Electrical interview question:what is meant by armature reaction?
Answer:The effect of armature flu to main flux is called armature reaction. The armature flux may support main flux or opposes main flux.
Electrical interview question:Give two basic speed control scheme of DC shunt motor?
Answer:1. By using flux control method:in this method a rheostat is connected across the field winding to control the field current.so by changing the current the flux produced by the field winding can be changed* and since speed is inversely proportional to flux speed can be controlled 2.armature control method:in this method a rheostat is connected across armature wdg.by varying the resistance the value of resistive drop(IaRa)can be varied*and since speed is directly proportional to Eb-IaRa the speed can be controlled.
Electrical interview question:what is the difference between synchronous generator & asynchronous generator?
Answer: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.
Electrical interview question:What is the Polarization index value ? (pi value)and simple definition of polarization index ?
Answer:Its ratio between insulation resistance(IR)i.e meggar value
for 10min to insulation resistance for 1 min. It ranges from 5-7 for new motors & normally for motor to be in good condition it should be Greater than 2.5 .
Electrical interview question:Why syn. generators r used for the production of electricity?
Answer:synchronous machines have capability to work on different power factor(or say
different imaginary power varying the field emf. Hence syn. generators r used for the production of electricity.
Electrical interview question:What is the difference between synchronous generator & asynchronous generator?
Answer: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.
Electrical interview question:1 ton is equal to how many watts?
Answer:1 ton = 12000 BTU/hr and to convert BTU/hr to horsepower*
12*000 * 0.0003929 = 4.715 hp therefore 1 ton = 4.715*.746 = 3.5 KW.
Electrical interview question:why syn. generators r used for the production of electricity?
Answer:synchronous machines have capability to work on differentpower factor(or say
different imaginary pow varying the field emf. Hence syn. generators r used for the production of electricity.
Electrical interview question:Enlist types of dc generator?
Answer
.C.Generators are classified into two types 1)separatly exicted d.c.generator 2)self exicted d.c.generator* which is further classified into;1)series 2)shunt and
3)compound(which is further classified into cumulative and differential).
Electrical interview question:What is Automatic Voltage regulator(AVR)?
Answer: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.
Electrical interview question:What is an exciter and how does it work?
Answer:There are two types of exciters* static exciter and rotory exciter.purpose of excitor is to supply the excitation dc voltage to the fixed poles of generator.Rotory excitor is an additional small generator mounted on the shaft of main generator. if it is dc generator* it will supply dc to the rotory poles through slip ring and brushes( conventional alternator). if it is an ac excitor* out put of ac excitor is rectified by rotating diodes and supply dc to main fixed poles.ac excitor is the ac generator whose field winding are stationary and armature rotates. initial voltage is built up by residual magnetism.It gives the starting torque to the generator.
Electrical interview questionifference between a four point starter and three point starter?
Answer: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
Electrical interview question:Why use the VCB at High Transmission System ? Why can't use ACB?
Answer:Actually the thing is vacuum has high arc queching property compare to air because in VCB *the die electric strengths equal to 8 times of air . That y always vaccum used as inHT breaker and air used as in LT .
Electrical interview question:What is the difference between surge arrestor and lightning arrestor?
Answer:LA is installed outside and the effect of lightning is grounded*where as surge arrestor installed inside panels comprising of resistors which consumes the energy and nullify the effect of surge.