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Module-1
a. Explain the clearly the factors which impose limitations on the design of electrical machines.
(08 Marks)
b. Discuss modern machine manufacturing techniques in the design of electrical machines.
(08 Marks)
OR
2 a. What are the desirable properties of insulating materials used in electrical machines? Give the classification of insulating materials based on thermal considerations with examples of materials used in each class. sourc
(08 Marks)
b. What are desirable properties of conducting materials used in electrical machines? Explain any two conductors with their properties.
(08 Marks)
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a. Discuss the various factors which govern the choice of number of poles in DC machines.
(08 Marks) b. Find the main dimensions and the number of poles of a 37 kW. 230 V. 1400 rpm shunt motor so that a square pole face is obtained. The average gap density is 0.5T and ampere conductor per metre is 22000. The ratio of pole are to pole pitch is 0.7 and full load efficiency is 90%.
(08)
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Important Note: 1. On completing your answers, compulsorily
2. Any revealing of identification, appeal to eva
10
OR
108 MarkS)
M b. Determine the main dimensions of core and window. number of turns and cross sectional arga of the conductors of a primary and secondary winding of a 3 phase core type transformer. 350 kVA. 11000/3300V, star-delta. 50 Hz. Assume volts/turn 11. Maximum flux density = 1.25T: A. = 0.6 d: a 0.9 d window space factor = 0.27: H 3W current density = 2.5 A/mm.
a. Discuss the design of shunt field winding of a DC machines.
(06 Marks)
b. A 8 pole. 500 de shunt generator with all the field coils connected in series requires 5000 AT pole. If the poles are of rectangular dimensions 12x20 cm and winding cross section is 12x2.5 cm, determine the cross sectional area of wire, number of turns and dissipation in watts/cm based on the outside and two end surfaces of the coils. The conductor of circular cross section is used. p = 0.021 2/m/mm and insulation increases the diameter of conductor by 0.02 cm. Allow a voltage drop in the field regulator of 50V. vtur
(10 Marks)
Activate Win
Module-3
Derive the output equation of a 3 phase core type transformer. Also derive the volts per turn
6 a Discuss the design of tank and cooling tubes of a transformer.
15EE64
b. Calculate the No-load current a power factor of a 3300/220V, 50 Hz. single phase, core typ transformer with the following data: Mean length of magnetic path 300 cm. gross area of iron core 150 cm. specific iron loss at 50 Hz and 1.11 is 2.1 W/kg. Ampere turns/cm for transformer steel at 162 The effect of joints is equivalent to that of an airgap of 1 mm in the magnetic crent Dersity of iron is 7.55 gm/cc. Iron factor is 0.92. source.
Module-4
7 a Discuss the factor affecting the length of airgap of a 3 phase induction motor.
b. Determine the diameter of stator bore and core length of a 70 HP 415 V, 3 phase, 50 Hz.
star connected. 6 pole. induction motor for which q3000
Take efficiency as 90% and power factor as 0.91. Assume pole pitch is equal to core length.
Estimate the number of stator conductors required for a winding in which the conductors are
connected in 2 parallel paths. Assume number of slots/phle phase
OR
(10 Marks)
(06 Marks)
(05 Marks)
Number of stator slots 54, stator conducte p 28, flux pole- 8.25 milliwaber.
airgap area pole 183,5 cm gap length 0.55 mm. iron loss-510 W: friction and windage
on contraction noton All iron parts of the magnetic circuit routines
8 a. Derive expression for rotor bar and end ring current of quirrel cage induction motor b. Discuss design of slip-ring rotor of a 3 phase indion motor c. Determine the Magnetizing current. No load current and power factor of a 15 HP. 6 pole. 440 V. delta connected slip ring Induction motor having the following data:
a Derive expression for rotor bar and end ring current of squirrel cage induction motor. b. Discuss design of slip-ring rotor of a 3 phase induction motors
(05 Marks) Determine the Magnetizing current. No load current and power factor of a 15 HP. 6 pole. 440 V. delta connected slip ring Induction motor having the following data: Number of stator slots 54, stator conductor per slot slot 28, flux pole 8.25 milliwaber. airgap area pole 183,5 cm, gap length 0.55 mm, iron loss-510 W: friction and windage loss 110 W: gap contraction coefficient 33, iron parts of the magnetic circuit requires 20% of ampere turns required for gap Stator winding factor-0.96 (05 Marks) C.
