What is Static unbalance?

Static unbalance is an eccentricity of the center of gravity of a rotor, caused by a point mass at a certain radius from the center of rotation. An equal mass placed on the opposite side (180 deg) will balance the rotor.

Static unbalance is classified as single-plane unbalance, meaning that it is represented by a single vector quantity and corrected by a single correction mass applied opposite to the unbalance location and in the axial plane of the mass center of the rotor. When there is no way to add (or remove) mass in the same plane as the unbalance, the correction can be split into two equal corrections at the ends of the rotor to achieve the same results. Static unbalance can be detected by nonrotational equipment and is characterized by the fact that the principal axis is displaced parallel to the shaft axis,