The technology of extra-high voltage multi-circuit transmission lines on same tower is one novel transmitting technology, which can obviously decrease the route way resource, and the transmission capacity per area is increased prominently. But its electromagnetic environment problem is one of the keys which affect the feasibility of EHV transmission lines, so it's important to study the electromagnetic environment. This paper calculates the electric field intensity and magnetic field intensity generated by transmission lines in different phase line sequences of different tower modes. We can accurately obtain the electric field and magnetic field distribution under EHV transmission lines using finite element analysis. From these simulating results, we can get the most reasonable position of transmission lines on tower and the best phase line sequence which has the least electromagnetic field intensity in 500 kV/220 kV mixed voltage four-circuit transmission lines on same tower. This can provide theoretic reference for construction of transmission lines.

It is well known that the use of slotted stators in motors produces undesirable effects, such as magnetic flux distortion, additional losses, ripple torque, and vibration. However, a large number of studies pay more attention to stator slots and magnetic slot wedges (MSW) in asynchronous motors and permanent magnet motors, ignoring the same problems in large capacity high voltage line start permanent magnet synchronous motors (HVLSPMSM). In order to disclose the effect of the stator slot on HVLSPMSMs, the no-load air gap magnetic field distribution and stator leakage reactance are studied. Meanwhile, the differences in the starting torque, pull-in torque and pull-out torque of four slot models are compared, and the starting performance is more affected by stator slot. In practical manufacturing, the application of MSWs is the main way to change the electromagnetic performance of stator slots, so the influence of MSWs under different permeabilities on the performance of HVLSPMSMs is investigated. Finally, the effect of a stator slot on the motor starting performance and the rated performance are verified by prototypes and experimental tests, which provide a reference for the application of MSWs in HVLSPMSMs.

This paper presents a method for reducing the cogging torque and ripple torque of interior permanent magnet synchronous motor (IPMSM) based on the magnetic field harmonic offset method. This method establishes the internal correlation between cogging torque harmonics and ripple torque harmonics. The suppression or cancellation of magnetic field harmonics in the rotor pole is utilized as transmission link to simultaneously weaken or eliminate lower order harmonics of cogging torque and ripple torque, which can improve operating quality of the IPMSM and obtain an acceptable total average torque. A mathematical and physical model of harmonic offset method for cogging torque is established, the distribution characteristics of permeability harmonics and field harmonics that affect cogging torque are analyzed, the analytical expression for the electromagnetic torque of the IPMSM including reluctance torque is derived, and the collaborative suppression mechanism of cogging torque and ripple torque, as well as common solutions, are studied. Finally, the suppression law of cogging torque and operating ripple torque is verified by the finite element simulation, and the compromise selection principle of permanent magnetic pole is summarized. Due to the absence of the average torque of motor in the offset method, the effects of effective pole arc of the combined rotor on the torque ripple and torque-speed characteristic curve of the IPMSM are compared and evaluated.

This paper attempts to present the structures and characteristics of multipolar permanent magnet synchronous submersible motor (MPMSSM) for screw pump. The structures of stator lamination, rotor lamination and stator winding are analyzed. And how temperature influences the performance of the motor is presented. Moreover, how to calculate air-gap length and the size of permanent magnet of MPMSSM are discussed. The MATLAB is used to design the prototype. And, the computer simulation results of magnetic field of the motor are shown by ANSOFT according to its model. The structure and design method of this motor can be used on common MPMSSM.