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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
How does a current transformer work?
A current transformer is used in high voltage circuits where it is not possible to measure current directly. A CT is a step up transformer with only one turn in primary. There will be as many cores based on the purposes like metering, protection etc. The secondary of a CT should never be kept open circuited bcoz very high flux will be developed in the secondary and hence it may be damaged.
Why aluminium can't be used as core of transformer?
Because aluminium is, in simple terms, 'non-magnetic' and will not support the formation of magnetic flux. 'Soft' ferrousmetals with low reluctance* (i.e. metals such as iron or silicon steel) must be used.
[*'reluctance' is equivalent to 'resistance' in an electric circuit]
Compare synchronous and asynchronous operation of sequential circuits?
A Synchronous Sequential Circuit is a system whose behavior can be defined on the timing of their signals , where in the case of asynchronous sequential circuit depend upon the order in which its inputs signals change and can be affected at any instance of time .
(reference : M. Moris Mano)
Why 2 wave traps are provided in the substation?
Line trap also is known as Wave trap. What it does is trapping the high frequency communication signals sent on the line from the remote substation and diverting them to the telecom/teleprotection panel in the substation control room (through coupling capacitor and LMU).
This is relevant in Power Line Carrier Communication (PLCC) systems for communication among various substations without dependence on the telecom company network. The signals are primarily teleprotection signals and in addition, voice and data communication signals.Line trap also is known as Wave trap. What it does is trapping the high frequency communication signals sent on the line from the remote substation and diverting them to the telecom/teleprotection panel in the substation control room (through coupling capacitor and LMU).
This is relevant in Power Line Carrier Communication (PLCC) systems for communication among various substations without dependence on the telecom company network. The signals are primarily teleprotection signals and in addition, voice and data communication signals.
The Line trap offers high impedance to the high frequency communication signals thus obstructs the flow of these signals in to the substation busbars. If there were not to be there, then signal loss is more and communication will be ineffective/probably impossible.
What happens when a capacitor is connected to a dc supply?
is it ? are you sure ? but i know so many circuit where capacitor is connected with ac supply .
still , if u connected a capacitor to dc supply , then :
1. if it is in SERIES with the dc supply , it will block all the dc current as capacitor
provides infinite resistance to dc current .
application : where u want to block dc current.(simple high pass filter)
2. if it is in PARALLEL with the dc supply , it will not block dc current , but if any ac
current comes out from the supply , the ac current will go through the
capacitor , as capacitor provides small resistance to ac current.
application : a) where u want to block ac current.(simple low pass filter)
b) to filter the noise (ac components) of dc supply.
Will decreasing the resistance in a circuit decrease current flow if voltage is kept constant?
You should answer this question yourself by doing a couple of examples using Ohm's law I=E/R (current equals voltage divided by resistance. Here they are: Base circuit: 10 volt supply feeding a 10 ohm resistor calculate the current... New circuit: 10 volt supply (voltage kept constant) feeding a 20 ohm resistor (increased resistance) calculate the current... Did the current increase, or decrease? This way you can prove to yourself the answer!
The inventor of AC, or alternating current, was Nicola Tesla. He invented it when DC, or direct current, from Thomas Edision was to innefficent. However, if one means AC as in air conditioning, then the inventor of the AC was Willis Carrier.
Capacitors are used in many different ways.
Here are a few instances where they are used:
- in amplifier circuits to isolate small signal circuitry from amplifier circuits' DC bias
- in power supplies to minimize AC ripple on the DC waveform
- in timer circuits to create specific patterns and frequencies
- with integrated circuits to prevent ripple from the power supply from reaching the IC
- in analog computation machines for creating integrators and differentiators
- in high voltage AC systems to "add VARs" to the system.
Convert kva to full load amps?
kva means 1000 x voltage x current
So in order to determine the current we need to know the voltage.
AnswerA kilovolt ampere (kV.A, not kva) is a measure of a circuit's apparent power, whereas the ampere(not amp) is a measure of current. These are two completely separate quantities, so your question is quite meaningless. You might have well have asked, "How metres are there in a kilogram of sugar?"
Why current transformer should be grounded?
If there is a short circuit between the transformer's high-voltage windings and its core (or any other metal parts, come to that) the fault will be recognised by the high-voltage supply's protective system, which will quickly disconnect the high-voltage line. For this to happen, the metal parts of the transformer, including its core and metal container, must be earthed or grounded to provide an electrical path back to the source of the high voltage.
What voltages should never be measured directly with a VOM?
A VOM 'Voltage Meter' measures from a electrical outlet. Any voltage over a 1000 should never be measured directly with it.
Which DC motor is constant speed motor?
