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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
USS comprises of a single substation factory built package having transformer, HT and LT controls. The safety features and mandatory requirements are fully complied with. USS is a fit and forget technology, where the connections are precise, secure and totally enclosed. Hence no chance for failure , corrosion and losses.
USS is built as a product in line with the thinking of the architects who are quite concerned with aesthetics, safety and ease of installation. Due to the enclosed construction, it avoids bird hit, human/animal contacts which may lead to fatal accidents, disruption of supply and power loss as may happen in the open execution.
Which is beter husky generators or centurion generators?
It depends on what the generator is being used for. But I would say these are what we call in the industry as disposables as either are built for continuous use.
What do you mean by resonance?
Resonant means something vibrates at a given frequency. Usually if you can get an object to resonate at its resonant frequency - it will disintegrate !
For example - if you tap a wine-glass, it 'rings' - that's it's resonant frequency. Now - take a speaker and play the exact frequency through it, while holding it close to the glass - after a few seconds it will shatter because the glass vibrates too fast.
How can relay fail to send signal to circuit breaker to trip?
A protective relay may fail to send a signal for many reasons - assuming it should have operated (so pickups, time dials, etc. are set so the relay should have operated), the relay may be out of tolerance, if it is a microprocessor based relay it may be in some state of failure or there may be a fluke situation that causes an element to hang up, if it is solid state, it's power supply may have failed (many solid state did not have any sort of monitoring for this condition). Battery power may not be sufficient to operate the breaker, or wiring to the breaker may be compromised (open test switch, lifted wire, rodent damage to wiring, etc.).
The analog connections to the relay may be bad, or wiring may have issues (such as multiple grounds on PT/CT connections). I've seen where a CT was supposed to be wye connected and one of the ground jumpers was missing, which caused some strange behavior.
A relay output contact may have failed as well - if not properly designed, these can get burned out fairly easily.
Microprocessor relays have an abundance of programming options; sometimes they get programmed wrong as well.
Is it ok not to ground the neutral at secondary side of transformer?
No. Neutral, by definition, is grounded at the secondary of the service transformer, and again at the distribution panel. It is also carried from pole to pole when there is secondary running between poles, or along other means, and it is grounded at each and every point. It is never connected to ground anywhere else downstream of the distribution panel, and it is not OK to use ground on a branch circuit as a current return.
The reason for this is to ensure that the hot to ground voltage potential at any point in the branch circuit cannot exceed a safe value. It is also used, in GFCI breakers, to detect a ground fault by noting that the current in hot and neutral do not balance each other.
In the worst case, theoretically possible, although highly unlikely because of the multiple grounds located upstream of the distribution panel, if neutral were completely ungrounded, the neutral/hot pair could rise in voltage up to the primary line voltage. In a typical 13.2 KV primary, stepping down to 120/240 V split phase with a neutral, the neutral/hot conductors could rise to 7.62 KV, relative to ground, although not relative to each other, a highly dangerous and lethal situation.
120 V x 0.75 A = 90 watts
2 minutes = 120 seconds
90 watts for 2 minutes = (90) x (120) = 10,800 watt-seconds = 10,800 joules
The motor consumes 10,800 joules of electrical energy during that 2 minutes.
If the motor is perfectly (100%) efficient, then that's the amount of work you
can get out of it.
In the general case, the amouunt of work the motor can do is (10,800 joules) x the motor's efficiency.
Why is a 3 phase synchronous motors not self starting?
A single phase induction motor is not self starting; thus, it is necessary to provide a starting circuit and associated start windings to give the initial rotation in a single phase induction motor. The normal running windings within such a motor motor can cause the rotor to turn in either direction, so the starting circuit determines the operating direction.
Why signal distorted after amplification?
Distortion can be caused by many things, and varying levels.
Two of the most common are;-
Clipping.
This is when the amplifier has reached maximum or minimum amplification and causes the wave form, to be flat top and bottom. It squares the waveform and sounds rough. Usually due to the input signal being too high.
Harmonic.
