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Permanent magnet (PM) machines have attracted much attention in the field of flywheel energy storage system (FESS) due to their merits of high power density and high efficiency. However, the flux generated by the PMs would cause large stator core loss during the idling state of FESS, which would reduce the energy conversion ratio and limit the application of FESS in long-term energy storage occasions. Addressing this issue, a novel dual-rotor single-stator coreless PM machine (DSSCPMM) with dual-flywheel is proposed in this article. The stator of the DSSCPMM is made of ceramic material, which can effectively eliminate the stator core loss. The rotor of the DSSCPMM contains inner and outer rotors, which are used as the flywheels and can be helpful to improve the energy storage density. First, the structure and operation principle of the proposed DSSCPMM are illustrated. Then, the influences of the key structure parameters and arrangement of PMs, winding configurations, and magnetization method on the electromagnetic performance of the proposed DSSCPMM are investigated. Finally, the optimized structure of the DSSCPMM is obtained and the efficiency is calculated. The result shows that the proposed DSSCPMM is a promising candidate for the application of FESS. [ABSTRACT FROM AUTHOR]

In order to resolve the starting problem for position sensorless interior permanent magnet synchronous motor, an improved initial rotor position estimation method based on square-wave signal injection is presented in this paper. Instead of the conventional sinusoidal voltage injection, square-wave voltage signals are injected into stator windings to obtain magnet pole position. On the basis of saturation and saliency principle, the voltage pulse injection method was adopted to identify the magnet polarity. Detecting the magnet pole position by using the square-wave voltage injection, the error signal can be calculated without low-pass filters and time delays. The proposed method is verified via a 1.5 kW interior permanent magnet synchronous motor drive platform. [ABSTRACT FROM AUTHOR]

In this paper, a new modular multi-stage axial flux permanent magnet synchronous motor is proposed for the traction motor applications, which has the features of slotted north–south-pole topology, segmented and yokeless stator, ellipsoidal similar Somaloy teeth, and flexible power circuits. To minimize the cogging torque, a cost-effective asymmetrical bidirectional magnet skewing (ABMS) technique is adopted in the motor. Various ABMS combinations are studied with different skew angles and cross positions. Both the theoretical analysis and finite-element method (FEM) illustrate that ABMS has both the skewing and phase shifting effects. Based on a 2 kW-1000 r/min, 10-pole 12-open-slot prototype, the experiments are developed. The results measured by experiments agree well with the ones predicated by 3-D FEM, which verifies the conclusions and design. [ABSTRACT FROM PUBLISHER]