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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
E dumbed down is a reference for slight degradation of a normal line voltage. It will vary for the "standard" set by your local electric company and guaranteed to vary as much as 10 volts...i.e Nominal line voltage may be anything from 115 volts to 127 volts as in my rural service territory.. In order to save those old rigs from frying to death, U need wire a 6 volt filament transformer in series opposing, so the 6 volts is reducing the normal power supplied. 126 volts becomes 120 volts and the secondaries in transformer begin to love you for not providing them with more input voltage than they are designed to work with. I endured lighting storm with line voltage surges and an old linear amp was cooking -slowly- the original 8 amp slo-blow fuses. I wired a ten ampere 6.3 volt filament transformer to reduce the line input voltage and the fuse failure became very much reduced, until the storm. I rewound the power transformer and when I did, added to the primary winding to accommodate the increased line voltage. Rig now works nicely on 5 amp fuses and doesn't blow them, even though they are normal fast-blow types. I still get 600 watts output and can work most anyone I hear...So, dumbing down your house voltage should not be taken lightly and if you have any older Ham Radio gear, U might seriously elect to add the six volt bucking transformer arrangement. The thing to remember is the ampere rating of the 6 volt winding has to be able to carry the current needed to run the equipment you operate. Good luck and Happy Hamming with those oldies-but-goodies still on the market!
Pulser coil used for spark timing in automotive. industry.
What is difference between nominal and terminal voltage?
The rated voltage of a motor listed on the nameplate is called the terminal voltage. This indicates the actual voltage on the motors terminals at which at which the manufacturer designed to operate. Whereas, Nominal voltage is the design or configuration voltage of the electricity distribution system.
How do you calculate holding current of scr when latching current is given?
we know that ratio of holding current to latching current in scr is 0.4.
What happens when a magnet is moved towards a coil?
You will generate electricity. As the wire cuts through the magnetic field.
As the magnet is moved, there will be an induced electro-motive force (EMF) which can cause a current in the coil. Once the magnet stops moving, the current will go to zero.
Indian Standard code for electrical earth pit?
IS 3043: EARTHING PITS
Abstract of IS: 3043 CODE OF PRACTICE FOR EARTHING
- All medium voltage equipment shall be earthed by two separate and distinct connections with earth.
- In the case of high and extra high voltage the neutral points shall be earthed by not Less than two separate and distinct connections with earth, each having its own electrode at the generating station or substation and may be earthed at any other point provided 'no interference is caused by such earthing.
- If necessary, the neutral may be earthed through suitable impedance.
- In cases where direct earthing may prove harmful rather than provide safety (for example, high frequency and main frequency coreless induction furnaces). Relaxation may be obtained from the competent authority.
- As far as possible, all earth connections shall be visible for inspection and Earthing Electrode Resistance measurement.
- No cut-out, link or switch other than a linked switch arranged to operate simultaneously on the Earthed or earthed neutral conductor and the live conductors shall be inserted on any supply System.
- This however does not include the case of a switch for use in controlling a generator or a transformer or a link for test purposes.
- Grounding is not likely to reduce the total magnitude of over-voltage produced by lighting or switching surges. It can, however, distribute the voltage between phases and reduce the possibility of excessive voltage stress on the phase-to-ground insulation of a particular phase.
- Plate electrodes shall be of the size at least 60 c m X 60 cm, Plates are generally of cut iron not less than 12 mm thick and preferably ribbed. The earth connection should be joined to the plate at not less than two separate points. Plate electrodes, when made of GI or steel, shall be not less than 63 mm in thickness.
- Plate electrodes of Cu shall be not less than 3.15 mm in thickness.
- Plate electrodes shall be buried such that ii. Top edge is at a depth not less than 15m from the surface of the ground. However, the depth at which plates are set should be such as to ensure that the surrounding soil is always damp.
- Pipes may be of cast iron of not less than 100mm diameter, 2.5 to 3 m long and 13 mm thick. Such pipes cannot be driven satisfactorily and may, therefore, be more expensive to install than plates for the same effective Area.
- Water pipes shall not be used as consumer earth electrodes.
- Under fault conditions, the earth electrode is raised to a potential with respect to the general mass of the earth that can be calculated from the prospective fault current and the earth resistance of the electrode. The results in the existence of voltage. In the soil around the electrode, that may be injurious to telephone and pilot cables, whose cores are substantially at earth potential, owing to the voltage to which the sheaths of such cables are raised.
- The voltage gradient at the surface of the ground may also constitute a danger to life, especially where cattle are concerned. The former risk arises mainly in connection with large electrode systems as at power stations and substation.
- Earth electrodes other than those used for the earthing of the fence itself, should not be installed
- In proximity to a metal fence to avoid the possibility of the fence becoming live and thus. Dangerous at points remote from the substation.
- The materials used for making connections have to be compatible with the earth rod and the copper earthing conductor so that galvanic corrosion is minimized. In all cases, the connections have to be mechanically strong.
- The cross-sectional area of every protective conductor which does not form part of the supply cable or cable enclosure shall be in any case, not less than
(a) 2.5 mm2, if mechanical protection is provided and
(b) 4 mm2, if mechanical protection ii not provided.
