Assembly Methods of Permanent Magnets for Synchronous Generators

This thesis examines and explains the procedure used to redesign the attachment of permanent magnets to the surface of the rotor of a synchronous generator. The methodology followed to go from the actual assembly to converge to the final purposed innovation was based on the systematic approach design. This meant that first a series of steps had to be predefined as a frame of reference later to be used to compare and select proposals, and finally to obtain the innovation that was sought. Firstly, a series of patents was used as the background for the upcoming ideas. To this end, several different patented assemblies had been found and categorized according the main element onto which this thesis if focused, meaning the attachment element or method. After establishing the technological frame of reference, a brainstorm was performed to obtain as many ideas as possible. Then these ideas were classified, regardless of their degree of complexity or usability, since at this time the quantity of the ideas was the important issue. Subsequently, they were compared and evaluated from different points of view. The comparison and evaluation in this case was based on the use of a requirement list, which established the main needs that the design had to fulfill. Then the selection could be done by grading each idea in accordance with these requirements. In this way, one was able to obtain the idea or ideas that best fulfilled these requirements. Once all of the ideas were compared and evaluated, the best or most suitable idea or ideas were separated. Finally, the selected idea or ideas was/were analyzed in extension and a number of improvements were made. Consequently, a final idea was refined and made more suitable at its performance, manufacture, and life cycle assessment. Therefore, in the end, the design process gave a solution to the problem pointed out at the beginning.

Direct-on-line axial flux permanent magnet synchronous generator static and dynamic performance

In distributed energy production, permanent magnet synchronous generators (PMSG) are often connected to the grid via frequency converters, such as voltage source line converters. The price of the converter may constitute a large part of the costs of a generating set. Some of the permanent magnet synchronous generators with converters and traditional separately excited synchronous generators couldbe replaced by direct-on-line (DOL) non-controlled PMSGs. Small directly networkconnected generators are likely to have large markets in the area of distributed electric energy generation. Typical prime movers could be windmills, watermills and internal combustion engines. DOL PMSGs could also be applied in island networks, such as ships and oil platforms. Also various back-up power generating systems could be carried out with DOL PMSGs. The benefits would be a lower priceof the generating set and the robustness and easy use of the system. The performance of DOL PMSGs is analyzed. The electricity distribution companies have regulations that constrain the design of the generators being connected to the grid. The general guidelines and recommendations are applied in the analysis. By analyzing the results produced by the simulation model for the permanent magnet machine, the guidelines for efficient damper winding parameters for DOL PMSGs are presented. The simulation model is used to simulate grid connections and load transients. The damper winding parameters are calculated by the finite element method (FEM) and determined from experimental measurements. Three-dimensional finite element analysis (3D FEA) is carried out. The results from the simulation model and 3D FEA are compared with practical measurements from two prototype axial flux permanent magnet generators provided with damper windings. The dimensioning of the damper winding parameters is case specific. The damper winding should be dimensioned based on the moment of inertia of the generating set. It is shown that the damper winding has optimal values to reach synchronous operation in the shortest period of time after transient operation. With optimal dimensioning, interferenceon the grid is minimized.

Design of marine generators for alternative diesel-electric power systems

This study compares different electric propulsion systems. Results of the analysis of all the advantages and disadvantages of the different propulsion systems are given. This thesis estimates possibilities to apply different diesel-electric propulsion concepts for different vessel types. Small and medium size vessel’s power ranges are studied. The optimal delivery system is chosen. This choice is made on the base of detailed study of the concepts, electrical equipment market and comparison of mass, volume and efficiency parameters. In this thesis three marine generators are designed. They are: salient pole synchronous generator and two permanent magnet synchronous generators. Their electrical, dimensional, cost and efficiency parameters are compared. To understand all the benefits diagrams with these parameters are prepared. Possible benefits and money savings are estimated. As the result the advantages, disadvantages and boundary conditions for the permanent magnet synchronous generator application in marine electric-power systems are found out.

