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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
Why secondary coil of ct is short?
A CT attempts to push a specific ratio of primary current through the secondary. If the secondary is open circuited, the resistance across the secondary will be very large. Following Ohm's law, V = I*R, so the secondary voltage will become very large, and will arc across the open, or damage the CT, or both.
What is the percentage voltage drop for feeders?
In the CEC (Canadian Electrical Code) voltage drop for feeders is stated in rule 8-102. Voltage drop in an installation shall not exceed 3% in a feeder or branch circuit. This percentage may differ in the NEC (National Electrical Code).
What is ultimate load test to bored pile?
The question itself is not correct.
It should be what is the ultimate load carrying capacity of bored pile?
Ans: Ultimate load carrying capacity of pile could be determined be conducting load test.
Ultimate load:
The load at which the pile continuously settle.
or
the load at which settlement of the pile reaches 10 percent of its diameter
What is system earthing and equipment earthing?
System Earthing is the earthing associated with current carrying conductor & is essential for the security of the system.
Equipment Earthing is the earthing associated with non-current carrying metal work & is essential for the security of human life and property.
What is phase between voltage and current in a pure inductive circuit?
The phase angle between voltage and current in a purely inductive circuit, under ideal circumstances where there is no resistance at all, is 90 degrees.
What are feeders in power system?
"Feeders" are conductors which carry electric power from the service equipment (or generator switchboard) to the overcurrent devices for groups of branch circuits or load centers supplying various loads.
How current increases when the load increases in a generator?
Power is voltage times current. If you want to maintain constant voltage and yet increase power, then current must increase. Its simple math.
How can an ammeter be connected in a circuit and not effect the flow of current?
The ammeter does affect the flow of current in a circuit, however, the resistance of the ammeter is so small in comparison to the circuit that the effect is negligible. It is connected in series.
Does the ohmmeter need to be parallel to the load when measuring resistance?
It does not matter, since the ohmmeter needs to be connected to the device in isolated mode. Series or parallel; they are both the same, in this case.
Why Kirchhoffs current law and Kirchhoffs voltage law cannot apply on distributed circuits?
Actually, they do apply.
Kirchoff's Current Law states that the signed sum of the currents entering a node is zero. This applies whether the node has only two connections, such as in a series cicuit, or more than two connections, such as in a parallel circuit. Some people confuse this with the rule that current at every point in a series circuit is the same. That is just a special case of KCL, but the real rule has to do with the node, and not the circuit.
Kirchoff's Voltage Law states that the signed sum of the voltage drops going around a series circuit is zero. This applies for simple series circuits as well as for complex series/parallel circuits. Pick any loop in a circuit and walk around it - you will find that the signed sum of the voltage drops is zero, no matter what.
What is the current drawn in star as compared to delta?
Star voltage is 1 / 1.732, or 0.577 delta voltage. (1.732 is the square root of 3.) It follows, then, that star current is 0.577 delta current.
Not asked, but answered for completeness, star power is 0.5772, or 0.3333 delta power. This is why large motors use a star-delta start sequence - to minimize startup thermal stress.
yes
Protecting Knob & Tube wires entering a panel, sleeves called "Loom Duct" were used to protect the conductors and held in place with a "Loom Clip". When Knob and Tube wiring was phased out in the late 30's a multi conductor cable was introduced. This cable had paper around each conductor and then enclosed in Loom duct. This new cable was called "Loomex".
What is back charging of power transformer?
Do you mean "back-feeding"?
Normally a power transformer takes a primary voltage and steps it up or down (usually down) to a secondary voltage. However, transformers are symmetrical; you can just as easily feed the secondary and generate the primary voltage.
This is particularly a problem with utility power distribution systems in a storm, such as a hurricane situation...
In a protracted power outage, some people are tempted to run backup generators to supply their inhouse loads while the utility company is effecting repairs. An intelligent user, one that reads the directions, will isolate the generator from the service distribution system so that it is impossible to back feed the service source.
Some people might ignore the directions and attempt to back feed their entire home. If they don't isolate the incoming mains breaker, this can back feed the distribution transformer and energize the primary line on the street, raising it to high voltage, such as 7620 volts.
This actually happened during Hurricane Gloria in 1985, and a utility worker was killed. Yes, the worker was at fault for assuming that the line was dead, but the homeowner was also at fault for ignoring the directions that came with the generator.
Unless you have the proper equipment to synchronize, backfeed, and isolate your generator, DO NOT EVER DO THIS.
What is the frequency of the power waveform in capacitive circuit?
The frequency of the power waveform in a capacitive circuit, or for that matter, an inductive circuit, is the same as the input voltage or current. Its just that the current leads the voltage (capacitor) or lags the voltage (inductor) by a phase angle, the cosine of which is the power factor.
It does not matter how many sine waves you have, or what their phase angle is; if they all have the same frequency, the resultant, by Fourier analysis, is still a sine wave of the same frequency.
Is stacking of cables in cable tray permitted?
See NEC Article 392. It depends on the voltage, conductor size and the type of cable tray selected.
we use Capital letters for the High Voltage ( Primary ) and we use small letters for Low voltage secondary so in this case:
YN: it's refer to High Voltage, and it means the high voltage connection is Star and Neutral is Brought out.
d: refer to Low Voltage and it means that low voltage connection is delta.
11: mean LV lead the HV by 30 degree.
and others number it will be like bellow
01 02 03 04 05 06 07 08 09 10 11 12
30 60 90 120 150 180 210 240 270 300 330 360 or 0
