T. Nussbaumer - Academia.edu (original) (raw)

Papers by T. Nussbaumer

Nature Communications, 2014

The subfamily of the Lemnoideae belongs to a different order than other monocotyledonous species ... more The subfamily of the Lemnoideae belongs to a different order than other monocotyledonous species that have been sequenced and comprises aquatic plants that grow rapidly on the water surface. Here we select Spirodela polyrhiza for whole-genome sequencing. We show that Spirodela has a genome with no signs of recent retrotranspositions but signatures of two ancient whole-genome duplications, possibly 95 million years ago (mya), older than those in Arabidopsis and rice. Its genome has only 19,623 predicted protein-coding genes, which is 28% less than the dicotyledonous Arabidopsis thaliana and 50% less than monocotyledonous rice. We propose that at least in part, the neotenous reduction of these aquatic plants is based on readjusted copy numbers of promoters and repressors of the juvenile-to-adult transition. The Spirodela genome, along with its unique biology and physiology, will stimulate new insights into environmental adaptation, ecology, evolution and plant development, and will be instrumental for future bioenergy applications.

Proceedings of The 7th International Power Electronics and Motion Control Conference, 2012

ABSTRACT

Fourtieth IAS Annual Meeting. Conference Record of the 2005 Industry Applications Conference, 2005., 2005

The digital control of a three-phase, three switch buck-type rectifier system is analyzed in this... more The digital control of a three-phase, three switch buck-type rectifier system is analyzed in this paper. Three main sources of delay times in the control loop can be identified for the implementation on a digital signal processor, namely: the delay time due to the sampling of the control quantities; the one due to the calculation time of the DSP; and the one due to the sample-and-hold function of the PWM modulator. Their influence on the stability of the inner current control loop is discussed and two prediction methods for compensation, namely a linear prediction and the Smith prediction, are comparatively evaluated. The control performance and the effect of the delay times and the prediction methods are finally shown by simulation results and through and measurements on a 5kW prototype.

We report measurements of the amplitude of the Aharonov-Bohm oscillations in a mesoscopic diffusi... more We report measurements of the amplitude of the Aharonov-Bohm oscillations in a mesoscopic diffusive gold ring as a function of the DC bias voltage VDC. The amplitude of the h/e oscillations increases with VDC once the Thouless energy Ec and thermal energy are exceeded, and decreases at higher values of VDC. The increase of the amplitude is interpreted in terms

2008 IEEE International Symposium on Industrial Electronics, 2008

In semiconductor industry, where bearingless pump systems are employed already as state-of-the-ar... more In semiconductor industry, where bearingless pump systems are employed already as state-of-the-art technology, the trend goes towards higher fluid temperatures (150 • C and more) in order to further increase process efficiency. This fact translates to the requirement of a high-temperature bearingless pump system and/or the elimination of thermal-critical components such as hall sensors. This paper introduces a new method for a hall-sensorless control of a PMSM bearingless pump in its operating range from 0 rpm to 8000 rpm and from zero load to full load. The sensorless operation is performed by three novel control functionalities, namely: a controlled start-up routine, enabling a sure levitation and zero angle setting; an open-loop angle estimation based on stator voltage and stator current measurement and known machine parameters; and an angle synchronization establishing a robust operation of the pump in the whole operating range even for a large machine parameter drift. Especially, considering the temperature degrading of the permanent magnet flux density, the novel robust control concept is of great benefit for bearingless pump systems employed in high temperature applications.

Fourtieth IAS Annual Meeting. Conference Record of the 2005 Industry Applications Conference, 2005., 2005

The modeling and control of a three-phase, threeswitch buck-type rectifier system with integrated... more The modeling and control of a three-phase, threeswitch buck-type rectifier system with integrated boost output stage (VRX-4) is analyzed in this paper. A cascaded multi-loop control structure is presented that has the following features: constant output voltage for a wide input voltage range and stepwise changes of load; sinusoidal input currents in phase with the mains voltages that also remain sinusoidal in case of asymmetric mains conditions; and active damping of the input filter resonance. For the control design an equivalent DC-DC small-signal model of the converter is derived and verified by simulations and measurements. Based on this and the identification of the critical operating point the controllers for the inner DC current and outer voltage control loops are selected. The stability of the closed loop system is discussed and the robust operation of the system is verified by measurements on a 5kW prototype.

