B.Tech. [SEM I (CE,EC,EE,EN)] QUIZ TEST-3beingmechanical.weebly.com/uploads/5/3/9/4/53940251/2012-13...... Write down the advantage and disadvantage of one wattmeter method. [1] (b)

EEE-101/Mr.B.K.Verma, Mr.Gaurav Sharma, Ms.Kavya Mittal, Mr.Gaurav Singh, Mr. Anjanee kr. Mishra Date: 17/11/2012

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SHRI RAMSWAROOP MEMORIAL COLLEGE OF ENGG. & MANAGEMENT

B.Tech. [SEM I (CE,EC,EE,EN)] QUIZ TEST-3

(Session: 2012-13)

ELECTRICAL ENGINEERING (EEE-101)

Roll No.

(To be filled by the Student) Note: Attempt All Questions.

Part – A (Questions from Tutorial Sheet) [10 Marks]

Q1) A balanced 3-phase load consists of three coil, each having resistance of 6 ohm & inductive reactance of 8 ohm. Determine line current and power absorbed when coils are (a) star connected (b) delta connected, across 400V, 3 phase supply. [Q-02] [2.5+2.5]

Q2) Explain the principal and operation of PMMC instrument. [Q-10] [5]

Part – B [20 Marks]

Q3) Short answer type question: (a) Write down the advantage and disadvantage of one wattmeter method. [1] (b)What are the standard primary and secondary transmission voltages? [1] (c) What do understand by ‘Shunt’? [1] (d) Why damping torque is required in instruments? [1] (e) Define turn ratio and transformation ratio. [1]

Q4) In an R-L series circuit the voltage and current is expressed as, [1+2+1+1]

v(t) = 30 sin (314t + 5π/6) and i(t) = 10 sin (314t + 2π/3)

find (i) Impedance of circuit (ii) R and L connected in circuit (iii) The average power (iv) Power factor of the circuit Q5) Draw and explain ‘hysteresis loop’, also write down the importance of hysteresis loop. [4+1] Q6) A 11000/230V, 150 KVA, single phase 50 Hz transformer has core loss of 1.4 KW and full load copper loss of 1.6 KW. Determine [3+2]

(i) KVA loading for maximum efficiency and value of maximum efficiency at unity power factor (ii) The efficiency at 50% of full load at 0.8 power factor lagging.

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Academic/26 Refer/WI/ACAD/18

Time: 1 Hour Max. Marks: 30


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Q1) A 400V supply is connected across a balanced load of three impedances each consisting of 32 ohm resistance and 24 ohm inductive reactance in series. Determine the current drawn from power mains if three impedances are (a) star connected (b) delta connected. [Q-04] [2.5+2.5]

Q2) Explain power measurement in three phase by two wattmeter method for balanced star connected load. [Q-07] [5]


Q3) Short answer type question: (a) Write down the advantage and disadvantage of three wattmeter method. [1] (b)What are the standard primary and secondary distribution voltages? [1] (c) What do understand by ‘Multiplier’? [1] (d) Why controlling torque is required in instruments? [1] (e) Define primary and secondary winding. [1]





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Q1) Explain (a) Phase current (b) Line current (c) Phase voltage (d) Line voltage. Prove that line voltage is 1.732 times its phase voltage in star connection. [Q-05] [2+3]

Q2) An energy meter has a registration constant of 100 rev/KWhr. If the meter is connected to a load drawing 20amp at 230V and 0.8 pf for 5 hrs. find the number of revolutions should be made to it. If it actually makes 1800 revolutions then find the percentage error. [Q-11] [3+2]


Q3) Short answer type question: (a) Write down any two advantage of three phase over single phase system. [1] (b)What is the role of circuit breaker in power system? [1] (c) Why PMMC instruments are not suitable for ac measurement? [1] (d) What are indicating type instrument? [1] (e) Define hv and lv winding in transformer. [1]





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Q1) The power input to a 200V, 50Hz 3phase motor running on full load at an efficiency of 90% is measured by two wattmeter which indicates 300KW and 100KW respectively. Find (a)Input power (b) Power factor (c) line current and power output. [Q-08] [1+2+2]

Q2) A PMMC instrument gives full scale reading of 25mA when a potential difference across its terminal is 75mV. Show how it can be used (a) As an ammeter for range 0-100A (b) As a voltmeter for range 0-75V. Also find multiplying power of the shunt and voltage amplification. [Q-09] [2+2+1]


Q3) Short answer type question: (a) Write down any two advantage of PMMC instrument. [1] (b)What is the role of Cu shading band in energy meter? [1] (c) Show analogy between electric and magnetic circuit in terms of driving force and response. [1] (d) What are recording type instruments? [1] (e) Define Ideal transformer. [1]





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Q1) Three identical resistors of 20 ohm each are connected in star to 415V, 50Hz 3 phase. Calculate (i)The total power consumed (ii)Total power consumed if they are connected in delta (iii) The total power consumed if one of the resistor is opened. [Q-06] [2+2+1] Q2) A three phase motor load has a p.f. of 0.397 lagging. Two watt meters are connected to measure power, shows the input as 30kW. Find the reading of each wattmeter. [Q-15] [5]


Q3) Short answer type question: (a) Define deflecting torque . [1] (b)What is creeping error occurs in energy meter? [1] (c) Show analogy between electric and magnetic circuit in terms of impedance and density. [1] (d) What are integrating type instruments? [1] (e) Define hysteresis loss in transformer. [1]





