Electrical Machine Design 2022 Question Paper — Government College of…
The 2022 Electrical Machine Design previous year question paper (Government College of Engineering and Technology, Jammu), with every question and its marks.
- University: Government College of Engineering and Technology, Jammu
- Subject: Electrical Machine Design
- Course: Electrical Machine Design
- Branch: Electrical Engineering
- Year: 2022
- Paper: end-term
- Duration: 180 minutes
- Total marks: 75
Instructions
- Attempt five questions in all selecting at least two questions from each Section.
- Use of calculator is allowed.
- Assume missing data if any.
- Each question carries 15 marks.
Questions
Section - A
Select at least two questions from this Section.
- Q1. Derive the equation of temperature rise with time in electric machine. What is heating time constant? [15 marks]
- Q2. Explain briefly the factors to be considered for the selection of motor power ratings. [15 marks]
- Q3. What is window space factor? Find the width of window for optimum output of a transformer. [15 marks]
- Q4. Calculate approximate overall dimensions for a 200kVA,6600/440V, 50Hz 3 phase core type transformer. The following data may be assumed. Emf per turn = 10V; Maximum flux density = 1.3 Wb/m^2; current density = 2.5 A/mm^2; Window space factor = 0.3 overall height = overall width; stacking factor = 0.9. Use a 3 stepped core for a three stepped core. Width of largest stamping = 0.9 d and Net iron area = 0.6 d^2 where d is the diameter of circumscribing circle. [15 marks]
Section - B
Select at least two questions from this Section.
- Q5. Explain the factors which are taken into consideration for the design of wound rotor of three phase induction motors. [15 marks]
- Q6. A 90KW, 500V, 50Hz, 3 Phase, 8 pole induction motor has a star connected stator winding accommodated in 63 slots with 6 conductors per slot. If the slip ring voltage on open circuit is to be about 400V. Find a suitable rotor widing stating: a. Number of slots. b. Number of conductors per slot. c. Coil Span. d. Slip ring voltage on open circuit. e. Approximate full load current per phase in rotor. Assume efficiency = 0.9 ; power factor = 0.86. [15 marks]
- Q7. The following is the design data available for a 1250KVA, 3 Phase, 50Hz , 3300 V, star connected , 300 r.p.m. alternator of salient pole type: Stator bore D = 19 m , stator core length L = 0.335 m; Pole arc/pole pitch = 0.66; turns per phase = 150; single layer concentric winding with 5 conductors per slot, short circuit ratio = 1.2. Assume that the distribution of gap flux is rectangular under the pole arc with zero values in the interpolar region.Calculate: a. Specific magnetic loading. b. Armature mmf per pole. c. Gas density over pole arc. d. Air gap length. mmf required for air gap is 0.88 of no load field mmf and the gap contraction factor is 1.15. [15 marks]
- Q8. Discuss the short circuit ratio with characteristics of a synchronous machine. Also discuss the effect of short circuit ratio(SCR) on machine performance. [15 marks]