- Joints of protective conductors shall be accessible for inspection and testing except m compound-filled or encapsulated joints.
- No switching device shall is inserted in the protective conductor, but joints which can be disconnected for test purposes by use of a tool may be provided.
- An auxiliary earth electrode shall be provided electrically' independent of all other earthed metal, for example, constructional metalwork, pipes, or metal-sheathed cables. This requirement i. considered to be fulfilled if the auxiliary earth electrode is installed at a specified distance from all other earthed metal (value of distance under consideration).
- The earthing conductor leading to the auxiliary earth electrode shall be isolated to avoid contact with the protective conductor or any of the parts connected thereto or extraneous conductive parts which are, or may be, in contact with them.
- In TN systems, for cables in fixed installations having a cross sectional area not less than 10mm2 for copper and 16mm2 for aluminum, a single conductor may serve both as protective conductor and neutral conductor, provided that the part of the installation concerned is not protected by a residual current-operated device.
- However, the minimum cross sectional area of a PEN conductor may be 4mm2, provided that the cable is of a concentric type conforming to Indian Standards and that duplicate continuity connections exist at all joints and terminations in the run of the concentric conductors.
- When the source of energy is privately owned, there should be no metallic connection with the General public supply unless there has been consultation with the electricity authority concerned.
- It should be emphasized that an installation together with its source of energy may not consist entirely of one particular type of system. In such cases, each part of that installation may be required to be treated separately without detriment to other parts of the same installation.
- RCD's having Minimum Operating Currents Greater Than 30 mA -- These devices are intended to give indirect shock risk protection.
- The neutral points of each separate electricity system which has to be earthed at the power station or substation.
- GI/Copper Plate Size: 500mmX500mmX10mm.
- Wood coal powder and salt are in same quantity.
- Size of GI Strip: 300mmX10mm
- Size of GI Pipe: 2.5" Diameter.
- Minimum 1Ω Resistance should be available at a distance of 15mt.
- IR value of Earth resistance is less than 10Ω.
- Earthing resistance of earthing rod is changed from 0.3Ω to 0...8Ω between summer to winter.
- Distance between two earthing pit is 2 X Length of earthing electrode.
- If ground resistance is less than plate earthing (if hard rock) than Pipe earthing shall be used.
- Resistance between two earthing pit is negligible.
- Earthing of lighting protection should not mix with power system earthing.
- Lighting protection earthing should be 10 time stronger than normal earthing (use copper bus strip instead of wire)
- Jointing of earthing strip shall be overlap of min 50mm and for earthing wire overlapping shall be min 40mm
Plate / Pipe Earthing:
Plate Earthing Electrode
- For copper shall be 600X600X31mm and
My Comments: Thickness is usually 3mm and not 31mm
- For Hot dip GI shall be 600X600X63mm.
Pipe Earthing Electrode.
- Earthing electrode shall consist of a GI pipe (class B of approved make), not less than 40 mm dia. and 3 meters long. CL pipe electrode shall be cut tapered at the bottom and provided with holes of 12 mm dia. drilled at 75 mm interval up to 2.5 meters length from bottom. The electrode shall be buried vertically in the ground as far as practicable below permanent moisture level, but in any case not less than 3 meters below ground level. The electrode shall be in one piece and no joints shall be allowed in the electrode.
Size of Excavation:
- Size of 1 meter diameter and 3 meter length shall be excavated after depth of 3 meter the size of excavation shall be 900X300X900mm depth.
- Plate / Pipe Electrode shall be in vertical position.
- GI/PVC pipe for Watering shall be used of 40mm Diameter, length of 3 meter ( contain hole of 12mm Diameter in Zigzag manner starting from 15cm away from bottom to 2 meter height ).
- At bottom 150mm layer of Salt and charcoal power shall be installed than Plate shall be installed.
- Min 120kg of charcoal power and 120kg of salt shall be used for each earthing pit.
- The plate \ pipe electrode, as far as practicable, shall be buried below permanent moisture level but in no case not less than 2.5 M below finished ground level.
What is a c200 current transformer?
This is a class of current transformers, and is a fairly low class. This has to do with what kind of burden can be placed on the secondary. A general rule is a C200 current transformer can supply ~200 volts at full ratio to its' secondary. If the burden (the CT resistance + cable resistance + relay or instrument resistance) times the maximum expected current is higher than 200 volts, the CT is likely to saturate.
During multiple fault events, a CT may keep some magnetizing current causing CT saturation to be higher on a reclose event. Typically CT's are sized and their ratios are chosen to minimize saturation when feasible.
How many Slip rings in synchronous motor?
If the synchronous motor is single phase then there are two slip rings & if this motor is three phase so the slip rings are three in number.
Correction;
I have never seen a single phase synchronous motor. It would cost more that it was worth.
A synchronous motor has a separately excited field. If the excitation comes from a stationary DC source it has 2 slip (collector) rings.
A brushless induction motor has no slip rings because the exciter armature rotates and so do the rectifiers.
A permanent magnet motor, used with variable frequency drives, is another type of synchronous motor that has no slip rings.
