The evaluation of rotor unbalance in flexibly mounted machines

A method is presented to determine the state of unbalance of a rotating machine. The only requirement of the procedure is a good numerical model for the rotor and an approximate model for the bearing behaviour. No assumptions are made concerning the operational mode shape of the rotor and the influence of the supporting structure is included in a consistent manner. For simplicity the analysis is presented in a single plane orthogonal to the rotor axis, but no difficulty is forseen in extending the method to two planes. Examples are given for a two bearing system.