Inrush Current Limitation for the Modular Reconnaissance Pod in F16 Jet Fighters

During the F16 fighter mid life update, the Over Current Protection Unit (OCPU) was changed to a faster type. The Modular Reconnaissance Pod delivered by TERMA is capable of triggering the new OCPU. The problem has been identified to be the inrush current to the compressor motor in the Environmental Control Unit (ECU). The problem was temporary solved by adding a Variable Frequency Converter (VFC) between the ECU and the OCPU. However, adding a VFC caused the Power Factor (PF) to fall below the given limits in MIL-STD-704A. A set of solutions has been investigated through simulations. Among the solutions we have: 1) Adding an inductor into the dc-link (dc-tank) 2) Adding three inductors in front of the VFC 3) A combination of the two The simulations revealed that the ?optimum? solution is to place one 90 µH (or two 45 µH) inductor into the dc-link. This will increase the power factor from 0.69 to 0.76 (inductive/lagging) at an input power of 2.47 kW and further up to 0.90 for an input power of 6.0 kW. An inductor made from the METGLAS POWERLITE AMCC 6.3 core will do the work. The turn number is calculated to 16 with a corresponding air-gab of 0.57 mm. The power losses in the inductor are estimated to 7.1 W at an input power of 6.0 kW. The power loss in the dc-link capacitors is estimated in the light of the simulated results. The loss in each of the four capacitors amounts to 1.75 W, which on the surface of the Earth correspond to a temperature increase of 26 K in proportion to the ambient temperature." Christian Klumpner, Gert K. Andersen, Frede Blaabjerg, Søren B. Kjær. Partner: Theiss Stenstrøm, Danfoss Corporate Ventures A/S