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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
Common conductors found around the house include copper wiring in electrical outlets, metal pots and pans for cooking, and metal doorknobs. These materials allow electricity or heat to flow easily through them.
Clearance between phase to earth?
for 415V phase to earth min clearance is 25mm pallav
Comment
You cannot have a voltage between a 'phase' and earth. You should be asking the clearance between a 'line' and earth.
Is a separate ground wire required for each circuit in a conduit?
No, a single ground wire can be used for multiple circuits in a conduit as long as it meets the sizing requirements based on the largest circuit conductor in the conduit. The ground wire provides a path for fault current to safely return to the source in case of a fault or short circuit.
Structure of human heart with its working?
Hear is a pumping organ. It consists of four chambers. upper two chambers called Auricles and lower called Ventricles.
Left side of the heart is filled with Pure blood and right side with impure blood.
How do you check a 3 phase motor?
Depends firstly on the type of motor and secondly what your testing for.
If you are the manufacturer, you test according to the IEC/AS Codes for electromechanical machines.
Considering just one type of 3 phase motor, the Squirrel Cage: if you are testing it electrically, then first of all you have to check the insulation resistance of each phase to earth with an appropriately sized megger (insulation tester). Then you measure the stator's winding resistance between each phase. (You don't check the phase-to-phase on the rotor as it's basically a dead short for Squirrel Cage motors.)
If you are load-testing, depending on the codes you are following, you start it up and run it for around 8 hours. During this period you take temperature measurements on the windings and the bearings and vibration measurements of the bearings. For the stator windings, you just measure the temperature of the stator housing unless the motor is big enough to have its own set of built-in RTDs. (Remote Temperature Detectors.)
What is one half breaker scheme used for 400220kv substation?
a method of interconnecting several circuits and breakers in a switchyard so that three circuit breakers can provide dual switching to each of two circuits by having the circuits share one of the breakers, thus a breaker and one-half per circuit; this scheme provides reliability and operating flexibility, and is generally used at 500 kV when more than five lines terminate in a substation.
The reason you were lucky not to have been electrocuted was probably because of these reasons:
1) This sequence took place within much less than a second: the pliers first cut through the Neutral wire, not the Hot wire, and that Neutral wire protected you when the pliers then went on to cut through the Hot wire.
2) The jaws of the pliers probably melted from the high current but that same high current caused the household power supply circuit's fuse or circuit breaker to cut off the currentbefore you could be electrocuted.
We all do something like that at some time or other, not only with electricity but using any tools we are unfamiliar with... driving a car... whatever. Now you must know that you were foolish to cut the cord without first making sure that the cord was unplugged from the supply outlet!
Sometimes we have to learn things the hard way and this was one good result from your mistake.
How are watt mega-watt giga-watt defined?
A megawatt is 1000 kilowatts (also equal to 1341 horse power) or 1*10^6 watts, a gigawatt is 1000 megawatts. A watt is equal to one joule per second and a joule is defined as the amount of work done when 1 ampre of electrical current is passed through 1 ohm of resistance. Ohm is defined as the amount of electrical resistance of a conductor in which 1 ampre of current is produced by a potential of 1 volt across its terminals.
To measure battery current, you can use a multimeter set to measure current in series with the battery. Connect the multimeter in series between the battery and the load to measure the current flowing from the battery to the load. Make sure to select the appropriate current range on the multimeter to avoid damaging the instrument.
It refers to unwanted current flow to ground.
This term is also called ground leakage, depending on what part of the world you live in.
For more information see the answers to the Related Questions shown below.
The merging of a free electron and a hole is called?
The merging of a free electron and a hole is called recombination. This process occurs in semiconductors when an electron fills a hole in the valence band, resulting in the release of energy in the form of light.
Cogging torque is the phenomenon where a permanent magnet motor experiences non-uniform force during rotation due to magnetic attraction between the rotor and stator teeth. This can cause vibrations, noise, and affect the smoothness of the motor operation. Design techniques such as skewing the rotor slots or using sinusoidal winding can help reduce cogging torque.
Atoms.
Electricity is not something you can "break down" into "elements".
You can use electric energy to drive certain chemical reactions. For example, you can split water into hydrogen and oxygen. But that does not mean that electricity is "made of" hydrogen and oxygen. Water is.
Electric current is made of electrons flowing in a conductor such as copper or aluminum. (e.g. wire)
The wire does not weigh any more, or less, for having electricity flowing in it, as the electrons in question were and are always there, even if no electricity is flowing. It is just that in conductive materials (like most metals, like copper) the outer electrons of the atoms are fairly loosely bound to the nuclei. So electric current involves shoving electrons into one end of the wire and taking the same number out the other end. This is done by applying "electromotive force", EMF, which we measure in volts and is commonly called "voltage". The total number of electrons in the wire remains the same. The electrons just move along from one atom to the next, so the net charge in the wire remains zero.
