Q10Electrical Machine Design

Cylindrical (non-salient pole, round-rotor) construction is generally used for high-speed alternators (turbo-alternators, operating at 3000/3600 rpm), since this smooth, mechanically robust cylindrical rotor forging can withstand the very high centrifugal stresses of high-speed rotation, whereas a salient-pole construction (with protruding poles) would be mechanically unable to survive such stresses at high speed and is instead used only for lower-speed machines (hydro-generators).

Heat flow (heat transfer) is defined as the transfer of thermal energy from a region of higher temperature to a region of lower temperature, driven by the temperature gradient between them, occurring through one or more of three mechanisms: conduction (heat transfer through a solid material or stationary fluid via molecular/lattice vibration, without bulk material motion), convection (heat transfer via the bulk motion of a fluid, natural or forced, carrying thermal energy away from a surface), and radiation (heat transfer via electromagnetic waves, requiring no intervening medium). In electrical machine design, all three mechanisms are typically relevant at different stages of the heat path from the internal loss-generating source (windings/core) to the final ambient environment, and understanding and correctly calculating each is essential to the thermal design verification of any electrical machine.