Design and testing of an armature-reaction-compensated permanent magnet synchronous generator for island operation

At present, permanent magnet synchronous generators (PMSGs) are of great interest. Since they do not have electrical excitation losses, the highly efficient, lightweight and compact PMSGs equipped with damper windings work perfectly when connected to a network. However, in island operation, the generator (or parallel generators) alone is responsible for the building up of the network and maintaining its voltage and reactive power level. Thus, in island operation, a PMSG faces very tight constraints, which are difficult to meet, because the flux produced by the permanent magnets (PMs) is constant and the voltage of the generator cannot be controlled. Traditional electrically excited synchronous generators (EESGs) can easily meet these constraints, because the field winding current is controllable. The main drawback of the conventional EESG is the relatively high excitation loss. This doctoral thesis presents a study of an alternative solution termed as a hybrid excitation synchronous generator (HESG). HESGs are a special class of electrical machines, where the total rotor current linkage is produced by the simultaneous action of two different excitation sources: the electrical and permanent magnet (PM) excitation. An overview of the existing HESGs is given. Several HESGs are introduced and compared with the conventional EESG from technical and economic points of view. In the study, the armature-reaction-compensated permanent magnet synchronous generator with alternated current linkages (ARC-PMSG with ACL) showed a better performance than the other options. Therefore, this machine type is studied in more detail. An electromagnetic design and a thermal analysis are presented. To verify the operation principle and the electromagnetic design, a down-sized prototype of 69 kVA apparent power was built. The experimental results are demonstrated and compared with the predicted ones. A prerequisite for an ARC-PMSG with ACL is an even number of pole pairs (p = 2, 4, 6, …) in the machine. Naturally, the HESG technology is not limited to even-pole-pair machines. However, the analysis of machines with p = 3, 5, 7, … becomes more complicated, especially if analytical tools are used, and is outside the scope of this thesis. The contribution of this study is to propose a solution where an ARC-PMSG replaces an EESG in electrical power generation while meeting all the requirements set for generators given for instance by ship classification societies, particularly as regards island operation. The maximum power level when applying the technology studied here is mainly limited by the economy of the machine. The larger the machine is, the smaller is the efficiency benefit. However, it seems that machines up to ten megawatts of power could benefit from the technology. However, in low-power applications, for instance in the 500 kW range, the efficiency increase can be significant.

Teollisuusverkon stabiilisuus saarekekäyttöön siirryttäessä

Työn aluksi on käsitelty sähkövoimajärjestelmien stabiilisuutta yleisesti. Myös teollisuuden sähköverkkojen erityispiirteitä on tarkasteltu. Teollisuusverkkojen komponentteja koskevassa selvityksessä eri laitteet on käsitelty siten, että niiden tärkeimmät ominaisuudet verkon erilaisissa muutostilanteissa tulevat esille. Tahtigeneraattorit ja epätahtikoneet on käsitelty yksityiskohtaisesti. Tutkimuksessa on esitelty teollisuusverkon saarekekäyttöön johtavia syitä, saarekkeeseen siirtymisen kriteereitä ja saarekekäytön toteutustapoja. Tehonvajaussuojaukseen liittyen on tutustuttu kuormanpudotusjärjestelyihin. Myös höyryverkon kuormien tasausten mahdollisuuksiin on luotu katsaus. Verkostolaskentaa käsittelevässä luvussa on keskitytty sopivan laskentamallin luomiseen liittyviin menetelmiin ja rajoituksiin. Lisäksi on kerrottu työn käytännön osan laskentamallin luomisen keskeiset periaatteet. Työn lopuksi on suoritettu simulointeja, joissa on tutkittu erään teollisuusverkon stabiilisuutta saarekekäyttöön siirryttäessä Calpos-verkostolaskentaohjelmistolla.

Erikoissähkökoneen tyyppitestaus

Uusien erikoissähkökoneiden testaus perinteisten standardien mukaan on osittain haasteellista. Erikoissähkökoneille, kuten kestomagneettitahtikoneelle ei ole esitetty suoranaisia standardin vaatimia testejä, joten siihen joudutaan soveltamaan olemassa olevia erillismagnetoiduntahtikoneen standardeja. Testien tavoitteena on olla luotettavia sekä vertailukelpoisia. Mittausten on oltava toistettavissa. Mittaustavasta riippuen voidaan saada erilaisia tuloksia, jotka vaikuttavat lopputulokseen. Standardien mukaisessa testauksessa saadaan mittauksista samanlaisia ja samalla saadaan mittausvirheen mahdollisuus pienemmäksi ja tällä tavoin tulokset keskenään vertailukelpoisemmiksi. Tässä työssä tarkastellaan kahta erilaista erikoissähkokonetta, kestomagneettitahtikonetta ja massiiviroottoriepätahtikonetta. Työssä selvitetään standardin IEC 60034 soveltuvuutta tyyppitesteihin, joita kyseiset konetyypit vaativat. Lisäksi työssä vertaillaan standardin IEC 60034 mukaisen hyötysuhteen määrittämistä. Se antaakin useita vaihtoehtoja hyötysuhteen määrittämiselle.

