B.TECH - Semester 8 electrical machine design Question Paper 2019 (nov)
Practice authentic previous year university questions for better exam preparation.
Sample Questions
- Define overload capacity of an electrical machine.
- Explain the electrical properties of insulating materials
- Derive the output equation of a single phase transformer.
- Obtain the condition for maximum efficiency of transformer,
- What are the main dimensions in machine design? What do you mean by specific loading?
- Enumerate the disadvantages of having higher specific magnetic loading in DC machines.
- Determine the number of turns on each commutating pole of 36 pole machine if the flux density in the air gap of the commutating pole is $0.5 \mathrm{~Wb} / \mathrm{m}^{2}$ at full load and the effective length of air gap is 4 mm . The full load curre...
- What are the effects of SCR on synchronous machine performance?
- Derive an expression for end ring current and rotor bar current.
- Explain Synthesis method of design ( $\mathbf{1 0} \boldsymbol{\times} \mathbf{4} \boldsymbol{=} \mathbf{4 0}$ Marks)
- (a) Design a $25 \mathrm{kVA}, 11000 / 433 \mathrm{~V} .50 \mathrm{~Hz}$, three phase, delta/star, core type, oil immersed natural cooled distribution transformer. Design must include core design, window dimensions, yoke design, overall dimensions of...
- (b) A $1000 \mathrm{kVA}, 6600 / 440 \mathrm{~V}, 50 \mathrm{~Hz}$. three phase, delta/star. core type oil immersed natural cooled transformer have the following design data: Distance between centers of adjacent limbs $=0.47 \mathrm{~m}$ Outer diamet...
- (a) Differentiate between radial and axial ventilation.
- (b) Determine the dimensions of the core, the number of turns and the cross sectional area of conductors in the primary and secondary windings of a $100 \mathrm{kVA}, 2200 / 480 \mathrm{~V}$ single phase core type transformer to operate at a frequenc...
- (b) A $5 \mathrm{~kW}, 250 \mathrm{~V}$, 4 pole, 1500 rpm shunt generator is designed to have a square pole face. The specific loadings are $0.42 \mathrm{~Wb} / \mathrm{m}^{2}$ and 15000A. Full load efficiency is 0.87 , ratio of pole arc to pole pitc...
- (a) Derive the output equation of a dc machine.
- (b) A 8 pole, 500 V dc shunt generator with all the field coils connected in series requires an mmf of $5000 \mathrm{~A} /$ pole. The pole arc of rectangular dimensions $120 \times 200 \mathrm{~mm}^{2}$ and the available winding cross section is $120...
- (a) A 1250 kVA , three phase, $50 \mathrm{~Hz}, 3300 \mathrm{~V}, 300 \mathrm{rpm}$ synchronous generator with a concentric winding has the following design data: $\mathrm{B}_{\mathrm{av}}=0.58 \mathrm{~Wh} / \mathrm{m}^{2}$. $\mathrm{ac}=33000 \math...
- (b) A 1250 kVA , 3 phase, 6600 V , salient pole alternator has the following data. Air gap diameter $=1.6 \mathrm{~m}$, length of core $=0.45 \mathrm{~m}$, number of poles $=20$. armature ampere conductors per metre $=28000$, ratio of pole arc to pol...
- (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 $23000 \mathrm{~A} / \mathrm{m}$. Using the data of this machine; d...
- (b) What is optimization process in the design if electrical machines?
- (c) Explain the general procedure for optimization.
- Define window space factor? How does it affect the over all dimension of a transformer?
- List and discuss at east four factors on which the number of poles of a d.c. machine depends.
- What are interpoles? How interpoles are designed for a d.c. motor?
- With a neat figure describe the various types of windings used in a synchronous machine.
- How rotor slots are designed in a squirrel cage induction motor? ( $\mathbf{5} \boldsymbol{\times} \mathbf{4} \boldsymbol{=} \mathbf{2 0}$ Marks) PART - B Answer any one full question from each Module.
- (a) Starting from the basic derive the output equation of a 3 phase core type transformer.
- (b) What is hot spot rating of an electrical machine? List the factor on which it depends. OR P.T.O.
- Calculate the Determine the main dimensions of the core and window for a $500 \mathrm{kVA}, 6600 / 400 \mathrm{~V}, 50 \mathrm{~Hz}$, Single phase core type, oil immersed, self cooled transformer. Assume: Flux density 1.2 T , Current density $=2.75 \...
- (a) Derive the output equation of a d.c. machine.
- (b) Determine the armature diameter and core length for the preliminary design of a $250 \mathrm{kw}, 4$ pole, $400 \mathrm{~V}, 1500 \mathrm{rpm}$, dc shunt generator assuming an average flux density in the air gap of 1.2 T and specific electric loa...
- (a) Explain the steps involved in designing height field system of a d c series motor.
- (b) A $500 \mathrm{kw}, 500 \mathrm{~V}, 375 \mathrm{rpm}, 8$ pole dc lap wound generator has an armature diameter of 110 cm and the number of armature conductor is 896 . Calculate the diameter of the commutator, length of the commutator, number of b...
- (a) Explain on the factors on which the specific electrical and specific magnetic loading of a synchronous machine depends.
- (b) Clearly explain the factor of which the volume of the synchronous motor depends.
- Design the stator frame of a $600 \mathrm{kVA}, 6.0 \mathrm{kV}, 50 \mathrm{~Hz}, 3$ phase, 12 pole, star connected salient pole alternator, giving the following informations. (a) Internal diameter and gross length of the frame
- Design the stator frame of a $600 \mathrm{kVA}, 6.0 \mathrm{kV}, 50 \mathrm{~Hz}, 3$ phase, 12 pole, star connected salient pole alternator, giving the following informations. (b) Number of stator conductors
- Design the stator frame of a $600 \mathrm{kVA}, 6.0 \mathrm{kV}, 50 \mathrm{~Hz}, 3$ phase, 12 pole, star connected salient pole alternator, giving the following informations. (c) Number of stator slots and conductors per slot Specific magnetic and ...
- Explain the steps the procedure for designing (a) End rings in squirrel cage induction motor
- Explain the steps the procedure for designing (b) Slip ring in slip ring induction motor OR
- (a) Derive the output equation a 3 phase squirrel cage induction motor.
- (b) Explain on different CAD and hybrid techniques used in electrical machine design.