A three phase motor with 3 slip rings is a Wound Rotor motor. Wound rotor motors are variable speed motors that were used for such applications as bridges and cranes before variable speed drives.
Zener Regulation with a varying load?
Zener diodes attempt to keep terminal voltage constant. If the load is fairly small, a single zener diode can be used for this purpose. If the load is large enough that the zener cannot hold the voltage within desired margins, I suggest using the zener to control the base of a power transistor; the emitter or collector (depending on transistor type) will be used as the output to the load.
What is the working principle of a Synchronous Generator?
synchronous generator is similar to the principle of laws of electro magnetic induction that is "whenever the magnetic flux linking in a conductor that time emf is induced at the ends of the conductor "
What are the 4 primary constant and secondary constant of transmission lines?
resistance (R)
inductance(L)
capacitance(C)
shunt conductance(G)
What small building contains transformers and electrical equipment?
a substation go to http://www.chacha.com/question/what-are-small-buildings-containing-Transformers-and-electrical-equipment is where i found the anser
How do you measure effective value of an alternating voltage?
The "effective" value of an alternating voltage is generally considered to be the RMS (Root-Mean-Square) value. The best way to measure that is with a True RMS voltmeter.
Lacking that, if the voltage is sinusoidal, you can use an older style peak measuring voltmeter that estimates RMS value by dividing internally by the square root of 2. Any other shaped waveform will be measured incorrectly, depending on the amount of deviation from sinusoidal. (Square wave is the best example of error in this case - RMS and peak should be the same, but they won't read the same except on a True RMS voltmeter.)
What will happen if a voltmeter has a low shunt resistance instead of having high shunt resistance?
The purpose of a voltmeter is to indicate the potential difference between two points in a circuit.When a voltmeter is connected across a circuit, it shunts the circuit. If the voltmeter has a low resistance,it will draw a substantial amount of current. This action lowers the effective resistance of the circuit andchanges the voltage reading.
Calculate the charge transferred in 25 minutes by a current of 500 mA?
The charge transferred in 25 minutes by a current of 500 mA is 750 coulombs.
Amperes is defined as coulombs per second, so 500 mA is 0.5 coulombs per second. 25 minutes is 1500 seconds, so the charge is 750 coulombs.
First KW-Month and MWh are different measures kilowatt-month (KW-month) is normally used to measure capacity. Megawatt hours (MWh) is a measure of energy. Using an airline as an analogy the number and size of planes would determine how many air travel miles it could possible carry passengers. This is its capacity. For electrical energy this ability to produce energy is measured in Kw-months. A small 1000 watt (1KW) generator sitting in a persons garage is 1KW of capacity. If that person sold the right to use that generator to a neighbor for a month then he\she has sold 1KW-month of capacity. In the electrical energy sector of the US this would be likely worth between $5 and $15.
Keep in mind this capacity charge is for the right to use the generator. Actually using it would incur additional costs of fuel and maintenance. The contract with the neighbor would need to include these also. The contract would have the charge for the capacity and another charge for the electrical energy actually used.
This little machine is only capable of producing 1KW running it at 1KW for one hour is 1kWh or one kilowatt hour around a dimes worth of power. Running this rate for a 1000 hours would produce one million watt hours or one megawatt hour (1MWh) Jerry Watson
What is the significance of using gravel on transformer areas?
The gravels allow the transformer oil to flow safely to the oil soak pit if the transformer oil is thrown out due to an internal fault in the transformer.Secondly,the gravels are good insulators and avoid direct contact with the earth.
What is the significance of a negative indication on a watt meter?
Power meters are used to measure power used or produced by a customer or generator. A negative power meter reading at a costumer site would mean the costumer is generating electricity that is being pushed back out on the grid, or (more likely) the customer figured out how to reverse the meter! On older meters, reversing would cause the meter to count down so you could hide how much electricity you were using. Newer customer meters do not have this flaw - they add a magnitude of use (ignore the sign, or direction of power flow).
At a generating site, it would mean power is being sucked into the generator, instead of created by the generator.
AnswerI assume that you are referring to a wattmeter, and not an energy meter?
If this is the case, then a reversed reading simply indicates that either its voltage coil or its current coil has been connected the wrong way around. It can be rectified by reversing the connection to either coil (not both!).
When connecting a wattmeter, it's essential to observe the instrument terminal's 'polarity marks' when connecting the voltage and current coils to the circuit. This is because the currents passing through each of these coils must act in the same direction relative to each other or the instrument will read 'down scale' (i.e. backwards!).
What happens when you stick a core into a coil inductor in an undriven circuit?
If the circuit is undriven, there is no power, so inserting a core does nothing.
In general, however, inserting a core into an inductor increases its inductance. Depending on the circuit, that lowers the resonant frequency.
In a transformer what induces a current in the secondary coil?
The current flowing in the primary generates a magnetic field which induces a current in the secondary winding.
AnswerNo current is induced into the secondary winding of a transformer. What is induced is voltage. Current will only flow in the secondary winding if it is connected to the load, and it is the load that determines the current, not the primary current.