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Part – A (Questions from Tutorial Sheet) [10 Marks] Q1) Describe the layout of electric power system in India and also explain the function of its various

elements in power system. [Q-01] [2+3] Q2) A single phase transformer is working at unity power factor has a efficiency of 90% at both full load and

half load of 500W.Determine the efficiency at 75% full load and maximum efficiency.[Q-09] [3+2] Part – B

[20 Marks] Q3) Short answer type question:

(a) Write down the advantage of two wattmeter method. [1] (b)Define slip and slip speed. [1] (c) Write down the role of Commutator used in dc machine. [1] (d) Why single phase induction motors are not self starting? [1] (e) Write down the use of 1:1 turn ratio transformer. [1]

Q4) A 3-phase delta connection 440V, 50Hz 4 pole induction motor has a rotor standstill emf per phase of 130V. If the motor speed is 1440rpm. Then calculate; (i) slip (ii) frequency of rotor induced emf (iii) rotor Induced emf per phase (iv) stator to rotor turn ratio. [2+1+1+1] Q5) Three coils having resistance of 20 ohm and inductive reactance of 15 ohm are connected in star to a 400V 50 Hz 3-phase supply. Calculate the line current, the active power and power factor. If three capacitors each having same value are connected in delta to the same supply so as to form a parallel circuit with above coils calculate…. (i)The capacitance to obtain the resultant power factor of 0.95 lagging. (ii)The line current taken by combined load. [2+3] Q6) A single phase 440V/110V transformer takes a no load current of 4A at 0.2 power factor. If the Secondary supplies a current of 100A at a power factor of 0.8 lagging. Determine (i)The current taken by primary winding. (ii)The magnetizing reactance and resistance representing core losses. [3+2]

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Part – A (Questions from Tutorial Sheet) [10 Marks] Q1) Enumerate the similarities and differences between Electric and Magnetic circuit. [Q-03] [3+2] Q2) A 10 KVA 2000/400V single phase transformer has R1=5 ohm, X1=12 ohm, R2=0.2ohm and X2=0.48 Ohm. Determine the equivalent impedance of transformer referred to primary and secondary side. [Q-10] [2.5+2.5]


Q3) Short answer type question: (a) What do you understand by magnetic leakage associated with magnetic circuit ? [1] (b)Write down the applications of dc series motor. [1] (c) Write down the role of Pole shoe used in dc machine. [1] (d) Why three phase induction motors are self starting? [1] (e) Why brake magnet is used in energy meter? [1]


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Part – A (Questions from Tutorial Sheet) [10 Marks] Q1) What is auto transformer? Give its advantages and disadvantages over single phase transformer.

[Q-12] [1+2+2] Q2) The efficiency of 400 KVA, single phase transformer is 98.77% when delivering full load at 0.8 power factor lagging and 99.13% at half load at unity power factor. Calculate the iron losses and the copper losses. [Q-11] [2.5+2.5]


Q3) Short answer type question: (a) Write down one difference between energy meter and wattmeter. [1] (b) Explain why series motor is never started on no load. [1] (c) Explain fringing phenomenon occurred in magnetic circuit . [1] (d) What is the role of auxiliary winding in single phase induction motor? [1] (e) Why copper losses are known as variable losses? [1]


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Part – A (Questions from Tutorial Sheet) [10 Marks] Q1) Derive emf equation of single phase transformer. A 25 KVA transformer has voltage ratio of 3300/400 volt, calculate primary and secondary currents. [Q-07] [3+1+1] Q2) An iron ring of cross sectional area 6 cm2 is wound with wire of 100 turns and has a saw cut of 2mm. Calculate the magnetizing current required to produce flux of 0.1 m Wb, if mean length of magnetic path is 30 cm and relative permeability of iron is 470. [Q-06] [5]


Q3) Short answer type question: (a) Write advantage of ‘Grid’ in power system. [1] (b) Draw Torque Vs Armature current characteristic for dc shunt motor. [1] (c) Write advantage of wound rotor over squirrel cage rotor. [1] (d) Why 3 phase induction motor also known as asynchronous motor? [1] (e) Why iron losses are known as constant losses? [1]


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Part – A (Questions from Tutorial Sheet) [10 Marks] Q1) Explain the principle of operation and working of single phase transformer. Also write a note on various winding parameters used in it. [Q-05] [1+2+2]

Q2) A coil is wound uniformly with 300 turns over a steel ring of relative permeability 900 having circumference of 40 cm and cross sectional area of 5 cm2. If the coil has resistance of 100 ohms and is connected to 250 V dc supply, calculate (a) Coil m.m.f. (b)Field strength (c)Total flux (d)Reluctance of the ring (e)Permence of the ring [Q-15] [1+1+1+1+1]


Q3) Short answer type question: (a) Write down the difference between core type and shell type transformer. [1] (b) Draw no load phasor diagram of ideal transformer. [1] (c) Write down the condition for maximum torque in 3 phase induction motor. [1] (d) Explain the term ‘back emf’. [1] (e) Which type of instrument is more accurate PMMC or MI? justify your answer. [1]


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B.Tech. [SEM I (CE,EC,EE,EN)] QUIZ TEST-3beingmechanical.weebly.com/uploads/5/3/9/4/53940251/2012-13...... Write down the advantage and disadvantage of one wattmeter method. [1] (b)