Dc shunt motor is constant speed motor.Its speed is constant with armature current.This shunt motor is used in paper mills and drilling machines
What is vector group YNd11 in transformer?
Vector group means it defines the primary & secondary side connection type of the transformer. It says D for the delta connections (windings connected between two phases) & Y for the star connections (windings connected from each phase to ground). The 11 stands for the phase displacement of the secondary referenced to the primary. Imagine a clock with only an hour hand; at 11 o'clock, the hand is at 30 degrees to the reference (12 c'clock), so the secondary is at 30 degrees to the primary.
- D or d means delta connection
- Y or y means star/wye connection
- z means zed/zigzag/interconnected star connection
- N or n means the Neutral point is accessible in the star connection. This is also sometimes taken to mean that the neutral point is earthed.
- A number means a phase shift in the secondary with respect to the primary, where the phase is measured in "hours"
A capital letter indicates primary winding and lower case secondary. Capital z does not occur as zed transformers are used only for creating an earth on an unearthed system and thus are always on the earthed secondary.
Primary is taken to be the higher voltage side, regardless of the direction of power flow.
So, Dyn11 means delta primary, star secondary leading the primary by 30 degrees, possibly with an earthed neutral
If rated voltage is applied to Transformer during S/C test, The secondary winding will burn out due ta heavy current flow through the winding. During S/C test the secondary winding is short circuited so the impedance between phase and neutral is very low(only winding resistance). But the voltage across the secondary winding is rated hence heavy current flows through the winding, as I=V/Z.
it depends which rated voltage is applied. if you are talking about primary winding voltage, transformer should withstand the primary rated voltage it's been designed for (OR it has been poorly designed). Otherwise, if rated voltage is the insulation voltage between a winding and earth OR winding-to-winding, you just have to check if: 1 - it is higher than the maximum primary winding voltage the transformer can withstand (could be, could not be..). Then, you can guess if your transformer is likely to burn or not. 2 - your test setup (usually a HV generator connected between primary and secondary winding) can deliver the requested current for the setup. I guess this won't be the case, since HV testers are usually designed to generate high voltages, but very small output currents.
What are the advantages of double wound transformer over a auto transformer?
The difference between a double wound step up transformer and an auto transformer is the double wound on the step up transformer and the single wound on the auto transformer.
What do you mean by DC generator?
DC generator is used to produce direct current. The basic DC generator have four basic parts
1. A magnetic field
2. A single conductor or loop
3. A commutator
4. Brushes
Definition from the National Electrical Code Article 100:
Feeder. All circuit conductors between the service equipment, the source of a separately derived system, or other power supply and the final branch-circuit overcurrent device.
Branch Circuit. The circuit conductors between the final overcurrent device protecting the circuit and the outlet(s).
How much voltage does an electric kettle need to work?
800 watts
Answer
It depends where you live. In North America the size of a kettle is limited by the supply at the receptacle (120 V/15 A) which means it cannot exceed 1800 W. In the UK, the supply is 230 v/13 A, so a kettle cannot exceed 2990 W.
What instruments used in measuring current and voltage?
Multi meter
AnswerInstruments that measure current are called ammeters, and instruments that measure voltage are called voltmeters. An instrument that measures resistance is called an ohmmeter. Each of these functions can be combined into one instrument, called a multimeter.
An electric circuit is a closed loop that allows a flow of electrons to begin from a source of the electrons and return to the same source.
Some of the energy carried by the current from the source may or may not be released to perform useful work.
Because of the resistance of the materials in the circuit, some of the energy carried by the current is always lost as heat emitted from the circuit into the surrounding environment.
The flow of electrons around the closed loop is called an electric current.
The source of the electrons must be a chemical battery or a mechanical generator which produces a potential difference, also known as a voltage.
What does the KAIC rating mean on a circuit breaker?
kAIC means the maixum current interruption capacity of circuit braker. IC stands for interruption capcaity. So if a CB has 10 kAIC means it can cut off current of up to 10 kA without damaging itself.
Voltage at a point is defined as the work done by a unit positive charge carrying it from infinity to that point. while volage diffrance between two points is the work done bye unit positive charge from one point to the other point.
work may be positive or negative depend upon the nature of charge that's why the potential will be negative or positive .
CommentBy definition, voltage means potential difference. For this reason, you cannot have 'a voltage at a point' because potential difference, or voltage, exists between two points. You can, however, have a potential at a point.
Why silver is not used for making electrical wires?
Even though silver is the best conductor of electricity, it is extremely expensive. Thus silver is not used to make electical wires. Silver is also very soft to be used as electric wires.
You can say DC voltage has a frequency of zero Hz.Because it is unidirectional in nature (may be positive or negative)
