Design of AC Machines — Winter 2020

o Q.6. 2. Q7 is compulsory. 3. Make suitable assumptions wherever necessary. 4. Figures to the right indicate full marks.

Explain factors to be considered for selecting specific magnetic loading for 3- phase I. M.

Sketch the different types of rotor slot in 3 phase I. M..

What is dispersion coefficient? How does it affect maximum power? f actor

What is the role of damper winding in synchronous generator and motor?

Explain step for designing the field winding of Synchronous machine.

A 1250 kVA, 3 phase, 50 Hz, 3300 V, 300 rpm, synchronous generator with a concentric winding has the following design data: specific magnetic loading, Bav = 0.58 Wb/m2, specific electrical loading, ac = 33000 A/m, gap length = 5.5 mm, field turn per pole = 60, winding factor = 0.955, short circuit ratio = 1.2, The effective gap area is 0.6 times the actual area. Peripheral speed is 30 m/s. Find stator core length, stator bore, turns per phase, mmf for air gap, armature mmf per pole and filed current for no load and rated voltage.

Which factors affecting the size of 3-phase induction motor? Explain in short.

Briefly discuss factors affecting determining air gap length in induction motor design.

Which types of slots are used for stator? How the number of slots is estimated? Which point are to be considered for selecting number of stator slots?

State and explain the factor to be considered for selecting specific electrical loading for 3 phase I. M..

State the rules for the selection of rotor slots in 3-phase squirrel cage induction motor.

List out the method for reducing harmonics in induction motor? Explain in brief.

Explain direct axis and quadrature axis synchronous reactance in synchronous machine.

Explain how mmf is calculated for magnetic circuit in synchronous machine.

Explain design of damper winding with equation.1

Explain the terms “peripheral speed” & “run-away speed” with reference to synchronous machine

State the important design different between turbo alternators and hydro generators.

What is SCR? Discuss its effect in synchronous machine performance.

Explain application of FEM technique for design problems.

State the procedure of designing an auxiliary winding in case of resistance spilt phase motor.