Leila Parsa

Five-phase permanent-magnet motor drives

A five-phase brushless permanent-magnet (PM) motor is introduced. The proposed motor has concentrated windings such that the produced back electromotive force is almost trapezoidal. The motor is supplied with the combined sinusoidal plus third harmonic of currents. This motor, while generating the same average torque as an equivalent PM brushless dc motor (BLDC), overcomes its disadvantages. The motor equations are obtained in the d/sub 1/q/sub 1/d/sub 3/q/sub 3/0 rotating reference frame. Therefore, the so-called vector control is easily applicable to this kind of motors and the motor has the same controllability as a PM synchronous motor (PMSM). For presenting the superior performance of the proposed five-phase motor, its three and five-phase PMSM and BLDC counterparts are also analyzed. Finite element method is used for studying the flux density and calculating the developed static torque. Also, the developed torque is obtained using the mathematical model in the d-q reference frame. The average torque and the torque ripple for all cases are calculated and compared. Experimental results are in good agreement with the simulation results.

Recent Advances in Modeling and Online Detection of Stator Interturn Faults in Electrical Motors

Online fault diagnosis plays a crucial role in providing the required fault tolerance to drive systems used in safety-critical applications. Short-circuit faults are among the common faults occurring in electrical machines. This paper presents a review of existing techniques available for online stator interturn fault detection and diagnosis (FDD) in electrical machines. Special attention is given to short-circuit-fault diagnosis in permanent-magnet machines, which are fast replacing traditional machines in a wide variety of applications. Recent techniques that use signals analysis, models, or knowledge-based systems for FDD are reviewed in this paper. Motor current is the most commonly analyzed signal for fault diagnosis. Hence, motor current signature analysis is a topic of elaborate discussion in this paper. Additionally, parametric and finite-element models that were designed to simulate interturn-fault conditions are reviewed.

Fault-Tolerant Interior-Permanent-Magnet Machines for Hybrid Electric Vehicle Applications

Multiphase interior permanent magnet (IPM) motors are very good candidates for hybrid electric vehicle applications. High torque pulsation is the major disadvantage of most IPM motor configurations. A five-phase IPM motor with low torque pulsation is discussed. The mathematical model of the five-phase motor is given. A control strategy that provides fault tolerance to five-phase permanent-magnet motors is introduced. In this scheme, the five-phase system continues operating safely under loss of up to two phases without any additional hardware connections. This feature is very important in traction and propulsion applications where high reliability is of major importance. The system that is introduced in this paper will guarantee high efficiency, high performance, and high reliability, which are required for automotive applications A prototype four-pole IPM motor with 15 stator slots has been built and is used for experimental verification.

Automotive Electric Propulsion Systems With Reduced or No Permanent Magnets: An Overview

Hybrid and electric vehicle technology has seen rapid development in recent years. The motor and the generator are at the heart of the vehicle drive and energy system and often utilize expensive rare-earth permanent magnet (PM) material. This paper reviews and addresses the research work that has been carried out to reduce the amount of rare-earth material that is used while maintaining the high efficiency and performance that rare-earth PM machines offer. These new machines can use either less rare-earth PM material, weaker ferrite magnets, or no magnets; and they need to meet the high performance that the more usual interior PM synchronous motor with sintered neodymium-iron-boron magnets provides. These machines can take the form of PM-assisted synchronous reluctance machines, induction machines, switched reluctance machines, wound rotor synchronous machines (claw pole or biaxially excited), double-saliency machines with ac or dc stator current control, or brushless dc multiple-phase reluctance machines.

Fault-Tolerant Control of Five-Phase Permanent-Magnet Motors With Trapezoidal Back EMF

This paper presents fault-tolerant control techniques for five-phase permanent-magnet motors with trapezoidal back electromotive forces under various open-circuit conditions. The proposed fault-tolerant control methods use only the fundamental and third-harmonic current components for the excitation of the healthy stator phases. The control techniques are developed by applying a concept that correlates the currents in the healthy phases based on their symmetry in space with respect to the fault in a machine. Optimum solutions under the single-phase open-circuit fault condition and double-phase open-circuit fault conditions are presented. The presented solutions are derived to increase the average output torque while reducing the torque pulsations and satisfying the zero-neutral-current constraint. Detailed experimental results are presented for the verification of the proposed solutions.

On advantages of multi-phase machines

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.

An Efficient High-Step-Up Interleaved DC–DC Converter With a Common Active Clamp

This paper presents a high-efficiency and high-step-up nonisolated interleaved dc-dc converter with a common active-clamp circuit. In the presented converter, the coupled-inductor boost converters are interleaved. A boost converter is used to clamp the voltage stresses of all the switches in the interleaved converters, caused by the leakage inductances present in the practical coupled inductors, to a low voltage level. The leakage energies of the interleaved converters are collected in a clamp capacitor and recycled to the output by the clamp boost converter. The proposed converter achieves high efficiency because of the recycling of the leakage energies, reduction of the switch voltage stress, mitigation of the output diodes reverse recovery problem, and interleaving of the converters. Detailed analysis and design of the proposed converter are carried out. A prototype of the proposed converter is developed, and its experimental results are presented for validation.

An Optimal Control Technique for Multiphase PM Machines Under Open-Circuit Faults

In this paper, an optimal control technique for n-phase permanent-magnet (PM) machines under various open circuit faults is presented. Under the fault conditions, the currents in the healthy phases are controlled to compensate phase loss and to produce the required output torque. The proposed control technique ensures continuous operation of the machines while producing minimum torque ripples and minimum stator ohmic loss. The control technique is based on the instantaneous power balance theory. To set the summation of the phase currents equal to zero, a constraint is incorporated in the derivation of the control technique. A five-phase PM machine is considered to demonstrate the proposed open circuit fault-tolerant control strategy. Simulation and experimental results are provided for validation.

Fault-tolerant five-phase permanent magnet motor drives

In this paper, a control strategy that provides fault tolerance to five-phase permanent magnet motors is introduced. In this scheme, the five-phase permanent magnet (PM) motor continues operating safely under loss of up to two phases without any additional hardware connections. This feature is very important in traction and propulsion applications where high reliability is of major importance. The five-phase PM motors with sinusoidal and quasi-rectangular back-EMFs have been considered. To obtain the new set of phase currents to be applied to the motor during fault in stator phases or inverter legs, the torque producing MMF by the stator is kept constant under healthy and faulty conditions for both cases. Simulation and experimental results are provided to verify that the five-phase motor continues operating continuously and steadily under faulty conditions.

Interior Permanent Magnet Motors With Reduced Torque Pulsation

In this paper, three-phase interior permanent magnet brushless DC motors are analyzed. The effect of magnetization direction, number of stator slots, winding distribution, skew angle, current waveform, and advance angle on torque pulsation is examined. Finite element method is used to calculate the torque, reluctance torque, back iron flux density, tooth flux density, detent torque, and back electromotive force of the motors. Switching instants are calculated such that the reluctance torque can be utilized and maximum torque with reduced pulsation is achieved. Experimental results to support the simulation findings are included in this paper.