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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
Houses are not wired for three phase power as there is typically no need for that much power. 120/240 volts is the typical home voltage. Even some vary large houses (mansions) are still the same single phase voltage, just a very large amperage service (voltage times amperage is wattage, and use is rated in wattage). Utilities charge a base rate for homes that is usually in the range of $10-$30 per month, this is the charge when no electricity is used. For a three phase service, the charge is typically $125-$250 (depending on location and utility) per month before any power is used. Most all wires installed in a house are single phase. The black and white in 2 conductor with ground NM cable are suitable for only two of the three phases. 3 conductor with ground can be used, but that is not installed unless there is a purpose for the third wire that makes it unusable for the third phase. Three phase power must be designed into the construction of the house before it can be considered for a service, and then the cost is likely too high for the average owner.
Alternative Answer
The above answer applies to North America. But in other parts of the world, three-phase supplies to residences are quite common. For example, my house, here, in Cyprus, has a three-phase service. In these cases, the consumer panel has three separate line busbars, and the residence's loads are balanced between each line.
How can electricity produce by using magnet?
Electricity is generated when a piece of conductive metal (such as copper) is passed through a magnetic field (or if the magnetic field is moved around the metal). A generator will have a copper wire in the center, surrounded by a magnet shaped like a torus (donut shaped, wire is in the hole in the middle). The wire is stationary. Electricity is generated when the magnet is spun (moving the magnetic field around the wire). This will generate an AC current (alternating current).
When the diameter of a conductor is doubled what happens to its resistance?
Resistance will decreases... Because R is inversely proportional to Area of the conductor.
AnswerIf the conductor has a circular cross-sectional area, then doubling the diameter will reduce the resistance to one quarter of its original distance. This is because area is proportional to the square of the radius, and resistance is inversely proportional to cross-sectional area.
Ohm's Law has nothing whatsoever to do with the factors that determine the resistance of a conductor.
The resistance of a conductor is directly-proportional to the resistivity of the conducting material and to its length, and inversely-proportional to its cross-sectional area.
How we select a transformer by vectorgroup?
A Vector group is the International Electrotechnical Commission (IEC) method of categorizing the primary and secondary winding configurations of three-phase transformers. Within a polyphase system power transformer it indicates the windings configurations and the difference in phase angle between them. The phase windings of a polyphase transformer can be connected together internally in different configurations, depending on what characteristics are needed from the transformer. For example, in a three-phase power system, it may be necessary to connect a three-wire system to a four-wire system, or vice versa. Because of this, transformers are manufactured with a variety of winding configurations to meet these requirements. Different combinations of winding connections will result in different phase angles between the voltages on the windings. This limits the types of transformers that can be connected between two systems, because mismatching phase angles can result in circulating current and other system disturbances. Symbol designation The vector group provides a simple way of indicating how the internal connections of a particular transformer are arranged. In the system adopted by the IEC, the vector group is indicated by a code consisting of two or three letters, followed by one or two digits. The letters indicate the winding configuration as follows: * D: Delta winding, also called a mesh winding. Each phase terminal connects to two windings, so the windings form a triangular configuration with the terminals on the points of the triangle. * Y: Wye winding, also called a star winding. Each phase terminal connects to one end of a winding, and the other end of each winding connects to the other two at a central point, so that the configuration resembles a capital letter Y. The central point may or may not be connected outside of the transformer. * Z: Zigzag winding, or interconnected star winding. Basically similar to a star winding, but the windings are arranged so that the three legs are "bent" when the phase diagram is drawn. Zigzag-wound transformers have special characteristics and are not commonly used where these characteristics are not needed. * III: Independent windings. The three windings are not interconnected inside the transformer at all, and must be connected externally. In the IEC vector group code, each letter stands for one set of windings. The HV winding is designated with a capital letter, followed by medium or low voltage windings designated with a lowercase letter. The digits following the letter codes indicate the difference in phase angle between the windings, with HV winding is taken as a reference. The number is in units of 30 degrees. For example, a transformer with a vector group of Dy1 has a delta-connected HV winding and a wye-connected LV winding. The phase angle of the LV winding leads the HV by 30 degrees. The point of confusion is in how to use this notation in a step-up transformer. As the IEC60076-1 standard has stated, the notation is HV-LV in sequence. For example, a step-up transformer with a delta-connected primary, and star-connected secondary, is not written as 'dY11', but 'Yd11'. The 11 indicates the LV phase lags 30 degree behind the HV side. Transformers built to ANSI standards usually do not have the vector group shown on their nameplate and instead a vector diagram is given to show the relationship between the primary and other windings.
