Speaker
Description
Small power converters operate roughly 800 steering magnets and approximately 900 auxial quadrupole magnets in SuperKEKB main ring. These power converters provide a bipolar output of 5 A or 10 A, and most were manufactured during KEKB construction. They did not undergo overhauls during the upgrade from KEKB to SuperKEKB, meaning a significant amount of time has passed since their manufacture. For these small power converters, the current control system uses its own correction coefficients to align the current command value, the actual output current, and the monitored value. An internal monitoring circuit consisting of a shunt resistor and an operational amplifier measures output current. However, over time, ageing-related current measurement errors have emerged, and many units now show significant discrepancies between the monitored output current and the command value. To address this issue, we established a test bench to enable offline powering and testing of the units; we measure errors between the actual output current and the monitored value, prioritising units with the largest discrepancies, and re-acquire and reconfigure correction coefficients. This report details the measurement methods used to assess current measurement errors in these small power converters and presents the results of the correction-coefficient reconfiguration.