2013 International Electric Machines & Drives Conference, 2013

In this paper, a concept is developed for a slotless bearingless disc drive with toroidal winding... more In this paper, a concept is developed for a slotless bearingless disc drive with toroidal windings for a rotational speed of 150'000 rpm. The topology and its working principles are explained and an already running prototype for lower speeds is introduced. To reach the high rotational speeds, the mechanical strength and the maximal diameter of the rotor is evaluated. Outgoing form the prototype, scaling laws are examined to identify the challenges for down-scaling of the bearingless motor. 3D FEM Simulations and optimizations are conducted to determine the influence of the magnetic gap length and to find the optimal stator and rotor height. At the end, the geometry of the high speed concept is presented and the performance results are compared to the prototype.

2011 IEEE Energy Conversion Congress and Exposition, 2011

Page 1. Rotor Position Measurement for a Magnetically Levitated 500'000 rpm Permanent Magnet... more Page 1. Rotor Position Measurement for a Magnetically Levitated 500'000 rpm Permanent Magnet Machine Claudius M. Zingerli, Philipp Imoberdorf and Johann W. Kolar Power Electronic Systems Laboratory Thomas Nussbaumer Levitronix GmbH Technoparkstr. 1 ...

The 13th international winterschool on electronic properties of novel materials- science and technology of molecular nanostructures, 1999

Equilibrium electric resistance R and tunneling spectroscopy (dI/dV) measurements obtained on sin... more Equilibrium electric resistance R and tunneling spectroscopy (dI/dV) measurements obtained on single multiwall nanotubes are reported. As a function of temperature T the resistance increases on decreasing T and saturates at ~1-10 K for all measured nanotubes. R(T) cannot be related to the energy-dependent DOS of graphene but is mainly caused by interaction and interference effects. On a relatively small

Bearingless motors offer contactless levitation and rotation through a hermitically closed proces... more Bearingless motors offer contactless levitation and rotation through a hermitically closed process chamber and satisfy the increasing demand for ultra high purity spin processes in chemical, biochemical and semiconductor industry. Most of these processes require a high acceleration capability for minimal process times and a large air gap in order to fit in a mechanical stable chamber wall. The combination of these requirements possibly causes saturation effect issues that may occur depending on the specific drive claw shape. In this paper, saturation effects which reduce the effective torque of the motor are investigated for two commonly known drive claw shapes. The investigations are exemplarily carried out for the Bearingless 2-Level Motor (B2M), since it allows the isolated examination of saturation effects caused by the drive flux due to the axial and circumferential separation of the bearing and drive units. The paper visualizes the flux density distribution and the flux trajectory change at the presence of saturation for the presented drive claw shapes by means of 3D finite element simulations. One drive claw type is found to be the more applicable concept and is subsequently optimized with respect to maximum torque by variation of the drive claw width. Finally, the superior performance of the designed claw is proven by the comparison of simulation results with measurement data of an experimental prototype.

Over the last few years industry branches with a growing demand for high purity and contamination... more Over the last few years industry branches with a growing demand for high purity and contamination-free highacceleration spin processes, such as biotechnology, chemical, pharmaceutical and semiconductor industry, have tightened their cleanness specifications for the process environments. A recent trend to meet these specifications is to use magnetically levitated slice motors with air gaps being large enough to insert a process chamber wall, which assures the hermetical sealing of the process. The drive design of these motors is challenging due to the employed large air gaps and the demand for maximum acceleration capability. Separate design considerations for a non-saturating stator drive claw geometry and for an appropriate drive winding number have been proposed in the past, not considering the interdependencies of these two designs. This paper presents an overall optimization procedure yielding for minimal acceleration times of magnetically levitated slice motors for different speed ranges and verifies the considerations by measurements on a prototype system. I.

