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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
Difference between synchronous generator and synchronous motor?
ASYNCHRONOUS is a mode whereby events happens irregardless of control. SYNCHRONOUS are this same events but controlled by a timing and/or control
Is Voltage the same all parts of a series circuit?
Voltage is an electrical force or pressure that causes current to flow in a circuit. It is an additive in a series circuit.
The higher voltage source forces current backwards into the lower voltage source, which can damage it or even cause it to explode.
The load current will lag the supply voltage by an angle called a 'phase angle', determined by the values of resistance and inductive reactance. The magnitude of the load current will be determined by the impedance of the circuit, which is the vector sum of the resistance and inductive reactance.
Why the resistance of a capacitor is infinite when measures with an ohmmeter?
The typical ohmmeter measures DC resistance by providing DC current and measuring the voltage drop accross the resistor. By definition, the 'ideal' capacitor is an open circuit to DC current and voltage. By definition, an open circuit has infinite resistance.
Of course, real-world capacitors are not ideal. They have a very high parallel leakage resistance and a very small series resistance. And, different meters can measure different ranges of resistance. So, you may not get an infinite/overload measurement on some capacitors with some meters. You may get a very high resistance instead. If so, you are not really measuring the resistance of the 'capacitor', but rather that of the imperfections in the component manufactured to be a capacitor.
ANSWER: The ohmmeter battery will charge the capacitor in 5 time RC after that it quirts there is no more current flow. Any body that claim to be able to check resistance of a capacitor i just a wannabe
Why does one line of 3 phase 480v show 0 volts and the other 2 have 480?
My first thought is this is probably a corner grounded delta system, but I'm confused by your voltages. If this was a 460v (L-L voltage) ungrounded or corner grounded system, the phase to ground voltage is meaningless, but the phase to phas voltage will be 460v all around the delta. If you have a 460v system and you're only seeing 230v, there's something wrong.
George Westinghouse invented a better way to deliver electricity to consumers in sweatshops and other jobs before and during the Great Depression. Westinghouse debated over the Alternative Current and the Direct Current with Thomas Edison.
What is the purpose of a coil spring?
A coil spring works by compressing and then expanding when a vehicle is going over pumps. Coil springs help make the ride a little smoother for most vehicles. The coils spring is attached to the undercarriage.
What device is used to increase or decrease the voltage of an alternating current?
A transformer is the device used to increase or decrease the voltage of alternating current (AC) This is done through a process referred to as inducing.
It's operation is based on the fact that electricity produces a magnetic field around itself. By placing 2 coils of cable beside each other, the magnetic field of one coil will induce a voltage in the other coil.
What are the advantages of sinusoidal wave form?
The main advantage of using sinusoidal waveform is that any waveform can be represented using a sinusoidal wave (by applying Fourier series). Also, analysing a circuit (or any other system) becomes simpler and easier using sinusoidal signal as test signal.
Can a 230 460 volt 3 phase motor be connected to a 277 480 volt 3 phase circuit?
Yes, that's possible, but only for low-powered motor.
You know that in order to start, the stator must be supplied with voltages that are shows shift phase between them,
so the trick is to use a capacitor (since it shifts phase current) to simulate a 3-phase source.
As indicated in the following picture:
http://freecircuitdiagram.com/wp-content/uploads/2010/10/Enabling-3-Phase-Motor-Operates-with-Single-Phase-Supply.gif
How many KVA is required to run 5HP 3 phase motor?
Keeping in mind that there is 746watts per Hp should lead you to the answer. For ex. Power(in KVA) = Voltage (1.73)x Current
Therefore, if you know the voltage, typically 480Vac, then 150(746) = 480 (1.73) x I
150Hp(746w/hp) = Voltage x Current
= about 135 amps current. Now you also need to factor in the Power Factor (PF) of the load (150Hp). The power factor depends on the type of load. A motor is mostly Inductive, a heater, or lighting bank is resistive, and capacitive loads aren't that common. Your question is a bit vague. If you'd like to rephrase your answer or send it directly to me, I'd be glad to assist you further. You might also want to check out a site called "Mike Holt's Code Forum'. If you're an EE student, I'm sure the path to your solution is in one of your 'Power' books.
What is the reason for a neutral wire becoming energized and the circuit breaker not tripping?
=== === This is known as a "Disconnected Neutral (Open neutral)" fault condition. It occurs whenever the Neutral wire for a circuit becomes disconnected from the household's main power supply panel whilst the Live or "hot" wire for the circuit still remains connected to the panel AND the circuit has appliances plugged into the socket outlets.
In that situation, if you put a voltage indicator, such as a test screwdriver with a neon lamp onto the Neutral wire it will glow just as if it was Live, because it is being fed with a very small current coming from the Live supply via the plugged-in appliance(s) to the Neutral wire.
If you unplug all appliances, lights and whatever else may be connected to the circuit, the Neutral will no longer seem to be Live because there is no longer any path from it to the Live supply.
