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Electrical and Electronics Engineering Interview Common Questions

Published on December 2016 | Categories: Documents | Downloads: 5 | Comments: 0

Some common questions regarding Electrical and Electronics Engineering Job Interview



Q1:whats is MARX CIRCUIT? # Marx ckt is An electric circuit used in an impulse generator in which capacitors are charged in parallel through charging resistors, and then connected in series and discharged through the test piece by the simultaneous sparkover of spark gaps. Q2:Why link is provided in neutral of an ac circuit and fuse in phase of ac circuit? #purpose of fuse to protect the appliances from high current, if we place fuse in neutral ,fuse will melt after the current passed thro the applncs, hence eqpmnt will b damaged instead if we place the fuse in phase, the s.c current wil nt flow thro the eqpmnt bcz fuse melts bfr the high current passes thro the eqpmnt. Q3: Define IDMT relay? #IDMT - Inverse definite minimum relay. This kind of relays tripping time decreases with increasing fault current. Q4:What is electric traction? # electric traction means to move the body with electrical machine.it is called electrical traction,like electric trains nd their maners etc. Q5:what is boucholz relay and the significance of it in to the transformer? # There are two types of faults incipient faults and major faults inside a transformer, for both faults we use bucholz relay. Wen load on the transformer increases the temperature of the oil increases if the oil is not gud one means if the dielectric strength of the oil is not sufficient and if there z any moisture content in that oil, bubbles wil produce in the oil. If we leave further the oil completely damages and become conducting medium rather than insulation b/w primary and secondary and transformer wil burst. Hence we use bucholz relay to overcome the above problem If the bubbles r small in number it wil give alarm and if the bubbles are high it wil trip the transformer from the ckt. Q6 Q7:what is power factor? whether it should be high or low? why? #Power factor is the ratio of real power and apparent power. It denotes loss between power generated and consumed. We should be maintain it at the value of 1.00 by maintaining the angle between voltage and current zero. Q8:Why is the starting current high in a DC motor?

# I=(V-Eb)/R during starting Eb is zero hence I = V/R since R <1 ohm starting current is very high. Q9:Explain the working principal of the circuit breaker #C.B is device which will make or break the ckt automatically or manually respectively when fault occurs in a ckt it means during abnormal or normal conditions. Q10:What are the advantages of speed control using thyristor? # a.Most economical operation when cost cosideration, accurate operation will possible . b. wide range of speed control is available because we can vary the firing angle from 0 to 180 degree c. we can switch on and off the device nd vary the waveform in accordace 2 the firing angle with the same ckt Q11:Give two basic speed control scheme of DC shunt motor # 1. Flux control method 2. Armature control method Q12:Define Ohm’s Law for A.C(Alternating Current) # When current I passing through conductor is directly proportional to applied voltage V & inversely proportional to resistance R i.e. I=V/R Q13:State and define Ohm’s Law #physical state of a conductor remaining same electri current flowing through it is directly proportional to the potenial differnce across its ends Q14:What is "pu" in electrical engineering? # per unit system which is used for power system calculations to make all the units into one category to ease the calculations Q15: Q16:Why use the VCB at High Transmission System ? Why can't use ACB? # VCB dielectric strength is equal to 8 times of air.vacum has high arc quenching property compare to air.that's why use VCB at HT system. Q17:If one lamp connects between two phases it will glow or not?

# If The voltage rating of bulb equal to the phase to phase voltage, then it glow. If voltage is high, then bulb fuses. If low, then it will be dim Q18:What is the one main difference between UPS & inverter and electrical engineering & electronics engineering? # UPS has the ability to back up the load during power interruption, it has rectifier, inverter and a battery within itself, where as the inverter is jus converts from DC to AC UPS is protective device and storage power when power is shutdown.The Inverter it convert DC to AC ups gives short time backup whereas inverter is used for long time backup ups provide continuous supply to connected appliences but inverter convert the power and then supply Eletrical engineer deal with HV.Eletronic engineer deal with small current(LV)

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