This article deal with non-conventional methods to affect the crystallization of Al-alloys by the application of electromagnetic field. The application of electromagnetic field is not technically complicated, it does not require mechanical contact with the melt, and the scale of the crystallization influence is not dependent on the thickness of the casting. Two experimental materials were used: AlSi10MgMn and AlSi8Cu2Mn and two values of electromagnetic induction: B = 0.1 T a B = 0.2 T. The best results for alloy AlSi10MgMn were achieved by application of electromagnetic field with induction B = 0.2 T; during this experiment the best mechanical properties were achieved - the biggest increase of mechanical properties was recorded. The best results for alloy AlSi8Cu2Mn were achieved by combination of electromagnetic field with induction B = 0.1 T and modification by 0.05 wt. % Sr. In this case we don´t recommend to use electromagnetic field with induction B = 0.2 T; because of deposition of coarse grains and decreasing of mechanical properties.
Induction surface hardening means the hardening of a thin zone of the material only, while its core remains soft. The paper deals with the modelling of the Consecutive Dual Frequency Induction Hardening (CDFIH) of gear wheels and its validation. For gear wheels with modulus m smaller than 6 mm a contour profile of hardness distribution could be obtained. The investigated gear wheel is heated first by a medium frequency inductor to the temperature approximately equal to the modified lower temperature Ac1m. It means beginning of the austenite transformation. Then the gear wheel is heated by the high frequency inductor to the hardening temperature making it possible to complete the austenite transformation and immediately cooled. In order to design the process it is necessary to identify modified critical temperatures and to obtain expected temperature distribution within the whole tooth.
The uncontrolled rectifier and controlled rectifier which use fixed switching frequency control strategy are applied usually during the working of a high-power high- speed permanent magnet generator (HSPMG). Even for the controlled rectifier, it will generate harmonics. The electromagnetic performance of the HSPMG is also affected by these harmonics. In this paper, the influences of the fixed switching frequency control strategy on a HSPMG were studied. Based on the Fourier theory, the harmonic currents of the generator were analyzed, and the change of harmonic distribution range and current total harmonic distortion (THD) were obtained. By using an indirect field-circuit coupling method, the influences of the fixed switching frequency control strategy on the losses and torque of the generator were analyzed. The relations between the switching frequency and the losses and torque of the generator were obtained, and the change mechanism of the loss was revealed. The obtained conclusions can provide reference for the optimized choice of the switching frequency of the distributed generation system with the HSPMG. It can also provide support for the HSPMG electromagnetic structural optimization and the optimization of the loss and harmonic on the system level.
In this paper, a three-air-gapped structure of a ferrite core for a resonant inductor is proposed. The electromagnetic and thermal field models are built using a 3D finite element method. Compared with the conventional signal-air-gapped structure of a ferrite core, the simulation and analysis results show that the proposed three-air-gapped ferrite core resonant inductor can reduce eddy-current loss and decrease temperature rise. In addition, the optimal position of air-gapped is presented.