No ordinary circuit breaker on the main supply panel would trip in this situation because the current flowing from the Live via the appliance(s) to the Neutral to the test instrument is not high enough to cause the circuit breaker to trip to shut off the current.
Even if there is a GFCI or an RCD in the circuit that too is unlikely to trip in this situation because the test current is so small and is of the same size - an equal current flow - in both the Live and the Neutral wires.
A "Disconnected Neutral" fault condition is VERY UNSAFEbecause somebody who does not know about the danger could easily touch the Neutral wire and get a bad shock whilst trying to find out why no appliances work when they are plugged into a circuit that actually has such a "Disconnected Neutral" fault condition.
Hence a "Disconnected Neutral" fault is a very unsafe condition and should be corrected at the earliest possible opportunity by someone who knows exactly which wires to check and then connect properly.
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For your safety and that of anyone else who may to use the appliance, ask a professional licensed electrician to advise you or to do the work for you. If you do this work yourself, always turn off the power
at the breaker box/fuse panel BEFORE you attempt to do any work AND
always use an electrician's test meter having metal-tipped probes
(not a simple proximity voltage indicator)
to insure the circuit is, in fact, de-energized.
: IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB
SAFELY AND COMPETENTLY
REFER THIS WORK TO QUALIFIED PROFESSIONALS.
What is single tuned voltage amplifier?
it is a circuit consisting of a tuned circuit with a capacitor in parallel with inductor and it is connected to collector terminal in common emitter configuration,, and it is used as frequency receiver
How much current carrying in neutral?
In the US , for example, the live wire changes from zero to +120 volts rms, then back to zero, then to -120 volts rms, then back to zero. It goes through that cycle 60 times every second. At all times throughout each cycle, the live wire "feeds" the current at the varying voltage and the neutral wire "returns" it to the power source.
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A neutral wire is always needed as the return path back to the power station for any single-phase circuit in which a single live wire feeds alternating current into the connected load.
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As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.
Before you do any work yourself,
on electrical circuits, equipment or appliances,
always use a test meter to ensure the circuit is, in fact, de-energized.
IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB
SAFELY AND COMPETENTLY
REFER THIS WORK TO QUALIFIED PROFESSIONALS.
For to keep the resonant frequancy constant L*C has to stay same. Lets say if you double L you have to divide C by 2 to keep the same resonant frequency. If only L increases Resonant frequency decrease, this is same for C.
Why are homes powered by ac and not by dc current?
power station may also provide dc voltage with using of dc generator but it is not economical to transmit the dc voltage. Since the step up and step down of dc voltage is not possible directly using transformers, we'll have to transmit domestic supply voltage (DC, as your inquiry). But transmission of a DC voltage over lengthy lines would result in a much less voltage at receiver's end.
So, considering the efficiency, economy and easiness, AC is preferred to DC.
How many amps in a low voltage light bulb?
Look on the light bulb for the voltage and the power in watts. Then divide the watts by the voltage and that gives the amps.
Some CFL bulbs also state the current as well as the voltage and power, which is because they can have a poor power factor.
Voltage is a measure of electrical potential. I understood voltage best when my first semester Electronics professor told the class that voltage is to an electrical circuit as water pressure is to a plumbing "circuit".
How many diodes are used to make a half wave rectifier?
You use a half-wave rectifier where the system design does not require a full-wave approach.
Half wave rectifier output is used for running ac motors.
Can a transformer work using dc?
no. because if we use dc source for transformer there will be no production of energy for the secondary side since they are mutually conducted, as the transformer is a static device which can transmite the energy from one circuit to other with out changing the frequency and also there is no movement of the conductors. in order to produce the emf there should be either conductor movement or moving flux so the dc source will produce constant field flux hence there is no production of energy in the secondary side.
What size feeder wire for three phase 320 amp meter serving two 200 amp panels?
2/0 if copper is used; 4/0 if aluminum is used. The neutral and ground are usually smaller.
2/0 is only rated for 185 amps.
3/0 copper is rated for 210 amps, 250 MCM is rated at 215 amps if aluminum is used.
How much horsepower to run 40 kw generator?
A watt (or kilowatt) is the unit of measurement for power, not energy. Power is the rate of transferring energy and, so, the watt is equivalent to a joule per second.
So, your question doesn't actually make any sense. It's rather like asking, "How many kilometres are there in 40 kilometres per hour?"
However, you could have asked how much energy is transferred at the rate of 40 kW (not 'Kw') over, say, one hour. In which case, the answer would be 40 000 x 60 x 60 = 144 MJ (megajoules).
What is difference between resistance and reactance while both are measured in ohms?
Resistance is constant no matter the frequency applied. Reactance varies depending on the frequency of the power applied to it.
What are some examples of a closed circuit?
A connection from a power source, through a load and a return back to the power source.
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An example: electricity is supplied to the light switch on the wall through an insulated copper wire, even though the switch is in the off position electricity is present. There is another insulated copper wire going to the light bulb. When you flip the switch the circuit is completed and the light bulb comes on.
