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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 regulator controls the speed of AC motor?
the motor should only rotate in a rated speed,if the speed is more than rated speed then the motor will be damaged........to control the speed of motor a rheostat should be connected to the field side of motor......by variying the rheostat we can control the speed of motor......
Neutral shift in 3 phase systems?
Neutral shift in a three phase system can occur when service transformers on long distribution lines are connected to provide four wire star service (like 277/480V) and the common primary connection (like three 14.4 kV transformers on a 24 kV line) on the transformers is left ungrounded. Observed Neutral shift can be so severe, depending on the situation, that in the example given here 480 Volts phase to phase and 470 Volts phase to Neutral were measured. This condition is only present while the load (this was a 100 HP pump) is not in service.
What is the definition of automation?
Automation or automatic control, is the use of various control systems for operating equipment such as machinery, processes in factories, boilers and heat treating ovens, switching in telephone networks, steering and stabilization of ships, aircraft and other applications with minimal or reduced human intervention. Some processes have been completely automated. Automation has been achieved by various means including mechanical, hydraulic, pneumatic, electrical, electronic and computers, usually in combination.
A coulomb is a measure of whereas an ampere is measure of?
Coulomb is a measure of electric charge:
One coulomb is the amount of electric charge transported in one second by a steady current of one ampere.
http://en.wikipedia.org/wiki/Coulomb
What is the definition of Electromechanical Control Relays?
an electrmagnet relay uses an electromagnet to pull a piece of iron or steel towards it such that it causes to contacts (pieces of metal such as gold) together and complete a circuit. They can range in size from as small as your fingernail (to switch low power signals such as the inputs to an audio amplifier) to as large as stuffed sofa (to switch the output of a power plant). An electromagnet is a coil of wire wound on a iron core. When a current is run through the coil, it becomes a magnet.
Why does a capacitor keep its charge after the supply is disconnected?
Yes, it can. Then you can use the charge to power something else. :)
Basically there are three types of inverters 1) Square wave Inverters 2) Quasi Square wave or Modified Square wave Inverters 3) True/Pure Sine wave Inverters The emerging trend among Inverters could be titled to Multi-Level Inverters which aim at the Increasing of Inverter Efficiency along with reduced Inverter Cost
Comparision between half wave and full wave rectifier?
A half wave rectifier conducts on every other cycle. The output is a train of half sine cycles, at a period equal to the input period. At 60 Hz, the period is 16.7 ms. Each half cycle (8.3 ms) will be interleaved with periods (8.3 ms) of no voltage. If you filter the output with a capacitor, you get DC - at no load, the DC will be the peak value less the forward bias voltage of the diode - at some load, the DC will fluctuate between that peak value and some value dependent on the size of the capacitor and the current draw. Again, the period (of this nearly sawtooth waveform) will be the input period.
A full wave rectifier conducts on every cycle. The output is a train of half sine cycles, at a period equal to half the input period. At 60 Hz, the period is 8.3 ms. Each cycle (8.3 ms) will be connected to the preceding cycle with no intervening delay. Each cycle will pulse in the same direction, instead of in alternating directions. If you filter the output with a capacitor, you get DC - at no load, the DC will be the peak value less the forward bias voltage of the diode - at some load, the DC will fluctuate between that peak value and some value dependent on the size of the capacitor and the current draw. Again, the period (of the nearly sawtooth waveform) will be half the input period.
Since the full wave output waveform is twice the frequency (half the period) of the half wave output, the capacitor can be about half its required value for the half wave circuit in order to achieve the same level of filtering.
How can a tone generator be used to locate a short circuit?
Yes you can use both. They are also acutally the easiest way to find a short in an automotive circuit.
What is Critical disruptive voltage?
In the transmission lines, there is no apparent change in the condition of air(CORONA) surounding the wires if the applied voltage is low.However,when the applied voltage exceeds the certain value,called disruptive voltage !!!
What are the advantages of Permanent magnet over Electromagnet?
Unlike a permanent magnet, an electromagnet can be turned on and off. One useful advantage of this: Place a metal bar inside the electromagnet, apply current through the electromagnet in one direction, and the magnetic field would move that bar one way -- reverse the current reverses the magnetic field and the bar would move the opposite way. You could use that effect and make an electronically controlled lock for a door.
What are line voltage and phase voltage?
There is no such thing as 'voltage between phases'. The voltage you are referring to is the voltage between LINES -which is why it is called a 'line voltage'!
That depends on the type, voltage, and phasing of the system in question. Residential single phase service in the US is 220V between the two lines, 110V from either line to neutral.
A common 207/110V 3 phase system is 110V from line to neutral, 207V between lines. This is mostly used in industrial settings. Beyond that you really need to look at the type of system in question, and gather your information from that. This question is too open-ended to answer specifically.
How does the current change in a circuit when the ammeter is placed in different spots?
the current value at any part of the circuit is dependent upon the circuit conditions and not the ammeter. The meter will simply allow you to read those currents, whatever they may be.
What will be output current for 30KVA Isolation Transformer?
who knows 30kva means 30000 volts per ampere so if the output is 100 volts the amps will be 300 amps so do the math.
What are the disadvantages of Electro pneumatic?
ADVANTAGES OF PNEUMATICS.
1. Simplicity of Design And Control
The control machines are easy to design. i.e they can be manufactured using standard cylinders & other components. Controlling mechanism simply contains two ON-OFF states, so its easy to implement and understand.