Lightweight, liquid-cooled, direct-drive generator for highpower wind turbines: motivation, concept, and performance

Thesis: A liquid-cooled, direct-drive, permanent-magnet, synchronous generator with helical, double-layer, non-overlapping windings formed from a copper conductor with a coaxial internal coolant conduit offers an excellent combination of attributes to reliably provide economic wind power for the coming generation of wind turbines with power ratings between 5 and 20MW. A generator based on the liquid-cooled architecture proposed here will be reliable and cost effective. Its smaller size and mass will reduce build, transport, and installation costs. Summary: Converting wind energy into electricity and transmitting it to an electrical power grid to supply consumers is a relatively new and rapidly developing method of electricity generation. In the most recent decade, the increase in wind energy’s share of overall energy production has been remarkable. Thousands of land-based and offshore wind turbines have been commissioned around the globe, and thousands more are being planned. The technologies have evolved rapidly and are continuing to evolve, and wind turbine sizes and power ratings are continually increasing. Many of the newer wind turbine designs feature drivetrains based on Direct-Drive, Permanent-Magnet, Synchronous Generators (DD-PMSGs). Being low-speed high-torque machines, the diameters of air-cooled DD-PMSGs become very large to generate higher levels of power. The largest direct-drive wind turbine generator in operation today, rated just below 8MW, is 12m in diameter and approximately 220 tonne. To generate higher powers, traditional DD-PMSGs would need to become extraordinarily large. A 15MW air-cooled direct-drive generator would be of colossal size and tremendous mass and no longer economically viable. One alternative to increasing diameter is instead to increase torque density. In a permanent magnet machine, this is best done by increasing the linear current density of the stator windings. However, greater linear current density results in more Joule heating, and the additional heat cannot be removed practically using a traditional air-cooling approach. Direct liquid cooling is more effective, and when applied directly to the stator windings, higher linear current densities can be sustained leading to substantial increases in torque density. The higher torque density, in turn, makes possible significant reductions in DD-PMSG size. Over the past five years, a multidisciplinary team of researchers has applied a holistic approach to explore the application of liquid cooling to permanent-magnet wind turbine generator design. The approach has considered wind energy markets and the economics of wind power, system reliability, electromagnetic behaviors and design, thermal design and performance, mechanical architecture and behaviors, and the performance modeling of installed wind turbines. This dissertation is based on seven publications that chronicle the work. The primary outcomes are the proposal of a novel generator architecture, a multidisciplinary set of analyses to predict the behaviors, and experimentation to demonstrate some of the key principles and validate the analyses. The proposed generator concept is a direct-drive, surface-magnet, synchronous generator with fractional-slot, duplex-helical, double-layer, non-overlapping windings formed from a copper conductor with a coaxial internal coolant conduit to accommodate liquid coolant flow. The novel liquid-cooling architecture is referred to as LC DD-PMSG. The first of the seven publications summarized in this dissertation discusses the technological and economic benefits and limitations of DD-PMSGs as applied to wind energy. The second publication addresses the long-term reliability of the proposed LC DD-PMSG design. Publication 3 examines the machine’s electromagnetic design, and Publication 4 introduces an optimization tool developed to quickly define basic machine parameters. The static and harmonic behaviors of the stator and rotor wheel structures are the subject of Publication 5. And finally, Publications 6 and 7 examine steady-state and transient thermal behaviors. There have been a number of ancillary concrete outcomes associated with the work including the following. X Intellectual Property (IP) for direct liquid cooling of stator windings via an embedded coaxial coolant conduit, IP for a lightweight wheel structure for lowspeed, high-torque electrical machinery, and IP for numerous other details of the LC DD-PMSG design X Analytical demonstrations of the equivalent reliability of the LC DD-PMSG; validated electromagnetic, thermal, structural, and dynamic prediction models; and an analytical demonstration of the superior partial load efficiency and annual energy output of an LC DD-PMSG design X A set of LC DD-PMSG design guidelines and an analytical tool to establish optimal geometries quickly and early on X Proposed 8 MW LC DD-PMSG concepts for both inner and outer rotor configurations Furthermore, three technologies introduced could be relevant across a broader spectrum of applications. 1) The cost optimization methodology developed as part of this work could be further improved to produce a simple tool to establish base geometries for various electromagnetic machine types. 2) The layered sheet-steel element construction technology used for the LC DD-PMSG stator and rotor wheel structures has potential for a wide range of applications. And finally, 3) the direct liquid-cooling technology could be beneficial in higher speed electromotive applications such as vehicular electric drives.

