a. Explain the clearly the factors which impose limitations on the design of electrical machines. h. Discuss modern machine manufacturing techniques in the design of electrical chines
4 a. Discuss the design of sunt field winding of a DC machines, b. A 8 pole. 500 de generator with all the field coils connected in series requires 5000 AT pole the pole are of rectangular dimensions 12×20 cm and winding cross section is 12x25 cm determine the cross sectional area of wire. number of turns and dissipation in watts/cm hased on the outside and two end surfaces of the coils. The section used, p-0.021 12 m/mm and insulation increases the conductor of rear oss is p diameter of condtreter by 0.02 cm. Allow a voltage drop in the field regulator of 50V.
OR
2 a. What are the desirable properties of insulating materials used electrical machines? Give
the classification of insulating materials based on mal conferations with examples of
materials used in cach class
(08 Marks)
Click here to join us on Social Media for getting instant update on every noticeb. What are desirable properties of conducting erals used in electrical machines? Explain
any two conductors with their properties
3 a. Discuss the various factors which gave 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 he average gap density is 0.51 and ampere
conductor per metre is 220
efficiency is 90%.
pole are to pole pitch is 0.7 and full load
(08 Marks)
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(06 Marks)
(10 Marks)
Module-3
Derive output equation of a 3 phase core type transformer. Also derive the volts per turn (08 Marks) b. Determine the main dimensions of core and window, number of turns and cross sectional ar 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 1.251: A-0.6d09d window space factor 0.27: H, 3W current density-25 Amm
6 a Discuss the design of tank and cooling tubes of a transformer.
(08 M)
b. Calculate the No-load current a power factor of a 3300/220V. 50 Hz single phase, core type 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 1.1 1 is 2.1 Wkg. Ampere turns/cm for transformer steel at 16.2. The effect of joints is equivalent to that of an airgap of 1 mm in the magnetic cent. Dersity of iron is 7.55 pm cc. Iron factor is 0.92
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 q-32000-c/m, Take efficiency as 90% and power factor as 0.91. Assume pble pitch is equal to core length. Estimate the number of stator conductors required for a windings which the conductors are connected in 2 parallel paths. Assume number of slots/pephase (10 Marks)
8
a. Derive expression for rotor bar and end ring current of squirrel cage induction motor.
(06 Marks) 105 Marks)
b. Discuss design of slip-ring rotor of a 3 phase induction mott Determine the Magnetizing current. No lone current and power factor of a 15 HP. 6 pole. Number of stator slots 54, stator conducte 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 coefficici iron parts of the magnetic circuit requires (05 Marks)
(08 Marks) of the stator bore. number of stator conductors and slots of a rator rated at 300 kVA, 50 Hz. Assume q-280 A-clem faces and pole arc 0.65 pole pitch, Voltage rating - 3300 V. (08 Marks)
10 a Dy the actors to be considered while selecting number of armature slots in a (06 Marks)
steps involved in the design of field winding of a salient pole alternator? (06 Marks) A SORVA, V, 50 Hz, 600 rpm, salient pole alternator has 180 turns phase. Estimate of airgap if the average flux density 0.575 Wbins. Pole arc/pole pach -0.66. gap extension factor-1.15. The mmf required for the gap is 82% of the No load (04 Marks)
a. Explain the principles of design of electrical machines. Whature the Imitations in design?
