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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
A switchgear room is a room in a building which contains switchgear. It is typically a locked room in the ground floor of a building where the service enters the property. It would usually contain the supply authority's meters and the main protective devices (fuses, breakers) for the building's electrical installation. The room should not be used for storage or any other use.
A different answer
A switchgear room is an enclosed space - within an electrical power generating station or substation - in which are located high-voltage circuit breakers, protective relays, battery supplies, etc. The types of circuit breakers located inside switchgear rooms are indoor types and not suitable for locating in the substation compound. In the UK, these types of circuit breaker are typically metal-clad 11-kV oil circuit breakers (OCBs), and are supplied from primary (33/11-kV) transformers located in the substation compound and, themselves, supplied from outdoor-type 33-kV circuit breakers in the same compound.
How many amps in 74 kva 3 phase?
If you are referring to line current, then you need to manipulate the following equation to make IL the subject of the equation (don't forget to convert kV.A into V.A when inserting that figure into the equation):
apparent power = 1.732 x UL IL
What is the difference between KVA and KW of a transformer?
Transformer power is given by P=V*I which takes the unit of KVA while that of KW has energy term which is not produced by the transformer.It only steps up or down the voltage.
Answer:
In a pure D.C. circuit, KW = KVA. However, in any A.C. circuit, there is real power {KW} and apparent power {KVA}, due to the voltage and current being out of phase. Power Factor is the ratio of KW to KVA. Transformers are rated in both KVA and PF. Multiplying the transformer KVA rating times the PF will yield KW.
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A transformer has separate ratings for maximum voltage and maximum current. Multiply the two together and that is called the VA rating, or kVA for larger transformers. So the transformer rating is independent of the power factor of the load.
My physics teacher wrote out homework answers for us. On a few EMF problems, he has the EMF unit listed as Weber. On others, he has it as volts. I have a quiz tomorrow so I need to know which SI unit i'm supposed to use. Thanks!
Few side notes: the formula we're using is E=delta I (subscript B) /delta t . There was no change in the formula for the different problems or what not. and somehow weber / time went to volts, other times it didn't.
BY: VOLT
How to calculate power loss in power cable?
The length of the cable is determined by the distance from the center of the distribution panel to the center of the load.
On the whole megger testing is non destructive. What happens is a DC voltage is applied to the device or winding under test. It is an insulation test to see is the insulation has been injured in any way to cause a short circuit when normal power is applied to it. On my megger there are 3 ranges 300V, 750V, and 1000 volts. Applying the proper voltage is essential to not damaging the device you are testing. Working voltages up to 240 volts should use the 300 range. Working voltages up to 600 volts use the 750 volt range and working voltages above 600 use the 1000 volt range. As you can see if you used the 1000 volt range on a device that had a working voltage of say 24 volts you could damage the insulation just by testing it. So meggering a device is non destructive if you use the tester as its instructions tell you to. To megger a cable connect one lead to the ground or outside sheath of the cable and the other to the inside wires one at a time. Test each wire separately. Then for a wire to wire test connect the meter across two of the conductors and test. For a three wire cable, test 1 to 2, 2 to 3, and then 3 to 1.
How is electricity transformed into sound?
1. Sound is energy.
2. Energy can be converted from one form to another.
Picture a microphone. A simple device that has a permanent magnet, a coil of copper wire, and a thin diaphragm.
The copper wire is coiled around a thin cylinder of paper so that it encircles the magnet without touching it.
That coil is attached to the diaphragm and positioned over the magnet.
When sound hits the thin diaphragm, the diaphragm vibrates moving the the copper coil back and forth over the magnet. This action creates electrical impulses in the coil. This is energy conversion.
To see this in action, take a speaker apart. A microphone and a speaker work on the same principals only in reverse.
If you connect a volt meter to the leads on a speaker and move the cone, you'll see the meter register small amounts of electricity.
How long will 100 watt bulb last?
Read the label on the container. The light bulb will be rated "B-10" life. This refers to a statistical number value. "B-10" Life is the average life span a bulb will last for 90% of those tested. If you went purely by the "average" time to burn out, then that is not specific. One brand of light bulbs can have a higher Average. But if it has a lot of scatter in the data, then that would mean some bulbs could fail much earlier and some much later. On the other hand, if you determine a bulb has a X hour "average" life with a minium scatter factor, then more of the bulbs will perform closer to the average. Read the label on the box.
How do you convert 3 phase power to 2 phase power?
You need to have a properly sized Phase Converter Installed. What do you need 2 phase for? Is it just one piece of equipment? If so it may be is easier and cheaper to convert the equipment.
If you are looking for a Licensed electrician you can find one at www.contraxtor.com
AnswerDo you really mean a 'two-phase' system? This is an archaic system in which the phase voltages are displaced by 90 electrical degrees. Many people mistake this term for the 'split-phase' system, used in North America, to provide a 240/120-V service. If you do mean a 'split-phase' system, then you will need a single-phase transformer whose primary is connected across any pair of the three-phase line conductors, and a centre-tapped 240-V secondary. The centre tapped connection is earthed (grounded) to provide the neutral connection, and the potential of each end of that winding is 120 V with respect to the neutral. Of course, the turns ratio of your transformer must be appropriate for your three-phase supply. As the original answer indicates, this work will need to be performed by a licensed electrician.
Importance of color coding in carbon resistor?
color coding of resistor:black,brown,red,orange,yellow,green,blue,voilet,grey,white
these colors are ranked as:0,1,2,3,4,5,6,7,8,9
tolerance:silver,gold,no color
ratings:5%,10%,20%
What is the best type of electric motor for heavy starting loads?
