Abstract
Electromagnetic analysis of hydropower generators is common practice but there is little emphasis on studying the effect of rotor whirling in the analysis. This paper demonstrates the use of the unbalanced magnetic pull (UMP) curves based on purely dynamic eccentricity motion for a wide range of whirling frequencies in the prediction of the steady state UMP in the case of mixed eccentricities motion. The latter motion type is more realistic in practice. Actual electromagnetic (EM) simulations are also carried out for these mixed eccentricities motion cases in order to verify the proposed method. Good agreement between the UMP from the actual EM simulations and the UMP predictions are made when low eccentricities exist. The proposed method is thus very useful since firstly, very few EM software packages can handle mixed eccentricities motion and secondly, since actual EM simulations of intricate rotor centre motion are time-consuming, the proposed method is a big time saver. A modified feature selective validation (FSV) method, the FSV-UPC, is also applied to assess the similarities and the differences in the force computations.
Highlights
R OTOR-stator eccentricity in electrical machines is an issue that has caught attention for a long time [1], [2] and is an important item in condition monitoring [3] in electrical machines
This section has as aim to present the forces obtained from the EM simulations with MagNet [17] for the truly simulated motion mixed eccentricities and those using Equation (9a)
In the purely dynamic eccentricity component of the mixed eccentricities motion, synchronous whirl was imposed as this is a common operating point of a hydropower generator
Summary
R OTOR-stator eccentricity in electrical machines is an issue that has caught attention for a long time [1], [2] and is an important item in condition monitoring [3] in electrical machines. Though many papers in the literature [4]–[8] have addressed the issue of eccentricity in rotating electrical machines, and other papers [9]–[12] have dealt with mixed eccentricities (where both static and dynamic eccentricities occur) motion, there has been generally a lack of papers that account for the effect of whirling of the rotor. Two publications that have considered whirling are [13], [14]. Rotor whirling in hydropower machines is not uncommon [15] in the forward direction of rotation though backward whirling of a rotor is considered to occur less frequently in practice. The rotor shaft in a vertical hydropower machine is directly connected to the turbine shaft. Any forces and dynamics from the water hitting the turbine blades will affect the rotor
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