ABSTRACT Bearingless drives and magnetic bearings allow the construction of contactless, wearless... more ABSTRACT Bearingless drives and magnetic bearings allow the construction of contactless, wearless and lubrication-free rotating systems. Utilizing a permanent magnet excited rotor disc permits the passive stabilization of three degrees of freedom (tilting and axial deflection) by reluctance forces. Hence, using these bearingless slice motors it becomes possible to design very compact magnetically suspended drive systems. The bearingless segment motor is a subtype of the bearingless slice motor, where the stator consists of single elements. As a matter of fact, all these stator segments are magnetically decoupled from each other. This article introduces different designs of the announced bearingless segment motor featuring different rotor and stator compositions. Especially the differences in the generation of bearing forces are outlined. The special features of the various considered drives are examined and their advantages and drawbacks are discussed. Finally these motors are compared qualitatively by different criteria (like the demands on power electronics, passive stiffnesses or bearing force and motor torque capacity).

We report high-resolution measurements of voltage (V) noise in the mixed state of micrometre-size... more We report high-resolution measurements of voltage (V) noise in the mixed state of micrometre-sized thin films of amorphous Nb0.7Ge0.3, which is a good representative of weak-pinning superconductors. There is a remarkable difference between the noise below and above the irreversibility field Birr. Below Birr, in the presence of measurable pinning, the noise at small applied currents resembles shot noise, and in the regime of flux flow at larger currents decreases with increasing voltage due to a progressive ordering of the vortex motion. At magnetic fields B between Birr and the upper critical field Bc2 flux flow is present already at vanishingly small currents. In this regime the noise scales with (1-B/Bc2)^2 V^2 and has a frequency (f) spectrum of 1/f type. We interpret this noise in terms of the properties of strongly driven depinned vortex systems at high vortex density.

Physical Review Letters, 2002

We have measured the differential conductance dI/dV of individual multi-wall carbon nanotubes (MW... more We have measured the differential conductance dI/dV of individual multi-wall carbon nanotubes (MWNT) of different lengths. A cross-over from wire-like (long tubes) to dot-like (short tubes) behavior is observed. dI/dV is dominated by random conductance fluctuations (UCF) in long MWNT devices (L = 2 . . . 7 µm), while Coulomb blockade and energy level quantization are observed in short ones (L = 300 nm). The electron levels of short MWNT dots are nearly four-fold degenerate (including spin) and their evolution in magnetic field (Zeeman splitting) agrees with a g-factor of 2. In zero magnetic field the sequential filling of states evolves with spin S according to S = 0 → 1/2 → 0 . . . . In addition, a Kondo enhancement of the conductance is observed when the number of electrons on the tube is odd.

Physical Review Letters, 2002

The Kondo effect and superconductivity are both prime examples of many-body phenomena.

Journal of System Design and Dynamics, 2009

Several processes in chemical, pharmaceutical, biotechnology and semiconductor industry require c... more Several processes in chemical, pharmaceutical, biotechnology and semiconductor industry require contactless levitation and rotation through a hermetically closed process chamber. A highly interesting topology for these applications is the "bearingless slice motor" concept, where already some research has been done in the past, especially focusing on topology and implementation issues. However, only little work has been done to evaluate the ideal number of motor phases. In this paper, a performance evaluation between 2-phase and 3phase bearingless slice motor concepts is undertaken. It is shown, that 3-phase systems can supply almost the same power as adequate 2-phase systems and achieve nearly the same acceleration behavior, although they have significantly less complex power electronics.

