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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
When a circut breaker is tripped can it cause a short?
When an more than rated current passes through it, because of short in equipments or mal functioning of equipments the mcb gets tripped. The reason is magnetic contact in mcb is rated and when that rating exceeds the contact may disconnect
Which welding process uses a constant current power source?
smaw and tig(gtaw) are using CC source. because these both types using manual wire feeding. so welder can not able to maintain constant arc length. change in arc length will change voltage. so it needs power supply which should not affected by this arc length = voltage changes. that's why CC type is used for these process. in CC type source change in voltage will not change current much.
How can I step down 48 volt DC to 12 volt DC?
Used the transformer. SO will be change 40vdc.
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Humm (no pun intended) - a DC transformer, must be something new in the market. A variable potentiometer will allow you to reduce the voltage to the required voltage you need. It will have to be of a higher wattage variety to dissipate the heat that will be generated depending on the wattage of the load at 40 volts.
How is an ohmmeter connected to a circuit?
ANY METER needs some kind of current flow to operate. Internal in the meter there are batteries that provide current that when passed trough a resistor will develop voltage as a function of the current. the meter will read this current and display the resistor size to cause this current to flow.
How does a ground fault circuit interrupter shuts down a circuit?
A ground fault circuit breaker detects leakage current between the hot wire coming off the breaker and the neutral/ground since the neutral is bonded to the ground in the panel, if it senses a current of 6 milliamps or more it will trip. Note: no sharing of the neutral for a circuit on a ground fault breaker
If a few milliamps from the hot (black) wire do not return on the neutral (white) wire, then a GFCI assumes that current it traveling harmfully elsewhere through your body. So it disconnects. A GFCI can monitor 15,000 milliamps. But if only 5 go missing, then a GFCI trips.
Ic 7805 we are mostly used for regulator & its minimum input voltage is 7.2 V.
Sandeep Chauhan
What is difference between residual current circuit breaker and earth leakage circuit breaker?
Voltage-ELCBs were first introduced about sixty years ago and Current-ELCB was first introduced about forty years ago. For many years, the voltage operated ELCB and the differential current operated ELCB were both referred to as ELCBs because it was a simpler name to remember. But the use of a common name for two different devices gave rise to considerable confusion in the electrical industry.
What are the three basic features all electric circuits must have?
Three things that an electrical circuit must have to operate is,
A) a source. Example- battery
B) a line. Example- conducting wires that allow the electricity to pass through
and C) a load. Example- A light bulb
What is 208 - 230 volt three phase?
In the United States, 208v can be either. It is generally the voltage supplied by a 120/208v 3 phase system. However, using 2 legs of this 3 phase system is called single phase. I won't go into the reasons for that but just understand that 208v can be either single phase or 3 phase.
Why is the transformer rated in KVA?
Because a transformer is only in use when it is under load. An actual power factor requires a load and it is neccessary if you are going to calculate for kilowatt.
The Power equation is
P = V I cos #
Where cos # is power factor
so its depend on load but
VA or Volt-Amperes is the unit that is used to rate how much apparent power the transformer can produce before saturating. transformers can all come in different shapes and sizes and all vary from VA rating. a 1KVA transformer is the equivalent of a 1000VA transformer(very big). the 'K' in front of any unit means 1000 i.e 1k resistor is the same as a 1000Ω resistor.
You might think it should be rated in kilowatts instead. KVA sound like they are algebraically identical to kilowatts.
Not all electrical loads will have voltage multiplied by current, equal the power consumed by the load. That is only the case for simple resistive loads.
Some electrical loads have the ability to store energy over the cycle, and cause the current and voltage to be "delayed" from one another. The total power, is therefore less than the product of the voltage and current that are supplied to the load.
A transformer must be sized, so that each of its windings can handle a given operating voltage, and a maximum current, and still supply the intended loads. Due to a loads delaying of current and voltage, the current might be much greater than the value of real power divided by voltage. We need to size wire windings according to what the current will be. I.e. the kVA rating divided by voltage.
