Q. Nonsalient-pole rotor construction?

The nonsalient-pole (smooth or cylindrical) rotor construction is preferred for high-speed turbine-driven alternators (known also as turbo alternators or turbine generators), which are usually of two or four poles driven by steamturbines or gas turbines. The rotors for suchmachines may be made either from a single steel forging or from several forgings shrunk together on the shaft.

The maximum value of the induced voltage is

which are identical in form to the corresponding emf equations for a transformer. The effect of a time-varying flux in association with stationary transformer windings is the same as that of the relative motion of a coil and a constant-amplitude spatial flux-density wave in a rotating machine. The space distribution of flux density is transformed into a time variation of voltage because of the time element introduced by mechanical rotation. The induced voltage is a single-phase voltage for single-phase synchronous machines of the nature discussed so far. As pointed out earlier, to avoid the pulsating torque, the designer could employ polyphase windings and polyphase sources to develop constant power under balanced conditions of operation.