Janne Keränen

Torque Density of Radial, Axial and Transverse Flux Permanent Magnet Machine Topologies

Torque density of radial, axial and transverse flux machine topologies is investigated. A 10-kW, 200-rpm motor is chosen as a test case. Radial and axial flux motors that fulfill the key specifications of the selected test case are designed employing in-house analytical dimensioning tools and MATLAB genetic multi-objective optimization. Rather simple numerical approach is taken to study the transverse flux motor. A 20-pole-pair radial flux motor is found to outperform its axial and transverse flux counterparts in terms of torque density.

Efficient Parallel 3-D Computation of Electrical Machines With Elmer

After its recent improvements described here, open source finite element software Elmer is shown to be a highly efficient option for electrical machine modeling. The parallelization of computational burden is shown to be a necessity. The methods implemented enable applying fully parallel computation to electrical machine models, including rotation and electrical circuits. Computational experiments performed demonstrate that Elmer can effectively utilize several hundreds of computational cores in parallel, making it an attractive alternative when computational speed is of high importance.

Multi-slice 2.5D modelling and validation of skewed electrical machines using open-source tools

This paper describes multi-slice modelling and validation of an axially skewed synchronous machine in 2D domain. The technique involves coupling of circuit and electromagnetic domains together with carefully constructed geometry. The model size in comparison with full 3D simulation reduces considerably. Developed 2.5D multi-slice model allows fast simulation in 2D domain, still taking into account 3D effect of skew on torque and back-EMF of the machine. Simulation results in 2.5D and 3D domains are compared to measurements. All simulations are performed using free and open-source tools.

Drying of foam-formed mats from virgin pine fibers

ABSTRACT The purpose of this work was to select an efficient drying technique for drying of highly porous thick fiber foam mats with minimum impact on their structure after forming and drainage. Thick fiber mats were produced from wood fibers using foam-forming technology and dried using several different drying methods. The mixture of pine fibers and surfactant (foaming agent) in water was blended using a high-speed blender. After fiber foam generation, a sample mold was filled with wet fiber foam, and after drainage, drying experiments were performed. For comparison, experiments were carried out in an oven, an impingement dryer assisted with a vacuum, and a combined impingement-infrared dryer. At low moisture contents, through-air drying experiments were also carried out. Drying curves, temperature profiles, and shrinkage were measured from the produced mat structures. The most promising drying technique in this study was the combined impingement-infrared drying, used until the fiber mat became permeable, followed by through-air drying until the desired final moisture content was achieved.

Magnetic bearing as Switched Reluctance Motor - feasibility study for bearingless Switched Reluctance Motor

This paper shows a general review of Switched Reluctance Motors (SRM), reports the conversion of Active Magnetic Bearing (AMB) to SRM and discusses methods to estimate the torque produced in SRM. AMB converted to SRM has been tested on a laboratory scale test rig and its torque production measured. The novelty of this paper is the modified analytical method to estimate fringing flux paths enabling more accurate mathematical model to estimate torque. The reason for careful analysis of the air gap forces is the demand for electromagnetic models of the motor to be used in the motor controller. The ultimate goal of our work is to develop self-bearing (self-levitating bearingless) SRM.

Validation of Model-Based Testing in Hardware in the Loop Platform

Model-based testing (MBT) in hardware-in-the-loop (HIL) platform is a simulation and testing environment for embedded systems, in which test design automation provided by MBT is combined with HIL methodology. A HIL platform is a testing environment in which the embedded system under testing (SUT) assumes to be operating with real-world inputs and outputs. In this paper, we focus on presenting the novel methodologies and tools that were used to conduct the validation of the MBT in HIL platform. Another novelty of the validation approach is that it aims to provide a comprehensive and many-sided process view to validating MBT and HIL related systems including different component, integration and system level testing activities. The research is based on the constructive method of the related scientific literature and testing technologies, and the results are derived through testing and validating the implemented MBT in HIL platform. The used testing process indicated that the functionality of the constructed MBT in HIL prototype platform was validated.

Detecting abnormal activities from multi-sensor surveillance systems

The main purpose of a surveillance system is to monitor valuable assets, such as office buildings and homes, and report any occurring security incidents. Sensor malfunctions or abnormal usages of the system are possible scenarios in a real life and a surveillance system with hundreds of sensors is creating a vast amount of data which is impossible to handle manually. This renders the fixing of these potential faults slow and expensive. This paper proposes a system which can analyse data received from a surveillance system. The proposed system will report abnormal activities, such as malfunctioning or dead sensors, abnormal usage, and abnormal events created by the surveillance system. The experimental evaluation is performed by using six cases describing different types of abnormal activity. The experiments indicate that the proposed system can effectively pinpoint faulty sensors and other abnormal activities. This will ease the task of the maintenance personnel to locate and fix possible problem in the surveillance system.

Parallel Performance of Multi-Slice Finite-Element Modeling of Skewed Electrical Machines

The multi-slice method allows approximation of the 3-D phenomena without carrying out a full 3-D analysis, e.g., in skewed radial flux electrical machines. The idea is to divide a 3-D machine into several 2-D finite-element models along the axis, connected by electrical circuits. Here we show how the multi-slice method is perfect for parallel computation; the computation efficiency is close to that of 2-D models in modern parallel hardware. The results are shown to agree with 3-D computation and experimental results.

Parallel performance of multi-slice method for skewed electrical machines

Multi-slice methods allow us to approximate the 3D phenomena without carrying out a full 3D analysis, e.g. in skewed radial flux electrical machines. The idea is to divide a 3D machine into several 2D FEM models, only connected by electrical circuits. Here we show how the multi-slice method is perfect for parallel computation; the computation efficiency is close to that of 2D models in modern parallel hardware. The results are shown to match with 3D computation and experimental results.

Computational and experimental segregation of deformations due to magnetic forces and magnetostriction

This paper presents a novel experimental set up to measure the deformation in an iron sheet under the influence of electromagnetic field, and the results of Finite Element Analysis used for segregating the magnetic forces and magnetostriction induced mechanical deformation. The magnetic forces are calculated using the virtual work principle and the magnetostriction is modeled by means of an energy-based model. The 3D computations are performed in an open source finite element software Elmer. The experimental results and numerical simulations were analyzed and the deformation due to magnetic forces and magnetostriction were identified.