This thesis is focused on the evaluation of rotor dynamics of the induction machine, which can be used as a basis for online diagnosis of driven load in the future. It describes the problem of time varying loading torque at its impact to electromagnetic variables in induction machine. Followed by the possible ways of monitoring and diagnostic of loading torque using Fourier analysis on supply current.

This thesis deals with the steady-state, dynamic and control aspects of new type of brushless configuration of a doubly-fed induction machine in which the slip rings and carbon brushes are replaced by rotating power electronics and a rotating exciter. The aim is to study the stability of this novel configuration of the generator under mechanical and grid disturbances for wind power applications. The derivation, development and analysis of the steady-state model of the brushless doubly-fed induction machine with a rotating excitor and the power electronic converters mounted on the shaft and rotating with it, is studied. The study is performed at rated power of the generator between ±20% slip range. Moreover unity power factor operation between ±20% speed range is also discussed. Furthermore dynamic modeling and control aspects of the generator are also analyzed. The controllers were designed using Internal Model Control principles and vector control methods were used in order to control the generator in a closed-loop system. It is shown that through the use of proper feedback control, the generator behaves in a stable state both at super-synchronous and sub-synchronous speeds. Moreover Low Voltage Ride Through of the generator during symmetrical and unsymmetrical voltage dips is also investigated. Passive Resistive Network strategy is employed for Low Voltage Ride Through of the generator during symmetrical voltage dips. On the other hand, Extended Vector Control is used in order to control the negative sequence currents during unsymmetrical voltage dips. Suppression of negative sequence currents is important as they cause extra heating in the windings and affects the lifetime of the mechanical and electrical components of the generator and system due to oscillations in power and torque. In addition to the above studies a steady-state model of a single-fed induction machine is also developed and investigated where the rotating exciter is removed and the rotor windings are short-circuited through the two rotating power electronic converters. In this way the slip power circulates in the rotor and with the help of the two rotating electronic converters, rotor current is used to magnetize the induction machine thereby improving the power factor. The steady state model is verified through experimental results. / <p>20120914</p> / Brushless Wind Generator with Rotating Power Electronic Converters

Electrical machines with more than three phases are usually called multiphase electrical machines and they can have several advantages compared to conventional three-phase electrical machines such as a lower content of space-harmonics, lower torque ripple and better fault tolerance. This degree project involves rewinding of a three-phase induction machine into an asymmetrical six-phase machine. The winding design is based on simulations of a machine model in a finite element method software and the method "the star of the slot" that computes winding layouts. A six-phase drive is developed based on an existing printed circuit board prototype that is not operating according to its original specifications. Debugging of the prototype is performed and solutions to the problems are identified. Design and layout improvements for better electromagnetic compatibility are also implemented. The drive including the electrical machine is tested and confirmed to be working according to the specifications. Speed control based on indirect rotor field orientation is implemented and tested for the six-phase induction machine as well with the machine connected as a standard three-phase induction machine. / Elektriska maskiner med fler än tre faser kallas vanligtvis flerfasiga elektriska maskiner och kan ha flera fördelar jämfört med konventionella trefasiga elektriska maskiner, som lägre innehåll av övervågor, lägre rippel i vridmomentet och bättre feltolerans. Detta examensarbete involverar omlindning av en trefasig asynkronmaskin till en asymmetrisk sexfasig asynkronmaskin. Lindningsdesignen baseras på simuleringar av en maskinmodell i mjukvara baserat på finita element metoden och metoden kallad the star of the slotsom räknar ut lindnings ritningar. En sexfasig drivlina utvecklas baserat på en existerande kretskorts prototyp som inte fungerar enligt dess ursprunliga specifikationer. Felsökning av prototypen utförs och lösningar till problemen identifieras. Design- och layoutförbättringar för bättre elektromagnetisk kompatibilitet implementeras också. Drivlinan med den elektriska maskinen inkluderad testas och bekräftas fungera enligt dess specifikationer. Hastighetsreglering baserad på indirekt rotorfälts orientering implementeras och testas för den sexfasiga asynkronmaskinen samt även med maskinen kopplad som en standard trefas asynkronmaskin.

An estimated 30% of the faults in Induction Machine (IM) are related to its stator. These faults are mostly in the form of an Inter-Turn Short Circuit (ITSC) fault i.e., when two winding inside the stator of IM are shorted due to insulation failure. However, ITSC fault can be avoided by detecting them in advance and then scheduling the maintenance of the IM. This thesis studies two methods for detecting this incipient ITSC fault in a three-phase IM and then estimating the stator resistance unbalance due to the ITSC fault. The first method is based on the asymmetry caused in the IM by the ITSC fault. As a result of this asymmetry, the negative sequence components of the stator voltages and the stator currents are generated inside the IM. A healthy IM also have these negative sequence components due to the manufacturing process and the supply voltage unbalances. The characteristics and the compensation methods of these negative sequence components in a healthy IM are discussed. The results show that after compensating the negative sequence components in a healthy machine, they can be used for detecting an ITSC fault and then to calculate the fault quantities as well as the stator resistance unbalances. The second method for detecting an ITSC fault is based on analysing the stator resistance unbalances. A three-phase drive is used to inject DC voltage in the stationary reference frame. The DC current generated by this DC voltage is measured and then by applying Ohm’s law stator phase resistances are calculated. In a healthy IM, the phase resistances are balanced. However, in case of ITSC fault in any of the phases, the phase resistance of that phase deviates from those of the other two phases which can be utilized for detecting ITSC fault. / Uppskattningsvis 30% av alla fel i induktionsmaskiner (IM) är kopplad till dess stator. Dessa fel är i huvudsak Inter-Turn Short Circuit (ITSC)-fel, dvs. två lindningar inom IM:ens stator blir kortsluta pga. ett isoleringsfel. Emellertid kan man undvika ITSC-fel genom att detektera dem i förhand och planera underhåll. Det här examensarbetet undersöker två metoder för att detektera ett förestående ITSC-fel i en tre-fas IM. Den första metoden är baserad på asymmetrin i IM:er pga. ITSC-felet. Resultatet av den här asymmetrin är att en negativ sekvens genereras i IM:ens statorspänning och statorström. En oskadad IM kan också visa dessa negativa sekvenser pga. tillverksprocessen och statorspänningsobalanser. Egenskaperna och kompensationsmetoderna för dessa negativa sekvenser i en oskadad IM kommer att diskuteras. Resultaten visar att efter kompenseringen av de negativa sekvenserna i en oskadad IM, kan de användas för att detektera ITSC-fel och efteråt för att beräkna felstorheter och även statormotståndobalanser. Den andra metoden för att detektera ITSC-fel är baserad på en undersökning av statormotståndobalanser. Ett tre-fas-drivsystem används för att injektera likspänning i den stationära referensramen. Likströmmen som följer av denna likspänning mäts och statorfasmotstånden beräkna efteråt med Ohms lag. I en oskadad IM är fasmotstånden balanserade. Däremot, när ett ITSC-fel uppstår i en fas, avviker fasmotståndet i den felaktiga fasen från de andra två fasernas, vilket kan användas för att detektera ITSC-fel.

Induction machine; outer rotor; water pump; thermal network; thermal analysis; optimization; electromagnetic model; finite element method; thermal insulation class