What does electrical engineering deal with?
technology is a study of how to put scientific knowlege to practical use
and engeniering has to deal with design of electrical machinery of power plants for producing electric energy from steam,water er other power, and of wire networks for distributing this energy efficiently to costumers
Why does one hear a hum when standing near a power tranformer?
Why do transformers hum?
We could use the tired saying 'because they don't know the words,' but that might get us sidetracked.
The short and simple answer is that transformers hum because of an effect known as 'lamination rattle' caused by DC voltage on the line or poor construction or both. 'Lam' rattle occurs in all transformers to some degree, that degree being related to the quality of the transformer and the quality of the line voltage.
What is a peak load voltage out of a bridge rectifier for a secondary voltage of 15 Vrms?
A: Peak voltage is RMS multiplied by a factor of 1.41
What is the purpose of open circuit test and short circuit test of a transformer?
An open-circuit test is done with the transformer running at its rated voltage but with no load. This measures the power lost in the magnetic core. (IR Losses)
A short-circuit test is done with the transformer running at its full rated current in all windings but at a low voltage. The secondary is shorted and the primary voltage is adjusted to give the rated current. This measures the power lost in the copper windings. (Copper losses)
Where can LED lights be found?
The are many companies online from which one could purchase red LED lights such as Amazon, Super Bright LEDs, and RadioShack to name a few. There are also other sites that specialize in these types of lights for beauty therapy treatment such as Hollywood Beauty Secrets, and Trueskin in the UK.
Neutral earth is very necessary for observe the unbalaced laod of the 3 phase system. it is also useful for single phase supply and in lighting purpose. neutral earth is also earthed the short ciruit fauly current , which is flowing through neutral. this type it is very essencial for protection and safety purpose.
AnswerThere are a number of reasons why the neutral of a supply is earthed (grounded). The first reason is to protect the low-voltage secondary side of the distribution tranformer in the event of a short circuit from the high-voltage secondary side (it will cause the protection on the high-voltage side to disconnect the transformer). The second reason is to establish a datum point for potentials measured on the secondary side of the tranformers -in particular, if the star-point of a three-phase transformer is not earthed, then an unbalanced load will result in unbalanced supply phase voltages, and a potential-difference between neutral and earth -both undesirable and dangerous.
The resonant frequency is set by the L and the C: 900 microhenrys and 0.014 microfarad would resonate at a frequency given by:
F = 1/ [2 pi sqrt(LC)]
If the components are in 'micros' the answer is in Megahertz.
In this case the resonant frequency in MHz is:
F = 1/ [2 pi sqrt(900 x 0.014)] or 0.0448 MHz, 44.8 kHz.
The reactance of the inductor and the capacitor is 253 ohms, so adding a 1000 ohm resistor in parallel would give a tuned circuit with a Q of 1000 / 253 or 3.9.
What is open loop and close loop system?
Q: What is the difference between 'Open Loop' and 'Closed Loop'? A: When the engine is first started, and rpm is above 400 rpm, the system goes into 'Open Loop' operation. In 'Open Loop', the ECM will ignore the signal from the Oxygen (O2) sensor and calculate the air/fuel ratio based on inputs from the coolant and MAF sensors, but mostly from a pre-programmed table in the memcal. The system will stay in 'Open Loop' until the following conditions are met: 1. The O2 sensor has varying voltage output, showing that it is hot enough to operate properly. (This depends on temperature)
2. The coolant sensor is above a specified temperature about 40oC/104oF.
3. A specific amount of time has elapsed after starting the engine. The specific values for the above conditions vary with different engines and are stored in the mem-cal. When these conditions are met, the system goes into 'Closed Loop' operation. In 'Closed Loop', the ECM will calculate the air/fuel ratio (injector on-time) based on the various sensors but mainly the O2 sensor. This allows the air/fuel ratio to stay very close to 14.7:1.
As many as you want. It depends on the capacity of your supply. Let me break this down. Current or amps is what is drawn by a device or a load. For example, lets say you plug in a 1500 watt 120 volt space heater and turn it on. Now you want to know what kind of amperage is being drawn by this device. Take 1500 watts and divide 120 volts into it. The answer will be your amperage or current. The current draw would be 12.5 amps. (I know there are other people out there who say no no that is not entirely right. I know this. I do not wish to give a lesson in calculating impedance when this answer is close enough and is with in a safe range of accuracy. Just keeping it simple)
Another fact that may be of interest to you is there is as much as a 8000 fault amp potential in the average 100 amp service panel. This means that if your two lines coming into your panel would short it would blow up. This is what is called an Arc Blast.
