases?
Assuming you are talking about a 120/240v delta system the color coding is as follows.
Phase A(120v)-Black
Phase B(208v "Wild leg/High phase")-Orange
Phase C(120v)-Blue
There are other color coding methods but this is the most common.
What happen when current transformer saturate?
I am assuming that we are referring to an ordinary power transformer working at 50-60 Hz of alternating current circuit system. Saturation in these transformers is the result of the magnetic field in the iron core reaching the saturation phase. At low current levels on the input side (currents are measured in amperes or amps) the magnetic filed produced in the core increases linearly with the current. Consequently, the current produced in the output coils is proportional to the input currents. If the amount of current in the input coil is large, the magnetic field in the core will not be a smooth sine wave, but a sine wave with tops and bottoms chopped as the magnetic core reaches saturation at the peak current level. This happens even if the input current remains a sine wave. The current induced in the output is directly proportional to the magnetic field and hence has the same shape - chopped off sine wave. Here are some of the implications:
1. Energy transfer from input to output is now limited by the chopping process which limits the peak current that can be induced into the output coil.
2. Energy transfer efficiency goes down - more energy may be poured in, but output energy does not increase significantly. Transformer will heat up as input coils experience greater currents. There will also be greater heating of the magnetic core due to magnetic hysteresis effects.
3. The output current has a chopped sine wave shape and hence has more 'harmonics' - waves with frequencies that are multiples of the input waves. The output current wave shape resembles a square wave more than the input sine wave. This is akin to waves produced by electric guitar distortion equipment. While this may not be important in some applications such as heating, it is usually unacceptable in audio transformers.