IET Power Electronics, 2008

ABSTRACT

IEEE/ASME Transactions on Mechatronics, 2000

This paper describes a novel and compact topology for contactless levitation and rotation of a wi... more This paper describes a novel and compact topology for contactless levitation and rotation of a wide annular rotor through the walls of a sealed process chamber. In the proposed setup, a homopolar magnetic bearing biased by permanent magnets is combined with a high-pole-number segment motor. The paper discusses the functional principle of the motor, and gives design and optimization guidelines for the bearing and the drive unit, respectively. An experimental system is presented along with a set of measurement results verifying the theoretical considerations.

IEEE/ASME Transactions on Mechatronics, 2000

Several processes in chemical, pharmaceutical, biotechnology, and semiconductor industry require ... more Several processes in chemical, pharmaceutical, biotechnology, and semiconductor industry require contactless levitation and rotation through a hermetically closed chamber wall. This paper presents a novel concept that combines crucial advantages such as high acceleration capability, large air gap, and a compact motor setup. The basic idea is to separate a homopolar bearing unit axially from a multipolar drive unit on two different height levels. Hence, the proposed concept is denominated as "magnetically levitated two-level motor." In this paper, the bearing and drive functionalities are explained in detail and design guidelines are given based on analytic equations and electromagnetic 3-D simulations. Furthermore, the influence of nonidealities such as saturation and coupling effects is evaluated and included in the design. Finally, extensive measurements on an experimental prototype exemplify the design considerations and prove the excellent performance of the new concept.

IEEE/ASME Transactions on Mechatronics, 2000

This article presents a novel topology for a bearingless permanent-magnet motor. This disk-shaped... more This article presents a novel topology for a bearingless permanent-magnet motor. This disk-shaped motor, featuring an exterior rotor, can be advantageously employed in delicate bioreactor processes. Both torque and bearing forces originate inside this magnetically levitated motor and are generated with concentrated combined windings. Using 3-D-FEM analysis, the optimal machine sizing parameters are evaluated with the goal to maximize torque while providing sufficient bearing forces to allow a precise and stable operation. The results from the sizing optimization and from the force and torque analysis have been implemented and tested with a real-size prototype setup.

Nature Communications, 2014

The subfamily of the Lemnoideae belongs to a different order than other monocotyledonous species ... more The subfamily of the Lemnoideae belongs to a different order than other monocotyledonous species that have been sequenced and comprises aquatic plants that grow rapidly on the water surface. Here we select Spirodela polyrhiza for whole-genome sequencing. We show that Spirodela has a genome with no signs of recent retrotranspositions but signatures of two ancient whole-genome duplications, possibly 95 million years ago (mya), older than those in Arabidopsis and rice. Its genome has only 19,623 predicted protein-coding genes, which is 28% less than the dicotyledonous Arabidopsis thaliana and 50% less than monocotyledonous rice. We propose that at least in part, the neotenous reduction of these aquatic plants is based on readjusted copy numbers of promoters and repressors of the juvenile-to-adult transition. The Spirodela genome, along with its unique biology and physiology, will stimulate new insights into environmental adaptation, ecology, evolution and plant development, and will be instrumental for future bioenergy applications.

Proceedings of The 7th International Power Electronics and Motion Control Conference, 2012

ABSTRACT

Fourtieth IAS Annual Meeting. Conference Record of the 2005 Industry Applications Conference, 2005., 2005

The digital control of a three-phase, three switch buck-type rectifier system is analyzed in this... more The digital control of a three-phase, three switch buck-type rectifier system is analyzed in this paper. Three main sources of delay times in the control loop can be identified for the implementation on a digital signal processor, namely: the delay time due to the sampling of the control quantities; the one due to the calculation time of the DSP; and the one due to the sample-and-hold function of the PWM modulator. Their influence on the stability of the inner current control loop is discussed and two prediction methods for compensation, namely a linear prediction and the Smith prediction, are comparatively evaluated. The control performance and the effect of the delay times and the prediction methods are finally shown by simulation results and through and measurements on a 5kW prototype.

