In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Ferromagnetic materials

An introduction to heat transfer

Although the concept of variable-speed drives, based on utilization of multiphase machines, dates back to the late 1960s, it was not until the mid- to late 1990s that multiphase drives became serious contenders for various applications. These include electric ship propulsion, locomotive traction, electric and hybrid electric vehicles, ldquomore-electricrdquo aircraft, and high-power industrial applications. As a consequence, there has been a substantial increase in the interest for such drive systems worldwide, resulting in a huge volume of work published during the last ten years. An attempt is made in this paper to provide a brief review of the current state of the art in the area. After addressing the reasons for potential use of multiphase rather than three-phase drives and the available approaches to multiphase machine designs, various control schemes are surveyed. This is followed by a discussion of the multiphase voltage source inverter control. Various possibilities for the use of additional degrees of freedom that exist in multiphase machines are further elaborated. Finally, multiphase machine applications in electric energy generation are addressed.

Multiphase Electric Machines for Variable-Speed Applications

The area of multiphase variable-speed motor drives in general and multiphase induction motor drives in particular has experienced a substantial growth since the beginning of this century. Research has been conducted worldwide and numerous interesting developments have been reported in the literature. An attempt is made to provide a detailed overview of the current state-of-the-art in this area. The elaborated aspects include advantages of multiphase induction machines, modelling of multiphase induction machines, basic vector control and direct torque control schemes and PWM control of multiphase voltage source inverters. The authors also provide a detailed survey of the control strategies for five-phase and asymmetrical six-phase induction motor drives, as well as an overview of the approaches to the design of fault tolerant strategies for post-fault drive operation, and a discussion of multiphase multi-motor drives with single inverter supply. Experimental results, collected from various multiphase induction motor drive laboratory rigs, are also included to facilitate the understanding of the drive operation.

/pdf/multiphase-induction-motor-drives-a-technology-status-review-1ir91893ja.pdf

Multiphase induction motor drives - : a technology status review

This paper investigates diagnostic techniques for electrical machines with special reference to induction machines and to papers published in the last ten years. A comprehensive list of references is reported and examined, and research activities classified into four main topics: 1) electrical faults; 2) mechanical faults; 3) signal processing for analysis and monitoring; and 4) artificial intelligence and decision-making techniques.

Advances in Diagnostic Techniques for Induction Machines

Solid Rotor Induction Machines (SRIM) gained lot of interesting in the last decades due to the increasing demand for high speed drives. The low manufacturing cost, the rotor robustness and the capability operating in of harsh environments comes along with the drawbacks of difficult design process, necessity of multi-physics analysis and poor power factor. The single phase lumped parameter equivalent circuit is widely adopted for design and analysis purposes. The impact of the solid rotor material properties as saturation flux density, relative permeability and electrical resistivity are discussed in this work for what concerns mainly the rotor resistance and rotor leakage inductance. Finite Element simulations are performed to determine the equivalent circuit parameters dependencies on the solid material selected for the rotor structure.

Sensitivity analysis of rotor parameters in solid rotor induction machine

This paper investigates detailed aspects involved in the electrical machine topology selection for high speed automotive superchargers, through a case study involving a 48V 15kW peak application. The transient nature of the application is taken into account together with the different cooling options available to the electrical machine within the vehicle.

Electrical machine type selection for high speed supercharger automotive applications

Electrical machines with high torque density are required for traction application. Availability of bonded magnets with complex shapes and magnetization pattern can significantly extend the design space of electrical machines. This paper introduces a hybrid flux barriers design to improve the torque density of permanent magnet assisted synchronous reluctance (PM -SynRel) machine using ferrite magnets. The torque density with hybrid flux barriers is found to improve along the entire range of speed compared to the conventional flux barriers. The hybrid barrier design achieves similar performance to that of curved barrier with relatively flat shaped magnets in the last flux barrier. Thus, the hybrid barrier is able to enhance the torque density at a potentially reduced cost of manufacturing. The hybrid flux barrier design is validated for both electromagnetic and mechanical performance using commercial finite element analysis (FEA) packages.

/pdf/enhancing-the-torque-density-of-conventional-pm-synrel-kyzzp7xg81.pdf

Enhancing the Torque Density of Conventional PM-SynRel Machine with Hybrid Flux Barrier

This paper describes the methodology adopted for the numerical thermal modelling of both submerged jets (single phase) and nebulized jets (multi-phase) used for the cooling of hairpin type end-windings. The work highlights the challenges arising when modelling discrete phases using computational fluidynamics (CFD) and proposes a setup for effectively capturing the physics whilst maintaining an acceptable level of computational cost of the simulations involving multi-phase cases. Additionally, a comparison of the cooling performance of the two strategies is carried out by observing the convective phenomena. Indeed, despite the overall lower fluid velocity achieved, the single-phase case shows an heat transfer rate double compared to the spray cooling and more uniform temperature distribution all over the winding surface thanks to the bigger level of penetration through the gaps in between the conductors.

Numerical Thermal Modelling of Multiphase Spray Cooling of Hairpin Windings

The present trend of aerospace industries is being shifted towards a “More Electric Aircraft” system which needs to be high power dense. For this purpose, the integration technologies have gained massive interest, providing the benefits of reduced losses, weight, volume and cost. In this article, the integration concept of a passive filter inductor is presented for a permanent magnet synchronous motor. The integrated motor eliminates the need of an external inductor, thus, eliminates the added inductor losses, mass, volume and cost associated with it. The motor utilizes its’s inherent inductance to use it as a filter inductor instead of implementing a discrete inductor that is commonly placed between inverter and the motor terminals. Optimization study is carried out, where the filter branch windings are tapped, in terms of improving mass and volume and performance parameters such as power losses and torque ripple. From the optimization study, the motor with minimum weight and volume is experimentally validated at the rated conditions, in order to prove the concept feasibility. Total system weight and volume of integrated and traditional motor drives are compared, which gives the minimum weight of 2.26 kg and 3.14 kg respectively, and the minimum volume of 0.54 L and 1.1 L respectively.

https://www.mdpi.com/1996-1073/14/15/4564/pdf

Chris Gerada

Papers

Sensitivity analysis of rotor parameters in solid rotor induction machine

Electrical machine type selection for high speed supercharger automotive applications

Enhancing the Torque Density of Conventional PM-SynRel Machine with Hybrid Flux Barrier

Numerical Thermal Modelling of Multiphase Spray Cooling of Hairpin Windings

Integrated Motor Drive: Mass and Volume Optimization of the Motor with an Integrated Filter Inductor