Electrical Engineering Interview Questions
When should I use fuse , mcb(b,c,d,k) tybes , mccb ?
I mean which applications should require any of the above circuit breakers.
Transformer with current source
Can the transformer be operated on current source instead of voltage source ??If ,, what will happen ?
I assume that by current source you mean constant current source. In such case the primary and secondary voltage of the transformer will depend on the impedance of the transformer and the load. The lo...
Transformers are required to work at higher efficiency. Current transformer will require a lot of conductors increasing copper losses and the over all cost. This type of transformers are used in instrumentation systems for lower current ratings.
How we can step-up or step-down the DC voltage directly?
A chopper is nothing but a thyristor/SCR/transistor circuit which operates with the principle of PWM (Pulse Width Modulation). If you need to boost DC voltage with chopper, additional circuits includi...
this can be done by using chopper.chopper is a dc equivalent of a.c transformer to which d.c input which is to be stepped up is applied at input terminals and output is taken from output terminals whi...
Why are we employing star type transformer at transmission end and delta type transformer at receiving end?
its not necessary to use only Delta type T/F at receiving end, we can also used star type but in this case at same voltage level two star neutral point create due to which Harmonic create for avoiding this we prefer opposite combination at sending end and receiving end.
bcoz at the transmission side especially for secondary distribution we need neutral wire for getting single phase supply and star type is only one which provide neutral. at receiving side to step up voltage we need delta type connection.
What is the standard size of a model of an electric tower for lab exhibition?
Can we measure reactive power by using only a single wattmeter? If yes, how?
Yes, we can measure reactive power using a single wattmeter. Connect current coil to one phase (let it be R of RYB) and connect pressure coil against the other two phases (Y and B) then W=VI Sin(phi)
We can't measure the reactive power by using wattmeter.
As all we know,induction stove works on the principle of electromagnetic induction.Thus an emf is induced in the vessel and eddy current flows through the vessel.Since the vessel is made of ferromagnetic material (high resistivity) larger amount of heat (h=i^2 r)is generated.What will happen if a human...
Human body under dry condition has much higher resistivity compared ferromagnetic material.
Ferromagnetic material is higher
How alternating current is produced in a single-loop a.C. Alternator?
The loop keeps on rotating in the same direction irrespective of the position of the conductors cutting the magnetic flux. Magnetic flux does not change its direction either. The only things which kee...
We have a 3 phase induction motor, having stator length greater than rotor length by 10mm. My question is that, is this will affect the operation of motor (means cause an abnormal condition like temp. Rise etc.)?
In my opinion, only in case the rotor is not centered axially with the stator will lead to vibrations. The difference in the lengths of the rotor & stator will lead to more leakage flux leading to poo...
How much output will reduce , if 25 mw, 13.8 kv, 1800 rpm alternator runs in 1500 rpm 50 hz? What are the disadvantages if continuously run in 1500 rpm?
Voltage will reduce by a factor 1500/1800. Reduction in output of the generator does not solely depend on rpm. The various other factors associated with the operation of the prime mover and load will govern the output.
What is advantage of GLand in main panel ?
Cable glands serve the following purposes:
1. Fixing the cable mechanically to the panel.
2. Making proper electrical bonding of the panel with the armour of the cable (grounding).
4. Ingress protection to the panel after cable termination.
Grounding of xlpe metallic screen
What size of grounding conductor should be used to ground an xlpe metallic screen? is there an international standard that supports it? thanks
The Indian & International standards for grounding are IS 3043 & IEEE 80 respectively. The size of the ground conductor for grounding the screen of an XLPE cable depends on the calculated ground fault...
If you make a capacitor out of aluminum plates, and electrically GLue carbon or resistive plates to the aluminum ones, and use a dielectric between the sets of plates. where the input is on the aluminum plates where the output is on the resistive plates. would it charge quickly thru the aluminum plates...
The capacitor would definite charge faster when a voltage source is connected to the Aluminum plates. The semi conducting layer will provide smoothness in the equipotential lines and reduce the voltag...
3phase rectified to single phase
If I got a 380v 3-phase supply and I want to rectify it with thyristors to single phase how much voltage will I get ?What is the relationship?Thanks
The dc output of the full wave rectifier is average value the amplitude of the sine wave. In short multiply the r.m.s value of the ac input voltage by its form factor (1.11 in case of pure sine wave) ...
i know the output will be dc my question is how much dc voltage will be the output
In a 50hz electrical machine what happens when we use more than or less than 50hz?
frequency affects on the speed and torque of the machine and thats is the principle of the drives
Speed and torque of the Electrical machines can be regulated by chanigng the supply frequency. Also harmonics produced are different than normal operation
List various methods to convert 1 phase to 3 phase.
this can be done with thyristors
This conversion is done by using mainly two methods. They are:1. Convert 1-ph ac to dc by using power electronic converter then convert that dc to 3-ph ac using power electronic inverter using PWM...
What types of tower & pole is used in power system distribution?
for lattice metal structure (High Voltage )
they can divided into (specifying the job)
suspension , angle , end , cross towers
I think "_punjabi_" forgot about the concrete poles or towers.
These towers are more practical in now a days in Power distribution sector.
Why do we rate transformer in kva not in kw?
bcox at the time of designing the transformer we do not know the power factor of the load which s going to be connected accross it.... i mean we do not know at what power factor it will operate... since KVA=V*I... KW=V*I*COS@... so its rated in KVA
Efficiency of transformer depends on core loss and copper loss. Core loss depends mainly on voltage and copper loss depends on current passing through the winding. So basically total loss i.e. efficie...
A 3phase wye/delta transformeris rated 225kv/24kv, 400mva and has a series reactance of 13.3ohms as referred to its high voltage side. The transformer is supplying a load of 325mva at 0.9 PF lagging at a voltage of 24kv(line to line)on its low voltage side. It is supplied from a feeder whose impedances...
???
incorrect information
you should specify at least on of the terminals voltages
What will happen if voltage applied to a load is less then the rating specified ?
the load will not work right as its performance design
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MCBs have relatively low breaking capacity and sluggish compared to fuse. Fuse is used when cost of cable is a factor. If MCBs are used proper cable sizing must be done considering fault level and duration.
Fuse is old technology to break d circuit in fault. MCB is for low fault currents starting 6Amps to, 63Amps either 1Phase or 3Phase. And (b,c,d,k) are depends on the fault current and the location u r going to use. MCCB for higher currents more than 63 Amps that to in 3 Phase only.