(06 Marks) b. What are the desirable properties of magnetic materials plain brief magnetic materials and its classification, Give a brief comparison between copper and aluminium wires 105 Marks) (05 Marks) C
a. Classify the insulating materials used in cloct stability. Give one example for each class b. Write brief note on Cold Rolled Grain Oriented e. What are the desirable properties of conducting according to their thermal (06 Marks) CRO steel used in electrical machines. 105 Markst 105 Marks) a. Define specific electric and magnetic loadings of DC machine What are the merits and 3
2
demerits of selecting higher values of specific loadings? Mention the factors to be b. A design is required for a voltage is 220V (08 Marks) 600rpm de shunt generator. The full load terminal maxintim gap density is 083Wb m and ampere late intable dimensions of armature core to give a square pole face. Assume the be full load armature voltage drop is 3 of rated terminal voltage ted full load current. The ratio of pole are to pole pitch is 0.67. (O8 Marks
OR ous fact which govern the choice of number of poles in a DC. machine. (0% Marks) coil has to develop an mmf of 9000A The voltage drop in the coil is 40V and f the round wire is 002152/mmmm The depth of the winding is 35mm approximately and the length of the mean tum is 14m Design a coil so that the power dissipated is 700 Wm of the total coil surface. Take diameter of the insulated wire 0.2mm 08 Marks
Module-3 Derive the output equation of a 3 phase core type transformer and hence deduce an
expression for output-emf turn.
(08 Marks) Calculate the main dimensions and winding details of a 100kVA, 2000 400V, 5011, 16 shell pe, oil immersed self cooled transformer Assume voltage per tum 10V, flux density in core 1.1 Wb m. current density 2mm window space factor 0.33, the ratio of window height to window width is 3, ratio of core depth to width of central limb 2.5 stacking factor-0.9 (08 Marks)
6 a Explain the procedure to calculate the no-load current for a single phase transformer.
b. A 250LVA, 6600 400V, 36 core type transformer has a total loss of 4800W at full load he transformer tank is 1.25m in height and Imx 0.5m in plan. Design a suitable scal for number of tubes, if the average temperature rise is limited to 35°C. The diameter of the t is 30mm and are spaced 75mm from each other. The average height of the tube is 1.05m Specific heat dissipation due to radiation and convection is respectively 6 and W/m Assume convention is improved by 35% due to provision of tubes
Module-4
a
Discuss the factors to be considered while deciding the length of air gap, number of stator
and rotor slots in an Induction motor,
(08 Marko
b. A 15kW, 34, 6 pole. 50Hz, squirrel cage Induction moto has following data: stator bone
7 With usual notations derive the output equations of a 34 induction machine b. Calculate the diameter of stator bore and core length of a Y connected. 6 pole Induction motor for which q 32000 Ac/m. efficiency-90%, pf-0.91. Assume pole pitch equal to core en Estime the number of stator conductors required for a winding in which the conductor parallel paths. Choose a suitable number of conductors/slot,bat the stor loading does not exceed 750 Ampere conductors (08 Marks)
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dia 0.32m axial length of stator core-25m umber 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 ca rotor giving number of rotor slots, section of each bar section of each ring. The load end to be 950rpm approximately. Use copper for rotor bars and endings Resistivity of copper - 0.0242m and m Assume &-7Amm for end rings (08 Marka)
9 a Denve
HP
an
synchronous machine and show that
(08 Marks) b A 1000KVA, 3300 50Hz 00 36 alternator has 180 slots with 5 conductors/slot. pitch coils is used. The winding is star connected with one circuit per pluse etern the specific electric and specific magnetic loadings, if the stator bore is 2.0m and there length is 0.4m. Using the same loadings, determine corresponding data for a SOLVA V 50Hz, 250rpm, 36 star connected alternator having 2 circuits (8 Marks) OR
synchronous machine? What are the effects of SCR on machine
(08 Markst
VA. 225rpm, 30, 60Hz. 2400V. Y-connected salient pole altemator has the design data: stator bore 25m, core length 0.44m, slot pole phase-3 cond slot 4 circuits phase 2. leakage factor 12, winding factor-0.95 The flux density in the pole core is 15 Wbm, the winding depth is 30mm, the ratio of full ield mmf to armature mmf is 2. field winding space factor is 0.84 and the field winding dipases 1800 Wim of inner and outer surface without the temperature rise exceeding nuble limit Leave 30mm for insulation flanges and height of pole shoe along the eight of pole Find 1) The Bux per pole i) Length and width of poke Ho Winding wg Pole height