Antila, M., Arkkio, A. & Jokinen, T.
Active Magnetic Bearing for High-Speed Electric Machines.
In this paper the basic theory and the design aspects of active magnetic
bearings are introduced. A properly designed active magnetic bearing is
almost an ideal bearing. It provides very low friction, contactless oil-free
operation in hard environmental conditions, active vibration control and
monitoring. Today, active magnetic bearing are being used in several industrial
applications, and many applications are under development.
In this paper the basic theory and the design aspects of active magnetic bearings are introduced. A properly designed active magnetic bearing is almost an ideal bearing. It provides very low friction, contactless oil-free operation in hard environmental conditions, active vibration control and monitoring. Today, active magnetic bearing are being used in several industrial applications, and many applications are under development.
This paper is an overview of the problem of noise in electrical machines. It presents the history of the problem as well as the methods used to study the problem. A brief overview of the causes of the noise is also presented here. As a case study, the magnetic field in as asynchronous generator is solved using finite elements method (FEM). The Maxwell stress on the inner side of the stator pack is calculated and developed into a two dimensional Fourier series. The spectra of the stress is then compared to the measured vibration and noise spectra and the correlation is shown.
The forces generated by the magnetic field in a synchronous generator are studied as a source of vibration and noise. Finite Element Method (FEM) is used to solve the magnetic field in the iron core and the air gap of the generator. The distribution of the radial force acting on the inner surface of the stator core is calculated using the classical Maxwell stress tensor method. The force distribution is then developed into a two dimensional Fourier series (space and time) and the spectral contents of the radial force distribution are analysed and compared to the spectra of the measured noise from the generator. The method is proved to be adequate for the prevention of noise components already in the design stage.
This paper presents an analysis of a new type of induction motor, designed
to operate with integrated brake. Usually, in many applications with electrical
drives, the braking period has to be very short when the supply voltage
is disconnected. The classical solutions are the induction motor with separate
brake, or the induction motor with conical rotor. The first one has a low
reliability, and the latter is characterized by complicated manufacturing
technology and high inertia. An original solution is the induction motor
with integrated brake. This motor type presents an important axial force
to open the brake, during starting and a normal axial force during operating
period. When the voltage supply is disconnected, the special device proposed
as integrated brake, permits a shorted braking period by comparison with
the above mentioned induction motor types.
A mathematical model is proposed, also experimental studies highlight
the performances of the induction motor with integrated brake.
The paper deals with various types of high-speed electric motors, and their limiting powers. A novel induction motor construction is presented, too. The rotor of the motor is solid and coated with a high-conductive layer. The materials and coating method permit the use of high rotor speeds, up to 550 m/s.
Optimisation has been described as "getting the best you can out of a given situation". In engineering design, the recipe for the getting calls for a blend of mathematical analysis, educated intuition, and a pinch of good luck. Insofar as the design problem can be quantified, mathematical optimisation methods can be power-full allies.
What follows is a survey. Each of a number of mathematical techniques is described, but only to the extent that its character and utility become evident. The survey is, inevitably, incomplete, but it does point to some of the promising methods so far proposed.
The electromechanical system of a wind power plant usually consists of three main parts: turbine, gearbox and generator. However, the gearbox-generator solution can be replaced by a directly driven low-speed generator. This paper presents an optimisation for a low-speed permanent-magnet synchronous machine. The rated power is 500 kW and the rotational speed 40 rpm. The machine has a three-phase, fractional slot winding. The excitation of the machine is made by NdFeB magnets mounted on the surface of the rotor yoke. The electrical performances of the machine are calculated by the finite element method with genetic algorithm. The main task of the optimisation is to minimise the cost of active material.
The aim of the project was to develop better rotor constructions for high-speed electric motors. A partly laminated squirrel cage rotor was designed and manufactured. Operating characteristics of a 50 kW, 30600 rpm motor were measured for a copper coated solid steel rotor and for the partly laminated squirrel cage rotor. It was found that the partly laminated rotor had adequate mechanical properties and better electromagnetic properties. While mechanical ageing of the laminated rotor design was not studied, it seemed a reasonable alternative for solid rotor designs in high-speed electric motors.
