Article

Comparison of the Unbalanced Magnetic Pull Mitigation by the Parallel Paths in the Stator and Rotor Windings

Helsinki Univ. of Technol., Helsinki
IEEE Transactions on Magnetics (Impact Factor: 1.42). 01/2008; DOI: 10.1109/TMAG.2007.906885
Source: IEEE Xplore

ABSTRACT An eccentric rotor creates an electromagnetic force between the rotor and stator of an electrical machine. This force tends to further increase the rotor eccentricity and may severely degrade the performance of the machine, causing acoustic noise, vibration, excessive wear of bearing, rotor and stator rubbing, and so forth. Parallel connections are known to be a simple yet effective remedy for the problems associated with rotor eccentricity. We have investigated two common types of electrical machines running with eccentric rotors. We examined operation over a wide whirling frequency range. We numerically evaluated and compared the effects of parallel connections in the stator and rotor windings on the eccentricity force. We found that the parallel stator windings can be more effective in mitigating the unbalanced magnetic pull than the rotor cage (or damper winding), which normally has many more parallel circuits.

1 Bookmark
 · 
194 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, a new eccentricity compensation method for Switched Reluctance Machines (SRMs) is presented. Eccentricity faults are very common in these machines; nevertheless there are little literatures addressing the control and compensation on this issue. It is theoretically shown that the occurrence and growth of the eccentricity fault change the amplitude of radial forces (RF) exerted on the rotor and accordingly the amplitude of the unbalanced magnetic force (UMF) is increased, these RFs can be controlled to compensate the fault. In this regard, the dependency of RF on variation of number of turns for stator coils and fault level is demonstrated analytically and principle of the new compensation strategy is introduced as well. This strategy is implemented on a SRM utilizing Finite Element Method (FEM). This approach is accomplished through switching among the various arrangements in the number of turns for the coils on the stator poles; hence, UMF is controlled without additional auxiliary coils.
    Power Electronics, Drive Systems and Technologies Conference (PEDSTC), 2013 4th; 01/2013
  • [Show abstract] [Hide abstract]
    ABSTRACT: This paper studies static eccentricity (SE) fault detection in axial-flux permanent-magnet (AFPM) machines using 3-D finite-element analysis. The use of numerical modeling makes it possible to precisely study the eccentricity fault detection in these types of machines. The simulations are validated using experimental measurements. To the best knowledge of the authors, SE fault detection in AFPMs has not been studied before. Hence, a new definition for the SE factor is presented in these types of machines. A motor with different degrees of rotor eccentricity is simulated, and the back electromotive force (EMF) of all coils of the stator is obtained. In addition, an appropriate criterion has been presented for the fault detection using the back EMF of the coils. This study indicates that the back EMF of the coils of the stator is a good criterion for eccentricity fault detection. It is observed that the unbalanced back EMF suggests a method for the indirect measurement of eccentricity that could be carried out during manufacturing and assembling processes or maintenance operation.
    IEEE Transactions on Industry Applications 01/2012; 48(6):1838-1845. · 1.67 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, formulas to calculate possible UMFs during assembly process are introduced in order to save calculation time and efforts without using a fully configured 3-dimensional (3-D) analysis model. To calculate the UMFs according to the degree of rotor eccentricity in every time that the rotor position is relatively changed to the stator position in axial direction, the proposed formulas are used with a fully configured 2-dimensional (2-D) model or 2-D and 3-D periodic analysis models. The reliance of the formulas is verified by comparing the results calculated by the formulas and showing the agreement. Then, assembly jigs are designed considering the calculated UMFs.
    Electromagnetic Field Problems and Applications (ICEF), 2012 Sixth International Conference on; 01/2012