0
Electrical Engineering
Electrical engineering is a field of engineering that deals with the study and application of electricity, electronics and electromagnetism.
23,056 Questions
What is the purpose of star delta connection in a transformer?
A star winding has a red yellow and blue phases. The centre point of every stay winding is used as d nuetral point. Hence the star winding in a transformer enables a nuetral point.
What measures the volume of electrons through a circuit?
Current measures the flow of electrons through a circuit and voltage basically measure the amount of available electrons.
Why current transformer secondary side short circuit?
A current transformer (or CT) is constructed in a specific way so as to step down the current in a high power circuit for measuring or protective relaying purposes. Typically, it will have a toroidal-shaped iron core with the secondary windings wrapped around it. the primary "winding" is usually the conductor of the main power system passing directly through the hole in the center of the CT. As a result of this construction, if the secondary windings are left open, a very large flux can develop, resulting in damage to the CT and possibly even the other equipment it is attached to. As such, if the CT is not going to be used, its secondary windings need to be shorted.
A tornado's spin originates in wind shear, which is a difference in wind speed or direction at different altitudes. If this wind shear is strong enough air may start to roll in a phenomenon called horizontal vorticity. The updraft of a thunderstorm can then turn this vorticity vertical and take on the rotation to become a mesocyclone. Under the right conditions the mesocyclone can tighten and intensify to produce a smaller, stronger vortex: the tornado itself.
Why powerful lamps have lower resistance than less powerful lamps?
Power is voltage squared, divided by resistance (P = V2/R) so, for a given voltage, the lower the resistance, the greater the power!
How does we calculate the AH in battery's?
Rather trying to explain all the technology that goes into battery construction, go to Related Links. All your questions will be answered there. AH means Amps Hour every battery has that term stated What it means is so many amps can be supplied for so many hours. Means amps Vs time
What is the electrical conductivity of hexane at room temperature?
0.77g/cm3
see specific gravity: http://www.jtbaker.com/msds/englishhtml/h1211.htm
What is the peak value of wave?
it's highest swing positive or negative. 90 and 270 degrees. the peak for a 10vAC generator would be 10vAC
What effect capacitor has on alternating current ac?
In the basic configuration, a capacitor is constructed with two parallel conductor plates with a layer of insulating material in between. When the cap is hooked up to the AC power supply, the voltage (v) across the plates and the charge (q) induced on the plates follow this capacitance expression:
C = dq/dv or i = C dv/dt, where C is determined by the properties of the insulating material and the geometry of the cap (in the case of the parallel plates, the separation between the two electrodes (t).
For the parallel plates, C can be written as (dielectric constant * plate area / t). Electrically, the change in the charge induced on the plates (dq), is directly related to the change in voltage difference (dv) between the two plates, since C is a constant. Theoretically, no energy is lost by charging and discharging the cap with an AC current. When the cap absorbs electrical energy from the power supply, it stores the energy in the electric field in the insulator. When discharging, the cap gives the stored energy back to the circuit -- hence, no energy loss.
In a circuit, we use the cap to prolong/smoothen/resist any voltage change in time or to absorb a sudden energy surge (electrostatic discharge and power-line glitches, for example).
What should be the primisable voltage between neutral and earth in a three phase system?
It is the line to line voltage divided by 1.73.
600V / 1.73 = 347V
480V / 1.73 = 277V
380V / 1.73 = 220V
208V / 1.73 = 120V
A load, at low frequencies, can be either capacitive, resistive, or inductive. At high frequencies, all three aspects exist.
At low frequencies (say <= 10 MHz), a capacitive load is a capacitor, represented by an ideal cap, the MOScap, or a junction cap. An unintentional capacitive load would be the wire or conductor to another wire or conductor or ground.
At high frequencies (say >= 1 GHz), all things have a capacitive nature. The higher the frequency, the worst is the capacitive leak A capacitive load means just that the load acts like a capacitor load as opposed to a inductor or resistive load
What would happen if a shunt-excited DC generator was operated at too low a speed?
A shunt generator is a type of DC generator that does not use a permanent magnet. Reducing the speed of the generator will reduce the output, but not the load the generator requires because the currents in the parallel branches are independent.
