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The unbalanced magnetic force (UMF) occurs in permanent magnet (PM) machines when there is rotor eccentricity. This paper investigates the influence of slot/pole combination and magnet thickness on UMF in PM machines having different rotor eccentricities and magnetizations. It shows the machines with different magnetizations have different UMFs due to rotor eccentricity when magnet thickness and slot/pole...
This paper presents a high-efficiency optimum frequency tracking scheme with the ability to control the velocity for the ultrasonic motor. Prior to developing the scheme, characteristics of the ultrasonic motor being excited at the optimum frequency are analyzed, based on the mechanical quality factor of the ultrasonic motor. Then, the amplitudes and frequency of the input voltages are applied to...
In this paper, the influence of magnet thickness on the electromagnetic performance of high speed machines is comprehensively investigated. The investigation is carried out based on a conventional 3-slot/2-pole high speed machine with diametric magnetization. Both the finite element method (FEM) and analytical models are used. The rated output torque is fixed when the magnet thickness varies. It is...
High speed machines have received much attention recently. However, unbalanced magnetic force (UMF) may occur in some slot/pole number combinations even there is no rotor eccentricity, which can cause high vibration and noise. In order to reduce the rated on-load UMF, three 3-slot/2-pole permanent magnet (PM) machines with different auxiliary slots are investigated and compared in this paper. In the...
Magnet eddy current loss is very important for any types of permanent magnet machines, especially for high-speed permanent magnet machine since it increases significantly with rotating speed and has a great effect on the temperature of magnet material, and hence the electromagnetic performance, as well as irreversible demagnetization of the magnets. In this paper, a new method is proposed to reduce...
Based on the basic voltage and flux equations of the Doubly Fed Induction Generator, this paper derived expressions of short-circuit current of wind turbines, which are expressed by transient equations of stator and rotor flux. The transient equations of stator and rotor flux were functions of initial values of stator and rotor flux and transient time constants of stator and rotor windings. The initial...
The light armored equipment has been widely used in modern wars, but it is vulnerable to be destroyed by the incoming projectile, so its battlefield survivability can not be guaranteed. In this paper, a four-channel security system has been designed based on further study of rocket fuze which is used in the light armored Active Protection System. It can quickly and reliably lift the arming and be...
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