This does make electricity "weightless", I suppose. However this would not cause the wires in transmission lines to "hang upwards" because the weight of the wires themselves would still be there. Again, the wires don't weigh any more - or any less - for having electric current flowing in them.
You can transport by train chemicals and materials which, when arranged in the proper way, produce an electromotive force. We call such an arrangement a "battery." However batteries are a very inefficient means of storing electrical energy. Just for comparison, a liter of gasoline contains the equivalent of 9000 watt-hours of energy; a liter's worth of lithium-ion battery, the best currently available, contains only 250 watt hours.
The materials from which primary batteries (those that start out charged and can only be used once) are not in infinite supply, either, so the idea of just making batteries instead of using fossil fuels won't work. There's a LOT more latent energy in the ground in the form of fossil fuels than there is in chemicals that could make batteries. And batteries aren't the most environmentally-friendly things either.
Electricity flowing in wires is an extremely efficient, clean, safe, and convenient way to move energy around. So much so that if you have electricity, about the last thing you want to do with it (from an energy efficiency point of view) is to use it to e.g. make hydrogen or charge a battery.
moving electrons
Can you convert a 3-phase heater to single phase?
This idea is not economic.
It would cost more to convert it safely than buying one or more single phase heaters (either second-hand or new) to give the same heating effect.
3-phase heaters are not usually intended for domestic use in homes, except for the latest new-builds which have 3-phase supplies. They are commonly used in industrial sites (factories, workshops, etc.) or large public areas (department stores, airline terminals, etc.) where a 3-phase power supply would be installed as standard at the site.
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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.
How do you convert a 3 phase car lift to single phase?
The best way is usually to buy a new single-phase motor and replace the 3-phase motor.
You can also buy something called a rotary phase converter, but for any amount of HP they are about as expensive as a new motor. Expect to pay 500 to 700 dollars US for a 10hp rotary converter.
Static phase converters are not a good choice for motors that start and stop or reverse often, such as yours.
How do you decide KVAR rating of capacitor bank?
Generally the capacitor rating of a bank are decided on the load factor.ie higher the KVAR higher the capacity.KVAR is the reactive power in which load angle differs with the load variation.If we know load factor multiply it by the sine angle which gives us the capacity of the cpapcity of the load bank. Generally the capacitor rating of a bank are decided on the load factor.ie higher the KVAR higher the capacity.KVAR is the reactive power in which load angle differs with the load variation.If we know load factor multiply it by the sine angle which gives us the capacity of the cpapcity of the load bank. Generally the capacitor rating of a bank are decided on the load factor.ie higher the KVAR higher the capacity.KVAR is the reactive power in which load angle differs with the load variation.If we know load factor multiply it by the sine angle which gives us the capacity of the cpapcity of the load bank.
The location of lightning arrestor is?
Lightning arrestors are typically installed at the highest point of a structure to provide a path for lightning to safely discharge into the ground, thus protecting the structure from damage. They are commonly found on rooftops, towers, or any high points where lightning is likely to strike.
What are the examples of conductivity?
Some examples of materials with high conductivity include metals like copper, silver, and gold. Other examples include materials like graphite, which is a good conductor of electricity due to its structure of delocalized electrons. Conversely, insulators like rubber, glass, and plastic have low conductivity.
The energy used by the heating element can be calculated using the formula: Energy = Power x Time. Power can be calculated using the formula P = V x I, where V is the voltage (110 V) and I is the current (3.2 A). So, P = 110 V x 3.2 A = 352 W. Therefore, the energy used by the element over 5 hours is 352 W x 5 hours = 1760 Wh or 1.76 kWh.
What is a Reverse current relay?
A reverse current relay prevents a generator from discharging the battery when generator output is less than battery voltage. When generator output is greater than battery voltage, the reverse current relay closes and connects generator to electrical bus.
What type of jobs can you get as a chemical engineer?
Typical jobs you can get as a chemical engineer:
1. Production Engineer
2. Process Engineer
3. Quality Control and Reliability Engineer
4. Plant Manager
5. Advanced Process Control Engineer
6. Operations Manager
7. Environmental Specialist
8. Project Supervisor
9. Energy Expert
10. Materials Technologist
What are the Advantages of circuit switching?
*Fixed delays, because of the dedicated circuit. *Guaranteed continous delivery (service), also because of the dedicated circuit.Abdulrahman N. Sayed FCI - Helwan -- Computer Science
Is silver tarnishing a physical change?
No, it is a chemical change. The tarnish seen on silver is silver sulfide which formed by the silver reacting from small amounts of hydrogen sulfide in the air. So silver sulfide has been created by a chemical reaction.
