Stefan Kulig

Technische Universität Dortmund | TUD

Purpose The phase-domain synchronous machine model has advantages compared to the d/q model, as no transformation of currents is necessary at each time step in a network analysis. The purpose of this paper is to enhance the phase-domain model to calculate the current distribution of the damper bars, including the saturation. Design/methodology/ap...

Purpose – Magnetic slot wedges are usually installed in open slot high-voltage induction machines. They reduce the no load losses and the magnetization current. Additionally, the leakage inductance increases. However, machines and the slot wedges are getting frequently damaged with a decreasing maintenance interval. The usage of magnetic slot wedge...

This paper presents the results of the DFG-project (Deutsche Forschungsgemeinschaft) Q-ELF ("Qualitätsorientierter Methodenworkflow für die Produktneuentwicklung eines Linearantriebs in der Fördertechnik") carried out in cooperation of the TU Dortmund University (support code KU 1307/12-1) with the BUW Wuppertal (support code WI 1234-11/1). The pro...

Long transmission lines have to be compensated to enhance the transport of active power. But a wrong design of the compensation may lead to subsynchronous resonances (SSR). For studies often park equivalent circuits are used. The parameters of the models are often determined analytically or by a three-phase short-circuit test. Models with this para...

In this paper a comparison of numerically determined and measured electromagnetically exited noise of an induction motor is presented. The calculations are accomplished using FEM for an example motor, which is a 290 kW inverter-fed asynchronous machine. The approach starts with the electromagnetic and mechanical consideration. The focus is set on a...

This paper investigates the stator winding short circuit characteristics in synchronous generators under rated operating conditions by combing the single-winding analytical method and the finite element method (FEM), which is still the effective method to determine currents and torques under specific fault conditions. Some special measures have to...

This paper focuses on a basic research of out-of-phase synchronization currents of a single phase transformer and its impact on a system of synchronous machine, transformer, switch and grid. The effect of transformer saturation is studied for different switching conditions using the finite element software FLUX 3D. The position of the switch has a...

A comprehensive study of electromechanical resonances in large drives caused by electric transients such as asynchronous start-up and system disturbances is presented. The electromagnetic and torsional torques on the shaft lines of two identical 5 MW compressors are simulated during electric transients aiming at the demands on the design of couplin...

Influence of constructional turbo-generator end region design on end winding inductances The paper introduces a comprehensive investigation in end winding inductances of large two-pole turbo-generators. With the aid of an analytic-numeric approach, where Neumann's formula is applied, the influence of geometric characteristics of double-layer stator...

Customary roller conveyors as a part of intralogistic facilities still show much room for improvement concerning the power consumption and design efficiency. Especially the electric drive is oftentimes oversized. Optimisation regarding an efficient design of the motor requires in-depth information about the coupled system of the drive itself as wel...

Based on a 3-D Finite Element Model built up in FLUX 3-D, this paper shows simulation results of a single phase transformer to study the behavior of its reactance during short circuits with respect to saturation effects. In the first step measurements on a real transformer were done to determine its equivalent circuit parameters and to verify the F...

The development of low-noise motors will help to protect the environment and result in a competitive advantage. Designing low-noise electric motors means that it is necessary to predict the noise characteristics of the electric motor in the early conceptual phase. Customizing means that it is necessary to be able to estimate how the modifications a...

Purpose Operation of synchronous machines in the power range of several 10 MW with variable speed up to 7,000 rpm using a current converter is, thanks to the development of power switches, possible and economically reasonable today. However, current harmonics, produced by converter, generate additional losses, especially eddy current losses on the...

This paper presents the validation of a method for a modal transformation of operational end winding vibrations, which can be monitored by fibre-optic accelerometers. The validation is done by the analysis of the vibrational behaviour of a mechanical finite element model which is excited by electro- magnetic forces and deformations of the stator co...

Grid disturbances can cause torsional vibrations of a turbo set shaft train which may reduce the lifetime or lead to serious mechanical damage also in the stator end windings of the generator. Because of this, it is very desirable not only to have a permanent online monitoring system for torsional vibrations, but it is also of high interest to have...

Purpose The purpose of this paper is to describe a systematic investigation of the currents, torques and other electromagnetic quantities in a machine after different short circuits by the means of coupled numerical field and network calculation. The behaviour of a synchronous machine after a stator‐winding fault still is a little known issue. Neve...

The following paper focuses on generator end winding vibrations. Monitoring systems have been developed for measuring them however sensible methods for analysis have not been found yet. A reduced end winding model and modal analysis of it are further described. The resulting analytical modal representation of vibration is used to evaluate a method...

Zusammenfassung: • Es treten auch heute neue Störfälle mit noch nicht bekannten Schadenswirkungen auf, besondere Aufmerksamkeit gilt den Umrichterantrieben • Moderne Berechnungsverfahren eröffnen neue Perspektiven, aber auch neue Fragestellungen • Dreidimensionale Berechnungen sind sehr aufwendig daher noch keine grundsätzliche Standardmethode -> E...

Combined Cycle Power Plants (CCPP) in single shaft arrangements consist of a gas turbine, a generator and a steam turbine on one shaft line. In order to enhance the plant availability and operational flexibility, Siemens Fossil Power Generation introduces a switchable clutch between steam turbine and generator. The clutch is a synchronous self-shif...

The efficiency of magnetic sheet metal forming processes is strongly depending on the facility s overall design. This mainly includes the geometric layout of forming tool, work piece and matrix but, however, will also expect the energy storage device being taken into consideration. Apart from field theoretic models the energy storage is describable...

Nach einem Fehler im elektrischen Übertragungsnetz findet ein Ausgleichsvorgang statt, an dem das Netz, der Generator und der Wellenstrang gleichzeitig beteiligt sind. In diesem Beitrag werden die Auswirkungen von Störfällen mit besonderem Blick auf den Wellenstrang behandelt. Es wird ein standarisiertes Verfahren vorgestellt, mit welchem die Schwe...

