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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
How do you set a variac to zero volts output?
One should be able turn the variac all the way to one end of its stroke (typically left), so that the brush contacts the windings right where the neutral connection is. If you cannot, perhaps the stops need adjusted, the brush needs re-aligned/replaced, or the windings need cleaned.
Who invented the first battery?
Alesandro Volta invented the first battery.
The first actual battery was invented by a man in Italy named Alessandro Volta in 1800. Volta was a physicist who was born in February of 1745 and died on March 5, 1827.
How do you install a ring main and how does it work?
Installing ring main circuits is what qualified licensed electricians do. To become licensed they have had to complete a lot of training and pass exams. All this helps to ensure that the work they do will be done safely and efficiently.
- In the UK - and maybe in other countries too - a "ring main" is the name given to what is literally a closed ring of cable installed at a property to supply current to the power sockets. (Power receptacles in US parlance.)
- If a ring main circuit was not used then a separate dedicated breaker and "spur" length of cable would have to be used to supply every small block of sockets, a "block" being, say, for a room or pair of rooms.
- A ring main circuit is preferred compared to the older idea of many separate cable spurs - using spurs is also known as a "star" layout - because, in general, a thinner cross-section cable can be used to connect many sockets distributed around a closed ring circuit compared to the size of cable that would have to be used for the longest spurs in a star layout. A star layout also needs a much larger number of separate breakers, one for each spur.
- A ring main circuit always starts and finishes at a dedicated breaker on the main consumer panel. The cable forming a ring main circuit always has three wires: live, neutral and earth. (Hot, neutral and ground in US parlance.) An office or factory would probably have many separate ring main circuits.
- In a typical domestic house wiring system there would be a dedicated breaker and ring main circuit for all the power sockets on each separate floor. An additional breaker and ring main circuit might also be installed to feed all the kitchen's power sockets but the cooker (range in US parlance) would usually have its own dedicated spur cable fed by its own circuit breaker. Similarly the house's boiler (= furnace) - and any other high-power-demand appliances such as 10 kWatt electric showers - would each have their own breaker and spur. (So the "star" cable layout still survives even though ring mains are great for all the rest of the power sockets around a house!)
The UK and Republic of Ireland use a power outlet plug and socket system which is totally different to the rest of Europe:
- All power socket outlets are rated at 13 amps to take a standard 13 amp plug.
- Each power socket has a protective insulated shutter that safely uncovers the live (or hot) and neutral holes when the plug of an appliance is inserted. The shutter immediately covers the holes over again when the plug is removed. The shutter is operated by the insertion of the earth (or ground) pin which is longer than the live and neutral pins.
- Each 13 amp plug has 3 rectangular (not round) pins: a live, a neutral and an earth pin. There is also a fuse that should be selected to be of the right size to protect the appliance it is attached-to.
- The actual plug type is known internationally as Type 'G'.
- It was designed for use on any normal house mains voltage or frequency and is used in the UK and other countries which have adopted the UK mains power plug and socket system for appliances.
It is a very good plug and socket system but not many other countries have adopted it - probably because they didn't invent it!
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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.
KVA is the vector sum of real and reactive power; put differently, KVA at a specified power factor will tell you how many KW you have:
KW = KVA * pf
You must provide a power factor or power factor angle (if angle, replace pf with cos (pf) in above equation) or total reactive power to calculate.
What is acceptable value of tan delta in oil filled and dry type 33 KV transformers?
Tan Delta is a condition monitoring test.
Value of Tan Delta very much depends upon the temperature and recommended values at 20Deg.C is 1.
Values at other temperatures can be determined by using correction factor given in IEC76
What is Friction in induction motor?
Friction is present at the motor shaft and also in various parts of the load. The friction torque is equivalent value of various friction torques referred to the motor shaft.
What causes a generator to stop?
There are many reasons why a generator should stop. If you are referring to a petrol (gasoline) generator, one reason is that it may be overloaded (i.e. its load draws too much current), causing the motor to stall.
