Influence of the Lamination Material and Rotor Pole Geometry on the Performance of Wound Field Synchronous Machines

This paper examines the influence of the lamination material and rotor pole geometry on the steady-state performance of a wound field synchronous machine operated in the generating mode. The investigations are carried out through 2D finite element analyses using a commercial software package. Non-Oriented silicon-iron alloys of various grades are selected to recognize the impact of their magnetic properties on the machine performance. Different methods for the extrapolation of BH curves from low medium field levels to saturation are reviewed and compared. The effect of using different materials on both the rotor and the stator core is assessed in terms of variation of the air gap power, the torque ripple and the core losses. The performance of a new machine featuring a higher-grade lamination material and a refined rotor pole geometry are compared at constant air gap power with those of the reference machine. The results show that, depending on the adopted strategy, it is possible to almost halve the torque ripple and slightly decrease the mass of the rotor core

Design and Analysis of High-Speed Induction Machines for Submerged Cryogenic Pumps

This paper discusses the electromagnetic design and loss analysis of a 15 kW, 13500 rpm induction machine for a single-stage submerged cryogenic pump. The study starts from an existing machine driving a three-stage cryogenic pump, rated 7.5 kW at 7300 rpm. The new motor design is approached by increasing the rotating speed of the reference machine at fixed outer diameter, aiming at an optimum between efficiency and power factor. Experimental investigations are carried out on the reference machine to analyze its thermal behavior. The results allow to obtain initial values for the electrical loadability of cryogenic induction machines. The electromagnetic design of the high-speed motor is successfully carried out with the help of detailed numerical simulations, particularly devoted to a precise analysis of the losses active in the machine. Special care is given to the iron losses, estimated with two different approaches

Losses Analysis of Induction Motors under Ambient and Cryogenic Conditions

Cryogenic induction machines have been re-emerging as a potential solution to increase the current power density for challenging specific power applications. Compared with an ambient temperature operation, cryogenic conditions allow higher power density and increased efficiency due to the decrease of electric resistivity of conducting materials and increased cooling capability. This work focuses on the losses analysis of induction machines immersed in liquid nitrogen. Under ambient and cryogenic conditions, experimental tests are performed and presented for two induction machines, a 90 W 40 V induction machine, and a 550 W 400 V induction machine, to evaluate the mechanical, iron and residual losses, and the change of their equivalent circuit parameters

Iron Loss Characterization in Laminated Cores at Room and Liquid Nitrogen Temperature

This paper presents the characterization of the magnetic properties of laminated cores for electrical machines at ambient and cryogenic temperature. Silicon-iron stator cores of different steel grades are characterized experimentally at room temperature and when immersed in a liquid nitrogen atmosphere. The magnetic characterizations involve the measurement of the normal magnetization curve, and the core losses in a wide range of frequencies and magnetic flux densities. The separation of the losses into their physical components is carried out with an energy-based approach aiming at a thorough analysis of each loss contribution. The results show that the cryogenic temperature does not significantly impact the magnetization characteristic of the material, regardless the tested steel grade. The core losses generally increase at cryogenic temperature. The separation of the losses into components shows that the hysteresis contribution is not much affected by the cryogenic temperature; the global dynamic losses increase at a rate that depends on the steel grade instead, at least in the examined frequency and flux density ranges