Electrical Engineering

The stator is the stationary part of an electric generator or electric motor. The non-stationary part on an electric motor is the rotor. Depending on the configuration of a spinning electromotive device the stator may act as the field magnet, interacting with the armature to create motion, or it may act as the armature, receiving its influence from moving field coils on the rotor. The first DC generators (known as dynamos) and DC motors put the field coils on the stator, and the power generation or motive reaction coils on the rotor. This was necessary because a continuously moving power switch known as the commutator is needed to keep the field correctly aligned across the spinning rotor. The commutator must become larger and more robust as the current increases. The stator of these devices may be either a permanent magnet or an electromagnet. Where the stator is an electromagnet, the coil which energizes it is known as the field coil or field winding. An AC alternator is able to produce power across multiple high-current power generation coils connected in parallel, eliminating the need for the commutator. Placing the field coils on the rotor allows for an inexpensive slip ring mechanism to transfer high-voltage, low current power to the rotating field coil. It consists of a steel frame enclosing a hollow cylindrical core (made up of laminations of silicon steel). The laminations are to reduce hysteresis and eddy current losses.

Divide 2.2 kW by (an assumed, because you did not state it) power factor of 0.85 to get 2.6 kVA. Divide that by 3 to get 0.863 KVA per winding. Divide that by 415 volts to get 2.08 amperes per winding. If you are running star, then that is the phase current. If you are running delta, then multiply by the square root of 3 (1.732) to get 3.6 amperes per phase.

slip ring is connect on shaft of motor to collect current from commutator without any complicate connection and with use of it resistors can be insert in circuit and therefore speed control of motor can easily achive

Because the armature (or rotor) has no external connection. The currents that produce torque from the rotor are induced by the magnetic field in the machine, so there is no commutator, no brushes and no armature reaction.

An Ammeter connects a low impedance on the test points, so the equivalent of that is a "short circuit" between the test points. This is done to avoid a drop of current on the tested circuit. A Voltmeter connects a high impedance on the test points, so the equivalent of that is a "open circuit" between the test points. This is done to avoid a drop of voltage on the tested circuit. ---------

In terms of external connections Ammeter (used to measure current) is connected in series of the circuit (through which the current flow need to be measured) and voltmeter (used to measure voltage) is connected in parallel to points in circuit (across which voltage needs to be measured).

When transformer secondary is short circuited & primary voltage is raised, current in the secondary winding increases from 0 to rated current (say, 667A at 433V), a small voltage appears at the secondary windings. This percentage of this voltage to the rated secondary voltage is expressed as %age impedance. IEC table 76-5 provides following details :

Rated KVA %impedance

Up to 630 4.0

631-1250 5.0

1251-3150 6.25

3151-6300 7.15

6301-12500 8.35

12501-25000 10.0

25001-200000 12.5

Also, it may vary from manufacturer to manufacturer. For example, for a transformer of 500kva, 4% impedance, rated current of 667A@433V , when secondary is short circuited & primary voltage is raised to drive a current of 667A in the secondary windings, 4% of 433V develops across it's secondary windings i.e. 17.32V.

Now, the impedance is calculated as

Z= V/I = 17.32/667 = 0.02596 ohms.

This percentage impedance also decides the amount of fixed KVAr compensation required at the secondary of transformer. This is

4% x 500KVA = 20 KVAr

Also, short circuit capability of transformer is calculated as

433/0.02596 = 16,679.50 Amps or approximately 17kA.

Hope this information is sufficient. Also, one may again find a good answer to the above question as I've seen a transformer of 500kva with % impedance of 5.13 also.

Regards,

Asif Mansoori, DEE, Mumbra-Thane, India.

asif_currents@hotmail.com

Fusing factor is the ratio of a fuse's minimum fusing current (the smallest current that will cause the fuse to melt) and the nominal rated current (usually the number in Amps marked on the fuse body).

generally open circuit test is performed on the low voltage side.....not on high voltage side.... becuase on low voltage side, we can apply that low voltage very easily ( i.e with a less amount of source is required)... whereas on high voltage side, we need a large power source in order to apply full voltage... in short circuit test, we will test on high voltage side by keeping Low voltage side being short circuit.because high voltage side needs less current source than low voltage side....

