Interdisciplinary Design of a High-Speed Drivetrain for a Kinetic Compressor in a High-Temperature Heat Pump
Daria Kepsu, Emil Kurvinen, Jonna Tiainen, Juha Honkatukia, Teemu Turunen-Saaresti, Rafał P. Jastrzębski
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.