Difference between revisions of "Balancing single/dual plane"

==Introduction==

A rotor is a shaft rotating around its axis during service. In general such a rotor consists of a shaft with one or more discs fitted to the axle. Such discs can be fly wheels, grinding wheels, turbine wheels, etc. The shaft is usually running in bearings allowing the rotation of the body.<br>

Depending on their rotational speed, rotors can be grouped in two basic categories: <u>rotors with rigid shaft</u>, and <u>rotors with flexible shaft</u>. If the operating speed remains below half of the first critical bending speed, the shaft does not deflect. At such operational speeds and non circular cross section of the rotor, the axis of rotation and the inertial axis does not coincide. This results in a tumbling movement of the structure, which amplitude depends on the bearing clearance and stiffness. In any case, the bearings are subjected to unnecessary or even non allowed loads. At higher speeds the shaft will deflect, due to the non symmetric circular cross section. Depending on the position of the discs on the shaft they can even be inclined and thus increase the oil whirl.<br>

An increase of the running quality is achieved through reduction of the asymmetry by means of addition or reduction of masses. Thus the inertial axis approaches the rotational axis. Rigid rotors can be sufficiently balanced in one or two planes. In practice depending of the number of transducers used and the number of planes four cases can be considered.