Operation of a versatile multi-power supply system driving non-axisymmetric coil sets on the DIII-D tokamak

We describe the development, and implementation of the DIII-D tokamak power supply system driving non-axisymmetric coil sets. The coil system operates in a broad range of 0 to 7 kA and dc up to 40 kHz using different combinations of power supplies. Three types of power supplies drive the tokamak´s non-axisymmetric coil sets; variable unipolar quasi-dc SCR supplies, bi-polar switching power amplifiers, and linear amplifiers. The coils are used primarily for error field correction, resistive wall mode studies, and edge localized mode suppression. A versatile computer program generates the power supply - coil interconnections in the patch panel area for a specific experiment. Control of individual coils, or combinations of coils, is accomplished using the plasma control system (PCS). An upgrade to a precision response of the high current unipolar SCR power supplies has been under development. We discuss routine operation, coil control using the PCS, and challenges in maintaining this complex system.