Is the brightness of a light bulb determined by its filaments?
Though there is a bit more to the story than this, yes, it is generally true that the brightness of a light bulb, sometimes called a lamp, is a function of its filaments. For a given voltage of operation, a less resistive filament will draw more current, run hotter and will glow more brightly (be more incandescent). A heavier, more resistive filament will draw less current, get less hot, and not produce as much light (be less incandescent). The former will run "hotter" as well as brighter, and the filament won't last as long, though it will be more efficient. The latter will not be quite as bright or as efficient, but the filament will have a longer operating life, and will probably be more shock resistant. Lamp filaments are usually made of tungsten, and these filaments are coiled to reduce evaporation of the metal when that metal is white hot. There is a "balance" engineered into the lamp to make it run "hotter" and more brightly to be more efficient, yet limit current somewhat, limit filament evaporation and extend the life of the lamp. Eventually, enough of the filament evaporates away in normal operation to create a "hot spot" that quickly degrades, and the filament fails. A link can be found below to learn more.
How do you decrease air resistance?
Resitance of air varies based on:
1. Percentage content of moisture (higher the moisture, lesser the resistance)
2. Percentage content of suspended dust particles and conductivity of those suspended particles (higher the content, lesser the resistance)
What does a standing wave result from?
Standing waves are also known as stationary waves. They are waves that remain in a constant position. This phenomenon can occur because the medium is moving in the opposite direction to the wave, or it can arise in a stationary medium as a result of interference between two waves traveling in opposite directions.
Which is the best Distributed Control System?
DCS selection shall based on the following criteria
- Ease for peer peer communication
- Global Tag database
- Ease for configuring Trends , Alarms , reports , documentation instaneously for the tag
- Third party connectivity
- Interface to standard communcation protocol
- Server redundancy
- Smart client possibility
- Loop tuning from the central location
- Standard Face plate and its configuration
- Centrally engineering can be done for all the connected devices and controller.
- Easy configuration
- Reporting facility
- Online documentation
- Alarm Management
- Integration with the HT relays.
- Single solution for the complete plant
This is wat one can get in ABB 800xA system.
From Meena
How do variable speed motors work?
A variable sped drive is sometimes also known as a variable frequency drive. These drives are used in electro-mechanical drive systems to control AC motor speed and torque.
How depletion width varies with biasing voltage?
when the diode is applied forward bias voltage the width of depletion region gets reduced the barrier voltage decreases there by facilitating the easy exchange of holes and electrons.
when the diode is reverse biased the width of depletion region increases there by hindering the flow or exchange of charge carriers.
When SF6 gas is decomposed it turns into what?
When used in breakers (arc extinguishing), SF6 can decompose to many things:
HF, SOF2(SF4), SOF4, SiF4, S2F10(SF5), SO2F2, SO2, SF2, SOF10, S2O2F10, H2S. It can also combine with metals to form CuF2, AlF3, WF6, WO3. I'm probably missing some byproducts, so don't consider this a complete list.
Flux powder is a chemical substance used in various industrial processes, particularly in metalworking and soldering. Its primary function is to remove oxidation and impurities from metals, promoting better adhesion during welding or soldering. Flux powder can come in different forms, including rosin, acid, or water-soluble types, depending on the specific application. It is essential for ensuring strong, clean joints in metal fabrication.
BIL is basic insulation level as per you or in other words it would be "basic impulse level" which implies the limit up to which an insulator could withstand impulse due to lightning strikes. Impulse is generated on the insulation due to the high voltage surges and spikes due to lightning strikes. BIL is generally much higher as compared to power frequency withstand voltage.
In other words BIL is lightning Impulse withstand voltage. Impulse withstand voltage is the voltage that is generated due to switching operation and it's much higher than power frequency withstand, but BIL or the lightning withstand voltage is a the voltage level that an insulation can withstand during surge or lightning strikes.