In this paper, the voltage distribution due to the PWM voltage pattern on the stator windings of induction motors is simulated. Two methods for simulation are presented. For the transient voltage calculation on the form windings, the turn capacitance to the ground and the inter-turn capacitance need to be modelled for both the slot and the over-hang parts of the coil. However, for similar calculation on the random windings it is shown in this work that computation of the capacitance to the ground in the over-hang region of the coil is enough to give information about the turn and the coil voltages. In order to validate the method adopted, the simulated results are compared with experimental results.
This paper extent the stationary reference frame , to the modeling
and analysis of the torque behavior of a two-phase unsymmetrical induction
machine with a shifted auxiliary winding. By computer simulation, compared
with experimental results, it is verified the influence of the electrical
auxiliary phase stator shift over the machine’s torque and currents. The
analysis is made for steady-state and transient state operation.
The two-phase induction machine (TPIM) is widely used in many
light-duty applications were three-phase supply is not readily available.
During the development of such a machine, there are several options, including
the spatial placement of the auxiliary winding. The torque-slip characteristics
can be manipulated by shifting the auxiliary winding from the quadrature
position.
The analysis of the single-phase or two-phase induction machine
with a shifted auxiliary winding was made by including time domain equivalent
circuit , symmetrical components, or multiple reference frames. The first
two methods are acceptable for analyzing the steady-state performance of
the machine, while the third method involves too many equations and variables
in order to describe the dynamic performance of the TPIM.
This paper presents the modelling and experimental studies, underlying
the analysis of a novel voltage regulator which is used as a supply for
a variable speed two-phase induction motor drive. A median point inverter
with full logic control is used as a voltage regulator. The machine stator
windings have a special distribution.
This voltage regulator drive achieves a wide speed range in both
directions. As supply a lead-acid battery or a bridge rectifier connected
to the AC supply voltage can be used.
The goal of this paper is to design a permanent magnet synchronous motor (PMSM) using genetic optimisation and timestepping analysis. The characteristics of the motor are computed using two-dimensional finite element method (FEM). In this work the PMSM with radial flux distribution are used. For these kinds of synchronous motors, the ship propulsion drive is a very interesting application, especially for podded drives, where the motor is incorporated in the propeller pod. This paper presents optimised PMSM designs, in which the stator slots effect on torque and electromagnetic losses were taken into account.
This paper describes the design of a large output power permanent magnet synchronous motor with radial flux distribution. In this paper, two different permanent magnet motor configurations were analysed. Numerical calculations of motor characteristics were performed with a two-dimensional finite element, time-stepping simulation program. The results are presented and the advantages and disadvantages of each rotor construction are discussed.
The aim of this paper is to design a permanent magnet synchronous motor (PMSM) with radial flux distribution, using genetic optimisation and time stepping analysis. The characteristics of the motor are computed using two-dimensional finite element method (FEM). For these kinds of synchronous motors, the ship propulsion drive is a very interesting application, especially for podded drives, where the motor is incorporated in the propeller pod. From these reasons, the study both of electromagnetic torque production and electromagnetic losses play a distinct meaningful as concerns the vibration and noise in the drive central unit.
An analytical approach based on a two-dimensional electromagnetic field analysis in polar coordinates is developed to predict the airgap magnetic field distribution in permanent magnet synchronous motor ( PMSM ). In this model, the influence of finite iron permeability, finite stator external radius and the embedding of the conductors in the iron are examined. This model is applied to a surface mounted permanent magnets configuration ( SMPM ) having a radial flux distribution. Predicted results are compared with finite element analysis.
A comparison between the Newton-Raphson method and the Fixed-Point technique in hysteretic magnetic field problems is presented. Four different approaches are studied and contrast between them in terms of the convergence rate and computation time consumption is highlighted. The Newton-Raphson-based approaches are found better than the iteration schemes associated with the Fixed-Point technique for a model problem.
This paper deals with the computation of the core losses in a squirrel-cage induction motor. The computational algorithm consists of the vector Preisach model incorporated in two-dimensional time-stepping finite element analysis. The hysteretic nonlinearity is handled by the Fixed-Point iterative technique. The comparison between calculated and measured core losses for a 37 kW motor at no-load is given and indicates a reasonable agreement.
