Electrical Engineering

The difference between a separately excited DC generator and a Shunt DC generator is that for a separately excited Dc generator , the excitation field winding is supplied by an external source different from that supplying the armature while for shunt generator, the excitation field windind is connected in series with the armature and supplied by a single source.

A dc series motor can work on dc and ac because dc motors are totally reversible.

in star-star neutral transformer at unbalanced load condition zerosequnce current will be flows in secondary side but this current can not be balanced by primary side because its not having neutral to circulate zerosequence current.due to this unbalance voltage will appeared in primary side but the tertiary delta winding allows circulate the zerosequence current so the primary voltage will get stabilized.

The current level that results in your brain's commands being swamped out; I've heard this called the "let go" threshold as well. If this amount of current is flowing through your hand, you won't be able to let go of whatever it is you were holding.

The peak of a waveform that is purely sinusoidal (no DC offset) will be RMS * sqrt(2). This is the peak to neutral value. If you are looking for peak to peak, multiply by 2.

An 'a.c. cable' is an electrical cable designed to work with alternating current, rather than with direct current (d.c.). There are a number of important differences, one of which is the level of insulation necessary. For example an d.c. cable designed to operate at 100 V would not be suitable for operating at 100 V a.c., because all quoted values of a.c. voltage are root mean square (rms) values -which means that a 100 V a.c. cable's insulation must be able to withstand a peak value of around 140 V.

To calculate the admittance if you are given the impedance, you take the inverse of the impedance ( that is 1/z).

"Auto" refers to the single winding used an auto transformer.

when is ripple fator minimum

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Semi-converter is an electronic circuit in which the rectification is done with the help of controled rectifiers and diodes. Had doides been not used and instead if we use all four tyristors, then the converter will become a full converter. Semi converter saves the cost by introduction of two diodes replacing two tyristors out of total four.

Farhan

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1. Wire resistance

2. Leakage around insulators

3. People stealing the power

it means that it's star connected on the motor part

Because the cable has capacitance, and an AC source would not be able to distinguish between capacitance and leakage.

Yes of course.. u just need some connecting wires to connect them in parallel

Watts = Volts x Amps x Power Factor

Power Factor is one for a resistive load and decreases toward zero as the voltage and current waveforms get out of phase with various inductive loads.

If the meter is developing more than the necessary forward breakdown voltage of the diode, typically 0.7 volts, then the diode is bad. However, some meters do not generate enough voltage in resistance mode to bias the diode on, unless you flip a switch that enables diode test mode. Use another meter at the same time to measure the voltage across the diode and compare that with the diode's published forward breakdown voltage.

Transformer oils are subject to electrical and mechanical stresses while a transformer is in operation. In addition there are contaminations caused due to chemical interactions with windings and other solid insulations, catalyzed by high operating temperature. As a result the original chemical properties of transformer oil changes gradually, rendering it ineffective for its intended purpose after many years. Hence this oil has to be periodically tested to ascertain its basic electrical properties, and make sure it is suitable for further use or necessary actions like filtration/regeneration has to be done.

There is no disadvantage of unity power factor, because at unity power factor all the electrical power is efficiently utilized by the the load, and at lagging power factor some power is lost in the load's magneticfield.

100MVA

explain why all the load must be removed when to conduct the insulation and resistance testing

"PU" can stand for multiple things, depending on what part of "electrical engineering" you're interested in. In the power world (power generation, transmission, distribution) "PU" may stand for per unit, or pickup if related to protective equipment like relays.

Single phase motor winding is often checked just by listening to the noise that the motor is making. An experienced person can tell if the motor is working at single phase or double phase.