This is a form of feedback, where the input is receiving signal from the output. Sometimes the amplifier 'rings' at a harmonic of the input and is re-amplified giving a tinny, squeaky, sound.
Caused by bad screening or component layout.
Ohm's Law: Resistance is voltage divided by current
Power Law: Power is current times voltage
Combining them gives: Resistance is voltage squared divided by power
220 volts squared divided by 100 watts = 484 ohms. Note that this is hot resistance. If you measure the bulb in the cold state, you will get an entirely different, smaller, value, due to the extreme temperature coefficient of the filament.
Independently of that, since you ask for peak voltage, that means you are talking about an AC voltage source. We have to assume a sinusoidal waveform, and that the 220 volts was the RMS value. In this case, the peak value is simply the RMS value multiplied by the square root of 2, i.e. 0.707..., making the peak value 311 volts.
What is time constant of capacitor when resistance is zero?
Time constant in an RC filter is resistance times capacitance. With ideal components, if the resistance is zero, then the time constant is zero, not mattter what the capacitance is. In a practical circuit, there is always some resistance in the conductors and in the capacitor so, if the resistance is (close to) zero, the time constant will be (close to) zero.
How are series circuits and parellel circuits alike?
Both take current and energy from the power supply and dissipate power.
How many phase are there from transmission line from Oregon?
AC transmission lines are 3-phase, DC transmission lines don't have phases. It doesn't matter where they are from.
Is 1200kv transmission line exist?
I believe PGCIL is developing a 1200kV test lab at Bina, India. I don't believe any 1200kV AC lines are in existence currently. 765kV is fairly common.
25 HP is 25 HP, no matter how you slice it and dice it.
Why induction motor should not start by direct switching?
because IM draws 4 to 5 times the rated current when it is connected to the supply directly
in order to start the IM smoothly we need starters
1.star delta starter
2.auto transformer starter
DOL starter for direct starting for smaller capacity IM (upto 1HP)
Note:IM means Induction motor
What is a closed electric circuit?
An example of a closed electrical circuit would be a battery to a light bulb, the only source of power being the battery and no other input from an outside source.
Like video cameras in a store they would be considered a closed circuit surveillance system so long as the signals stay inside the store and don't leave to a remote location.
In the old days of Cathode Ray Tubes, the beam is controlled by a circular transformer around the yoke or long part of the CRT.
Frequency does not change when you use a step-up or step-down transformer. Only current and voltage is changed.
What var is drawn by a 5kw induction motor?
You need to know the power factor, the phase angle, or the KVA in order to determine KVAR from KW.
Power factor is the cosine of the phase angle between voltage and current, and is also the ratio of KW over KVA.
Once you know one of those other things, you simply consider that reactive power factor is the sine of the phase angle between voltage and current, and is also the ratio of KVAR or KVA.
It is simple arithmetic from there. You don't even need trigonometry, as I've already given you the ratios.
Does the current generates if there is no resistance in the circuit?
You can have current without resistance. You would just have zero voltage drop across that zero resistance.
However, the question is very interesting, because if you really had zero resistance in the entire circuit, it would be impossible to have any voltage at all without generating an infinite current, so the answer in the theoretical case is no, you can have no current, nor voltage, if there is no resistance at any point in the circuit.
Residual current as in a residual current device or RCD (sometimes known as a earth leakage detector), refers to the current both entering and leaving a circuit. If more current flows into a circuit then comes out (if there is a ground fault or if someone gets a shock) the RCD will switch off the circuit. Typically the current required to trip a RCD is around 5-20mA, however even 5 mA can be enough to stop your heart, so RCDs are a good safety device but should not be relied on.
Can a power surge cause a motor to go into reverse polarity?
No. If you have phase 1, 2, 3 (in that order), and phase 1 is the highest voltage at the instant a switching event occurs (causing a power surge), the surge voltage will be highest in phase 1. For polarity to change, you would need phase 2 to instantaneously change to greater than 1, which will not happen.
Yes. Input DC voltage would be root2 times the input AC voltage.