Can aluminum foil store electricity?
The answer is YES. One can build an energy storage capacitor, using aluminum foil and a suitable insulator, in the comfort of one's own kitchen.
The following essay is provided based on my analysis of this question several decades ago, early on in my career as an electrical engineer. The cost estimates which I used for the concluding paragraphs were based on prices available at the time; but times change, so things might pencil out differently today; I'll leave that to someone else.
I designed a large storage capacitor using aluminum foil and mylar film used for preserving food in the refrigerator.
The amount of VOLTAGE that can be applied to this storage device is strictly limited by the characteristics of the insulating material. Newspaper could work. Wax paper is better than newspaper. And Mylar is better than wax paper. All three of these can be used to build a quick and dirty storage device in the comfort of your own living room. Mylar, as available on a household roll from the supermarket, can handle a lot more than 12 volts. Wax paper has been used in the distant past for very low power applications. Newspaper has never been used, to my knowledge.
I cut all the sheets in a square format, roughly 1 foot square using the materials I found in the kitchen cupboard, with the mylar squares being just enough larger than the aluminum squares that every aluminum square will be definitely and positively separated from its neighbor sheets. This is important.
The wife spotted me and I had to make an emergency trip to the grocery for replacements. This is important, too.
I started placing the sheets in the following pattern:
One sheet of insulator
One sheet of aluminum foil, offset to the left about 1/4 inch so that it was slightly exposed;
One sheet of insulator
One sheet of aluminum foil offset to the right
One sheet of insulator
One sheet of aluminum foil offset to the left
...and so on, repeating that procedure.
All the exposed aluminum edges on the left are connected together electrically. and all the exposed aluminum edges on the right are connected electrically. One side is meant to be connected to the positive electrode and the other to the negative electrode. Doesn't matter which; just don't accidentally touch the two together.
Charge it up to twelve volts, and it will take and hold that charge for quite a long time. Connect it to a (12 volt) device that uses minimal current, such as a small radio or an LED light, and it could power that device for quite a while.
It behaves in every way like a battery. It is charged up using DC (Direct Current) electricity, and its energy is fed out to DC devices only.
CAUTION: This device will NOT store AC (Alternating Current) electricity. This will make the circuit breaker out in the garage go pop, and you will have to go find it to turn it back on again. DO NOT connect this device to a wall socket.
Using DC, a larger pile of sheets will store commensurately more electricity.
Theoretically, one could build one of these things without limit.
However, there is a certain hazard, and the risk from this hazard can be devastating. I never went beyond designing a modest storage device, because of the risk of having anything larger. Here's what I mean by THE HAZARD:
None of these insulating materials were produced with the idea of storing electricity. So from an electrical point of view, the insulating properties of each of these materials is variable. The thickness is variable, and there may be tiny holes. Newspaper will show the most variation. Wax paper will be slightly better in this regard, as the wax fills in the weak spots somewhat. Mylar will be best ... but there are still variations, not only in thickness but in the occasional tiny hole, too small to see.
Consider this scenario: You and your friends decide to build a GREAT BIG storage device in your buddy's garage. You plan to use it to jump start vehicles which have dead batteries, without having to wait around while the vehicle battery gets enough charge to help out. You want to make it start NOW, so you want a big storage device.
You get hold of the cardboard carton that once held his new refrigerator and you start building an enormous storage capacitor. You place it in the garage, in between the wife's SUV and the riding lawn mower.
After several weeks of cutting sheets, laying them out, going to the grocery for more aluminum foil, more mylar and more beer, finally everything checks out and you start charging it up. One of you plugs in the battery charger. The battery charger makes a complaining noise and pops its little safety circuit breaker.
This has never happened before, but every time you reset it and try it again, it pops again. Eventually one of you puts down the beer can and digs out the instruction manual for the battery charger. You discover that this charger has a safety feature that detects a short circuit, such as when your 5-year-old hooks the leads together. This is to keep the battery charger from burning itself up.
The storage capacitor looks like a short circuit to the battery charger, at least at the first. Once some charge has built up, then the current requirement will drop and the battery charger will be able to handle the job.
Gotta limit the current flow.
Eventually someone thinks of the idea of including some form of resistance to put into the charging circuit. After several unsuccessful tries, one of you finds a spare headlight bulb with one working filament, and hooks that in series. The battery charger is capable of pushing current through the headlight bulb without popping its circuit breaker, and doesn't even know that the storage capacitor is there. The storage capacitor happily begins storing up energy.
Two or three days go by and eventually you notice that the headlight bulb is getting dimmer. This means that the current flow is slowing down. This is normal. It means, in turn, that the voltage which has built up in the storage capacitor is now at some respectable percentage of the capacity of the battery charger. A voltage meter (DC) applied to the storage capacitor will probably show that it is around 4 or 5 volts now.
