B.TECH - Semester 8 electrical machine design Question Paper 2008 (may)
Practice authentic previous year university questions for better exam preparation.
Sample Questions
- Explain any five types of enclosures used in rotating electrical machines.
- Define continuous and short time rating of machines.
- The initial temperature of a machine is $40^{\circ} \mathrm{C}$. Calculate the temperature of the machine after one hour if its final steady temperature rise is $80^{\circ} \mathrm{C}$ and the heating time constant is two hours. The ambient temperatu...
- Prove that for a range of transformers voltage per turn $=K \sqrt{K V A}$, where K is a constant.
- Define field form factor.
- Find the minimum number of poles for a $1,200 \mathrm{k} \mathrm{W}$ generator the average voltage between commutator segments is not to exceed 15 and the armature mmf per pole is not to exceed $10,000 \mathrm{~A}$.
- What are the advantages and disadvantages of higher number of poles in dc machine?
- What are the advantages of Hydrogen Cooling in Alternators?
- Obtain the output equation of three phase induction motor.
- Enumerate the factors affecting the selection of number of stator slots of three phase induction motor. ( $\mathbf{1 0} \boldsymbol{\times} \mathbf{4} \boldsymbol{=} \mathbf{4 0}$ Marks) PART - B
- (a) Derive the output equation of a single phase transformer.
- (b) Calculate the kVA output of a single phase transformer from the blowing data: $\frac{\text { core height }}{\text { distance between core centres }}=2.8, \frac{\text { diameter of circum scribing circle }}{\text { distance between core centres }}...
- (c) Define window space factor. OR
- (a) The tank of a 1250 kVA natural cooled transformer its the dimensions length × width × height as $1.55 \mathrm{~m} \times 0.65 \mathrm{~m} \times 1.85 \mathrm{~m}$. The full load loss is 13.1 kW . Find the number of tubes. Assume $\mathrm{W} / \m...
- (b) The ratio of flux to full load mmf in a $400 \mathrm{kVA}, 50 \mathrm{~Hz}$, single phase core type power transformer is $2.4 \times 10^{-6}$. Calculate the net iron area and the window area of the transformer. Maximum flux density in the core is...
- (a) Determine the main dimensions, number of poles and the length of air gap of a $600 \mathrm{k} \mathrm{W}, 500 \mathrm{~V}, 900 \mathrm{rpm}$ generator. Assume average gap density as $0.6 \mathrm{~Wb} / \mathrm{m}^{2}$ and ampere conductors per me...
- (b) A $350 \mathrm{~kW}, 500 \mathrm{~V}, 450 \mathrm{rpm}, 6$ pole dc generator is built with an armature diameter of 0.87 m and a core length of 0.32 m . The lap wound armature has 660 conductors. Calculate the specific loadings.
- (a) A $250 \mathrm{~kW}, 500 \mathrm{~V}, 600 \mathrm{rpm}$ dc generator is built with an armature diameter of 0.75 m and a core length of 0.3 m . The lap connected armature, has 720 conductors. Using the data obtained from this machine, determine th...
- (b) Discuss the factors to be considered while selecting ampere conductors per metre for a dc machine.
- (a) A $1,000 \mathrm{kVA}, 3.3 \mathrm{kV} 50 \mathrm{~Hz} 300 \mathrm{rpm}$ three phase alternator has 180 slots with 5 conductors per slot. Single layer winding with full pitch coils is used. The winding is star connected with one circuit per phase...
- (b) What are the factors considered for the selection of armature slots of an alternator? OR
- (a) A $15 \mathrm{~kW}, 440 \mathrm{~V}, 4$ pole 50 Hz , three phase induction motor is built with a stator bore 0.25 m and a core length of 0.16 m . The specific electric loading is $23,000 \mathrm{~A} / \mathrm{m}$. Using the data of this machine, ...
- (b) Obtain the relation between D and L for best power factor. ( $3 \times 20=60$ Marks)