Electrical engineering Interview Questions Part 1

Electrical engineering Interview Questions
1.What are the maximum number of joints you can make in a (3x300mm, 22KV) cable over +/- 610m?
2.Why 2-phase induction motors are NOT used in industries even though they have rotating magnetic field?
3.How we can change the direction of rotation of Induction motor?
4.What happens with squirrel induction machines if the ends of rotor conductors are kept open?
5.Why do we maintain 50hz frequency? What happens when we change this frequency to any other value?
6.What is Stray Capacitance?
7.What would happen if two voltage sources of different magnitude are connect in parallel?
8.What is the link between Voltage and Form Factor?
9.Why the roots of the network function are +ve?
10.What is the Specific Gravity of Fully charged Lead Acid Batteries?
11.What is the caliberation procedure and its requirement of belt weigh feeders?
12.What is the effect of hysteresis loss in transformer/machines especially in DC one?
13.What measures will take for cost saving in utility and power generation?
14.Describe briefly about key functions of Utility and Power House ?
15.What is the best method to connect two capacitor bank?
16.Is it possible to increase the capacity of a synchronous generator upto 30% to 50% ust to modify the cooling system but the other component remain same? Explain ?
17.Why do 3 phase motors rotate in the opposite direction when any two phases are interchanged?
18.How do we solve for poles and zeros in a circuit dynamics ?
19.What is the frequency of DC Voltage?
20.Does the stator of the Induction machine consume only reactive power? If this is the case, so where does the active power in the rotor come from? Explain ?
21.What happens to the power factor of a transformer when the input voltage exceeds the rated voltage? Will it increase or decrease? Give explanation?
22.If v=220V, I=25A, power factor=0.8, frequency=400Hz. If the motor runs for 3 hours, What is the power consumed?
23.How to can calculate voltage drop in a cable?
24.Where do we locate lightining arrestor in transmission line?
25.Why the capacitors are connected in delta? What advantage it having than star connection?
26.What happens when a transformer is supplied with direct current?
27.Why tapings of Transformer is always provided on HT side? why not on LT side?
28.How to calculate voltage drop in cables?
29.If the capacity of a Transformer is 20/26 then what does 20/26 shows? what is its purpose?
30.How reactive power is related to alternator? Wheather it is generated or consumed? Explain ?
31.A motor rated 230V, 50HZ taking 100KW no load amps, what happen if just frequency goes to 60Hz?
32.How much min BDV of oil in transformer is required when charged it first time in 11kv, 66kv and 132 kv of transformer?
33.Why star point of star connected motor is not grounded?
34.Why alternator is operated at lagging power factor? How alternator responses with changing the load?
35.Why most of the alternator is connected in star and have high regulation around 30% as compared to transformer?
36.We have enough category of AC machines more relliable than DC machine then why we are using DC machines in some application yet?
37.How much load is required to convert 100 KW Single Phase load to 3 Phase Load?
38.Why pressure coil is named so in wattmeter circuit?
39.What will be the body impedance of human body>What will be the maximum allowable earthing resistance value?
40.Why OC test is carried out on low voltage side of transformer?
41.Why OC test is carried out at rated voltage and frequency?
42.Why do you get a typical sound when the transformer is put into operation?
43.What is the value of insulation resistance between Neutral and earth of a 65 KVA Generator?
44.What is the thumb rule for insulation value in bus bars, phase to phase and phase to earth for 11 & 33 KV system?
45.How can we control or deduct harmonics?
46.What are the various types of LT panels?
47.Which of the following test are to be conducted for the determination of voltage regulation of a transformer?
48.What is single and 2 pole circuit breaker?
49.How we can step-up or step-down the DC voltage directly?
50.Explain what are Single and 2 Pole circuit breaker?
51.What is the power factor?
52.Can VFD step up to 60 Hz if it is designed to receive 50 Hz input? Explain?
53.Why the Substaions are labled as 11KV/33KV or 66/11KV etc instead of label with the POWER TRANSFORMERS Rating (In MVA/KVA)?
54.How is UPF Wattmeter different from LPF Wattmeter?
55.Why do we use phase shifting at Current Transformer?
56.What is dynamic time of a numerical or electromagnetic relay?
57.In a three phase system three wires are of colour red, yellow and blue are used to discriminate each phase. Now how will you identify each phase wire without knowing the colour and without any pre information?