Also these components have versatile usage, they can be used in many situations. Pneumatics are easy to install and have useful mechanical movements. For an instance Straight-line movements can be obtained without further adjustments, such as levers, cams...etc
2.Reliability
pneumatic control mechanism is well known for its long lasting operation life time. In fact they need very little maintenance but operates continuously with high reliability.
Air /gas used as the working fluid is less likely to damage the equipments since gas are good in absorption of shock, and excessive forces, but hydraulics react directly transferring the stress to mechanical parts.
3.Safe to use
Pneumatic controls have high safety profile due to many reasons. Air used in these are fire proof, and less vulnerable to explosions and electric hazards. These are adoptable in extreme weather conditions, and we can rely on their continuous operation. This is because compressed air can stay in good condition in high temperature fluctuations, unlike hydraulic s ystems that tend freeze or boil in these situations.
Even a leak occur there is less chance of getting fire. Also there is no toxicity in air used, so we can expect no harm to living beans. Since pneumatics are sound in safety, very less precautions need to be taken.
4.Storage
Compressed Gas can be stored easily, and once compressed, above a certain threshold level they can be operate with out further need of compressing. This feature allows the use of machines when electrical power is lost.
5. Clean
Since working fluid is purified air, there is no messy waste produce at the end of the day. A little leak will not make the surrounding shady. Also, since ir is used no risk of toxic hazards t o machines or humans. Industries like pharmaceutical, food..etc tend prefer pneumatics for their cleanness.
6. Easily transported
Air is easily obtainable from atmosphere and can be used with little purification. Air can be pumped to long distances in pipelines, so can control pneumatic equipments for long distances. This makes central controlling possible. These also requires no return line, so easy to manage and cost effective.
7. Light in weight
Air is very light compared with other fluids, which are very heavy. They don't need high power to transfer.
8.Cost Effective
This is a very economical controlling mechanism. The Pneumatics require low maintenance cost, since wear of equipments are very less. These operates at low pressure , so equipments can be produced for low cost using cheap materials. In contrast hydraulic controlling systems require high pressure, so need tough materials, which comes in high prices.
9 high speed working medium
Compressed air controllers are able to achieve high work speeds, the flow rate may go up to 20 m/s, while hydraulics is restricted around 5m/s.
10.safe operation in Overloads
The shock absorbent properties of air make overloading safe. Under excessive forces air can compress easily avoiding damage to equipments.
11 Variable pressure
Pneumatic systems can work in various pressures, this also alow the speed control.
DISADVANTAGES OF PNEUMATICS.
1. Air is largely compressible, which may be good for some reasons, but the major draw back is the inefficiency in accurate positioning and speed controlling. These often need to be tuned to work correct and sound. Since Compressible,not possible to achieve uniform and constant piston speeds.
2.Unable to work with heavy loads (commonly used working pressure of 7 bar, the require output force is economical only up to about 20 KN to 30 KN ) Unlike hydraulics or electrical system these cant be used for heavily loaded operation.
3. Air used needs to be purified, air containing moisture may lead to corrosion of the equipments.
Power = (voltage) x (current) = 110 x 5 = 550 watts
If operated at this level for 1 hour, then
Energy = (550 watts) x (1 hour) = 550 watt-hours = 0.55 kilowatt-hour.
Another Answer
As microwave ovens don't operate continuously, but in short bursts, it's not really possible to determine an answer to your question without knowing the frequency and duration of these bursts of energy.
it is a high resistive paralell rezonans circuit which allows to cary signals between to electric station with limited bandwith
AnswerLine traps are a large inductors, suspended at the end of a high-voltage transmission line which prevents high-frequency communications/protection signals from travelling beyond that point, by attenuating those signals. The inductive reactance of the inductor presents a high reactance to high-frequency signals but a low reactance to mains frequency (50/60 Hz).
What will you attempt to do in the post reading phase?
In the post-reading phase, I will summarize the main ideas and key points of the text to reinforce my understanding. I will also reflect on how the content relates to my existing knowledge and experiences, and consider any questions or insights that arise. Additionally, I may discuss the material with others or apply the concepts in practical contexts to deepen my comprehension.
Why neutral ground voltage is 120v sometime 0v?
There should be no voltage on the neutral wire to ground. This is a serious situation. Call a qualified electrician to check this out.
Where isolators are placed in substation?
An isolator is a non load-breaking switch, and is provides a visible means of isolating a component, such as a circuit breaker, transformer, etc., from the high-voltage lines, whenever it is necessary to perform maintenance of that component. Normally, isolators come in pairs, with one on each side of the component to be isolated. Isolators are only opened afterthe load current has been broken using a circuit breaker, and must be closed before the circuit breaker is reclosed.
To work on, say, a h.v. circuit breaker, the breaker must be tripped, the isolators on either side must be opened and locked off, temporary earths attached to either side of the circuit breake- to-work card, detailing the maintenance work, must be issued to the crew by the supervising engineer.
What is 'electrical potential' - 'energy difference' or 'voltage'?
Electrical potential deals with moving a charge in a direction opposite to an electric field. So what we are actually dealing with is Potential Energy. This can be calculated by the equation of PE = QEd where Q is the charge of the particle, E is the electric field and d is the distance the charged particle has been moved. The units of all this ends up being Joules (J).
Now, electric potential difference is another story. This is the work per unit charge. In this case the unit will be V (volts).
Can generator power a washer machine?
A washing machine uses between a half and one horsepower while working.
As one horsepower is equal to 746 watts per hour, it would be approximately 373 to 746 watts of power while operating
What is constant speed DC 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