This paper concentrates on the evaluation of the core losses in a squirrel-cage induction motor. The numerical procedure of the loss computation is based on a two-dimensional time-stepping finite element analysis, which takes the hysteresis loss into account through the vector Preisach model. The highly nonlinear system of equations is solved by the Fixed-Point iterative technique. Since the eddy-current loss is not included in the field analysis, it is evaluated from the computed space and time evolution of the magnetic flux density by using the empirical formulae. The numerically obtained results of the core loss computation are compared with the measured ones for a 37 kW motor at no-load, indicating a reasonable agreement.
Raportissa on käyty läpi tehokertoimen korjauspiirinä toimivan boost-hakkurin kuristimen optimointimenetelmä sovellettuna esimerkkitapaukseen. Optimointia varten on muodostettu teoreettiset lausekkeet kuristimen häviöille ja induktanssille. Laskentamalleissa on huomioitu virran ei-sinimuotoisuus ja syntyvät suurtaajuiset ilmiöt, kapasitiivisiä ilmiöitä lukuunottamatta. Laskennan varmentamiseksi on käytetty numeerista kenttälaskentaohjelmaa Maxwell 3D.Tutkitussa esimerkissä hakkurin toimintataajuus oli noin 100 kHz, mutta tulokset ovat sovellettavissa myös suuremmille taajuuksille.
In the finite element analysis of electrical machines the multi-conductor winding in a stator slot is usually modeled simply by a single conductor with constant current density. The size of a finite element problem due to the precise modeling of eddy currents in the multi-conductor windings can be much larger compared to the single conductor model. The paper investigates a new FEM approach for the consideration of eddy-currents in multi-conductor windings surrounded by nonlinear media, a case typical in electrical machinery. The method called elimination of inner nodes is evaluated in the paper as a possible solution for multi conductor eddy current problems. The paper presents examples and concludes in what circumstances the method of elimination is efficient.
The paper introduces a new FEM technique for considering eddy-currents in multi-conductor windings surrounded by magnetically nonlinear media. Traditional finite element formulation is combined with the so called elimination of inner nodes to achieve fast solution. The effectiveness and “behavior” of the technique was investigated. The presented results are discussed and finally concluded in the paper.
The use of macro elements which replace the multi-conductor winding in the time-stepping finite element analysis of electrical machines is presented in the paper. The effect of eddy-currents in the windings is considered by a traditional finite element formulation combined with the so called elimination of inner nodes to achieve fast solution. The elimination method is incorporated into time stepping analysis so that the elimination of unwanted variables is performed only once in a whole time stepping analysis. The eliminated region is represented by an unchanging numerical macroelement in the whole time stepping analysis from the beginning.
Raportissa on esitetty hakkuriteholähteiden magneettisten komponenttien mallintamisen perusteita ottaen huomioon EMC-imiöiden tutkimuksen tarpeet. Koska näille ilmiöille on ominaista laaja taajuusalue, niin huomio on keskitetty johtuvien häiriöiden taajuusalueeseen (50 Hz ... 30 MHz). Mallintamisen tuloksena magneettisille komponenteille on kehitetty piirimallit, jotka on toteutettu SABER-piirisimulaattorissa. Keskeisenä tutkimuksen sovellusalueena on ollut taajuusmuuttajan ja sen verkkovirtasuodattimen mallintaminen.
The paper describes a new technique of noise reduction from induction motors. Traditional motor has the equi-slot pitched design in rotor. In this paper the inequality slot pitched rotor is studied. This asymmetric rotor slot pitch makes energy distributing for wide frequency range. The spectra of the air gap radial tensile stress are calculated for motors with different kind of rotors and results of calculation are presented in this paper. According to these calculations the spectrum can become wider when rotor slotting is modified.
The paper describes a new technique of noise reduction from induction motors. Traditional induction motor has the equi-slot pitched design in the rotor. Some of these motors have open slots in the rotor. Because of the slot openings, flux density can not pass the slots, but it is forced to go around the slots. In this paper the effects of inequality slot opening pitched rotor is studied. This asymmetric rotor slot opening pitch makes energy distributing for wide frequency range. The spectra of the air gap radial tensile stress are calculated for motors with different kind of rotors and results of calculation are presented in this paper. According to these calculations the spectrum can become wider when the rotor slot opening is modified.
In the paper, a new class of actuator materials and some of its applications are presented. They are active materials called Magneto Straining Materials or Magnetic Shape Memory (MSM) materials. They can develop in a magnetic field large and precise controlled strains theoretically up to 20 %. Actuators made from MSM could replace conventional electromagnetic devices in many applications.