58.If we connect a voltmeter between earth and ground wire, how much it will measure?
59.Location of lighting arrestor should be near transformer or not? Why?
60.Why the transmitted voltage is multiple of 11 like 11, 22, 33, 132 etc? Is their any technical reason for that?
61.Why the Voltage rises when Leading Power Factor is occurs?
62.How and when synchronous generator acts as a synchronous condenser?
63.Consider you have a tripper at your house. The instant you switch on your motor, the tripper drops. What could be the problem?
64.Why capacitors are used in 1 phase induction motors?
65.Why capacitors are not used in 3 phase induction motors?
66.How many units will a 40W tube consume in 1hr 15 minutes 20 seconds?
67.Why transformer does not rotate like induction motor. Inspite both having same principle?
68.Why magnets are used in audio speaker?
69.Is current a Vector quantity? If yes, then two wires on 90 degree angle must have resulting current equal to zero?
70.What is the differance between shutdown and trip?
71.Is it possible to generate electrostatic power? If yes, how?
72.In residential building electrical installation has been completed. How will you test this new electrical installation of building?
73.What is vector group of transformer? Why is it required?
74.Why neutral point is not required in high transmission line?
75.Wattmeter has two coils in it-the current coil & pressure coil, why is the pressure coil so named? How is the power being measured by the Wattmeter?
76.What is mean by reactive power? How it is generated?
77.In DC only resistive component exists where as in AC system resistive, capacitive & inductive component exists. Why its so?
78.What is mean by form factor of the AC current?
79.What is neutral earthing and equipment earthing?What are the advantages of grounding a neutral of a transformer and gernator?
80.What is Earthing Resistance?
81.Give brief detail on PID Control ?
82.Why does Table Fan rotates Clockwise while Ceiling Fan rotates anti-clockwise? Any technical reason?
83.How will you calculate the leakage current?
84.What is a busbar?
85.Why is alternating current used for transmission?
86.What is a brush alternator?What is a brushless alternator? What is the difference between brush and brushless alternator?Which is better between brush and brushless alternator?
87.Can you test a VFD panel with Resistive load banks? If Yes, How?
88.Does using a AC MCB in a DC circuit affect the tripping time or the perfromance?
89.How harmonics are produced in m/c what is its physical significance?
90.What do you mean by skin effect?
91.What is the 5p 10 , burden in current transformer?
92.Why do we use neutral ct in a transformer?
93.Explain what are busduct and rising main? Where it is used?
94.How to calculate the voltage drop in cable?
95.When is star-delta, Dol or VFD starters used for the motor? How many times the current rating of the motor wil be drawn on a Dol starter if no OLR used?
96.How to design inductive load for 3 phase 440v and maximum 5 amps for star or delta?
97.What are the major causes of a generator breakdown?
98.How to calculate and manufacture the 5P20 class CT with require knee point volt?
99.How to design inductive load for 3 phase 440v and maximum 5 amps for star or delta?
100.Why PNPN is used as thyristor NPNP is not used?
101.Why we use sine wave in supply system rather than square and triangular wave?
102.What is the current carrying capacity of Moose conductor? What are the factors detrmine the current carrying capacity of any conductor?
103.What is the fuction of electrical current transducer, voltage transducer in control panel?
104.What are the applications of pure sine wave inverter?
105.What is the distance between R, Y and B wires when the line is going from one sub-station to another sub-station?
106.What is the constructional diffrence between LPF wattmeter and ordinary AC wattmeter?
107.Can we measure reactive power by using only a single wattmeter? If Yes, How?
108.Why does wattmeter's reading go negative?
109.What is universal motor?
110.Is the transformer induced emf E1 and E2 in same phase or in opposite phase? Explain Why?
111.Why the transformer will burn if DC supply is given?
112.In syncronous machines, less slip is useful or more slip is useful? Why?
113.Can we recognise if motor is series or shunt by visual inspection? If yes how?
114.Why soft starter is provided for higher rating motor?
115.What is the difference between Earthing and Grounding?
116.The ceiling fan rotates in anticlockwise direction, Why?
117.If the position of rheostat is changed from minimum position to maximum position in D.C shunt motors speed is increased, how?
118.Why ceiling fan rotates in anticlockwise direction?

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