# Electrical Engineering Interview Questions

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#### MOHAMMED MUZAMMIL

• Apr 1st, 2018

So net voltage in the primary winding will be (Vin-0) more due to which primary winding draws more current which leads to burning of winding. ... But when a particular High DC voltage is applied to th...

• Sep 13th, 2017

Windings get burned

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#### What is the power ratio between power in Star and Delta circuit?

KaranSorout

• Member Since Jul-2006 | Jul 13th, 2006

The power ratio between Star to Delta is 1:3

Explanation:

Let?s suppose Vs be the supply voltage per phase.

So the line voltage of the supply will be ?3Vs.

Now assume any type of load; for simplicity I?m assuming it a only resistive load.

And let it be ?R? per phase.

Calculation for per phase power; PD= I2R

Where I ? load current (per phase)

And,

I = ?3Vs/R       {as line voltage of the supply is directly applied to the phase of the delta load}

So,

Pd = (?3Vs/R )2R = 3Vs2/R  watts per phase.

For 3 phases:

P3D = 3Pd = 3*3Vs2/R = 9Vs2/R watts.

PS = I2R = (Vs/R)2R = Vs2/R watts

For 3 phases: P3S = 3PS = 3 Vs2/R watts

Conclusion:

P3S / P3D  =  3Vs2/R / 9Vs2/R = 1/3

It may be better concluded by drowing figures. If any variations, can connect to me through karan.sorout@gmail.com

#### RUP KAMAL KUTUM

• Feb 3rd, 2018

Well first you assumed voltage per phase as Vs and Line voltage as sqrt(3) x Vs: Which is for star connection. Then, you assumed the same thing for Delta Connection(where line and phase voltages are t...

#### Anbumozhi R

• Dec 3rd, 2017

Power is Same. Whether it is star to Delta conversion or Delta to star conversion. Power is 1:1

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#### For a 100kw generator, only 50kw of load is connected. Will the generator generate only 50kw or 100kw? If it generate 100kw what happens to rest of the 50kw. What happens if we connect more than 100kw of load?

• Dec 23rd, 2006

100 kw is the full load rating of the generator..... ..that means it can supply 100 kw without exceeding in specified temperature limits .that doesnt mean that it wont be able to supply a load more than 100 kw,it can but not for a longer period of time.after sometime the generator will burn out.if a load of 50 kw is connected to generator the generator will generate only 50 kw& not more than that.the generator will generate power only according to the requirement.

#### Dharmender

• Feb 7th, 2018

#### Mayilsamy Kasipandi

• Jul 11th, 2017

The Generator produce the power is exactly what we withdraw as load. 100 kw genset can produce 1 kw to 115kw power depending upon the connected/withdrawing load. Normally the generator can produce 115% of designed rating.

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#### Why is the transformer rated in KVA?

• Oct 5th, 2007

Any device is rated depending on losses of the machine. In a transformer the losses are iron losses which depends on voltage and copper losses which depends on current so there are no losses which depend on power factor hence transformer is rated in KVA.

#### Raghu

• Feb 9th, 2018

In transformer there is two losses
1. Iron loss
2. Copper loss
The iron loss is depands on Voltage
And the Copper loss is depands on current.

#### Umar Naik

• Nov 26th, 2017

There are cu losses and iron losses which are not dependent on power factor thats why we rated it in KVA.

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#### DC Voltage Frequency

What is the frequency of DC Voltage?

#### Gaj

• Oct 30th, 2017

Frequency is no. of cycles per second i.e. rate of change w.r.t time. DC has constant amplitude it means no change w.r.t. time. So it has Zero frequency.

#### Anup Kumar

• Sep 13th, 2017

Zero

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#### A.Rajasekharreddy

• Sep 13th, 2016

Brush less alternator is nothing but stationary armature, Brush alternator is a rotating armature.

#### Shan

• Aug 24th, 2016

Is there a exciting stator in brushed generator? If not what is the reason?

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#### Q-point in transistor?

What is the purpose of Q-point in transistor?

• Nov 9th, 2015

It is a DC operating point between saturation and cutoff. It must be selected in a way that it does not go into saturation or cutoff.

#### bala

• Oct 24th, 2015

It is more important for a transistor because according to this value, it may operate as an amplifier or a switch and most importantly the point should not vary with temperature hence we normally prefer voltage divider bias.

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#### M.SANTHOSH KUMAR

• Aug 7th, 2015

Why we do not give DC supply in transformer means DC current is a direct current, so alternating flux is not produced, because input supply and flux will be same, so emf will not produced and same tim...

#### avdhesh sharma

• Aug 2nd, 2015

Current=voltage/impedance, When DC is applied then Z=R =>I= V/R and R is low for transformer, so I increases very high, so heating as current is not allowed to flow further and hence intuitively you c...

