Electrical Engineering

CL of a CT is its accuracy class.. it is an approximate measure of the CT's accuracy.

e.g. The ratio (primary to secondary current) error of a Class 1 (CL:1.0) CT is 1% at rated current

If at battery,parallel circuit shorts then equivalent resistance of circuit becomes approximately 0 Ohms,and therefore as current follows low resistance path infinite amount of current due to low resistance will flow through the wire so,entire parallel circuit will short out,but wire will burn and battery may get damaged.

Name:Sumit Karnik.

ASIC is an Application Specific Integrated Circuit. In other words, an IC that was designed and nade just to do one specific job.

The rotor of an alternator need a DC voltage applied to it to generate a magnetic field, this magnetic field will generate the AC power in the AC windings.The AVR(Automatic Voltage Regulator) is regulating this DC voltage so that the magnetic field is strong enough to maintain the output AC voltage. As soon as more current is drawn from the output, this output voltage will drop and a stronger magnetic field is needed to sustain the output voltage, so the AVR step up the exiting voltage to get a stronger magnetic field to compensate for the voltage loss in the AC windings.

This question relates to the economic decisions that electricity utilities make in designing their power networks. During peak load periods, power is transmitted at the maximum current that is safe for the network, but at other times power transmission simply depends on demand.

Ideally, utilities would transmit power at maximum efficiency because, by minimising losses over the lines and in transformers, they minimise generation costs. However, each increase in efficiency results in increased capital costs. A compromise is always made between purchasing efficient power transformers and distribution transformers or less expensive ones with higher losses.

500 MW Boiler is sub-critical Boiler which generates steam at pressure lower than the critical pressure ie below 221.2 kg/sqcm. where as the 660 MW boiler is super critical boiler which operates steam pressure above critical pressure.

First understand that every electrical conductor (wire) with current flow through it will produce an invisible magnetic field around it. This field is directly proportional to the magnitude of current flowing. Second (and inversely) realize that any conductor moving through a magnetic field will produce a voltage, And if provided with a complete circuit (a path to flow in) will result in current flow in that conductor. The movement can be from the conductor moving, or from the magnetic field moving, as long as there is 'relative motion' between the conductor and the magnetic field. In short, a conductor with current flow produces a magnetic field , a conductor and a magnetic field with relative motion between them produces current flow. (This is also the basis for how a motor works) AC means 'Alternating Current'! The current flow moves in one direction along a conductor, then reverses to zero and to equal magnitude in the opposite direction. Each time this current changes direction it produces a magnetic field, as it returns to zero the field collapses. As the current builds in the opposite direction the magnetic field builds again. In an AC transformer circuit, two conductors are placed in close proximity to each other and an alternating current is applied to the first conductor. This alternating current causes a magnetic field to build around the conductor, then collapse, build again in the opposite polarity and so on. This expanding and collapsing magnetic field creates relative motion between the field and the second conductor which then produces current flow of its own. This is called "transformer Action". In steady state DC circuits, the magnetic field is constant and there is normally no relative motion, therefore no "transformer action". There is however still a relative motion created when the circuit is first energized, and when it is de-energized. This collapsing field is how the ignition coil in your car works. In the simplest form, contacts (points) were opened by a cam, the open contacts de-energized the first conductor (the 12VDC primary). The resulting collapsing field cut across the secondary conductors. Because these conductors were wound into many turns or "coils" it actually multiplies the effect producing a high voltage in the secondary (connected to the ignition wires). This produced a voltage and current strong enough to jump across the gap of a spark plug. And, Yes Virginia, there is such a thing as a DC transformer.

An inductor is a magnetic device that resists a change in current. It is constructed with windings that can be backed by ferro-magnetic cores. The equation of an inductor is ...

di/dt = V/L

... meaning that the rate of change of current per time is proportional to voltage and inversely proportional to inductance.

Inductors, since they work on magnetic fields, can be coupled, as transformers, motors, and generators.

A capacitor is a charge device that resists a change in voltage. It is constructed with parallel plates. The equation of a capacitor is ...

dv/dt = I/C

... meaning that the rate of change of voltage per time is proportional to current and inversely proportional to capacitance.

Inductors and capacitors, since they work in opposite phasor angles, can be coupled to make resonant filters, giving bandpass or bandcut to particular frequencies.

can Hysteresis motor use like alternator

One of my friends overdosed and died off of two of them.

To find the specific gravity of cement

because there is ahigh current flowing through it at the start...

Based on the principle of the D'Arsonval galvanometer, the main function of a multimeter is measuring a circuit's voltage, current, and resistance.

The 'Safe Isolation Procedure' is a procedure carried out to ensure that you are working safely on electrical equipment.

Firstly, you isolate the power at the fuse board. It's best to switch each circuit off one by one starting furthest away from the main red switch (I'm not 100% sure why but its something to do with voltages). You then erect barriers and signs.

You then lock off at the main switch and remember to keep the key on your person.

After this you use a certified voltage tester (preferably a gs38) to check if the board is dead. Give the tester a thorough inspection check leads and probes and then use the proving unit to check it's not faulty. After this you then test at the board main L to main N, then main L to man E, then main N to main E (3 point test). You then test at your proving unit again to check testers not faulty and then commence work.

a.) Io = no load current consists of 5% of the full-load primary current.

b.) Iom = magnetising current/component responsible for setting up the magnetising flux in the core.

c.) Iol = Ic = power loss component responsible for supplying the core losses and the windings losses.

why need dielectric test for transformer

K-factor is a weighting of the harmonic load currents according to their effects on transformer heating, as derived from ANSI/IEEE C57.110. A K-factor of 1.0 indicates a linear load (no harmonics). The higher the K-factor, the greater the harmonic heating effects.

Sag (dip) a decrease to between 0.1 and 0.9 pu in rms voltage or current at the power frequency for durations of 0.5 cycles to 1 minute. Swell - an increase to between 1.1 pu and 1.8 pu in rms voltage or current at the power frequency durations from 0.5 to 1 minute.

I think you will find (in the US at least), that almost all utilities will refuse to provide 3-phase power to a residence. If you have just one thing such as a motor that you need three-phase to run, you can purchase a phase convertor to convert your single-phase to 3.

The value of resistance when there is a short circuit varies depending on the nature of the fault, but it could be fractionally above zero or higher.

Well as you said, it is self explanatory. The current density should not be more than 1000 A per square inch roughly coming to about 1.6 Ampere per square mm. Consider the case when the current density is high i.e. it could be high because of either reduced area with same current OR with more current through same area. Any of this case would lead to increase in the thermal lossess which could eventually lead to thermal runaway without the temperature rise getting stabilized (Stability being defined as temperature rise not exceeding 1 deg C per hour).

Rgds,

Fency Anthony, ABB Limited, India

Increases

Checked Stephen J. Chapman's Electric Machinery Fundamentals page 287. It says:

Short Circuit Ratio (SCR) for the synchronous generator is the ratio of the field current required for the rated voltage at OPEN circuit to the field current require for the rated armature current at SHORT circuit.