Doubly fed induction generator versus direct drive permanent magnet synchronous generator in wind power applications

The objective of this master's thesis is to compare two different generator systems for wind turbines. It is the doubly fed induction generator system with three stage gearbox and the direct drive permanent magnet generator system. The comparison of generator systems is based on annual energy production for a given wind climate. For comparison a 3 MW, 15 rpm wind turbine is used. Modelling of a turbine rotor, gearbox and converters were done. Design of two generators was done and their performance was examined.

Design Aspects of Megawatt-Range Direct-Driven Permanent MagnetWind Generators

Direct-driven permanent magnet synchronous generator is one of the most promising topologies for megawatt-range wind power applications. The rotational speed of the direct-driven generator is very low compared with the traditional electrical machines. The low rotational speed requires high torque to produce megawatt-range power. The special features of the direct-driven generators caused by the low speed and high torque are discussed in this doctoral thesis. Low speed and high torque set high demands on the torque quality. The cogging torque and the load torque ripple must be as low as possible to prevent mechanical failures. In this doctoral thesis, various methods to improve the torque quality are compared with each other. The rotor surface shaping, magnet skew, magnet shaping, and the asymmetrical placement of magnets and stator slots are studied not only by means of torque quality, but also the effects on the electromagnetic performance and manufacturability of the machine are discussed. The heat transfer of the direct-driven generator must be designed to handle the copper losses of the stator winding carrying high current density and to keep the temperature of the magnets low enough. The cooling system of the direct-driven generator applying the doubly radial air cooling with numerous radial cooling ducts was modeled with a lumped-parameter-based thermal network. The performance of the cooling system was discussed during the steady and transient states. The effect of the number and width of radial cooling ducts was explored. The large number of radial cooling ducts drastically increases the impact of the stack end area effects, because the stator stack consists of numerous substacks. The effects of the radial cooling ducts on the effective axial length of the machine were studied by analyzing the crosssection of the machine in the axial direction. The method to compensate the magnet end area leakage was considered. The effect of the cooling ducts and the stack end area effects on the no-load voltages and inductances of the machine were explored by using numerical analysis tools based on the three-dimensional finite element method. The electrical efficiency of the permanent magnet machine with different control methods was estimated analytically over the whole speed and torque range. The electrical efficiencies achieved with the most common control methods were compared with each other. The stator voltage increase caused by the armature reaction was analyzed. The effect of inductance saturation as a function of load current was implemented to the analytical efficiency calculation.

Liquid cooling solutions for rotating permanent magnet synchronous machines

In the design of electrical machines, efficiency improvements have become very important. However, there are at least two significant cases in which the compactness of electrical machines is critical and the tolerance of extremely high losses is valued: vehicle traction, where very high torque density is desired at least temporarily; and direct-drive wind turbine generators, whose mass should be acceptably low. As ever higher torque density and ever more compact electrical machines are developed for these purposes, thermal issues, i.e. avoidance of over-temperatures and damage in conditions of high heat losses, are becoming of utmost importance. The excessive temperatures of critical machine components, such as insulation and permanent magnets, easily cause failures of the whole electrical equipment. In electrical machines with excitation systems based on permanent magnets, special attention must be paid to the rotor temperature because of the temperature-sensitive properties of permanent magnets. The allowable temperature of NdFeB magnets is usually significantly less than 150 ˚C. The practical problem is that the part of the machine where the permanent magnets are located should stay cooler than the copper windings, which can easily tolerate temperatures of 155 ˚C or 180 ˚C. Therefore, new cooling solutions should be developed in order to cool permanent magnet electrical machines with high torque density and because of it with high concentrated losses in stators. In this doctoral dissertation, direct and indirect liquid cooling techniques for permanent magnet synchronous electrical machines (PMSM) with high torque density are presented and discussed. The aim of this research is to analyse thermal behaviours of the machines using the most applicable and accurate thermal analysis methods and to propose new, practical machine designs based on these analyses. The Computational Fluid Dynamics (CFD) thermal simulations of the heat transfer inside the machines and lumped parameter thermal network (LPTN) simulations both presented herein are used for the analyses. Detailed descriptions of the simulated thermal models are also presented. Most of the theoretical considerations and simulations have been verified via experimental measurements on a copper tooth-coil (motorette) and on various prototypes of electrical machines. The indirect liquid cooling systems of a 100 kW axial flux (AF) PMSM and a 110 kW radial flux (RF) PMSM are analysed here by means of simplified 3D CFD conjugate thermal models of the parts of both machines. In terms of results, a significant temperature drop of 40 ̊C in the stator winding and 28 ̊C in the rotor of the AF PMSM was achieved with the addition of highly thermally conductive materials into the machine: copper bars inserted in the teeth, and potting material around the end windings. In the RF PMSM, the potting material resulted in a temperature decrease of 6 ̊C in the stator winding, and in a decrease of 10 ̊C in the rotor embedded-permanentmagnets. Two types of unique direct liquid cooling systems for low power machines are analysed herein to demonstrate the effectiveness of the cooling systems in conditions of highly concentrated heat losses. LPTN analysis and CFD thermal analysis (the latter being particularly useful for unique design) were applied to simulate the temperature distribution within the machine models. Oil-immersion cooling provided good cooling capability for a 26.6 kW PMSM of a hybrid vehicle. A direct liquid cooling system for the copper winding with inner stainless steel tubes was designed for an 8 MW directdrive PM synchronous generator. The design principles of this cooling solution are described in detail in this thesis. The thermal analyses demonstrate that the stator winding and the rotor magnet temperatures are kept significantly below their critical temperatures with demineralized water flow. A comparison study of the coolant agents indicates that propylene glycol is more effective than ethylene glycol in arctic conditions.