Numerical methods of calculating the electromagnetic forces and of simulating the oscillation behavior of the stator end winding are introduced. The end winding oscillations of different turbo generators under forced vibrations are computed in a combined simulation. Also eigenfrequencies and eigenmodes are determined. The obtained results are surve...

Electromagnetic forming (EF) is a high speed forming process in which strain rates of over 103 s^(-1) are achieved. The workpiece is deformed by the Lorentz force resulting from the interaction of a fast varying electro magnetic field with the eddy currents induced by the field in the workpiece. Within a research group (FOR 443) funded by the Germa...

A new method of measuring torsional vibrations is presented. Based on a contactless sensor and under the use of a robust observer it is possible to measure and calculate torsional torques appearing at a shaft train online. The new concept allows to prevent shaft trains from serious damages caused by torsional oscillations. Il is shown that the obse...

A 2D finite-difference time-stepping method is applied to simulate the dynamic behaviour of a turbine generator during asynchronous acceleration. The obtained simulation results, like the time functions of terminal voltages and currents, rotational speed and torque, are verified using the simulation program NETOMAC ® . The applied finite-difference...

Sensitivity and robustness analysis are important tools in order to guarantee an efficient construction and error free running of a turbine generator shaft. It is very important to test different design parameters simultaneously before the machine is in use. Therefore, the knowledge of the characteristic frequencies of the system is crucial since t...

Subsynchronous resonance phenomena (SSR) belong to the most severe incidents that occur in large synchron generators. The ultimate hazard of SSR is generator shaft fracture at rated speed. In addition personal safety is endangered. But as clearly shown in this paper, the actual protection measures for SSR are not sufficient because there exist more...

In this paper the design of a turbogenerator with high voltage stator winding is presented. In distinction from conventional techniques the stator winding is not built with isolated bars. For this concept, common high voltage cables are used. Therefore it is possible to raise the stator voltage from 110 kV to 400 kV. The advantage of this concept i...

Subsynchronous resonance (SSR) phenomena are usually discussed in case of systems with turbine generators and compensated transmission lines. The present paper offers an entirely new point of view to the subject of SSR. It is shown that this phenomenon does not only occur in the mentioned but also in other cases, where it can also cause severe dama...

The measurement and calculation of end winding deformations for different turbo generators is presented. The measurements have been realized on three turbo generators of ratings from 94 MVA to 550 MVA. They have been done both for full load operation and for a three phase short circuit and were compared with calculation results. The nonlinearity an...

Turbo generators, which generally consist of different turbines, an excitator and a generator, are used for electrical power production. Online-monitoring of those machines is an important task, since torsional moments that arise in the shaft couplings during malfunction situations reduce their life-time expectancy. The shaft model is obtained by F...

Correct modeling of turbogenerators is difficult, as currents are flowing during transients not only in the field and damper winding but also in the solid rotor iron. To model this effect, especially at high frequencies, new model structures called ladder networks are introduced. Their parameters are identified by combining the standstill frequency...

For pt.II see IEEE Winter Meeting, New Orleans, LA, 1986. A novel method for analyzing the steady-state and transient currents in the stator, rotor, and damper windings of a large generator is discussed, and the application of the method to five classes of problems of practical importance is described. These are (1) internal phase-to-phase fault in...

Compared with turbine generators of conventional design, which already have very high power-weight ratios, superconducting generators offer big advantages in the way of the required capacity range and improved efficiency. Now that the fundamental thoretical studies have been completed and the first test rotors are being proof-tested by a number of...

To investigate the torsional performance of turbine generators with a superconducting rotor an advanced digital program was developed which simulates the very complex electromagnetic and electromechanical interaction of the multi-shell damper system of the rotor with both the electrical power system and the turbine generator shaft system [1, 2]. Fi...

The significant potential advantages of superconducting generators have stimulated large-scale efforts throughout the world to develop such generators for utility application. A thorough study of the transient performance of superconducting generators requires improved generator modeling in an efficient program for power system dynamics to adequate...

Novel iterative T-network equivalent circuits are derived for the direct and quadrature axes of a generator with superconducting field winding and stator air-gap winding. They enable the treatment of the complex skin effect phenomena in a multi-shell damper system for any non- periodical time variation as well as of the mutual inductive couplings o...

Interaction between the electrical transmission system and the turbine generator may induce torsional stresses to the shaft system whose magnitude and risk of damage have to be carefully analyzed in advance to ensure undisturbed operation and to preclude any damage from the unit. Within this task, the present paper investigates the torsional stress...

The torsional vibrations of turbomachinery shafts in the event of electrical system faults are greatly influenced by the electromechanical coupling between shaft assembly and electrical system (generator, network). The entire system must be simulated by models for calculation. The influence of the electro-mechanical coupling is indicated for the mo...

The successive electrical transients caused by system faults and subsequent switching operations associated with the widely practiced technique of automatic high-speed reclosing give rise to mechanical stresses in nearby turbine-generators. Depending upon many factors, these stresses may exceed the endurance limit of certain machine parts and thus...

The torsional stresses that occur in large steam turbine- generator shafts due to both planned and unplanned system switching operations are discussed. These operations include routine line switching, reclosing line-to-ground faults by either triple-pole or single-pole breaker operation, reclosing line-to-line and three-phase faults, malsynchroniza...

In some industrial plants conductors carrying strong alternating currents are surrounded by ring-shaped mechanical construction parts. Magnetic fields of high strength caused by these currents induce eddy-currents in such parts leading to electrical power dissipation. In the following, for an axisymmetric ring of rectangular cross-section made of f...