Latest Electrical Interview Questions Part – 8
1.Why temperature rise is conducted in bus bars and isolators?
Bus bars and isolators are rated for continuous power flow,that means they carry heavy currents which rises their temperature. so it is necessary to test this devices for temperature rise.
2.What is the difference between synchronous generator & asynchronous generator?
In simple,synchronous generator supply’s both active and reactive power but asynchronous generator(induction generator) supply’s only active power and observe reactive power for magnetizing.This type of generators are used in windmills.
3.What is Automatic Voltage regulator(AVR)?
AVR is an abbreviation for Automatic Voltage Regulator.It is important part in Synchronous Generators,it controls theoutput voltage of the generator by controlling its excitation current. Thus it can control the output Reactive Power of the Generator.
4.Difference between a four point starter and three point starter?
The shunt connection in four point stater is provided separately form the line where as in three point stater it is connected with line which is the drawback in three point stater
5.Why the capacitors works on ac only?
Generally capacitor gives infinite resistance to dc components(i.e.,block the dc components). it allows the ac components to pass through.
6.How many types of oiling system it transformers?
1. ONAN (oil natural,air natural)
2. ONAF (oil natural,air forced)
3. OFAF (oil forced,air forced)
4. ODWF (oil direct,water forced)
5. OFAN (oil forced,air forced)
7.Operation carried out in Thermal power stations?
The water is obtained in the boiler and the coal is burnt so that steam is obtained this steam is allowed to hit the turbine ,the turbine which is coupled with the generator generates the electricity.
8.What is 2 phase motor?
A two phase motor is a motor with the the starting winding and the running winding have a phase split. e.g;ac servo motor.where the auxiliary winding and the control winding have a phase split of 90 degree.
9.What is the principle of motor?
Whenever a current carrying conductor is placed in an magnetic field it produce turning or twisting movement is called as torque.
10.What is meant by armature reaction?
The effect of armature flu to main flux is called armature reaction. The armature flux may support main flux or opposes main flux.
11.What is the difference between synchronous generator & asynchronous generator?
In simple,synchronous generator supply’s both active and reactive power but asynchronous generator(induction generator) supply’s only active power and observe reactive power for magnetizing.This type of generators are used in windmills.
12.What is MARX CIRCUIT?
It is used with generators for charging a number of capacitor in parallel and discharging them in series.It is used when voltage required for testing is higher than the available.
13.What are the advantages of speed control using thyristor?
Advantages :
1. Fast Switching Characterstics than Mosfet,BJT,IGBT
2. Low cost
3. Higher Accurate.
14.What is ACSR cable and where we use it?
ACSR means Aluminium conductor steel reinforced,this conductor is used in transmission & distribution.
15.What the one main difference between UPS & inverter ?And electrical engineering & electronics engineering ?
Uninterrupt power supply is mainly use for short time . means according to ups VA it gives backup. ups is also two types : on line and offline . online ups having high volt and amp for long time backup with with high dc voltage.but ups start with 12v dc with 7 amp.
but inverter is startwith 12v,24,dc to 36v dc and 120amp to 180amp battery with long time backup.
16.What will happen when power factor is leading in distribution of power?
If their is high power factor,i.e if the power factor is close to one:
a)Losses in form of heat will be reduced,
b)Cable becomes less bulky and easy to carry,and very cheap to afford,&
c)It also reduces over heating of tranformers.
17.What are the advantages of star-delta starter with induction motor?
(1). The main advantage of using the star delta starter is reduction of current during the starting of the motor.Starting current is reduced to 3-4 times Of current of Direct online starting.(2). Hence the starting current is reduced ,the voltage drops during the starting of motor in systems are reduced.
18.Why Delta Star Transformers are used for Lighting Loads?
For lighting loads,neutral conductor is must and hence the secondary must be star winding. and this lighting load is always unbalanced in all three phases. To minimize the current unbalance in the primary we use delta winding in the primary. So delta / star transformer is used for lighting loads.
19.Why computer humming sound occurred in HT transmission line?
This computer humming sound is coming due to ionization (breakdown of air into charged particles) of air around transmission conductor. This effect is called as Corona effect,and it is considered as power loss.
20.What is rated speed?
At the time of motor taking normal current (rated current)the speed of the motor is called rated speed. It is a speed at which any system take small current and give maximum efficiency.