Unequal Teeth Widths for Torque Ripple Reduction in Permanent Magnet Synchronous Machines With Fractional-Slot Non-Overlapping Windings

Permanent magnet synchronous machines with fractional-slot non-overlapping windings (FSPMSM), also known as tooth-coil winding permanent magnet synchronous machines (TCW PMSM), have been under intensive research during the latest decade. There are many optimization routines explained and implemented in the literature in order to improve the characteristics of this machine type. This paper introduces a new technique for torque ripple minimization in TCW PMSM. The source of torque harmonics is also described. The low order torque harmonics can be harmful for a variety of applications, such as direct drive wind generators, direct drive light vehicle electrical motors, and for some high precision servo applications. The reduction of the torque ripple harmonics with the lowest orders (6th and 12th) is realized by machine geometry optimization technique using finite element analysis (FEA). The presented optimization technique includes the stator geometry adjustment in TCW PMSMs with rotor surface permanent magnets and with rotor embedded permanent magnets. Influence of the permanent magnet skewing on the torque ripple reduction and cogging torque elimination was also investigated. It was implemented separately and together with the stator optimization technique. As a result, the reduction of some torque ripple harmonics was attained.

Sähkökoneen staattorikäämityksen kehittäminen

Tämä insinöörityö tehtiin ABB:n Pitäjänmäen konetehtaalle Tahtikoneet-tulosyksikölle. Työssä tutkittiin mahdollisuuksia valmistaa murtovakovyyhtejä kestomagneettituuligeneraattoreihin, joissa vakoluku on alle yhden. Työ tehtiin tutustumalla aluksi Pitäjänmäen konetehtaan käytössä oleviin vyyhden valmistus- ja käämintämenetelmiin. Lisäksi tutkittiin erilaisia mahdollisia murtovakovyyhden valmistusmenetelmiä, joista lupaavimpia myös kokeiltiin. Saatujen kokemusten pohjalta valittiin vyyhden valmistusmenetelmä, jonka mukaan valmistettiin koe-erä. Koe-erälle suoritettiin mittauksia, joilla varmistettiin niiden sähköinen kestävyys Työn tuloksena valitulla valmistusmenetelmällä valmistettiin vyyhdet prototyyppi tuuligeneraattorin.

