Martin Reisinger

High-Speed Drive for Textile Rotor Spinning Applications

This paper presents a novel high-speed drive and frictionless suspension system for a rotor spinning unit which opens up the field for further textile technology development, potentially leading to higher productivity, reduced power consumption, and dust deposit. In contrast to conventional rotor spinning machines, individually driven rotors are open on both sides, which allows better arrangement of related spinning components. To achieve a very high lifetime, the rotor is suspended by means of active magnetic bearing. Outstanding energy efficiency can be achieved due to the frictionless magnetic suspension of the rotor and a slotless electronically commutated permanent-magnet motor in conjunction with an optimized frequency inverter.

Ripple Current Reduction of DC Link Electrolytic Capacitors by Switching Pattern Optimisation

The use of electrolytic capacitors in automotive applications is critical. High ambient temperatures lower lifetime and reliability, while further disadvantages arise from costs and installation space. The presented work shows a method to reduce the capacitor ripple current, which accordingly leads to a reduced demand on DC link electrolytic capacitors. The proposed method is based on applying an optimised switching pattern to the power transistors. Thereby, the ripple current can be reduced to approximately one third compared to conventional PWM signals. The optimisation is also described graphically, and measurements verify the practicability

Design of a highly reliable fan with magnetic bearings

Bearing failures are, according to long-term analyses at ebm-papst St. Georgen GmbH & Co. KG, responsible for 90% of all compact fan breakdowns. The working life of a fan can be increased considerably by using a magnetically levitated fan, where the impeller has no contact with the stator. This paper presents the design of a low-cost magnetically levitated fan with passive magnetic bearings (PMBs) to stabilise radial and tilt deflections of the rotor. The application of an optimised viscoelastic support to the stator introduces sufficient damping to the passively stabilised degrees of freedom. The optimisation of the stiffness and damping and the design of the key components, namely the PMB, the active magnetic bearing and the passive damping device is discussed. Finally, the built prototype is presented and the measurement results are analysed.

Single Phase PWM Controlled Voltage Converter for Pumps and Fans without DC Link Electrolytic Capacitors

Single-phase induction motors are widely-used to drive pumps and fans up to several kilowatts. To satisfy the increased requirements in various application areas like modern air conditioning systems, speed-variable drives have become inevitable. Furthermore installations in homes, shops and offices make high demands on the running smoothness of the drive. With basic concepts like a phase-controlled single-phase AC voltage controller it is difficult to settle these claims. Moreover the indicated application areas are very cost sensitive. Advanced solutions including frequency converters often do not have a competitive position. This paper shows a novel concept to cope with these difficulties. The introduced converter is controlled by a high frequency pulsewidth modulation (PWM) signal. This allows an almost sinusoidal motor current with small distortions and therefore low noise emissions of the drive. The proposed circuit topology introduces low harmonics in the line current. This circumstance permits to comply with the relevant regulations without the need of bulky inductors or an active front end. The converter has a high efficiency even at high PWM frequencies. The absence of DC link electrolytic capacitors allows a space-saving design without drawbacks concerning reliability and lifetime at higher ambient temperatures.

Magnetic Levitation Systems for Cost-Sensitive Applications—Some Design Aspects

Alongside technical performance features, low system costs are the highest priority in the field of low-power electric drives. This makes adoption of magnetic bearing technologies difficult in applications with higher production volumes. Since published literature on cost-saving measures in this field is scarce, we present in this paper some ideas and stimuli using three selected examples: 1) a highly integrated hybrid bearing that provides active stabilization in 3 degrees of freedom (DOF); 2) a brushless permanent magnet motor with additional axial bearing capability; and 3) a bearingless flux-switching motor. We describe their particular designs and operational features, and compare the additional mechanical and electrical costs of these and similar systems with those of standard motor technologies. This paper concludes with a stability analysis of example 2), since it features passive permanent magnetic bearings, which are inherently only weakly attenuated.

A hybrid solenoid model comprising eddy currents

In modern injection systems and pneumatic valves the volume flow is commonly adjusted by controlling the electromagnet. The influence of eddy currents on the dynamic response of the nonlinear magnetic system is well covered in the recent literature. The large scale actuators like high force lifting magnets with strong nonlinearities require a high fidelity model, due to the big air gap change. Furthermore, the ohmic losses caused by eddy currents have to be taken into account during dynamic operation. It is shown in the paper that the nonlinear eddy current problem can be approximated using quasi-static finite element methods and magnetic equivalent circuits. A comparison of the hybrid model with finite element methods shows a promising coherence.

Bearingless segment motor with Halbach magnet

Today magnetically levitated rotors are mainly used in applications where wearless operation and high life cycle are of importance (e.g. in the pharmaceutical, biomedical, chemical and semiconductor industry). The bearingless slice motor features a very compact design because three degrees of freedom (one translational and two rotatory) are passively stabilized by reluctance forces. Therefore, only two translational degrees of freedom remain to be actively controlled. This paper introduces a new bearingless segment motor (a subtype of the bearingless slice motor) featuring a Halbach magnet ring mounted on the rotor. Thus, no back iron is needed on the rotor and therefore the overall weight of the permanent magnet excited disc-shaped rotor is reduced to a minimum. The bearing forces which can be created by one optimized stator segment are calculated analytically. These results allow conclusions for the total force locus. A prototype is built and measurements verify the results of the analytic considerations.

An electromagnet model comprehending eddy current and end effects

In modern injection systems and pneumatic valves, solenoid valves are widely spreaded for a volume flow control. The recent literature covers the influence of eddy current on the dynamic response for solenoid valves in depth. Basically pot core assemblies were taken into account and small air gap scenarios were investigated. The large scale actuators like high force lifting magnets are regarded in the present work and the proposed model is not limited to pot cores, because end effects are considered. The inverter operation opens opportunities for different excitation voltages and a high precision model including nonlinearities is required for the loss reduction of the total actuator. It is shown that the proposed model exhibits a promising coherence with the measurements. The proposed model utilizes magnetic equivalent circuits and quasi-static finite elements methods.

Magnetic levitation systems for cost-sensitive applications

Alongside technical performance features, low system costs are the highest priority in the field of low-power electric drives. This makes adoption of magnetic bearing technologies difficult in applications with higher production volumes. Achieving success in such cost-sensitive applications requires abandoning classical magnetic bearing designs and simplifying magnetically suspended drive systems by using mechatronic approaches. This paper presents ideas and stimuli in relation to meeting the demands for high-scale integration and cost-reducing design measures. Three examples selected from recent and current research and development projects of the mechatronic research center LCM and Johannes Kepler University Linz (JKU), Austria, illustrate conceptual simplifications of magnetic bearing systems and permanent magnet synchronous drives, and their integrative combinations.

Active position control of high speed drive systems

High speed drive systems are often described at an operating point above the critical speed. Therefore, the resonance frequencies have to be passed twice (start up / run down). In the worst case, the strong vibrations at critical speeds can lead to self-destruction. Unbalanced rotors are the main cause for the self-excited vibrations. Over the past years, the focus of investigations [1] was laid on the improvement of the operating characteristics by using passive elements to guarantee stability of the system. However, the transition through the critical speed is still an unwanted high mechanical strain. In this paper, an innovative concept for rotary drives will be presented, which is able to compensate excessive vibrations or deflections actively. A permanent magnet excited synchronous motor (PMSM), which is able to generate motor torque and radial force simultaneously [2], with a large air gap is used. The capability of generating a highly dynamic and active control variable for the rotor position opens up new opportunities for drive applications. In this work, many different technical disciplines are combined, creating a truly mechatronic product.