Multiphase PM Research Articles

Semianalytical Model of Multiphase Halbach Array Axial Flux Permanent-Magnet Motor Considering Magnetic Saturation

This paper proposes a nonlinear semi-analytical model (SAM) of the multi-phase Halbach array axial flux permanent magnet motor (AFPMM) to speed up the computation of its magnetic field. Compared to the existing analytical models, the proposed nonlinear SAM can directly consider magnetic saturation to obtain more accurate results. To this end, the multi-phase Halbach Array AFPMM is equivalent to several 2-D models by the Quasi-3D method under the Cartesian coordinate system. Then, the nonlinear SAM is developed by using the convolution theorem and the fast Fourier factorization. The proposed nonlinear SAM is studied on a five-phase Halbach array AFPMM with different rotors, and the nonlinear finite element (FE) model and experiment verify its effectiveness. The proposed SAM is computationally efficient and accurate, and it is also applicable to other types of multi-phase Halbach array PM electrical motors in Cartesian coordinates.

A method to distinguish local demagnetization and short-circuit faults of six-phase interior permanent-magnet machine based on voltage in synchronous frame

Short-circuit fault and local demagnetization faults are two common fault types of permanent-magnet machines, aiming to improve the reliability of multi-phase PM machines in safety-critical applications, a method to distinguish these two kinds of faults in six-phase interior PM machines is proposed. The voltage characteristics in synchronous frame of local demagnetization fault and short-circuit fault are investigated, and the influences of load current and internal power factor angle on the voltage harmonic characteristics are analyzed. To solve the problem of the interaction between the extracted harmonic amplitudes in integer and non-integer orders, the average and variance of the harmonic coefficients of the voltages in synchronous frame are utilized to distinguish two types of faults. Through comparing the fault indices under different load conditions of the six-phase interior PM machine, the distinguishing ability of the method is validated.

Harmonic Model and Remedy Strategy of Multiphase PM Motor Under Open-Circuit Fault

Modular multiphase (MMP) PM motors have the ability to work continuously under a faulty mode. However, ripples in the spin torque of the motor and unbalanced forces incur rotor vibrations in postfault operations, which seriously degrade the performance of the PM motors. This paper presents a computationally efficient method to derive harmonic models for characterizing the pulsating torque and unbalanced forces of an MMP-PM motor under an open-circuit fault, and the corresponding optimal solutions to its inverse current model to remedy the fault. The model formulation, current harmonic identification, and remedial strategy for suppressing torque ripples and unbalanced forces are illustrated with an MMP-PM motor under an open-circuit fault; both odd and even number of phases are considered. The effectiveness of the harmonic models and remedy strategies are numerically validated with two typical (5- and 6-phase) MMP-PM motors under a one-phase/open- circuit fault and evaluated experimentally on a custom-designed 6-phase duplex motor .

Fuzzy hysteresis current control of five phase permanent magnet motor under open-circuit faults

This paper presents a new current controller of a PWM of multiphase PM machines with a fuzzy logic band. With this kind of system it is possible to determine optimal currents references which maximize the torque density of the system when one or two phases are open circuited. We propose in this paper to combine this optimal reference current generation with fuzzy hysteresis control band. This solution allows a good tracking of these unconventional reference currents with a fixed switching frequency for the VSI. The study carried on simulation via software MatLab/Simulink.

Energy-Efficient and Fault-Tolerant Control of Multiphase Nonsinusoidal PM Synchronous Machines

This paper presents development of energy-efficient and fault-tolerant control of multiphase nonsinusoidal PM synchronous machines by making use of the Hamiltonian of optimal control theory. An analytical solution for the optimal linearization control is derived in a closed form that eliminates machine torque ripples, maximizes machine efficiency, and defers output voltage saturation for nonconstant operational torque and speed. The controller can achieve voltage-to-torque linearization even for faulty motors with open-circuited phase(s) making it suitable for high-risk applications. This study is complemented by presenting an optimal indirect-torque control scheme based on internal current feedback loop with finite bandwidth. Simulation and experimental results are appended to underpin the performance of the energy-efficient and fault-tolerant controller.

FPGA Based Robust Open Transistor Fault Diagnosis and Fault Tolerant Sliding Mode Control of Five-Phase PM Motor Drives

The voltage-source inverters (VSI) supplying a motor drive are prone to open transistor faults. To address this issue in fault-tolerant drives applicable to electric vehicles, a new open transistor fault diagnosis (FD) method is presented in this paper. According to the proposed method, in order to define the FD index, the phase angle of the converter output current is estimated by a simple trigonometric function. The proposed FD method is adaptable, simple, capable of detecting multiple open switch faults and robust to load operational variations. Keeping the FD in mind as a mandatory part of the fault tolerant control algorithm, the FD block is applied to a five-phase converter supplying a multiphase fault-tolerant PM motor drive with non-sinusoidal unbalanced current waveforms. To investigate the performance of the FD technique, the fault-tolerant sliding mode control (SMC) of a five-phase brushless direct current (BLDC) motor is developed in this paper with the embedded FD block. Once the theory is explained, experimental waveforms are obtained from a five-phase BLDC motor to show the effectiveness of the proposed FD method. The FD algorithm is implemented on a field programmable gate array (FPGA).