A perfect transformer would have the same operating kVA on both sides of it, just with voltage traded for current differing between the windings.
How do you find ampere readings in a parallel circuit?
Either add the two in series measured currents or find where they split or joined and measure the combined currents there. Kirchhoff laws.
How capacitance effects are taken into account in transmission lines?
Natural capacitance exists between conductors at different potentials, including between those conductors and earth (ground). The value of such capacitance is significantly higher with underground cables than with overhead lines, due to the close proximity of the individual conductors in an underground cable.
Capacitance results in line losses in both a.c. overhead and underground systems, due to the corresponding capacitive reactance (opposition to a.c.). In the case of long, high-voltage, underground or under-sea cables, the capacitance losses can be so high that d.c. transmission is used instead of a.c. (d.c. eliminates capacitive line losses).
In addition to the line losses, the electric fields resulting from the capacitance can lead to insulation breakdown -making it essential that 'sharp corners', etc., are avoided in their design and construction. One of the reasons that high-voltage overhead conductors are 'bundled' (i.e. more than one conductor per line) is to reduce the stress on individual line conductors that would otherwise occur due to their relatively small diameters.
The magnetization current can be broken-down into two components: the first is in phase with the supply voltage and is responsible for the losses, whereas the second component lags the supply voltage by 90 degrees and in responsible for the magnetic field.
Why short circuit test is done at high voltage side?
1)Short circuit test is performed at rated current. As the rated current on high voltage side is much less than low voltage side, so the rated high voltage side current is easily achieved compared to low voltage side.
2)Also because we cannot short circuit high voltage side, as, if we short circuit high voltage side, voltage of high voltage side essentially falls to zero and since VI=constant, so the high voltage side current will be very high and will burn the winding.
Can a shunt generator build up its voltage without residual magnetism?
no...because before producing voltage needed to connect the generator to the grid then after it will produced voltage.
Answer
Yes, but only if you have an external d.c. supply to supply the field windings. Such machines are called, 'separately-excited'.
Does transformer has high or low efficiency?
Since, transfformer is a Static device (ie. no moving parts in it) hence it is the most efficient machines ever made by man.
However, in rotating machines there are various losses like friction and windage, losses in commutator etc.
So, yes, Transformers are highly efficient devices.
How do you convert a 3 phase power supply to a single phase supply?
If the 3 phase circuit has a neutral (4th) wire, you can connect from one of the 3 phase wires to the neutral wire for a single phase circuit. You need to check the voltage with a DVM voltmeter or equivalent to make sure the 3 phase circuit is the correct voltage from one leg (wire) to the neutral for the equipment you wish to power. Be careful with this one as it may exceed your capabilities to do this work safely.
Another answer
You don't need to "convert" a three phase service to a single phase service, you only need to take a single phase service from one of the lines of a three phase service.
Working with a 3-phase electrical service is not a safe DIY project to be attempted by anyone who has not had the proper training and practical experience of working with high voltage electrical services. So, if you needed to ask this question, you should not be attempting to do this work by yourself!
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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.
How does voltage fluctuation affect an electrical system?
Whenever you are working over a device and getting a constant voltage supply ,, and all of a sudden .. the light gets off and the device is off. it means a device was working over some specified voltage and it comes to 0 instantly . the voltage changes . this is called voltage fluctuation .
It is 6 times 8 and the answer is in volts.
What will happen if one phase of 3 phase synchronous machine is short circuited?
The fuses that protect the individual legs of the three phase system will blow open.
The mains frequency in Europe and other 230 Volt areas is 50 Hz (Cycles per second) compared to 60 Hz in US, Canada and other 120/240 Volt areas. Some 60 Hz appliances will work fine but others with simple motors will run too slow on the lower frequency of 50 Hz.
However the most important difference is in the way that the Neutral wire is connected in appliances designed to run on 240 Volt 60 Hz supplies: in addition to a safety "Ground" conductor there are 3 wires, a Neutral wired as a "central" common return conductor and two 120 Volt 60 Hz live "hot legs" which are wired in opposing phase to one another. When one hot leg is "+" (120 Volts positive) the other leg is "-" (120 Volts negative).
