Interdisciplinary Design of a High-Speed Drivetrain for a Kinetic Compressor in a High-Temperature Heat Pump

Abstract

Bearingless motor (BM) technology offers a competitive solution to active magnetic bearings (AMBs) in high-speed applications. A bearingless drivetrain (BDT) working as a part of a kinetic compressor in a heat pump exceeding 0.5 MW and 25 000 rpm is open for questions: how should the geometry, materials and parameters be chosen without exceeding electromechanical and thermal limits; what rotor configuration suits the heat pump; how can the working fluid of the heat pump be used in the motor cooling? This paper presents the interdisciplinary design process of a BDT as a part of the compressor of a high temperature heat pump (HTHP). The motor -as the core driving the compressor of the heat pump, each interacting with the other, bringing about various design challenges -design process is summarized in a flowchart and subsequently elaborated. Dimensioning rules for the bearingless structures are presented. Finite element analysis (FEA) is used in evaluating the considered surface and interior permanent magnet BM structures. Different stack materials are considered and preliminary electromechanical optimization by a genetic algorithm is carried out. To ensure structural rigidity, FEA of electromagnetic, mechanical, thermal, and rotor dynamic performance is conducted. FEA of drive losses is carried out and cooling alternatives are considered, based on which temperature distributions and thermal stresses with the chosen cooling arrangements are calculated again with FEA. Power and performance of the structures are discussed. As a result of the analyses, a suitable hermetic motor design is chosen for the HTHP compressor drive INDEX TERMS Bearingless motor, interdisciplinary, multiobjective optimization, electromagnetic analysis, high-speed, high-temperature heat pump application, kinetic compressor, rotor dynamics, thermal analysis, thermal stresses I. INTRODUCTION

Dynamics of a High-Power AMB–Multirotor Drivetrain

“…However, because of the integrated solution, the scalability for higher speeds or powers requires large and timely design iterations, as the speed and size are limited by the dynamics and stresses. In addition, alternatives to AMBs, such as high-power bearingless technology, are still in the early commercialization stage for compressor applications, as reported, e.g., in [8] and [24]. To overcome the scalability issue, a flexural coupling is proposed.…”

“…AMBs have been applied in high-speed rotating machines for decades, especially in integrated applications, such as compressors [22]. The scalability of integrated solutions is very limited because of the operation is close to the physical limits compromising dynamical behavior, mechanical rigidity, and thermal load [23], [24] to which, e.g., changes in geometry are significantly interconnected. Thus, the upscaling or application adjustments of these types of machines require extensive design iterations where all the factors have to be taken into account simultaneously.…”

“…Thus, the upscaling or application adjustments of these types of machines require extensive design iterations where all the factors have to be taken into account simultaneously. To design these machines, multidisciplinary convoluted approaches have been suggested, e.g., in [24]. We propose the deployment of a flexural coupling to allow the use of an AMB-rotor with different applications.…”

Research Progress of Enhanced Thermal Evacuation and Cooling Technology for High-Speed Motors

“…High-speed motors can also provide a driving force for turbo-machinery [14][15][16][17]. Both rotor speed and power requirements are imposed on high-speed motors.…”

Dynamics of High-Power Multi-Rotor System

“…The process is multidisciplinary, convoluted, laborious and demands highly skilled team to be accomplish, e.g. in [10], [11] and [12].…”