B.TECH - Semester 8 electrical machine design Question Paper 2019 (nov)
Practice authentic previous year university questions for better exam preparation.
- Derive the output equation of a single phase transformer.
- (a) Starting from the basic derive the output equation of a 3 phase core type transformer.
- (a) Derive the output equation a 3 phase squirrel cage induction motor.
- 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 current is 500 A and the armature is lap wound with 540...
- (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: $\mathrm{B}_{\mathrm{av}}=0.58 \mathrm{~Wh} / \mathrm{m}^{2}$. $\mathrm{ac}=33000 \mathrm{Am}$, air gap length $=5.5 \mathrm{~mm}$, field...
- (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 loading of 21000 ampere- conductors per metre. Assume...
- (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 brushes per spindle Assume single turn coils.
- (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 pitch is 0.66 . Find the main dimensions of the machin...
- (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; determine the core dimensions, number of stator slo...
- (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 frequency of 50 Hz , assuming the following data, volt per...
- (a) Explain on the factors on which the specific electrical and specific magnetic loading of a synchronous machine depends.
- Define window space factor? How does it affect the over all dimension of a transformer?
- What are the effects of SCR on synchronous machine performance?
- (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 diameter of high voltage winding $=0.44 \mathrm{~m}$ Hei...
- (b) What is optimization process in the design if electrical machines?
- List and discuss at east four factors on which the number of poles of a d.c. machine depends.
- (a) Derive the output equation of a dc machine.
- (a) Derive the output equation of a d.c. machine.
- 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
- Define overload capacity of an electrical machine.
- Explain the electrical properties of insulating materials
- 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.
- 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 frame and winding details. Suitable assumptions c...
- (a) Differentiate between radial and axial ventilation.
- (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 $120 \times 25 \mathrm{~mm}^{2}$. Determine: (i) the c...
- (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 pole pitch $=0.68$, stator slot pitch $=28 \mathrm{~m...
- (c) Explain the general procedure for optimization.
- 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.
- (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 $=2.75 \mathrm{~A} / \mathrm{mm}^{2}$, Window space factor...
- (a) Explain the steps involved in designing height field system of a d c series motor.
- (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. (c) Number of stator slots and conductors per slot Specific magnetic and electric loadings may be assumed as 0.6 Tesla 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
- (b) Explain on different CAD and hybrid techniques used in electrical machine design.
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