Three-Phase and Five-Phase Motor Windings Common Point Potential Ripple with Respect to the Converter Zero Termina

The aim of the study is to determine the parameters characterizing the ripple of a motor's three- and five-phase windings common point potentials (for the star winding connection diagram) with respect to the converter zero point. One of the reserves for decreasing electromagnetically induced vibration of an electric motor with a rotating field is to increase the number of working winding phases. The study subject is a five-phase motor winding connected to a bridge converter, namely, its ability to reduce electromagnetically induced vibration in comparison with that in using a three-phase winding. The common point potential ripple parameters are studied, and an approach is proposed to estimating the amplitude modulation of the space-time voltage vector of three- and five-phase windings under the influence of the common point potential ripple with respect to the converter zero point. Theoretical studies were carried out using the Fourier series expansion method and vector analysis methods. To confirm the theoretical results, experimental studies of the prototypes of three-phase and five-phase synchronous motors with inductors made on the basis of permanent magnets were carried out. The main results have shown the following. With increasing the number of phases of the rotating field motor working winding connected to a bridge converter, the common point potential ripple amplitude with respect to the converter zero point decreases, and the ripple frequency increases. The product of ripple amplitude by frequency remains unchanged. It is assumed that the common point potential ripple of the motor multiphase winding with respect to the converter zero terminal results in the amplitude modulation of the space-time voltage vector. With increasing the number of winding phases, the modulation amplitude decreases, and the modulation frequency increases. A five-phase motor has a lower level of the working winding common point potential ripple with respect to the converter zero point in comparison with a three-phase motor. Thus, it can be assumed that there will be a lower level of electromagnetically induced vibration in using a simple converter operation algorithm. The obtained results can be used in designing electric traction systems with vector control on the basis of multiphase motors. With increasing the number of phases, the common point potential ripple amplitude in a multiphase winding with respect to the converter zero point decreases, and the ripple frequency increases. Thus, the common point potential ripple amplitude in a five-phase winding is 5/3 times less than that in a three-phase winding, and the ripple frequency increases by 5/3 times, respectively. With increasing the number of working winding phases, the amplitude modulation of the resulting space-time voltage vector decreases. This circumstance has a positive effect on decreasing the electromagnetically induced vibration.

Construction of Stability Regions in the Parameter Space in a Penning Trap with a Rotating Electric Field

The dynamics of particles in a Penning trap with a rotating dipole electric field and a buffer gas is considered. A transition is made to a coordinate system that rotates together with the electric field, which makes it possible to reduce the system of ordinary differential equations with periodic coefficients to a linear differential system with a constant matrix. Using one of the modifications of the Hurwitz stability criterionthe Lienard-Chipart criterion, the stability analysis (according to Lyapunov) of particle motions in the trap is carried out and the stability regions in the trap parameter space are found.Calculations were carried out for a trap with “typical” main parameters. The biggest degree of stability was obtained at frequencies of rotation of the field close to “resonant”. Small relative deviations from these frequencies led to a significant decrease in the degree of stability and loss of stability at “small” values of the amplitude of the rotating field. At the same time, it was possible to partially compensate this by increasing the amplitude of the rotating field, but only to certain limits, after which stability was again lost.

Adiabatic quantum estimation: A numerical study of the Heisenberg XX model with antisymmetric exchange

In this paper, we address the adiabatic technique for quantum estimation of the azimuthal orientation of a magnetic field. Exactly solving a model consisting of a two-qubit system, where one of which is driven by a static magnetic field while the other is coupled with the magnetic field rotating adiabatically, we obtain the analytical expression of the quantum Fisher information (QFI). We investigate how the two-qubit system can be used to probe the azimuthal direction of the field and analyze the roles of the intensities of the magnetic fields, Dzyaloshinskii–Moriya (DM) interaction, spin–spin coupling coefficient, and the polar orientation of the rotating field on the precision of the estimation. In particular, it is illustrated that the QFI trapping or saturation may occur if the qubit is subjected to a strong rotating field. Moreover, we discuss how the azimuthal direction of the rotating field can be estimated using only the qubit not affected by that field and investigate the conditions under which this strategy is more efficient than use of the qubit locally interacting with the adiabatically rotating field. Interestingly, in the one-qubit scenario, it was found that when the rotating field is weak, the best estimation is achieved by subjecting the probe to a static magnetic field.

3D motion of flexible ferromagnetic filaments under a rotating magnetic field

Experimental and numerical study of flexible ferromagnetic filaments reveal different regimes, when subjected to a 2D rotating field. The filaments were found to have a 3D motion at higher frequencies.