We report measurements of the amplitude of the Aharonov-Bohm oscillations in a mesoscopic diffusi... more We report measurements of the amplitude of the Aharonov-Bohm oscillations in a mesoscopic diffusive gold ring as a function of the DC bias voltage VDC. The amplitude of the h/e oscillations increases with VDC once the Thouless energy Ec and thermal energy are exceeded, and decreases at higher values of VDC. The increase of the amplitude is interpreted in terms

2008 IEEE International Symposium on Industrial Electronics, 2008

In semiconductor industry, where bearingless pump systems are employed already as state-of-the-ar... more In semiconductor industry, where bearingless pump systems are employed already as state-of-the-art technology, the trend goes towards higher fluid temperatures (150 • C and more) in order to further increase process efficiency. This fact translates to the requirement of a high-temperature bearingless pump system and/or the elimination of thermal-critical components such as hall sensors. This paper introduces a new method for a hall-sensorless control of a PMSM bearingless pump in its operating range from 0 rpm to 8000 rpm and from zero load to full load. The sensorless operation is performed by three novel control functionalities, namely: a controlled start-up routine, enabling a sure levitation and zero angle setting; an open-loop angle estimation based on stator voltage and stator current measurement and known machine parameters; and an angle synchronization establishing a robust operation of the pump in the whole operating range even for a large machine parameter drift. Especially, considering the temperature degrading of the permanent magnet flux density, the novel robust control concept is of great benefit for bearingless pump systems employed in high temperature applications.

Fourtieth IAS Annual Meeting. Conference Record of the 2005 Industry Applications Conference, 2005., 2005

The modeling and control of a three-phase, threeswitch buck-type rectifier system with integrated... more The modeling and control of a three-phase, threeswitch buck-type rectifier system with integrated boost output stage (VRX-4) is analyzed in this paper. A cascaded multi-loop control structure is presented that has the following features: constant output voltage for a wide input voltage range and stepwise changes of load; sinusoidal input currents in phase with the mains voltages that also remain sinusoidal in case of asymmetric mains conditions; and active damping of the input filter resonance. For the control design an equivalent DC-DC small-signal model of the converter is derived and verified by simulations and measurements. Based on this and the identification of the critical operating point the controllers for the inner DC current and outer voltage control loops are selected. The stability of the closed loop system is discussed and the robust operation of the system is verified by measurements on a 5kW prototype.

2013 International Electric Machines & Drives Conference, 2013

In this paper, a concept is developed for a slotless bearingless disc drive with toroidal winding... more In this paper, a concept is developed for a slotless bearingless disc drive with toroidal windings for a rotational speed of 150'000 rpm. The topology and its working principles are explained and an already running prototype for lower speeds is introduced. To reach the high rotational speeds, the mechanical strength and the maximal diameter of the rotor is evaluated. Outgoing form the prototype, scaling laws are examined to identify the challenges for down-scaling of the bearingless motor. 3D FEM Simulations and optimizations are conducted to determine the influence of the magnetic gap length and to find the optimal stator and rotor height. At the end, the geometry of the high speed concept is presented and the performance results are compared to the prototype.

2011 IEEE Energy Conversion Congress and Exposition, 2011

Page 1. Rotor Position Measurement for a Magnetically Levitated 500'000 rpm Permanent Magnet... more Page 1. Rotor Position Measurement for a Magnetically Levitated 500'000 rpm Permanent Magnet Machine Claudius M. Zingerli, Philipp Imoberdorf and Johann W. Kolar Power Electronic Systems Laboratory Thomas Nussbaumer Levitronix GmbH Technoparkstr. 1 ...