Depending on the capacity of the battery charger, it will be desirable to remove the light bulb from the circuit and connect the battery charger directly across the storage capacitor. The battery charger hums loudly, and the voltage meter shows that the voltage is slowly building up.
You plan for the moment when you can disconnect the charger and provide a demonstration of the power of this device. You decide to use your kid's pickup, which has been sitting dormant in the street for weeks because he can't afford a new battery. You push it into the garage, in front of the storage capacitor, and lay out the jumper cables.
Next Saturday comes. The guys all arrive with beer and families and prepare to see the storage battery begin to do its work. A small crowd arrives at the driveway in front of the garage. They are just about ready to open the garage door to inspect the storage capacitor at full readiness, and shut off the charger ... when something unexpected happens.
There is a pop, immediately followed by a BANG, and the garage door is tossed out in front of the garage. Smoke and flames billow out, a wave of heat hits everyone with enough force and heat energy to curl the hair of the closest bystanders. The inside of the garage is totally engulfed in flames. Every container of gasoline (such as the gas tank in the pickup, in the lawn mower, and in the wife's SUV) is totally on fire and busily destroying everything around it.
We won't go into the visits by the fire department, the insurance investigator and the contractor hired to rebuild the front half of the house. Let's cut to the chase: What happened?
Somewhere inside of that storage capacitor, a weak point in the mylar insulation allowed a tiny trickle of current to get through. It wasn't much, but it was just enough for the current to build up a bit of heat. This hot spot began melting the mylar from a solid to a liquid, and when the liquid got hot enough to turn into vapor, it made a hot bubble ... the pop ... and escaped from the capacitor as a gas, like air leaving a popped balloon.
Then the two opposing aluminum sheets came together and made positive contact.
The stored energy developed an enormous instantaneous short circuit entirely within the storage capacity ALL AT ONCE, and ALL IN THE SAME PLACE. That produced an enormous amount of heat ... nearly instantaneously ... and vaporized chemicals from the mylar, which made a flammable gas, which ignited, thus producing the BANG, which spread the heat, which ignited everything around it (the interior of the garage).
The mylar sheets are good for a hundred volts DC or more. Twelve volts is an eighth of that. So why did it happen?
It's because the household mylar sheets were never designed to hold back electricity; they were designed to hold back microbes, and air molecules. And the household mylar does this just fine. But every now and then there is the tiniest imperfection, much smaller than the size of an air molecule ... yet it's big enough to let electrons through.
There aren't many imperfections like that.
But all it takes is one.
Caution Notice: Don't use household materials for purposes for which they were never designed. Not without a very large safety factor.
OK, so now I'll back away from giving the caution notice, and give a bit of advice.
If you've gotta have an electrical storage device for the kid's science fair project, and you've gotta have it TOMORROW, and Radio Shack is closed, then go ahead and build a small storage capacitor as described above. Choose a demonstration such as a light bulb that runs on low voltage and requires low amperage. LEDs are much better than light bulbs using a filament.
Next, what if you really do want to make a really big storage device?
Advice: Stack the odds in your favor: Use two sheets of mylar in between every sheet of aluminum.
Up side: Your safety factor just went up by a huge amount.
Down side: The storage capacity of your device just went down. (Because the aluminum sheets are now twice as far apart, and this decreases the storage capacity.)
As a science fair project, this is a good, fun thing to build.
If you want a rugged, reliable and safe storage device for your home for permanent use, use large size capacitors from Radio Shack. These are all designed by the best engineers to use the thinnest mylar films, made to stringent standards, with the minimum of aluminum films, resulting in devices which have a remarkable amount of energy storage for their size. They can be connected in a series-and-parallel arrangement to give considerable power storage capacity. Safely. Except for the risk from the do-it-yourself connections. All it takes is one unwanted cross-connection and everything will go up in flames before you can say"Oh! No!"
Yet, even here, there is a safety factor in comparison with the do-it-yourself aluminum foil and mylar; because every commercial capacitor is encased in a capsule which gives considerable protection from the smoke-and-flames scenario described above.
When you do the calculations, be sure to compare the total cost (aluminum foil, mylar sheets, soldering equipment and BEER) to the cost of a deep-cycle (RV-type) lead-acid battery. When I did that, years ago, I found that it was MUCH less expensive to go with the battery. Holds more energy, in a smaller package, for LOTS less money, LOTS less risk...
And LOTS less beer.
Morry
What is meant by Kpf in capacitors?
Kpf is the power factor of a capacitor, indicating its ability to store and release electrical energy efficiently. A higher Kpf value represents a more efficient capacitor in terms of energy storage and release.
