A direct rotor-field-oriented control of a dual-three phase induction motor drive is described in this paper. The induction machine has two sets of stator three-phase windings spatially shifted by 30 electrical degrees. The stator windings are fed by a current-controlled pulsewidth-modulation (PWM) six-phase voltage-source inverter. Three key issues are discussed: (1) the machine dynamic model is based on the vector space decomposition theory; (2) the PWM strategy uses the double zero-sequence injection modulation technique which gives good results with low computational and hardware requirements; and (3) to eliminate the inherent asymmetries of the drive power section, a new current control scheme is proposed. Experimental results are presented for a 10-kW dual three-phase induction motor drive prototype.

Digital field oriented control for dual three-phase induction motor drives

In this paper, a literature survey on the work accomplished in the area of multi-phase, split phase and dual stator machines will be presented. Although, reducing torque pulsation caused the early interest in dual stator, split phase and multiphase machines, there are other important features that this kind of machines present to the drive designer. Additional degrees of freedom in multi-phase machines are employed to improve the overall performance of the system. They can be used to improve the reliability of a multiphase system, to enhance the torque production capability of the machine by injecting harmonics of current or to control multi-motors from a single inverter. Also, the presence of more space voltage vectors, allows better adjustment of torque and flux in a direct torque controlled system.

On advantages of multi-phase machines

One of the significant tasks in data-driven fault diagnosis methods is to configure a good feature set involving statistical parameters. However, statistical parameters are often incapable of representing the dynamic behavior of planetary gearboxes under variable operating conditions. Although the use of deep learning algorithms to find a good set of features for fault diagnosis has somewhat improved diagnostic performance, the lack of domain knowledge incorporated into deep learning algorithms has limited further improvement. Accordingly, this paper developed a variant of deep residual networks (DRNs), the so-called deep residual networks with dynamically weighted wavelet coefficients (DRN+DWWC) to improve diagnostic performance, which takes a series of sets of wavelet packet coefficients on various frequency bands as an input. Further, the fact that no general consensus has been reached as to which frequency band contains the most intrinsic information about a planetary gearbox's health status calls for “dynamic weighting layers” in the DRN+DWWC and the role of the layers is to dynamically adjust a weight applied to each set of wavelet packet coefficients to find a discriminative set of features that will be further used for planetary gearbox fault diagnosis.

Deep Residual Networks With Dynamically Weighted Wavelet Coefficients for Fault Diagnosis of Planetary Gearboxes

Multiphase (more than three phases) drives possess several advantages over conventional three-phase drives, such as reducing the amplitude and increasing the frequency of torque pulsations, reducing the rotor harmonic currents, reducing the current per phase without increasing the voltage per phase, lowering the dc-link current harmonics, and higher reliability. By increasing the number of phases it is also possible to increase the power /torque per rms ampere for the same volume machine. This paper, therefore, presents a simple and straightforward approach to develop an indirect field-oriented control (FOC) scheme for a six-phase induction machine with an arbitrary displacement between the two three-phase winding sets. The two current-controlled pulsewidth-modulation three-phase voltage-source inverter independently feeds the two sets of three-phase stator windings. The scheme is based on simple two-axis (d-q) model of the six-phase induction machine, and can be easily extended to any number of phases, which are multiples of three. The unbalanced current sharing between the two three-phase stator-winding sets observed in earlier schemes is automatically eliminated, and the practical implementation of the scheme is simple. Necessary experimental and simulation results are presented to show the effectiveness of the proposed indirect FOC scheme. In the study, online analysis has been performed using C/sup ++/, while MATLAB /SIMULINK has been used to perform the offline analysis.

A simple indirect field-oriented control scheme for multiphase induction machine

This paper presents an analytical subdomain model to compute the magnetic field distribution in surface-mounted permanent-magnet (PM) motors with semi-closed slots. The proposed model is sufficiently general to be used with any pole and slot combinations including fractional slot machines with distributed or concentrated windings. The model accurately accounts for armature reaction magnetic field and mutual influence between the slots. The analytical method is based on the resolution of two-dimensional Laplace's and Poisson's equations in polar coordinates (by the separation of variables technique) for each subdomain, i.e., magnet, air gap, slot-opening, and slots. Magnetic field distributions, back-EMF, and electromagnetic torque (including cogging torque) computed with the proposed analytical method are compared with those issued from finite-element analyses.

https://hal.archives-ouvertes.fr/hal-00558543/document

2-D Exact Analytical Model for Surface-Mounted Permanent-Magnet Motors With Semi-Closed Slots

The major drawback of usual dual-stator ac machines, when supplied by a voltage-source inverter (VSI), is the occurrence of extra harmonic currents. These extra currents circulate only in the stator windings and cause additional losses. This paper deals with the modeling and design of dual-stator winding ac machines for safe operation with a VSI. A new reference frame model for a dual-stator induction machine (DSIM), including mutual leakage coupling, is proposed. This model allows us to highlight the previously mentioned circulating harmonic currents. The leakage inductance associated with these harmonics is shown to have quite a small value, highly depending on the coil pitch. It is also shown that full pitch is required, and that special slot shape designs should be investigated, to limit the magnitude of circulating currents. Experimental results on a prototype of a DSIM are presented and they show a very good correlation with theoretical curves.

On the modeling and design of dual-stator windings to minimize circulating harmonic currents for VSI fed AC machines

The paper deals with the possibility of replacing a mechanical planetary gear system by a magnetic planetary gearbox. The magnetic planetary gearbox has many advantages such as contact-free, no gear lubrication, high-speed-reduction ratio and high durability. Firstly, the principle of operation, design equations and Willis relation for the magnetic and the mechanical planetary gears are given. A comparative study between the two systems in terms of torque transmission capabilities is presented.

Comparative Study Between Mechanical and Magnetic Planetary Gears

This paper deals with an analytical method for magnetic field calculation in the air gap of cylindrical electrical machines including slotting effects. The analytical method is based on the resolution of the two-dimensional Laplace's equation in polar coordinates by the separation of variables technique. The originality of the proposed model is to take into account the mutual influence of slots on the air-gap magnetic field. The proposed method is sufficiently general to be used as a tool for air-gap magnetic field calculation of slotted electrical machines as reluctance or permanent magnet motors or actuators. Magnetic field and electromagnetic torque computed with the proposed analytical method are validated through finite-element analysis.

/pdf/exact-analytical-method-for-magnetic-field-computation-in-4d4iudwha3.pdf

Exact Analytical Method for Magnetic Field Computation in the Air Gap of Cylindrical Electrical Machines Considering Slotting Effects

This paper compares the prediction of two independent methods for calculating electromagnetic torque and inductances of a synchronous reluctance machine under linear condition. One method is based on winding function analysis (WFA) and the other on finite-element analysis (FEA). Both methods take into account the rotor geometry, the stator slot effects and the stator winding connections. The simulation results obtained by the WFA are compared with the ones obtained by two-dimensional FEA. It is shown that the two methods give approximately the same results but require different computation times.

/pdf/comparison-between-finite-element-analysis-and-winding-cppewq5ar6.pdf

A. Rezzoug

Papers

2-D Exact Analytical Model for Surface-Mounted Permanent-Magnet Motors With Semi-Closed Slots

On the modeling and design of dual-stator windings to minimize circulating harmonic currents for VSI fed AC machines

Comparative Study Between Mechanical and Magnetic Planetary Gears

Exact Analytical Method for Magnetic Field Computation in the Air Gap of Cylindrical Electrical Machines Considering Slotting Effects

Comparison Between Finite-Element Analysis and Winding Function Theory for Inductances and Torque Calculation of a Synchronous Reluctance Machine