The classic heavy starting load is a tram starting off from stationary, and for this the series-would dc motor is the preferred motor.
Will the lightbulb be brighter in series circuit or brighter in a parallel circuit?
This question is the wrong way round. Assuming you the light bulbs are identical, they are brighter when connected to the power source in parallel than in series. This is because each bulb uses the entire potential difference of the power source, whereas in series, the bulbs act as potential dividers, reducing the voltage across the others and therefore the current passing through all of them.
Is ohms bigger unit to megohms?
An ohm is a unit of electrical resistance. A kilohm is 1,000 ohms resistance, while a megohm is 1,000,000 ohms resistance.
In electronics, an SPDT is a type of switch. It stands for "Single Pole, Double Throw." In America, it's known as a three-way switch.
What is the difference between watt meter and kvar meter?
the difference is that the former is fitted with some type of registration mechanism whereby all the instantaneous reading of power are summed over a definite period of time whereas the latter indicates the value at particular instant when it is read.
Why do you use Two Winding run and start winding in the single phase motor?
Any transformer uses a minimum of two windings to change the voltage value. The primary side of the transformer is usually connected to the existing voltage. The secondary side of the transformer is usually connected to the load, who's voltage could be higher or lower voltage than the primary voltage.
If the secondary voltage is increased the transformer is known as a step up transformer and if the secondary voltage is decreased the transformer is known as a step down transformer.
The transformer terminal markings for the primary are H1 and H2 on a single coil primary and H1 to H4 on a dual voltage primary winding. Like wise the secondary terminal markings are X1 and X2 on a single coil secondary and X1 to X4 on a dual voltage secondary winding.
What happen to the parallel circuit if one resistance is removed?
assume the following configuration: battery connected to 2 parallel resistors with an ammeter in series with the battery... observe the current measurement ... remove one of the resistors .... observe the current again, it will have decreased: if the resistors were of equal value, the current will decrease to half of its original value when one of the resistors is removed. Mathematics:
V=IR (V- voltage, I - current, R - resistance
in a parallel circuit, R=(R1*R2)/(R1+R2) where R1 and R2 are the values of resistance of the resistors. Before removal- Ib=V*(R1+R2)/(R1*R2)
After removal (assume R2 is removed)- Ia=V/R1
so Ia/Ib=(R1*R2)/(R1*(R1+R2))
or Ia=Ib*(R2/(R1+R2)
if R1=R2 then Ia=Ib*R2/(2*R2) or Ia=Ib/2 so the current after is 1/2 of that before.
Can two transformers with different vector groups be connected in parallel?
Not unless you want to see some cool pyrotechnics!
Circulating current will be induced between the two transformers if this is done. This current magnitude will be limited by the phase angle difference and the impedance of the two transformers. It is likely this current will be high enough to cause protective devices to operate regardless of loading on the secondary - fusing, overcurrent relays, sudden pressure relays, etc. If the impedance of the transformers is high enough, and the phase angle is fairly small (few degrees), LTC tapping may occur (some paralleling schemes use the circulating current between transformers to determine correct paralleled tap values). If they are "close enough" in phase angle, no serious problems will occur, other than (possibly) a small derate due to a small amount of circulating current.
Can a motor works as a dynamo I'mean produce electricity?
Yes, but if you are asking if that configuration can be sustained, i.e. as a perpetual motion machine, the answer is no. There will always be losses associated with power conversion, and these losses make a perpetual motion machine an impossibility.
Can you reduce 12 volt 5 amp powers supply to power a 12 volt to 150 milliamp camera?
You don't need to reduce the power supply. A device will only draw as much as it needs. A power supply of 12 volts 5 amps is the same as 12 volts 5000 mA. So you see that the power supply has more that ample capacity to operate a 150 mA camera. The thing to watch for is that both supply and camera need the same type of voltage, be it AC or DC. You can not cross that up and use AC on a DC device or vice versa.
What is it meant by a slip sheet load?
A load on the truck or container using slipsheets instead of pallets. In some cases the edge of the slipsheet can be "grabbed" by a special attachment on the forklift and pulled onto the forks. Sometimes they will use slipsheets to allow for more usable room for the freight, other times they use slipsheets because of issues with wood or the cost of plastic pallets.
When the voltage applied to a circuit increases the power an the also increases?
When you lift the voltage V that goes to a circuit, also the flowing amperage A will go up and so does the power. The lamps will give more light, the equipment will get warmer up to the point where everything goes down.
To understand this all you need to know ohm's law.
Scroll down to related links and look at "Ohm's Law - Wikipedia".
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It has nothing to do with Ohm's Law: that's inductance.
P = I E is what answers this question.
If I have a motor pulling 15 A @ 110V, that same motor will pull 7.5 A @ 220V (assuming it's capable of that much voltage fluctuation)
As voltage rises, current drops for the same net work done. It doesn't climb.
That's why heavy appliances are 220 V when outlets are 110 V. That's also why industrial equipment is three-phase vs single-phase residential wiring.
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What is meant by the turns ratio of a transformer?
Hi,
The turns ratio depends on the amount of windings in a transformer that are needed to provide a secondary voltage/current that's different from the primary AC source. The ratio is derived from how many windings on the primary side as compared to the secondary side.
Hope this helps,
Cubby
Can you use the compass under the power lines?
If the power lines were Direct Current, sometimes used for efficient long distance transmission, then your compass would definitely be affected, and may be quite useless. The high currents in such a long distance DC line will generate a magnetic field.
With an Alternating Current power line, the alternating current itself should not cause any problem with the compass, but the steel of the towers themselves may certainly do so.
