Permanent magnet synchronous machines (PMSMs) can provide excellent performance in terms of torque density, energy efficiency and controllability. However, PMs on the rotor are prone to the centrifugal force which may break their physical integrity, especially at high-speed operation. Typically, PMs are bound with carbon fiber or retained by alloy sleeves on the rotor surface. This paper is concerned with the design of a rotor retaining sleeve for a 1.12-MW 18-krpm PM machine; its electromagnetic performance is investigated by the 2D finite element method (FEM). Theoretical and numerical analysis of the rotor stress are carried out. For the carbon fiber protective measure, the stresses of three PM configurations and three pole filler materials are compared in terms of operating temperature, rotor speed, retaining sleeve thickness, and interference fit. Then a new hybrid protective measure is proposed and analyzed by the 2D FEM for operational speeds up to 22 krpm (1.2 times the rated). The rotor losses and machine temperatures with the carbon fiber retaining sleeve and the hybrid retaining sleeve are compared and the sleeve design is refined. Two rotors using both designs are prototyped and experimentally tested to validate the effectiveness of the developed techniques for permanent magnet machines. The developed retaining sleeve makes it possible to operate MW PM machines at high speeds of 22 krpm. This opens doors for many high-power high-speed applications such as turbo-generators, aerospace and submarine motor drives.

Electromagnetic design of a 1.12-MW, 18,000-rpm high-speed permanent-magnet motor (HSPMM) is carried out based on the analysis of pole number, stator slot number, rotor outer diameter, air gap length, permanent magnet (PM) material, thickness and pole arc. The no-load and full-load performance of the HSPMM is investigated in this paper by using 2-D finite element method (FEM). In addition, the power losses in the HSPMM including core loss, winding loss, rotor eddy current loss and air friction loss are predicted. Based on the analysis, a prototype motor is manufactured and experimentally tested to verify the machine design.

Background It remains unclear whether retroperitoneal laparoscopic adrenalectomy (RLA) is safe and effective for the treatment of large pheochromocytoma (PHEO). This retrospective study aimed to identify the advantages and disadvantages of RLA compared to open adrenalectomy (OA). Methods This study included 147 patients who underwent RLA ( n = 101) or OA ( n = 46) for PHEO larger than 5 cm. Groups were balanced by propensity score matching (PSM) into 46 pairs. Perioperative variables and long-term follow-up results were compared between the two groups. Results After PSM, patients in the RLA group had a shorter operative time (218 vs. 245 min, P = 0.040), quicker bowel recovery (2 vs. 3 days, P = 0.046), and a shorter hospital stay (8 vs. 9 days, P = 0.010) compared to the OA group. The results of multiple linear regression analyses showed that the operative method (OA vs. RLA) had an influence on the above three postoperative variables ( β = 31.84, P = 0.046; β = 0.76, P = 0.044; and β = 1.25, P = 0.025, respectively). There was no significant difference in the proportion of patients with improved blood pressure (82.61% vs. 69.57%, P = 0.143) between the two groups. Conclusions Both RLA and OA provide similar perioperative and long-term outcomes for the surgical management of large PHEO. RLA is an efficacious and safe surgical method for patients with PHEO larger than 5 cm in diameter.

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