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The Smart Current Limiter is a switching DC to DC converter that provides a digitally pre-set input current control for inrush limiting and power management. Being able to digitally adjust the current level in combination with external feedback can be used for control systems like temperature control in high power DC appliances. Traditionally inrush current limiting is done using a passive resistance whose resistance changes depending on the current level. Bypassing this inrush limiting resister with a Mosfet improves efficiency and controllability, but footprint and losses remain large. A switched current mode controlled inrush limiter can limit inrush currents and even control the amount of current passing to the application. This enables power management and inrush current limitation in a single device. To reduce footprint and costs a balance between losses and cost-price on one side and electromagnetic interference on the other side is sought and an optimum switching frequency is chosen. To reduce cost and copper usage, switching happens on a high frequency of 300kHz. This increases the switching losses but greatly reduces the inductor size and cost compared to switching supplies running on lower frequencies. Additional filter circuits like snubbers are necessary to keep the control signals and therefore the output current stable.
Fontys University of Applied Science’s Institute of Engineering, and the Dutch Institute for Fundamental Energy Research (DIFFER) are proposing to set up a professorship to develop novel sensors for fusion reactors. Sensors are a critical component to control and optimise the unstable plasma of Tokamak reactors. However, sensor systems are particularly challenging in fusion-plasma facing components, such as the divertor. The extreme conditions make it impossible to directly incorporate sensors. Furthermore, in advanced reactor concepts, such as DEMO, access to the plasma via ports will be extremely limited. Therefore, indirect or non-contact sensing modalities must be employed. The research group Distributed Sensor Systems (DSS) will develop microwave sensor systems for characterising the plasma in a tokamak’s divertor. DSS will take advantage of recent rapid developments in high frequency integrated circuits, found, for instance, in automotive radar systems, to develop digital reflectometers. Access through the divertor wall will be achieved via surface waveguide structures. The waveguide will be printed using 3D tungsten printing that has improved precision, and reduced roughness. These components will be tested for durability at DIFFER facilities. The performance of the microwave reflectometer, including waveguides, will be tested by using it to analyse the geometry and dynamics of the Magnum PSI plasma beam. The development of sensor-based systems is an important aspect in the integrated research and education program in Electrical Engineering, where DSS is based. The sensing requirements from DIFFER offers an interesting and highly relevant research theme to DSS and exciting projects for engineering students. Hence, this collaboration will strengthen both institutes and the educational offerings at the institute of engineering. Furthermore millimeter wave (mmWave) sensors have a wide range of potential applications, from plasma characterisation (as in this proposal) though to waste separation. Our research will be a step towards realising these broader application areas.
