B.TECH - Semester 8 electrical machine design Question Paper 2013 (apr)
Practice authentic previous year university questions for better exam preparation.
Sample Questions
- Discuss the advantages and disadvantages of having stepped cores.
- Mention the advantages of having large number of poles in DC machine.
- List the factors to be considered for the choice of number of slots in synchronous machine.
- What are the factors to be considered for estimating the length of air gap in induction motor?
- Discuss the leakage flux associated with three phase induction motors. $$ (5 \times 4=20 \text { Marks) } $$
- (a) Describe with relevant diagrams different ventilating systems used for cooling of electrical machines.
- (b) A 15 MVA transformer has an iron loss of 75 KW and a copper loss of 100 KW at full load. The tank dimensions are $3.5 \times 3.0 \times 1.5$ meters. The transformer oil is cooled by 2.4 litres of water per second through a cooling coil. Estimate ...
- (a) Derive the expression for output equation of a three phase Transformer.
- (b) Calculate the dimension of the core, the no of turns and cross sectional area of conductors in the primary and secondary windings of a 100 kVA , $2300 / 400 \mathrm{~V} 50 \mathrm{~Hz}$, single phase shell type transformer. Ratio of magnetic and ...
- (a) A $350 \mathrm{Kw}, 500 \mathrm{~V}$ dc generator has 8 poles, an armature diameter of 1.3 m and a core length of 0.35 m . A duplex wave winding is accommodated in 114 slots with 6 coil sides per slot. The axial length of commutating poles is 10 ...
- (b) Discuss the factors that influence the choice of number of poles of a DC machine.
- (a) Calculate the main dimensions, number of poles and air gap length of a $500 \mathrm{~V}, 600 \mathrm{KW}, 900 \mathrm{rpm}$ dc generator with following data : average gap density $0.6 \mathrm{wb} / \mathrm{m}^{2}$, ampere conductors per m 35000 ,...
- (b) Define specific loading and specific electric loading and obtain an expression for output coefficient for a DC machine.
- (a) Deduce the expression for the mmf required for the air gap of an armature with slots and ducts.
- (b) Determine the mmf required for the air gap of a DC machine having open slots, given the following particulars : slot pitch $=4.3 \mathrm{~cm}$, slot opening = 2.1 cm , gross length of core $=48 \mathrm{~cm}$, pole arc $=18 \mathrm{~cm}$, air gap ...
- (a) For a 250 kVA 1100 V 12 pole 500 rpm three phase alternator, determine air gap diameter, core length, number of stator conductors, and number of stator slots and cross section of stator conductors. Assuming average gap density as $0.6 \mathrm{~Wb...
- (b) Explain the factors influencing the choice of specific magnetic loading in synchronous machines.
- (a) Explain the general procedure for optimization of electrical machine design.
- (b) Find the main dimensions, no of stator turns, size of the conductor and no of stator slots of a 5 HP 400 V 3 phase 50 HZ induction motor. Star delta starting is used. Use the following data : Ampere conductor per meter of arm.periphery = 22000 Av...
- (a) Derive the output equation for an Induction motor.
- (b) A 15 HP 400 V 1430 rpm 3 ph . Induction motor with an efficiency of $80 \%$ and pf of $81 \%$ has inner diameter of stator 30 cm and length 12 cm . Estimate the diameter and length for a 50 HP 406 V 4 pole 5 OHz induction motor to be designed for...