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#### Transformer Neutral Earthing

Why the transformer neutral point connected to earth?

#### GARGI VERMA

• Jul 30th, 2015

In Simple words, There are two type of losses in a transformer; 1. Copper Losses 2. Iron Losses or Core Losses or Insulation Losses Copper losses ( I2R)depends on Current which passing through tran...

#### Ayaz Shaik

• Jun 30th, 2015

It does not mean always the t/f neutral is connected to ground..only in case of power t/f it happens mainly for two reasons 1) We know all things like harmonics, fault occurrence, lightning, over cur...

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#### How much voltage is present in neutral resistance?and how much voltage is present in earth resistance

abbasanwarali

• Member Since Oct-2008 | Oct 16th, 2008

Actually there is no volt during normal condition. In case of any fault resistor will act as a low resistance path. because above mentioned components are high impedence components. so the huge fault (volt) will be grounded and the equipment remains safe.

#### HARESHKUMAR KHATRI

• Apr 4th, 2015

Absolutely there is no any voltage.

#### Rahulshelke

• Jul 12th, 2010

The voltage is null or Zero.

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#### Power System

Difference between pi and pid controller

#### shreya

• Mar 28th, 2015

Pi is nothing but the proportional integrator controller.it is used improve steady state stability i.e used to reduced steady state error.and pid means proportional integrator and derivative controlle...

#### Rakesh

• Mar 23rd, 2015

Power system is technology to transporting the energy to industry and home .And the power system basically work on three principle Generation,Transmission,and distribution.

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#### Electrical Interview Question

1)What is the latest generation of circuit breakers called?

2)What are the special cables required for explosion proof wiring?

3)What are the different types of soft starters for large motors?

4)What is the similarity and what is the difference between relays and PLC?

#### priyobrato

• Dec 7th, 2014

Relay can be used as potential free dry contact,with less switching speed cause its a electro mechanical device .PLC has better switching speed.BOTH are controlling device.

#### Chakry

• Nov 30th, 2014

The cables used in Inflammable and explosive situations should be Mineral insulated Copper sheathed complying with BS 6207.

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#### vishnu sharma

• Nov 27th, 2014

Catch the wire from both hands at a time in air, then potential difference is zero, so that current does not flow in body.

#### Santanu

• Jul 10th, 2013

There is no risk of any shock as the whole body is at same potential. However, if the persons body touches ground or for that matter, anything which may create a potential difference, there will be el...

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#### Phase and Neutral

What is the difference between phase and neutral?

#### sarita

• Nov 16th, 2014

Phase contain supply voltage i.e heavy electrons or protons and neutral contain no supply voltage and neutral charges.

• Oct 26th, 2014

1- in one phase case : Phase is supply voltage weather neutral is returning path the same current for that supply voltage. 2- in three phase case : - in balanced load current returned to earth = 0 - ...

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#### What is the main difference between current and voltage?

• Oct 25th, 2014

Current is the electron motion through external force. ? ? ? ? ? ? ?External force is applied voltage.

#### lalit

• Sep 27th, 2014

Voltage is the driving force that causes the current to flow in the closed path of the circuit. so if there is no voltage , there would be no current in that part of the circuit across the element

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#### SC Test

Why SC test is performed on LV side?

#### Umesh

• Sep 25th, 2014

We generally performs Short circuit test keeping initial voltage at lower value and then gradually increases it up to the level to get a full load current (or Max) through testing device or circuit. B...

#### KM Mahesha

• Jul 22nd, 2014

Load are in LV side and also max SC faults occurred in Load side. If SC Faults occurs protect load and Net work system

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#### Transformer design and construction

What is shape of the coils used in a transformer ? choose the correct one from the bracket (rectangular,oval,circular,cylindrical ) & justify it with detail reason.

Is transformer a machine ?choose the correct one from the bracket (yes/no) & justify it with detail reason.

#### manikandan.l

• Jul 18th, 2014

Rectangular

#### AlHussein Abdallah

• Jul 17th, 2014

Star connected rotor of induction motor has a standstill impedance of (0.4+4j)ohm per phase and rheostat impedance per phase is (6+2j)ohm. The motor has induced voltage of 80v between slip-rings at st...

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#### ilamurugan

• May 4th, 2014

Both source becomes single source of higher capacity and at the time of syn only entities are taken for reference. Once syn done its.single.source so need of current flow within that source

#### atul sudhakar

• May 2nd, 2014

In that case ,current flows due to the difference in load angle. synchronizing the system increases the efficiency of the power flow

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#### Star/Delta transformer

What is neutral transformer?

#### Alok Behera

• Feb 12th, 2014

If the earthing transformer on the Delta Side is outsides the Zone of protection the Earth Fault(E/F)in the delta system outside Current Transformer(CT) locations would produce current distributions a...

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