High-speed solid-rotor induction machines (HSIMs) are popular within high-speed (HS) applications because of their high rotor structural integrity and their fairly well-established manufacturing process guaranteeing high quality series products. Designing a new HS electric machine requires a multidisciplinary team to accomplish the machine performance desired. In case of a HS machine design, the components and applied materials often reach their physical limits at the rated operating condition. Therefore, the design process is highly iterative and, thus, a systematic approach has a high potential to reduce the time of the design phase significantly. In this article, a systematic design process is proposed for a modular, multimegawatt (MMW) HSIM with three radial active magnetic bearings. The process includes a traditional multidisciplinary design flow with extra critical aspects of MMW HS machines: manufacturability, bearing system, housing, and operating unit. In addition, the manufactured machine is reported. The proposed systematic design process is described, including several multidisciplinary critical design aspects of HS machinery.

Active magnetic bearings (AMBs) offer frictionless suspension, vibration insulation, programmable stiffness, and damping, among other advantages, in levitated rotor applications. However, AMBs are inherently unstable and require accurate system models for the high-performance model-based multi-input multi-output control of rotor position. Control electronics with high calculation capacity and accurate sensors of AMBs provide an opportunity to implement various identification schemes. A variety of artificial excitation signal-based identification methods can thus be achieved with no additional hardware. In this paper, a selection of excitation signals, namely the pseudorandom binary sequence (PRBS), chirp signal, multisine, and stepped sine are presented, applied, and compared with the AMB system identification. From the identification experiments, the rotor-bearing system, the inner current control loop, and values of position and current stiffness are identified. Unlike recently published works considering excitation-based identification of AMB rotor systems, it is demonstrated that identification of the rotor system dynamics can be carried out using various well-established excitation signals. Application and feasibility of these excitation signals in AMB rotor systems are analyzed based on experimental results

In high-speed compressor and turbine applications, active magnetic bearings are employed to increase reliability, reduce maintenance, and provide contact-free and oil-free operation. Evidently, the dynamic performance of active magnetic bearings must correspond to application-specific events like compressor surge or thrust disturbances. This article presents a segmented stator as one of the solutions to increase the bandwidth of axial active magnetic bearings (AMBs) and further improve the stability of the shaft system. We analyze the effects and discuss the tradeoffs of axial active magnetic bearing stator segmentation and slitting to alleviate bandwidth limitations. Finite element method design optimization and control plant modeling methods, open- and closed-loop tests, and identification of the overall thrust AMB–rotor control plant are studied.

Bearingless motor (BLM) technology offers a competitive solution to active magnetic bearings (AMBs) in high-speed applications. A bearingless drivetrain (BLDT) working as 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 the electromechanical and thermal limits; what rotor configuration would suit the heat pump; and how can the working fluid of the heat pump be used in the motor cooling? This paper presents the interdisciplinary design process of a BLDT as part of the compressor of a high-temperature heat pump (HTHP). The motor design process—the motor constituting the core driving the compressor of the heat pump, each interacting with the others, thus bringing about various design challenges—is summarized in a flowchart and subsequently elaborated on. Dimensioning rules for the bearingless structures are presented. Finite element analysis (FEA) is used to evaluate the surface and interior permanent magnet BLM structures under consideration. 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. The 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 drivetrain.

In active magnetic bearing control systems, the performance of the closed-loop control and the application can be impaired by external disturbances. This article analyzes the unbalanced magnetic pull forces produced by the eccentricity of a high-speed 1MW 3-phase solid rotor induction motor. The effect of unbalanced magnetic pull on a five-degree-of-freedom active magnetic bearing control and the resulting vibrations are studied. Finite-element-method-based modeling of the electrical machine unbalanced magnetic pull and active magnetic bearing forces is carried out, and the results are used in the harmonic force analysis and modeling of an active magnetic bearing–rotor system. The overall engineering model comprising the rotor dynamics, unbalanced magnetic pull derived by the finite element method, active magnetic bearing forces, and the controller is tested by time-stepping simulations. The simulations and experimental results are reviewed. The severity of the unbalanced magnetic pull and its effects on the robustness of the active magnetic bearing closed-loop system in a hermetic steam turbogenerator applied in marine waste heat recovery systems are evaluated.

The paper reports on the implementation and the design of a controller for a fuel cell blower (FCB) with active magnetic bearings (AMBs). The cascaded position-fluxcentralized controller is comprised of a centralized position control loop and an inner flux control loop. The last one is based on state estimation without explicit flux measurements. As the position control is not dependent on the magnetic field nonlinearities, such a control structure enables operation under a zero bias. The practical working implementation of a flux control for the industrial levitated rotor is shown for the first time. The flux control gives better results than current control for both normal and zero bias operation. The system is analyzed fully, combining rotor dynamics and power amplifier analyses simultaneously. The importance of using the coil voltage in addition to current and practical treatment of the flux control is revealed. The centralized position-flux controller is compared with a state-of-the-art cascaded position-current control, which has inner current control loops. The proposed control solution with a zero bias can achieve a dynamic performance comparable that of a controller with the classical bias current.