Module-5
9 a Derive the output equation of a phase synchronous machine. (08 Marks) b. Determine the main dimensions of the stator bore, number of stator conductors and slots of a 3 phase, star connected. 8 pole, alternator rated at 300 kVA. 50 Hz. Assume q=280 A-c/cm B 0.61, square pole faces and pole arc 0.65 pole pitch. Voltage rating 3300 V. Take number of Shats pole/phuse 3.5. (08 Marks)
OR
10 a Discuss the factors to be considered while selecting number of armature slots in a synchronous machine (06 Marks) b. Who are the steps involved in the design of field winding of a salient pole alternator?
(06 Marks) c. A SKVA. V. 50 Hz, 600 rpm. salient pole alternator has 180 turns phase. Estimate the legh of airgap if the average flux density-0,575 Wb/m. Pole are/pole pitch - 0.66. SCR gap extension factor 1.15. The mmf required for the gap is 82% of the No load field mm. KW, -0.955.
Explain the principles of design of electrical machines. What the hmitations in design?
b. What are the desirable properties of magnetic materialsExplain in brief magnetic material and its classification.
(05 Marks
(05 Marks
C Give a brief comparison between copper and aluminum wires
Classify the insulating materials used in electrical machines according to their therma stability. Give one example for each class. (06 Marks Write brief note on Cold Rolled Grain Oriented (CRO) steel used in electrical machines (05 Marks
a Define specific electric and magnetic loadings of DC machine What are the merits and demerits of selecting higher values of specific loadings? Mention the factors to be (08 Marks A design is required for a 50kW pole 600rpm de shunt generator. The full load termina voltage is 083Wb m and amper conductors 30.000 m, calculate stable dimensions of armature core to give a square pole face. Assume that the full load armature voltage drop is 3% of rated terminal voltage b resourc
a
b
B
3
A
and field current 1% of rated full load current. The ratio of pole are to pole pitch is 0.67
(08 Marksl OR Discuss the various factor which govern the choice of number of poles in a D.C. machine
Explain the procedure to calculate the no-load current for a single phase transformer.
a
(08 Mark b A 250kVA, 6600 400V, 36 core type transformer has a total loss of 4800W at full load. The transformer tank is 1.25m in height and Im x 0.5m in plan. Design a suitable scale for number of tubes, if the average temperature rise is limited to 35°C. The diameter of the tube is 50mm and are spaced 75mm from cach other. The average height of the tube is 1.05m. Specific heat dissipation due to radiation and convection is respectively 6 and 65 W/m C Assume convention is improved by 35% due to provision of tubes
Module-4
7 a With usual notations derive the output equations of a 30 induction machine b. Calculate the diameter of stator bore and core length of a 70HT 415 36. 50Hz. Y connected, 6 pole Induction motor for which q= 32000 Ac/m. = 0.51 T. efficiency 90%, p = 0.91 Assume pole pitch equal to core length. Estimate the number of stator conductors required for a winding in which the conductors are connected in two parallel paths Choose a suitable number of conductors/slot, so that the slot loading does not exceed 750 Ampere conductors. (08 Marks) ource.
OR
8 Discuss the factors to be considered while deciding the length of air gap, number of stator a and rotor slots in an Induction motor, (08 Marks) b. A 15kW. 34. 6 pole. 50Hz, squirrel cage Induction motor has the following data: stator hore dia 032m, axial length of stator core=125m, qumber of stator slots 54, number of conductors stator slot 24. current in each stator conductor 17.5A, full load power factor 0.85 lagging. Design a suitable cage rotor giving number of rotor slots, section of each bar, section of each ring. The full load speed to be 950rpm approximately. Use copper for rotor bars and endings, Resistivity of copper-0.0202/m and mm. Assume 6-7A mm for end