Paper 7: Fluid Flow Losses Associated with the Cooling of Electrical Machines

Abstract

One of the limitations in the design of electrical machines is that of the temperature rise of the machine components. The most effective method of limiting the temperature rise is to duct the cooling medium to the source of loss, without unduly inhibiting the electrical design. This often results in complicated fluid flow paths, which cannot be designed exclusively from the point of view of maintaining ideal flow conditions, in both stationary and rotating members.

As the fluid flow conditions, generally, are not ideal, the only effective method of determining the loss factors is by practical means. To establish the duct losses and flow distribution under simulated conditions, full-size and scale models of components of electrical machines (e.g. direct hydrogen-cooled turbine generators, a.c. machines, and d.c. machines) have been made and tested. The loss factors which have been obtained are compound factors for a particular geometry and result from the effects of entry and exit conditions, changes of section and, where applicable, the effects of rotation. No attempt to separate the losses has been made, except where well-documented losses, such as friction, are involved.

This paper illustrates the types of fluid flow paths encountered in electrical machines and presents the loss factors, obtained from tests, for some of these arrangements.