Design of synchronous reluctance motors with multiobjective optimization algorithms

The automatic design of Synchronous Reluctance (SyR) machines is considered in this paper by means of Finite Element Analysis and Multi-Objective Optimization Algorithms (MOOA). The research focuses on the design of the rotor geometry which is the key aspect of the SyR machine design. In particular, the performance of three popular MOOAs is analyzed and compared in terms of quality of the final design and computational time. A procedure to minimize the computational burden of the optimized design process is introduced and applied to a three layer and to a five layer rotors. Two prototypes demonstrate experimentally the feasibility of the design procedure

Automatic design of Synchronous Reluctance motors focusing on barrier shape optimization

The automated design of Synchronous Reluctance motors based on Multi-Objective, Genetic Optimization and Finite Element Analysis is considered in this paper. Three types of barrier shapes are considered, all described by an effective, limited set of input variables. The three solutions are investigated to establish which of the geometries can give the best torque output and also which one represents the best compromise between output performance and computational time. The analysis presented in this paper shows that Synchronous Reluctance motors designed automatically can give a good performance, can be designed in a reasonable time and it is also shown that not all design degrees of freedom are useful in terms of motor performance. Two prototypes of automatically designed machines have been fabricated and experimentally compared to a third prototype designed according to state-of-the-art design principle

A two degrees of freedom system for wheel traction applications

In this paper, the use of conical induction machines is proposed for an in-wheel traction application. Such machines offer a rotational movement combined with a translational motion of the rotor. The horizontal movement is essential when active engagement and disengagement of the motor from the wheel without any extra mechanical component is required. This paper first investigates the basic concepts of how the conical machine functions and then proposes a mission strategy for a relevant traction application. A detailed description of the full scheme is given. In order to achieve the required performance, an innovative control method for both degrees of freedom of the machine (i.e. torque production and axial movement) is proposed and validated against a small-scale demonstrator of the whole system

Axial position estimation of conical shaped motor for green taxiing application

This paper considers the possibility of adopting a conical shaped motor for Green Taxiing (GT) application. This topology of motor has been selected in order to obviate the presence of external declutching system (i.e. mechanical or electromagnetic clutch) interposed between the electric actuator and the wheel. An axial force contributes to move the rotor inside-out of the stator (principle of sliding-rotor). The axial movement of the rotor can be monitored acting on the magnetizing current. The axial sensor-less position estimation method described hereafter envisages the possibility of evaluating the axial position of the rotor during the engaging and disengaging movement from the wheel. The axial position calculation is dependent on the inductance of the motor. An “on¬line” computation of the position has been implemented through the use of high-frequency injection signals

Axial position estimation of conical shaped motors for aerospace traction applications

This paper is concerned with the use of conical induction machines. Such machines are extremely valuable when apart from the rotational torque output, an axial translation of the rotor is also required. The inherent attraction between the stator and rotor of any machine, combined with the geometry of a conical machine will provide the required axial movement. However, when applied to aerospace applications, where reliability is very important, then full monitoring of the axial position is required. In this paper, an innovative approach aimed at monitoring and controlling the axial translation of a conical induction machine is proposed and investigated. In order to increase the system reliability and also decrease component count, as demanded by the application, the methodology is a sensor-less technique, based on an innovative variant of the high-frequency injection approach. In this paper, the technique has been fully investigated and experimentally validated on a purposely-built, instrumented test-rig

Effect of the numbers of slots and barriers on the optimal design of synchronous reluctance machines

This paper analyzes the impact of the numbers of stator slots and rotor layers on the optimal design of synchronous reluctance (SyR) machines. Eighteen SyR machine examples have been designed by means of a multi-objective optimization algorithm and finite element analysis so to maximize torque and minimize torque ripple. Twelve, twenty-four and forty-eight slot stators are considered, associated to rotors with fourpoles and one to six flux barriers per pole. The results of the comparative analysis show that high numbers of slots and layers are beneficial for maximizing the torque and the power factor, and that torque ripple and iron loss minimization require precise matches between the slots and the layers, which are not necessarily the same for the two purposes. Finally, for some slot/layer combinations the optimization algorithm produces nonconventional barrier distributions, very promising is some cases. A fast finite element evaluation is used for the evaluation of thousands of candidate machines during the optimization, whereas an accurate transient with motion finite element analysis stage is used for the off-line characterization of the final designs

