Electrical Engineering

This can be done, but is usually not done because a metering CT is made to be very accurate at expected load current levels. A protection CT is made to be accurate at fault current levels (which is often significantly above load current). If the CT is too small, and has too small of a ratio, the CT will likely saturate, which will skew the results the protective device expects to get.

An example: a metering CT may have a ratio of 100:5 (made for 100A load current, which will produce 5 amps secondary current). Fault current levels may be ~10,000A. You'd expect the secondary output of a perfectly linear CT to be 500A. One way resistance of the cable connecting the protective device to the CT may be on the order of .5 - 2 ohms. Ignoring the resistance of the CT and connected devices, secondary voltages would reach 250 - 1,000 volts for a phase fault, and 500 - 2,000 volts for a ground fault. The biggest CTs may be rated for 800 volts output below the knee point, so this 100:5 CT would clearly saturate. The real output current would likely be on the order of 150A at the most.

...And the above is ignoring any DC offset, which would cause the CT to saturate at unpredictable AC current levels.

A single-phase cable will have a line and a neutral conductor and, possibly, but not necessarily, an earth (ground) conductor.

A high-voltage three-phase cable will have three line conductors. A low-voltage three-phase cable is likely to have three line conductors and a neutral conductor.

dielectric strength is tested by transformer dielectric strength oil testing machine. at first, oil which is to be tested is pour near the two electrode. both the electrode should be dipped in oil . then adjust the distance between the electrode .now start the machine.when a sound came from machine then note down the dielectric strength of the oil.

One of the main disadvantages of copper cables is that copper is expensive compared with other metals such as iron or aluminum. Copper can also corrode, though not as much as some other metals.

power factor depends on the load being fed if the load is entirely resistive power factor will be unity ..if the load includes an inductor or capacitpr due to phase displacement between v and i the pf will be lag or lead respectievly

Here you find the formula to convert voltage levels to decibels.

Scroll down to related links and look at "How to calculate dB?"

In a passive circuit, the current will decrease.

In an active industrial circuit, it will usually decrease.

In a theoretic manner - it is an unknown.

A soft start is a starter that bring a motor from the starting point of a slow speed in to a multiple speed that can be programmed in the starter

Imagine you have a big plant in your factory, the voltage will go down/up when the plant start/stop, cause the sharp start/stop

The soft starter is controlling AC motor in soft start/stop to eliminate such problems.

Reference: http://www.softstarter.org

They're not! The relationship you describe is derived from the definition of the ohm, not from Ohm's Law. This tells us that resistance is equal to the voltage divided by the current.

Ohm's Law merely tells us that the ratio of voltage to current is constant for variations in voltage -which, unfortunately, is not actually true. In other words, Ohm's Law is not true!

The primarys are marked with the letter H and the secondary terminals are marked with the letter X. The rest depends on how many phases, single transformer, bank transformes, secondary outputs desired, delta or wye or both, etc.....

A: most of the time there are not marked with anything. for a power transformer the primary will offer a resistance of 15 ohms the secondary can be more or less depends on applications

the formula is (no. of turns at main)/(no. of turns at out)=(In volts)/(out volts)

Electrical resistance increases because the density of charge carriers decreases with increased temperature. High temperature resistivity is predominantly characterized by collisions between electrons and metal atoms. Decreasing the density of charge carriers increases resisistance.

Answer: At the zero end, the measurement is more reliable, because all materials have some conductivity, so even the plastic grip of a meters probe, with both your hands making contact with both the probes, will give you some reading at infinity side of the scale.

LOw voltage shocks aremore dangerous than high voltage shock because at low voltage the electrical source pumps a lot of energy through the body for a longer time damaging vital organs. where as high voltage shock cause a layer of burnt insulting tissues which limits the current that flow through the body there by causing lesser damage.Also low voltage shock tend to 'stick' to the body while High voltage shock tend torepell the body causing superficial burn close but not close enough at low voltage your body react NOT with extreme convolsions therefore you are there to the end. at hi voltage your body will widly shake maybe to the point of disconnection. it is not the voltage that kills but ruther the current. a 2 v battery can killyou if it gets to your blood supply [SODIUM] METAL GOOD CONDUCTOR A 'D' CELL CAN DO IT ON A SHORT IT CAN DRAIN 2 AMPS ENOUGHT TO KILL ANYBODY.

electrical burns

CONDITIONS REQUIRED FOR TRANSFORMER PARALLEL operation are..

1. Voltage turn ratio.

2. phase sequence

3. Impedence should be same

4. polarity

Hitesh

Difference between field controlled and armature controlled is that field control is open loop and armature current is closed loop.

The wave with the maximum RMS value, in comparision with the peak value, is the square wave.

You check and adjust instrument zero and, if you are measuring ohms, you also check and adjust ohms zero.

A switch is a device which can be used to make or break a circuit.

If that circuit carries a voltage which would be dangerous to people or animals then the handle of the switch must be made of a good insulator and the rest of the switch must be well shielded to stop anyone - or anything else - from touching any live wires.

If you get a chance to visit a science museum ask them to show you a "knife switch". Another place to see one is the Physics Lab at your local college or high school. Once you have seen a knife switch you will understand exactly how a basic switch works. It's quite simple really

No, you will not obtain 230 volts. From a wye connected three phase 480 volt supply, 277 volts can be obtained from one phase leg and the neutral on the wye connection. 480 volts/1.73 (sq. root of 3) = 277 volts.

The main advantage of using ac is that you can step up and step down the voltage by means of a transformer,since transformer works only with ac.

another thing is that if dc power is used for transmission,then the power loss associated with t will demand the use of transmission lines which are very thick(have a larger cross section)..for long distance transmission this may lead to the requirement of power lines with impractical dimensions.

The electrical wires covered in PVC insulation, because the electrical wires are required to save exposure from weather effect (which may leads to the deterioration of the cables and short circuiting). secondly cables are save in the PVC sheets and the danger of short circuiting is minimzed

a battery in an electric circuit is used to generate the power supply.