The 13th international winterschool on electronic properties of novel materials- science and technology of molecular nanostructures, 1999

Equilibrium electric resistance R and tunneling spectroscopy (dI/dV) measurements obtained on sin... more Equilibrium electric resistance R and tunneling spectroscopy (dI/dV) measurements obtained on single multiwall nanotubes are reported. As a function of temperature T the resistance increases on decreasing T and saturates at ~1-10 K for all measured nanotubes. R(T) cannot be related to the energy-dependent DOS of graphene but is mainly caused by interaction and interference effects. On a relatively small

Bearingless motors offer contactless levitation and rotation through a hermitically closed proces... more Bearingless motors offer contactless levitation and rotation through a hermitically closed process chamber and satisfy the increasing demand for ultra high purity spin processes in chemical, biochemical and semiconductor industry. Most of these processes require a high acceleration capability for minimal process times and a large air gap in order to fit in a mechanical stable chamber wall. The combination of these requirements possibly causes saturation effect issues that may occur depending on the specific drive claw shape. In this paper, saturation effects which reduce the effective torque of the motor are investigated for two commonly known drive claw shapes. The investigations are exemplarily carried out for the Bearingless 2-Level Motor (B2M), since it allows the isolated examination of saturation effects caused by the drive flux due to the axial and circumferential separation of the bearing and drive units. The paper visualizes the flux density distribution and the flux trajectory change at the presence of saturation for the presented drive claw shapes by means of 3D finite element simulations. One drive claw type is found to be the more applicable concept and is subsequently optimized with respect to maximum torque by variation of the drive claw width. Finally, the superior performance of the designed claw is proven by the comparison of simulation results with measurement data of an experimental prototype.

Over the last few years industry branches with a growing demand for high purity and contamination... more Over the last few years industry branches with a growing demand for high purity and contamination-free highacceleration spin processes, such as biotechnology, chemical, pharmaceutical and semiconductor industry, have tightened their cleanness specifications for the process environments. A recent trend to meet these specifications is to use magnetically levitated slice motors with air gaps being large enough to insert a process chamber wall, which assures the hermetical sealing of the process. The drive design of these motors is challenging due to the employed large air gaps and the demand for maximum acceleration capability. Separate design considerations for a non-saturating stator drive claw geometry and for an appropriate drive winding number have been proposed in the past, not considering the interdependencies of these two designs. This paper presents an overall optimization procedure yielding for minimal acceleration times of magnetically levitated slice motors for different speed ranges and verifies the considerations by measurements on a prototype system. I.

ABSTRACT Bearingless drives and magnetic bearings allow the construction of contactless, wearless... more ABSTRACT Bearingless drives and magnetic bearings allow the construction of contactless, wearless and lubrication-free rotating systems. Utilizing a permanent magnet excited rotor disc permits the passive stabilization of three degrees of freedom (tilting and axial deflection) by reluctance forces. Hence, using these bearingless slice motors it becomes possible to design very compact magnetically suspended drive systems. The bearingless segment motor is a subtype of the bearingless slice motor, where the stator consists of single elements. As a matter of fact, all these stator segments are magnetically decoupled from each other. This article introduces different designs of the announced bearingless segment motor featuring different rotor and stator compositions. Especially the differences in the generation of bearing forces are outlined. The special features of the various considered drives are examined and their advantages and drawbacks are discussed. Finally these motors are compared qualitatively by different criteria (like the demands on power electronics, passive stiffnesses or bearing force and motor torque capacity).

We report high-resolution measurements of voltage (V) noise in the mixed state of micrometre-size... more We report high-resolution measurements of voltage (V) noise in the mixed state of micrometre-sized thin films of amorphous Nb0.7Ge0.3, which is a good representative of weak-pinning superconductors. There is a remarkable difference between the noise below and above the irreversibility field Birr. Below Birr, in the presence of measurable pinning, the noise at small applied currents resembles shot noise, and in the regime of flux flow at larger currents decreases with increasing voltage due to a progressive ordering of the vortex motion. At magnetic fields B between Birr and the upper critical field Bc2 flux flow is present already at vanishingly small currents. In this regime the noise scales with (1-B/Bc2)^2 V^2 and has a frequency (f) spectrum of 1/f type. We interpret this noise in terms of the properties of strongly driven depinned vortex systems at high vortex density.