How do you carry out short circuit test on power transformers?
For carrying Short Circuit Test on Power Transformer Do the following:
1] Isolate the Power Transformer from service.
2] Remove HV/LV Jumps and Disconnect Neutral from Earth/Ground.
3] Short LV Phases by Cu/Al plate which could withstand short circuit current and connect these short circuited terminals to Neutral
4] Energise HV side by LV supply (440 3ph Supply) with OLTC tap position on Normal.
5] Measure Current in Neutral, LV line voltages, HV Volatage and HV Line Currents on various OLTC Tap position.
Analysis:
If Neutral current is near to zero transformer windings are OK
If Neutral current is higher or equal to Line current between LV Phase one of the winding is Open.
What is the International color code for DC wiring?
"What is the International color code for DC wiring?" "What is the International color code for DC wiring?" "What is the International color code for DC wiring?" "What is the International color code for DC wiring?"
What are the difference between high voltage and low voltage?
Hi, The main difference is Fuel consumption. High current genertors always consumes much fuel because the load on the engine will be high. The high voltage low current generators doesn't need much fuel to run. You can understand this by comparing 1 kva and 5 kva single phase generators. For both generators voltage will be same (230v) But output current differs. So the fuel consumption also differs. But you get a high current source. Low voltage high current generators can be used for welding kind of stuffs which needs high current to do the job. If you have step down transformer then you can save the fuel.
How does wireless printer connect to wireless laptop?
Some printers have a wireless adapter, but most of them don't. There are two cases. You connect the printer to a computer which has a wireless adapter, or if your printer has a lan card you can connect it to your wireless router and use advantages of wireless networking in that way.
What is the difference between shock load and gradually applied loads and suddenly applied Load?
The only difference between a shock load and a gradually applied load is something called an impulse; defined as the integral of a force with respect to time. When a force is applied to a rigid body it changes the momentum of that body. A small force applied for a long time can produce the same momentum change as a large force applied briefly, because it is the product of the force and the time for which it is applied that is important.
Why inductor does not allow the sudden change of current?
an inductor has inductance(L). its unit is henry. when any change in currentin a inductor occurs it produces an self induced emf equal to e=-Ldi/dt volt. minus(-) sign indicates the direction of the induced voltage which is in opposition to the cause which is producing it. here the case is change in current(di/dt). that's why, whyan inductor opposes any change in voltage and hence current in it.
What do you need to make a simple series circuit to light a bulb?
To make a simple series circuit to light a bulb, the simplest components are a power source (such as a battery); a switch (to turn the power on or off); the bulb (obviously !); and some wires to connect everything together.
What is the resistance in a parallel circuit with resistances of 2 ohms 4 ohms 6 ohms and 10 ohms?
In a parallel circuit, the total resistance is the inverse of the total of 1 over the value of the first resistor plus 1 over the value of the second resistor. Said another way, if you take 1 over the value of R1 plus 1 over the value of R2, and then take 1 over that, you will find Rtotal. So let's do that. 1/10 + 1/2 = 1/10 + 5/10 = 6/10 1 divided by 6/10 = 10/6 = 1 2/3 ohms for the total resistance. As a quick check, in any parallel network where a group of resistive elements are all connected in parallel, the total resistance will be less than the value of the smallest one. The smallest one in this case is 2 ohms, so we are good to go by that simple check.
Current in a parallel circuit?
In any parallel connection The original current gets divided into the parallel branches, however the division is solely based upon the resistances of the parallel paths. Current always tries to flow through the branch having the least resistance. Thus More current will flow in the branch having less resistance and vice-versa. The currents flowing in the parallel branches can be found out by using the current divider rule. Suppose if R1 & R2 are two branches of a parallel connection & i1 & i2 is the current flowing through them respectively. Let 'I' be the original current then the current through R1 can be given as
i1=R1/(R1+R2) * I similarly current through R2 can also be calculated.
What is the difference between a standard capacitor and a coupling capacitor?
Coupling capacitors are used to couple different stages so as to prevent DC from the o/p of one stage to go into the i/p of the next stage. For instance in coupling two BJT (bipolar junction transistors) it is required to use coupling capacitor to allow only ac signal from the o/p of fisrt stage to go to i/p of next BJT as incoming dc can distrub the biasing of the other BJT.
Bypass capacitors are used to bypass the ac signal to ground. A capacitor is connected b/w the gnd and the wire. For ac signal capacitor will behave as short and will bypass it. However dc will not be bypassed as capacitor will behave as open for DC.
