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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
What are the advantages of using star connection?
The inrush current is reduced. This is the reason for star delta starters. Motor starts on star and after about 10 to 15 seconds, depending on the load of the motor, it switches to a delta configuration to run.
There would be no rectified output. The transformer primary has to be closed to induce a current into the secondary winding. At this point of the secondary the voltage is still AC. This voltage is then applied to the rectification bridge to change it to DC. So you can see how no voltage on the primary, the same as the unit being unplugged, affects the output voltage.
How is The RPM of an electric motor is determined?
The two main factors are the frequency and the number of poles of the motor. A formula for RPM is HZ x 60 x 2/ number of poles the motor has.
What is meant by fundamental overload in reference to a receiver?
Fundamental Overload refers to the receiver picking up a source so powerful it causes overload. IE, the receiver is picking up the fundamental output of the functioning transmitter, but is overpowered by it.
What is power factor in electrical?
Ratio of voltage rating and current rating is called power factor in electrical
AnswerPower factor can be defined in a number of ways -for example:
- cosine of the phase angle
- ratio of true power to apparent power
It has nothing to do with the ratio of voltage rating to current rating!
What are the conditions in parallel operation of generator?
the operation of connecting an alternator with other alternator or with common bus-bars is known as synchronizing.Generally alternator used in power system where they are connected in parallel with other alternator.
condition for parallel operation of an alternator
1. The terminal voltage of incoming alternator must be same as the bus-bars voltage.
2. The speed of incoming alternator must be such that its frequency f =pn/120 as the same frequency of the bus-bars.
3. The voltage of incoming alternator and the bus-bars voltage are in same phage.
State faradays law of electromagnetic induction?
It is defined as when the conductor is placed between the magnetic field and since when the conductor cuts the path of the magnetic field emf is produced...
The basic Faraday's Law of electromagnetic induction...
Define the term induced current?
a current can be induced by changing the area of a coil in a constant magnetic field. By Faraday's Law: the induced current is proportional to the rate of the change of flux in a loop of wire. With magnetic flux being defined as the product of the magnitude of the magnetic field and the area of the loop. The direction of the current is found from Len's Law: The induced current produces an induced magnetic field that opposes the change of flux causing the current.
CommentYou don't induce a current, you induce a voltage. And Faraday's Law states that the induced voltage, not current, is proportional to the rate of change of flux! If the coil is open circuited, a voltage is still induced into the coil but no current will flow. For current to flow, the coil must be connected to a load (or short circuited), and this current is dependent upon the values of the induced voltage and the resistance of the load.
What is Pin configuration of transistor sl100?
The pin configuration of sl 100 is B C E with ground as the base of the transistor.
What is a Current Reversing Transformer?
This is a transformer built into electrical appliance to make electricity meter to stop reading or made to read in reverse order. This reduces the consumption reading and cheats the system. That is bad.
What does R mean in an electrical circuit?
it's generally the resistance.
its generally the energy dissipiating component called Resistor
What is need of space vector pulse width modulation?
due to space vector modulation we can eliminate the lower order harmonics
How is grid frequency and power plant output frequency matched?
contrary to the belief that the 50-60 Hz is stable in reality it is not frequency changes constantly during the day as power is increased or reduced but the average for a day is pretty much constant. a generating plant is a thermal or hydro machine it cannot responds very fast. so the average is stable for the grid since all plants have reserve spin power available constantly
What is the Formula to calculate KVA?
to calculate kva rating of single phase transformer:
kva rating= Q =Vp * Ip * 10^-3
where,
Vp= terminal voltage of primary winding
Ip= current of primary winding
so,
Q = V * I *10^-3
=2.22 * f * phi *Kw *Aw *delta * 10 ^-3
where,
f= frequency in hertz
phi= maximum flux in weber
Kw=window space factor
Aw=window area in m2
delta= current density in A/m2
but,
phi (maximum flux) =maximum flux density * net area of core
=Bm * Ai
so,
Q=2.22 * f *Bm * Ai *Kw *Aw *delta * 10 ^-3 kva
to calculate three phase transformer,
Q= 3.33 *Bm* Kw* Aw*Ai * 10 ^-3
What is percentage reactance of trasformer?
Percentage reactance of a transformer (or in general, a circuit) is the percentage of phase voltage drop when full load current flows through it, i.e
%X=(IX/V)*100.
Now Short Circuit Current is V/X
So short Circuit current is I*(100/%X).
How are logarithms used in electrical engineering?
It refers to a device any device whereby the device has limit to carry current. Therefore the term current capacity
How is a isolation transformer constructed?
It is made of two windings which are separated by very good insulation and also may be separated by a faraday shield.