Physical Review Letters, 2002

We have measured the differential conductance dI/dV of individual multi-wall carbon nanotubes (MW... more We have measured the differential conductance dI/dV of individual multi-wall carbon nanotubes (MWNT) of different lengths. A cross-over from wire-like (long tubes) to dot-like (short tubes) behavior is observed. dI/dV is dominated by random conductance fluctuations (UCF) in long MWNT devices (L = 2 . . . 7 µm), while Coulomb blockade and energy level quantization are observed in short ones (L = 300 nm). The electron levels of short MWNT dots are nearly four-fold degenerate (including spin) and their evolution in magnetic field (Zeeman splitting) agrees with a g-factor of 2. In zero magnetic field the sequential filling of states evolves with spin S according to S = 0 → 1/2 → 0 . . . . In addition, a Kondo enhancement of the conductance is observed when the number of electrons on the tube is odd.

Physical Review Letters, 2002

The Kondo effect and superconductivity are both prime examples of many-body phenomena.

Journal of System Design and Dynamics, 2009

Several processes in chemical, pharmaceutical, biotechnology and semiconductor industry require c... more Several processes in chemical, pharmaceutical, biotechnology and semiconductor industry require contactless levitation and rotation through a hermetically closed process chamber. A highly interesting topology for these applications is the "bearingless slice motor" concept, where already some research has been done in the past, especially focusing on topology and implementation issues. However, only little work has been done to evaluate the ideal number of motor phases. In this paper, a performance evaluation between 2-phase and 3phase bearingless slice motor concepts is undertaken. It is shown, that 3-phase systems can supply almost the same power as adequate 2-phase systems and achieve nearly the same acceleration behavior, although they have significantly less complex power electronics.

IET Power Electronics, 2008

ABSTRACT

IEEE/ASME Transactions on Mechatronics, 2000

This paper describes a novel and compact topology for contactless levitation and rotation of a wi... more This paper describes a novel and compact topology for contactless levitation and rotation of a wide annular rotor through the walls of a sealed process chamber. In the proposed setup, a homopolar magnetic bearing biased by permanent magnets is combined with a high-pole-number segment motor. The paper discusses the functional principle of the motor, and gives design and optimization guidelines for the bearing and the drive unit, respectively. An experimental system is presented along with a set of measurement results verifying the theoretical considerations.

IEEE/ASME Transactions on Mechatronics, 2000

Several processes in chemical, pharmaceutical, biotechnology, and semiconductor industry require ... more Several processes in chemical, pharmaceutical, biotechnology, and semiconductor industry require contactless levitation and rotation through a hermetically closed chamber wall. This paper presents a novel concept that combines crucial advantages such as high acceleration capability, large air gap, and a compact motor setup. The basic idea is to separate a homopolar bearing unit axially from a multipolar drive unit on two different height levels. Hence, the proposed concept is denominated as "magnetically levitated two-level motor." In this paper, the bearing and drive functionalities are explained in detail and design guidelines are given based on analytic equations and electromagnetic 3-D simulations. Furthermore, the influence of nonidealities such as saturation and coupling effects is evaluated and included in the design. Finally, extensive measurements on an experimental prototype exemplify the design considerations and prove the excellent performance of the new concept.

IEEE/ASME Transactions on Mechatronics, 2000

This article presents a novel topology for a bearingless permanent-magnet motor. This disk-shaped... more This article presents a novel topology for a bearingless permanent-magnet motor. This disk-shaped motor, featuring an exterior rotor, can be advantageously employed in delicate bioreactor processes. Both torque and bearing forces originate inside this magnetically levitated motor and are generated with concentrated combined windings. Using 3-D-FEM analysis, the optimal machine sizing parameters are evaluated with the goal to maximize torque while providing sufficient bearing forces to allow a precise and stable operation. The results from the sizing optimization and from the force and torque analysis have been implemented and tested with a real-size prototype setup.