Lightweight High Energy Density Capacitors for NASA AMPS and PPUs

All NASA Power Processing Units (PPUs) including DC to DC and DC to AC converters and inverters require a DC-link capacitor, placed between the DC source (PV solar array or battery) and the switching power semiconductors. NASA technical personnel has identified a failure mode in Multi-Layer Ceramic (MLC) DC-link capacitors currently used in PPUs that can cause them to short. Polymer Multi- Layer (PML) capacitors that Sigma Technologies proposed as a solution, have self-healing properties and do not short. The Phase I development demonstrated that the PML parts have superior capacitance stability with temperature and voltage bias. MLC capacitance drops by as much as -80% at -196oC and -40% at +200oC , while PML capacitance variation is limited to -15% and 0% respectively. Furthermore, PML capacitors have approximately 5X higher energy density and 10X higher specific energy. In the Phase II program plug compatible PML capacitors with multi-pin electrodes will be produced and evaluated with a voltage rating specifically designed for 120V PPUs. Some PML parts will be produced with the same capacitance as that of MLCs and others with higher capacitance but equal or lower volume. Equal capacitance parts will dramatically reduce capacitor size and weight and will improve reliability. Higher DC-link capacitance is always desirable in PPU circuits, because and it can further minimize ripple current, voltage fluctuations and transient suppression. Use of higher capacitance PML parts, will improve the functionality and reliability of the overall PPU circuit, without a penalty in weight and volume. PML capacitors will be supplied to NASA technical personnel during the development period for electrical and environmental evaluation. The potential business opportunity of expanding the PML capacitor market to that of high voltage and high capacitance MLCs, which are prone to micro-cracking, are costly and have inferior dielectric properties, will be explored.