Magnetic Flux Controllers in Induction Heating and Melting
MAGNETIC FLUX CONTROLLERS are materials other than the copper coil that are used in induction systems to alter the flow of the magnetic field. Magnetic flux controllers used in power supplying components are not considered in this article. Magnetic flux controllers have been in existence since the development of the induction technique. Michael Faraday used two coils of wire wrapped around an iron core in his experiments that led to Faraday’s law of electromagnetic induction, which states that the electromotive force (emf) induced in a circuit is directly proportional to the time rate of change of the magnetic flux through the circuit. After the development of the induction principle, magnetic flux controllers, in the formof stacks of laminated steel, found widespread use in the development of transformers for more efficient transmission of energy (Ref 1, 2). Magnetic cores gained widespread use in the transformer industry because they increased the amount of magnetic flux produced with the same alternating current. The higher the magnetic flux, the higher the emf, which results in an increase in energy transfer efficiency from the primary winding to the secondary winding. Similar to transformers, magnetic cores were used on early furnaces for induction melting (Ref 1, 2). The benefits of magnetic flux controllers vary depending on the application. For induction heating, magnetic flux controllers can provide favorable and unfavorable paths for magnetic flux to flow, resulting in increased heating in desired areas and reduced the heating in undesirable areas, respectively. Magnetic flux controllers are not used in every induction heating application, but their use has increased (Ref 3, 4).
Improving induction tube welding system performance using soft magnetic composites
This paper aims to demonstrate the benefits of using different impeder materials for induction tube welding systems.,To show the difference in using various impeder materials, a new approach was taken to model tube welding systems in two and three dimensions. Three-dimensional (3-D) electromagnetic models were used to determine the current distribution along the weld vee as well as the permeability of the tube along the length of the welding system. Two-dimensional (2-D) coupled electromagnetic plus thermal models with rotational movement were used to determine the temperature distribution in the heat-affected zone.,Simulation results suggest upwards of 25 per cent system power savings when using a soft magnetic composite (SMC) impeder rather than the traditional ferrites.,There is currently a lack of experimental data to validate the models, but future work will include comparison of models to real-world trials.,When dealing with tube welding systems, there are possibilities to improve process efficiency or increase production quality and output by improving the impeder material.,While simulations of tube welding systems have been done previously, studies on improving impeder materials are rarely carried out. This paper brings to light possible improvements to be made to induction tube welding systems.
17 &mgr;m pixel 640 x 480 microbolometer FPA development at BAE Systems
BAE Systems has developed an advanced 640 x 480 focal plane array (FPA) with a 17 &mgr;m pixel pitch. Sensitivity of ≤ 50 mK was demonstrated and the FPAs were used in imaging demonstrations. Successful scaling of BAE Systems' patented single contact per pixel, single-level microbolometer process to 17 &mgr;m pitch provides a path toward next generation microbolometer imaging systems.