In 240 Volts 50 Hz appliances there are only 3 wires altogether, a "Ground" conductor, one single 240 volt "live" or "hot" wire and a Neutral wire connected as a return to the single "hot". So there is a 230 Volt voltage difference between the "Neutral" and the "Hot" conductor in the 50 Hz system and only a 120 Volt voltage difference between the "Neutral" and either of the "Hot"conductors in the 60 Hz system. At the point where the "Neutral" gets connected to the "Ground" (never in the appliance itself but at the point where the incoming supply enters the main fuse/breaker panel) - this difference will cause serious problems! That is why an appliance designed to be connected onto the 60 Hz system cannot be used safely on the 50 Hz system without first having proper technical modification work done. A licensed electrician or electrical engineer would be able to consider whether or not a particular large appliance, that was manufactured to work on 60 Hz-only, could be modified safely to run at the lower 50 Hz frequency. However it won't usually be worth the expense of doing the work because it would be more cost-effective to buy (new or secondhand) an equivalent large appliance designed to work on 50 Hz. Further information which may be useful to mention here but is not part of the answer to this question: Some 120 Volt appliances, such as electric shavers, etc., have been designed to run safely on different supply voltages and frequencies. If that is so, it would be stated on their rating plates. In many cases, where the power needed is low, such as (say) less than 30 Watts, a cheap and simple "International Travel Socket Adapter" is all that is needed to make such a 120 Volt appliance plug-in and work. Many international airports have shops selling such adaptors.
How DC motor converted into DC generator?
Both dc generator & dc motor are the same and known dc machine.when we give an electrical supply to the dc machine a torque developed due to flux intraction & works as motor.but we used dc machine as a generator we rotate the rotor or prime mover by using external sourse.due to this the rotor conductors cut by the stationary magnetic field and electrical power is generated as per faradays law.
Here the main difference is when we giving electrical energy to the rotor of dc machine produce torque(motor)but when we give the mechanical energy to rotor it produce electrical energy(generator)
What is the difference between 12.2 and 12.3 wire?
The 12 refers to the size of wire in AWG - American Wire Gauge. 12 gauge wire can legally carry 20 Amps, and would be used if the circuit breaker is 20 A. 14 AWG can carry 15 Amps, used on a 15 A breaker.
The 2 or 3 refers to the number of ungrounded conductors in a cable (such as romex or NM). 12-2 would contain a hot (black) and a neutral (white). 12-3 would contain two hots (black and red), and a neutral (white). Additionally, these cables are available "with ground," meaning a bare ground wire is added to the cable. So a "12-2 with ground" would actually contain three conductors including the bare ground wire.
A 12-2 with ground cable would be used where you needed to run a single 20 A circuit. You are allowed to share a ground and neutral when running two circuits if the circuits are on different legs (phases) in the panel. 12-3 is used for this purpose. It can also be used where you need 240 volts (between the black and red) with a neutral (and ground).
How a nuclear power plant generates electricity?
A nuclear power plant generates electricity by turning turbines that turn
generators. This is no different than fossil fueled plants.
The difference in nuclear power is the source of the steam. Instead of a fossil fuel
boiler, there is a nuclear reactor that uses the power of the release of binding energy
(Strong Atomic Force) from the fissioning of (generally) Uranium-235.
There are several designs. The two primary designs are the Boiling Water Reactor (BWR)
and the Pressurized Water Reactor (PWR).
The BWR forms steam in the reactor vessel which is transported to the turbines.
The spent steam is condensed, reheated, treated, and returned to the reactor.
The PWR forms heated water in the reactor vessel which generates steam in
a separate steam generator (heat exchanger) which then is transported to the
turbines. The rest of the cycle is similar to the BWR, but the return water goes
to the steam generators instead of the reactor.
10.2 kilo ohms is the resistance necessary for 1 volt to induce a current of 98.04 micro amperes. Ohm's law: voltage equals current times resistance.