Performance assessment of ferrite- and neodymiumassisted synchronous reluctance machines

Growing attention towards environmental sustainability of energy conversion and stricter efficiency standards are encouraging the market penetration of high-efficiency electrical motors. Current regulations define international efficiency classes and the testing procedures for direct-on-line machines only, commonly induction motors. Synchronous reluctance machines are a valid alternative to the widely employed induction motors for variable-speed applications, due to their low manufacturing cost and higher efficiency. With proper design, torque ripple can be mitigated as much as to make rotor skewing unnecessary for most of applications. The low power factor downside can be fixed by inserting low-cost ferrite magnet into the rotor barriers, with benefits also on the torque capability and constant power speed range. The aim of this paper is to assess the performance and efficiency potential of one synchronous reluctance and two permanent magnet-assisted synchronous reluctance machine prototypes, obtained by replacing the rotor of a general-purpose induction motor with the said synchronous reluctance ones. The rotor barriers have been designed by means of a genetic optimization algorithm has and then adapted to insert commercially available magnets, compliant with minimum extracost requirements. The two prototypes were comprehensively characterized, to validate the design phase and to investigate the performance of the machines. The provided experimental results are critically examined and commented

Analysis and Application of the Direct Flux Control Sensorless Technique to Low-Power PMSMs

In the field of sensorless control of permanent magnet synchronous motors (PMSMs), different techniques based on machine anisotropies have been studied and implemented successfully. Nevertheless, most proposed approaches extract the rotor position information from the measured machine currents, that, when applied to low-power machines, might require high-bandwidth current sensors. An interesting alternative is given by sensorless techniques that exploit the star-point voltage of PMSMs, such as the direct flux control technique. This work aims at analyzing the conditions of applicability of such technique by considering a more thorough description of the machine inductance matrix. After a comprehensive mathematical description of the technique and characterization of the machine anisotropy information that is extracted from the star-point voltage, simulation as well as experimental results conducted on a test machine are presented and discussed in order to validate the proposed theory

Transient Overload Characteristics of PM-Assisted Synchronous Reluctance Machines, Including Sensorless Control Feasibility

Synchronous reluctance machines are a highefficiency alternative to induction motors for variable-speed applications. To mitigate the well-known downside of their lower power factor, permanent-magnet-assisted topologies, in which either rare-earth or ferrite magnets are inserted into the rotor in suitable quantities, are often adopted. The design and optimization procedures for PM-assisted topologies have been thoroughly discussed in the related literature. This paper compares synchronous reluctance machines assisted with NdFeB and ferrite magnets, focusing on torque overload capability and feasibility of saliency-based position estimation algorithms. Three prototypes were realized and tested. They all have the stator of a commercial induction motor and the same customdesigned synchronous reluctance rotor laminations. Of the three prototypes, one is a pure synchronous reluctance motor, and the other two have NdFeB and ferrite magnets, respectively; both are designed to give the same torque at rated current. Results from simulations and experiments are presented comparing the transient overload capability of the three machines, in terms of torque capability and de-magnetization limit. A dynamic thermal model of the machines was developed within this scope. Moreover, the feasibility of saliency-based sensorless methods was investigated and is presented here for the three machines, both at high- and low-current loads. The results of the paper suggest that the ferrite-assisted solution is the best candidate for replacing induction motors in variable-speed applications, for its optimal tradeoff between performance and cost

Analysis and Detection of Electrical Aging Effects on High-Speed Motor Insulation

© 1972-2012 IEEE. The use of fast wide-bandgap devices in high-speed electrical drives with steep pulsewidth modulation voltage waveforms is the main cause of increased stress on the electric machine insulation system and consequently, of reduced reliability of the whole system. This represents a major concern in safety-critical applications, such as in the aerospace and electric transportation fields. The novel contribution of this work is to assess the effects of electrical aging on complex insulation systems (i.e., a whole stator winding) by analyzing easily measurable macroscopic quantities. To this purpose, an electrical aging procedure is defined, and the effects produced on three tested motors are presented. Three different analysis methods are adopted with the aim of assessing the damage caused to an ac motor winding by such steep voltage waveforms and hence to evaluate the state of aging of the insulation system