Update of beam dynamics requirements for HL-LHC electrical circuits

Since the publication of the document providing the specifications of the new circuits of the HL-LHC (see CERN-ACC-2017-0101), using criteria based on beam dynamics considerations, more accurate performance expectations of the power converter technology have been made available. Moreover, cost optimisation and technological considerations on the initially-proposed choices made it necessary a review of the previous document together with some clarifications of some details of the previous analysis. The impact on beam parameters of the newly-proposed solutions and new power converter specifications is carried out in this document, and a summary of the new choices is presented.