Turbo alternators have rotors of small diameter and long axial length.
Turbo alternators are large power-generating machines that are commonly used in power plants and other industrial applications.
These machines typically consist of a stationary stator and a rotating rotor, which is driven by a steam turbine or a gas turbine.
The rotors of turbo-alternators are designed to operate at high speeds, typically in the range of 3000-3600 rpm.
To achieve this high rotational speed, the rotors are made with a small diameter and a long axial length. This design helps to minimize the centrifugal forces on the rotor and reduce the stresses on the shaft and bearings.
The small diameter of the rotor also helps to reduce the weight and size of the alternator, making it easier to install and operate.
However, the small diameter of the rotor also means that the magnetic field in the machine is relatively weak, which can lead to issues with magnetic saturation and voltage regulation.
To overcome these issues, the rotor is often designed with a high number of poles, typically 10-24 poles, which helps to increase the magnetic flux density and improve the performance of the machine.