Synchronous Digital Hierarchy implementation to a Radio Transmission Node

Kiristyville markkinoille on aina tuotava jotain uutta tarjottavaa ja SDH-kortti on yksi sellainen tuote jonka Nokia Networks julkistaa osaksi uutta Nokia Flexihub Nodea. Tavoitteena on suunnitella VC-12kanavoitu STM-1 kortti yhdistämään ylemmän tason tietoliikenneverkko suuren kapasiteetin radioon. Ennen kuin markkinoilla on valmis tuote, on sen takana valtaisa määrä työtä. Erilaisia dokumentteja on pitänyt tuottaa ja sopimuksia tehdä. Esimerkiksi vaatimusmäärittelyt on oltava selvät, jotta tiedetään mitä tuotteelta halutaan. Tätä ennen on kuitenkin pitänyt ymmärtää miten SDHtoimii ja miten otsikkotavuja käsitellään. Myös erilaiset piirivalinnat aiheuttavat miettimistä, sillä markkinoilla on runsaasti valmiita piirejä SDH signaalinkäsittelyyn. Varma tiedonsiirto on tärkeää puhelinoperaattorille ja siksi joudutaan miettimään varmennuksia ja niiden toteuttamista. Myös synkronointi on tärkeä osa SDH järjestelmää ja sen toteuttaminen hyvin on tärkeää. Hälytykset on otettava huomioon ja mietittävä, miten niiden käsittely saadaan hoidettua järkevästi, ilman että mikään järjestelmän osa ruuhkautuu kohtuuttomasti. Tässä Diplomityössä on tutustuttu SDH-järjestelmään, otsikkotavujen käsittelyyn ja vaatimusmäärittelyihin.

Fractional slot permanent magnet synchronous motors for low speed applications

This study compares different rotor structures of permanent magnet motors with fractional slot windings. The surface mounted magnet and the embedded magnet rotor structures are studied. This thesis analyses the characteristics of a concentrated two-layer winding, each coil of which is wound around one tooth and which has a number of slots per pole and per phase less than one (q < 1). Compared to the integer slot winding, the fractional winding (q < 1) has shorter end windings and this, thereby, makes space as well as manufacturing cost saving possible. Several possible ways of winding a fractional slot machine with slots per pole and per phase lessthan one are examined. The winding factor and the winding harmonic components are calculated. The benefits attainable from a machine with concentrated windingsare considered. Rotor structures with surface magnets, radially embedded magnets and embedded magnets in V-position are discussed. The finite element method isused to solve the main values of the motors. The waveform of the induced electro motive force, the no-load and rated load torque ripple as well as the dynamic behavior of the current driven and voltage driven motor are solved. The results obtained from different finite element analyses are given. A simple analytic method to calculate fractional slot machines is introduced and the values are compared to the values obtained with the finite element analysis. Several different fractional slot machines are first designed by using the simple analytical methodand then computed by using the finite element method. All the motors are of thesame 225-frame size, and have an approximately same amount of magnet material, a same rated torque demand and a 400 - 420 rpm speed. An analysis of the computation results gives new information on the character of fractional slot machines.A fractional slot prototype machine with number 0.4 for the slots per pole and per phase, 45 kW output power and 420 rpm speed is constructed to verify the calculations. The measurement and the finite element method results are found to beequal.

Permanent magnet synchronous motor for industrial inverter applications - analysis and design

During the latest few years the need for new motor types has grown, since both high efficiency and an accurate dynamic performance are demanded in industrial applications. For this reason, new effective control systems such as direct torque control (DTC) have been developed. Permanent magnet synchronous motors (PMSM) are well suitable for new adjustable speed AC inverter drives, because their efficiency and power factor are not depending on the pole pair number and speed to the same extent as it is the case in induction motors. Therefore, an induction motor (IM) with a mechanical gearbox can often be replaced with a direct PM motor drive. Space as well as costs will be saved, because the efficiency increases and the cost of maintenance decreases as well. This thesis deals with design criterion, analytical calculation and analysis of the permanent magnet synchronous motor for both sinusoidal air-gap flux density and rectangular air-gapflux density. It is examined how the air-gap flux, flux densities, inductances and torque can be estimated analytically for salient pole and non-salient pole motors. It has been sought by means of analytical calculations for the ultimate construction for machines rotating at relative low 300 rpm to 600 rpm speeds, which are suitable speeds e.g. in Pulp&Paper industry. The calculations are verified by using Finite Element calculations and by measuring of prototype motor. The prototype motor is a 45 kW, 600 rpm PMSM with buried V-magnets, which is a very appropriate construction for high torque motors with a high performance. With the purposebuilt prototype machine it is possible not only to verify the analytical calculations but also to show whether the 600 rpm PMSM can replace the 1500 rpm IM with a gear. It can also be tested if the outer dimensions of the PMSM may be the same as for the IM and if the PMSM in this case can produce a 2.5 fold torque, in consequence of which it may be possible to achieve the same power. The thesis also considers the question how to design a permanent magnet synchronous motor for relatively low speed applications that require a high motor torqueand efficiency as well as bearable costs of permanent magnet materials. It is shown how a selection of different parameters affects the motor properties. Key words: Permanent magnet synchronous motor, PMSM, surface magnets, buried magnets