Engineering BE Electrical Engineering Sem 7 December 2018 2018 Electrical Machine Design Question Paper - Mumbai University | munotes

Questions asked in this paper

1. Q1 Question No | is Compulsory
2. Q2 Solve any three out of the remaining
3. Q3 Figure to the right side indicates marks
4. Q4 Assume the suitable data and mention the same if required QNo Answer the following
   • a. Discuss the classification of insulating materials based on temperature 5
   • b. What is gross and net iron area? How stepping of core affects it? 5
   • c. What are the various factors affecting the sizing of a machine? 5
   • d. How the relationship between D and L affect the design of motor? 5
5. Q2 a Derive the output equation of a three phase transformer. 10 marks
6. Q2 b Calculate the overall dimensions of a 200 KVA, 6600/440V, 50 Hz, 3 phase core type transformer with data, emf per turn= 10V, maximum flux density=1.3 current density=2.5 A/mm?, window
7. Q3 a What are the various assumptions in the leakage reactance calculation for a transformer. 10 marks
8. Q3 b 250KVA, 6600/400V, 3 phase, core type transformer has a total loss of 4,800 W at full load. The transformer tank is 1.25m in height and 1m x 0.5m in plan. Design a suitable scheme for tubes if the average temperature rise is to be limited to The diameter of tube is 50mm and is spaced 75mm from each other. The average height of tube is 1.05m. Specific heat dissipation due to radiation and convection is6 and 6.5 that convection is improved by 35% due to provision of tubes
9. Q4 a Derive the output equation fora three phase induction motor. 10 marks
10. Q4 b Determine the main dimensions, total conductors, area of a slot and conductor area, for a 250 HP, 3 phase,4 pole, 50Hz, delta connected squirrel cage induction motor with the data, average flux density in air gap= ampere conductor per meter=30,000A/m, efficiency= 0.9, power factor=0.9,winding factor = density= space factor =0.4,ratio of length of core to pole pitch=1.2, Assume 5 slots per pole per phase. [10]
11. Q5 a Explain the terms total magnetic loading, total electric loading, specific magnetic loading, and specific electric loading in case of motors [10]
12. Q5 b A 11 KW, 3 Phase, 220V, 6 Pole, 50Hz, 220V, Star connected squirrel cage induction motor has following data. The machine has efficiency of 0.86 and power factor of 0.85. The other data is Stator Data:-Number of slots = 54, conductor per slot = 9; Rotor Data:- Number of slots= 64,rotor mmf= 0.85 times stator mmf. Find the area of rotor bar, area of end ring if current density is [10]
13. Q6 a Discuss the design features of cross over winding and helical winding 10 marks
14. Q6 b Discuss the design modification in the stator and rotor of a energy efficient motor. 10 marks

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