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Altering Flux Density Harmonics in the Air-gap of Synchronous Machines by Active Control of the Field Current
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.ORCID iD: 0000-0001-8237-3107
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.ORCID iD: 0000-0003-4265-6545
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
(English)In: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948Article in journal (Refereed) Accepted
Abstract [en]

Flux density harmonics in the air-gap of electrical machines create distorted voltage waveforms and can induce vibrations. These problems are difficult to mitigate when the machine is already in operation and therefore a lot of effort is made during the design phase to eliminate them. Still, many in-operation machines experience problems related to harmonics and often the solution is to mechanically reinforce and change modal shapes which is expensive and inconvenient. Using a current controlled switched power supply to excite a synchronous machine and adding specific harmonics to the DC-field current it is shown that it is possible to alter the harmonic content of the flux density in the air-gap, and thus affect  voltage harmonics and the exciting magnetic forces. The method is verified and compared with simulations and experiments on an existing electrical machine. 

Keywords [en]
Air-gap flux density, Finite element, Harmonic waves, Noise reduction, Power electronics, Synchronous machines
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
URN: urn:nbn:se:uu:diva-333565OAI: oai:DiVA.org:uu-333565DiVA, id: diva2:1157148
Available from: 2017-11-15 Created: 2017-11-15 Last updated: 2017-11-20
In thesis
1. Improving the functionality of synchronous machines using power electronics
Open this publication in new window or tab >>Improving the functionality of synchronous machines using power electronics
2017 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

With the advent of modern power electronics there is reason to explore what can be achieved when it is applied to a mature technology like synchronous machines. In this text several concepts will be presented on how it is possible to control forces and how to get better performance out of synchronous machines by using power electronics. Methodologies to create radial forces by controlling the field current in a standard series connected rotor winding as well as when the winding is split in to several segments is presented. By segmenting the rotor a resulting force vector can be created to cancel forces due to unbalanced magnetic pull.

It is also shown that inverting the field current with respect to the stator field enables line start of synchronous machines without using damper bars, frequency converters, or starting motors.

Some first results from the installation and testing of an electromagnetic thrust bearing installed in unit U9 in the hydropower station in Porjus are presented. The benefits of the system is increased reliability and higher efficiency of the thrust bearing system.

An evaluation of a 2-stage brushless excitation system was done, different rotating power electronics topologies were tested in the stationary frame connected to a six-phase permanent magnet brushless exciter. The rotating control and measurement system for the power electronics is presented. Potential benefits of the system is that there is no need for brushes to transfer the field current to the rotor winding, fast response time due to actively controlled electronics, independence of the station bus voltage, and reduced maintenance.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017
Series
UURIE / Uppsala University, Department of Engineering Sciences, ISSN 0349-8352 ; 352-17L
Keywords
Power electronics, Synchronous machines, Excitation systems, Magnetic thrust bearing, Starting synchronous machines, Split rotor, Rotating electronics, Magnetic fields, Measurement systems, Unbalanced magnetic pull, Harmonics
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-333940 (URN)
Presentation
2017-12-18, Häggsalen (Å10132), Ångströmslaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2018-01-08 Created: 2017-11-20 Last updated: 2018-01-08Bibliographically approved

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IEEE transactions on industrial electronics (1982. Print)
Electrical Engineering, Electronic Engineering, Information Engineering

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