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 ldquomagnetically levitated two-level motor.rdquo 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.

In this paper, the design and operating principle of a slotless bearingless slice motor for high rotational speeds is presented. The performance of the proposed concept is evaluated using an experimental prototype. Measurement results demonstrate a stable dynamic behavior during acceleration and an achievable rotational speed of 150 000 rpm, which is, to the knowledge of the authors, the highest rotational speed attained by a bearingless slice motor to date. The system performance is outlined at its maximum speed and power loss measurements are carried out over the entire speed range.

This paper describes important design considerations for a bearingless brushless motor (permanent magnet synchronous motor, PMSM) in exterior rotor construction. In order to come up with a compact energy-dense setup which can provide both bearing forces and high torque, several parameters have to be accounted for while considering mutual dependences. Moreover, the magnetic bearing and the drive are interlinked for this disk-shaped bearingless motor (with combined concentrated windings). A detailed analysis about the design of the stator teeth has been undertaken, and the influence on torque and active and passive radial forces has been investigated.

Stirred tank bioreactors are still the predominant cultivation systems in large scale biopharmaceutical production. Today, several manufacturers provide both reusable and single-use systems, whereas the broad variety of designs and properties lead to deviations in biological performance. Although the methods for bioreactor characterization are well established, varying experimental conditions and procedures can result in significantly different outcomes. In order to guarantee a reliable comparison and evaluation of different single-use and reusable bioreactor types, standardized methods for their characterization are needed. Equally important is the biological capability of bioreactors, which must be accessed by standardized cultivation procedures of industrially relevant organisms (bacteria, yeasts as well as mammalian and animal cell cultures). In addition, the implementation of well-defined uniform procedures for biological and engineering characterization during the development phase can support a fast assessment of the suitability of a bioreactor system. Based on stirred bioreactors, we describe the aspects of the engineering characterization in order to discuss further the biological characterization as a valuable complement. Finally, a case study is presented.

Highly compact magnetically levitated pump systems are of growing interest in semiconductor processing applications due to the increasing costs of clean room space. The need of a higher hydraulic pressure in a smaller mounting volume raises the necessity of a complete integration of the power and signal electronics together with the motor and the pump into one compact system. Thereby, the system complexity is increased in the first instance and problematic issues such as thermal interaction between the system parts and overheating have to be solved. However, the integration opens the door for an optimization of the complete system. Based on a thermal model and on analytical relations between the hydraulic, electric and mechanical system variables the integrated pump system is optimized aiming for maximum pressure density. Exemplarily, the optimum point is calculated for an existing magnetically levitated pump and the dependency of the hydraulic efficiency is discussed.

For magnetic bearing manufacturers, the installation situations in systems in the field are often unknown and not accessible. Hence, the final system vibration spectrum with respect to excitations by operating the system and therefore mechanical resonances are unknown as well. But to avoid failure, they need to be known before the speed is initially ramped-up in a magnetic bearing suspended system. Therefore, there is a need for an experimental method to predict and prevent already at rotor standstill risks due to plant mechanical resonances. This article shows theoretically and experimentally that conventional magnetic bearing rotor displacement measurement is insensitive on mechanical system resonances. As a solution, two new acoustic response methods are proposed, which can completely detect the system mechanical resonances that will occur during operation already in the standstill levitating state. Furthermore, it is shown with application case studies that these methods can be used for condition monitoring to detect deteriorating changes in the system before rotor speed ramp-up.