Papers by Keyword: Permanent Magnet

Abstract: This paper presents a quantitative comparison between the non-rare-earth permanent magnet (PM) and rare-earth PM based linear magnetic gear. By using the finite element analysis, three linear magnetic gears adopting either the non-rare-earth PM or rare-earth PM are analyzed and discussed. Hence, the cost-effectiveness comparison among different types of PMs is conducted. The results indicate that the non-rare-earth PM is preferred to the rare-earth PM for application to linear magnetic gears when cost-effectiveness is emphasized.

Abstract: According to the requirement for variable-frequency power supply when a liner motor runs in a household appliance, a variable frequency speed regulation system of three-phase SPWM is designed based on ATmega48 Micro-controller. The hardware structure, the SPWM technology of software program and V/f control strategy are analyzed. In the end of this paper, experiment waves are illustrated. The results show that the running of the system is simple and convenient; the reliability of the system is excellent.

Abstract: When designing a magnetic levitation system it is assumed that the magnets are ideally magnetized. In practice, however, this is not the case and deviations occur in the magnetization. In this paper two types of deviations are considered, namely a constant angular deviation and the magnetization error. Calculations show that a constant error has larger impact on the performance of a gravity compensator than the magnetization error.

Abstract: A new frog-leg winding permanent-magnet (PM) brushless DC motor is proposed in this paper. Besides PM excitation and electric commutation, the motor has a type of mesh winding inherited from the conventional brushed DC motor. With the aid of a position sensor, the new motors operation principle is basically as same as the brushed one. Based on the frog-leg winding configuration of simplex lap and duplex wave, the motor is designed with 4 poles and 22 slots, and the number of phases is set as 11. Furthermore, an exact analytical method for predicting the instantaneous magnetic field, electromotive force (EMF) induced in the armature winding, cogging torque and output torque of the new motor is introduced. Results from this analytical method are compatible with corresponding finite element analyses (FEA).

Abstract: The operation of linear oscillating system is complicated, involving system nonlinearities of both actuator and load, and variations of driving frequency in order to track the mechanical resonance. In this paper, the state-variable modeling technique is used to analytically investigate the influence of actuator reluctance force on the performance of linear oscillating systems. The analytical derivations will be validated by simulations, and good agreements are achieved.

Abstract: The new Nd-Fe-B magnets were prepared by powder metallurgical processing. The thermal stability and magnetic properties were found to be remarkably improved after annealing at 680 °C for 2 h. The B_r, and H_c, BH of annealed magnets were improved by-0.04 T, 132 KA·m^-1, 22 KJ·m^-3, from 1.25 T, 882 KA·m^-1, 286 KJ·m^-3 of the as-sintered magnets, respectively. The losses and average temperature coefficients of magnetic properties were very low at 373 K. Compare with the as-sintered magnets, the magnetic property losses of the annealed magnets decreased by half at different temperature. Scanning electron microscopy on magnets did reveal a noticeable difference in phase morphology, and found that the improvements of thermal stability and magnetic properties can be attributed to the change of magnetic domain wall motion, composition, stray demagnetizing fields, and microstructure. The new Nd-Fe-B preferment magnets are promising to use in the all-electric bus hub direct drive motor.

Abstract: Nd_3-xY_xFe_27.5Ti_1.5(0.6≤x≤2.4) and Nd_3-x’Y_x’Fe_27.5Mo_1.5 (0.6≤x’≤2.4) alloys have been synthesized successfully and studied by means of powder neutron diffraction. The structural analyses indicate that the main phases in all cases crystallize in the monoclinic Nd₃(Fe,Ti)₂₉-type structure with a space group A2/m. Ti and Mo prefer to occupy 4g, 4i1 and 4i2 sites exclusively and the elemental site occupancies are dominated by the site sizes and thermodynamic effects.

Abstract: A novel magnetic suspension platform is studied in this paper. Three sets of suspension apparatus is adopted to produce suspension force, each of which consists of the permanent magnet, the U shape yoke and suspension coils. Material of yoke is laminated transformer silicon steel (30ZH100).Material of Permanent magnet is Nd2Fe14B. The mathematical model of suspension was established by analyzing the force exerting on rotor. In view of the levitation system with multi-variable, nonlinear, strong coupling characteristics, ADRC is applied to realize decoupling and disturbance rejection. The rule of ADRC parameter setting was obtained through lots of simulations. The simulation and experimental results indicate this suspension altitude control system has better dynamic characteristics and robust.

Abstract: Barium - Strontium Hexaferrite and Barium Strontium Titanate are both well established materials which widely used respectively as permanent magnets and piezoelectric devices. As the properties are a structure sensitive, materials structure as well as crystal structure must be properly designed to meet a specific application. In this paper, we report our recent investigation on material structure analysis of Ba_0.3Sr_0.7Fe₁₂O₁₉ and Ba_0.7Sr_0.3TiO₃ composite system prepared by a mechanical alloying process to promote feroic properties. The average of particle size for composites system was found initially increased to a large size of 9 μm after mechanically milled for 30 hours and then start to decreased to smaller size of ~ 5μm when the milling time was extended to 80 hours and showing trend toward further reduction in mean particle sizes. In the latter case, the XRD trace for milled powders showed broadened diffracted peaks pattern due to deformation during mechanically milling. After sintering at a temperature of 1050 °C much finer crystallites of 7-13 nm size in a dense pellet were observed. Hence, sintering to the milled particles has promoted formation of nanocrystal containing particles. The mean crystallite size for magnetic phase was about more than 350 times smaller than the mean particle size of composite particles. Finer crystallite sizes were found in B₃SF in which the mean was about 700 times smaller than the mean particle size. The magnetic and electric properties of the composite system are also discussed.

Abstract: Savonius windmill having advantages high starting torque and simple construction is applicable for Indonesia as a developing country with annual average wind speed 4,5 5,0 m/s. The purpose of the experiment is to identify characteristics of an electric machine used for low speed electric generator. The electric machine for the experiment is a permanent magnet electric motor usually used for electric bicycle. The electric motor is tested as an electric generator and rotated with variations of speed. Outputs of the generator are torque, voltage and current with 1) variation of lamps-load, 2) constant voltage-load for 12 volt and 24 volt battery charging and 3) combination of 12 volt battery charging and variation of lamps-load. The average efficiency of the generator is 59,8% and 65,4% for 12 volt and 24 volt battery charging. Battery charging starts at 95 rpm and maximum electric generating current is 20 Ampere at generator speed about 175 rpm.