Megger testing is done with DC or AC votage?
Earth testing results should be related to the voltage source, i.e., AC in most situations. AC reacts to resistive and reactive loads, DC to resistive loads only.
Not all earth testers, however, use AC.
Does the ratio of voltage in a primary coil to secondary coil depends on the turn of each coil?
Yes, although the question is poorly formed. The ratio of the voltage in the primary winding to the voltage in the secondary winding is the same as the ratio of the number of turns in the primary winding to the number of turns in the secondary winding. For example, if the primary had 1200 turns with the secondary having 120 turns, and the primary voltage was 50 volts, then the secondary would be 5 volts. This is a ratio of 10:1.
What is the function of a automatic voltage regulator?
It protects your sensitive electronic equipment from brownouts and over-voltages. Uncorrected voltage fluctuations gradually degrade the life of electronic components, potentially causing premature failure. An AVR not only adjusts voltages to safe levels, but also provides surge protection against electrical surges and spikes and lightning.
Can a copper wire be used as a variable resistor in a circuit?
Because copper is a very good conductor, it isn't used for making the main body of a resistor. The body must be made of high resistance metals, such as nickel and chrome alloys. Copper is only used for making the connecting leads of a resistor.
How many poles are within a DC motor?
It depends on the motor. They can be purchased with different numbers of poles. The number of poles mainly changes the speed of the motor.
Can you run single phase on three phase?
Yes, you can use one of the three phase service lines to run the single phase device. However, before you connect it, you must first make sure that both the voltage and the current rating of the device will be suitable for the single phase service that your new connections to the service wiring will produce.
The single phase voltage you will get between any one phase line and the neutral point is less than the voltage between any two of the three phase service lines by a factor of 1/1.73. So, because 415/1.73 is about 240, a 415V 3-phase service will produce a single phase voltage of 240V.
If you are in one of the many countries which use split single phase wiring - such as USA and Canada - that 240V will actually be available as two 120V "hots" (usually with red and black colored insulation) balanced about the neutral point i.e. +120V / Neutral / -120V.
Thus you can actually connect up a new branch circuit either for one 240V single phase device or two 120V branch circuits to supply power to 120V devices.
After you have made sure that the current demanded by your single phase device can be supplied by the available 3-phase service, it is vital that you make sure you install the correct size of circuit breaker (voltage and ampacity) and branch circuit wiring having the correct wire size to carry the current load drawn by the single phase device, together with the correct types and sizes of socket outlets. All these details are specified in your country's national electrical codes or regulations.
(1.73 is the square root of 3).
<><><>
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 is a single phase 230V motor wired?
Wiring of pressure switch on an air compressor
Take a wire from one of the line terminals L1 to one side of the contactor coil. Take another wire from the second line terminal L2 and put it to one side of a N.C. contact on the overload block. From the other side of the N.C. contact on the O/L block take a wire to the N.C. terminal on the pressure switch. From the other side of the N.C. contact on the pressure switch terminal connect the wire to the other side of the coil. This configuration will be using the same coil voltage on the contactor as that of the supply voltage.
Connect the motor leads to T1 and T2 on the bottom end of the overload block.
<><><>
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.
What if surge protector had high resistance?
If a surge protector had a very high resistance at all voltages, the wires in the surge protector would short out. It would kick off the protector and make it useless. A new surge protector would need to be purchased.
Does a toaster have a series or parallel circuit?
Normally I would expect the elements to be wired in parallel so that the loss of one element does not cause the others not to work. It is possible for some manufacturers to wire a pair of elements in series so that they could use say 110v elements as standard so that they can be utilized on 230v toasters as well.
It is apples and oranges--kVA and volts are different units describing different things. Determining kVA requires measuring both voltage and current.
What is a split phase motor with relay and capacitor called?
A capacitor start motor is a split phase motor that uses a capacitor in series with the start winding to cause a greater phase shift, resulting in greater starting torque. It uses a centrifugal switch to switch out the start winding and capacitor once the motor is up to speed. I assume this switch is what you're referring to as a "relay".
