Abstract: The concept of rigid rotor and the basis of rigid rotor classification were introduced. The reasons of rotor unbalance fault were analyzed. The classification and characteristics of the unbalance faults were expounded. The method for field dynamically balancing was given. By listing some examples, the experiences of field dynamical balance handling were summarized. 

Key words: rigid rotor, dynamical unbalance fault, dynamically balancing technology, influence coefficient method