Relative dimensions of Turbo and water wheel alternators - Design of Synchronous Machines

Relative dimensions of Turbo and water wheel alternators:

Turbo alternators are normally designed with two poles with a speed of 3000 rpm for a 50 Hz frequency. Hence peripheral speed is very high. As the diameter is proportional to the peripheral speed, the diameter of the high speed machines has to be kept low. For a given volume of the machine when the diameter is kept low the axial length of the machine increases. Hence a turbo alternator will have small diameter and large axial length.

However in case of water wheel generators the speed will be low and hence number of poles required will be large. This will indirectly increase the diameter of the machine. Hence for a given volume of the machine the length of the machine reduces. Hence the water wheel generators will have large diameter and small axial length in contrast to turbo alternators.

Introduction to Design

Synchronous machines are designed to obtain the following information’s.

(i)                                                 Main dimensions of the stator frame.

(ii)                                                 Complete details of the stator windings.

(iii)                                                 Design details of the rotor and rotor winding.

(iv)                                                Performance details of the machine.

To proceed with the design and arrive at the design information the design engineer needs the following information.

(i)                                                 Specifications of the synchronous machine.

(ii)                                                 Information regarding the choice of design parameters.

(iii)                                                 Knowledge on the availability of the materials.

(iv)                                                Limiting values of performance parameters.

(v)                                                 Details of Design equations.