Lights at home are connected in parallel. (Switches are connected in series with the lights in order to turn them on and off.) This way, each light receives the same voltage. Placing the lights in series would divide the voltage between the lights, reducing the power of each, and it would have the effect that one light burning out would cause all the others on the same circuit to stop working.

Since resistance is the ratio of voltage to current, if the voltage is constant then increasing the resistance will result in a reduction in current.

Yes and no. Voltage is directly proportional to current from Ohm's Law (V=IR.) Thus, when voltage increases, so does current.

However, voltage can be inversely proportional to current in some situations. This can be seen in a transformer, where current and voltage are inversely proportional due to the law of conservation of energy, in which P(in) must equal P(out). Thus, a greater input voltage leads to a small output current.

The equation you are looking for, R = E/I, is derived from the definition of the ohm, not from Ohm's Law. Ohm's Law is properly-called 'Ohm's Law of Constant Proportionality', which states that, for certain (linear) loads, the ratio of voltage to current is constant for changes in voltage. The above equation applies whether Ohm's Law does or does not.

Short circuit is caused due to connection of earth and current wire.Because electrons start transferring from current wire to earth wire that is from high potential to zero potential and sparking occures due to electron transfering with high energy and heat is also evolved.

Net voltage in the Neutral of a three phase electrical system is called residual voltage.

A circuit that has only one path for the current is called a series circuit. In a series circuit, the components are connected end-to-end, creating a single pathway for the flow of electricity. This means that the current passing through each component is the same, making series circuits useful for applications where a consistent current is needed.

Typically, the desired frequency of operation is known, and the purpose of the
calculation is to identify the best size for the dipole antenna. The most often
used formula to find that length is
Length = 468/frequency, MHz feet, or 142.6/frequency, MHz meters.
That gets you close, but some tweaking and trimming is usually required after
construction, because some of the characteristics of the installation, such as
the antenna's height above ground and method of supporting its ends, affect
the antenna's properties.

The wavelength corresponding to that frequency is
Wavelength = 300/frequency, MHz meters, or 984/frequency, MHz feet.

The way your question is written, it appears that you already have the antenna, and
now you want to know the frequency at which it will operate best. I must tell you
how peculiar this sounds to anybody in the radio business. But I'm here to answer
questions if they make sense, not to judge how impractical or useless they may
actually turn out to be. So here goes:

For the first time ever, you've just noticed a horizontal wire hanging between two
trees in your back yard. Rather than simply tearing it down, you're curious to know
the frequency/wavelength at which it could most efficiently transmit/receive when
operated as a half-wave dipole. So you measure its length somehow, and call the
length ' L ' .

-- If you measured ' L ' in feet, then the best frequency to try first is 468/L MHz.
The corresponding wavelength is 2L feet, or 0.6096L meters.

-- If you measured ' L ' in meters, then the best frequency to try first is 142.6/L MHz.
The corresponding wavelength is 6.562L feet, or 2L meters.

First off, not all electrical wiring is copper. There's a fair bit of aluminium wiring being used too, as well as some other alloys.

"Pure" is a difficult word. You can have copper that is purer than what's used for electrical wiring. But outside a lab setting, copper wire is indeed pretty darn pure.

2.4m or 5ft high

In an electric generator, the function of a capacitor is to provide reactive power and improve the power factor of the generator.

When a generator is connected to a load, the load may have a combination of resistive, inductive, and capacitive components. Inductive loads can cause the power factor of the generator to decrease, resulting in lower efficiency and voltage regulation.

By adding a capacitor in parallel with the generator, the reactive power generated by the capacitor can offset the reactive power of the inductive load, leading to improved power factor correction. This helps to enhance the efficiency of power transfer and stabilizes the voltage. The capacitor absorbs and supplies reactive power, reducing the strain on the generator and ensuring a steady and efficient supply of electrical energy.

Inductance is measured in henrys.

GFI

When checking in a load, what must be done with cases that say "Mixed" on them

The load is composed of silk sheets