Foreword This standards publication is a NEMA Adoptive Standard based on IEC 62040-3@ Uninterruptible power systems (UPS) ?? Part 3: Method of specifying the performance and test requirements. The current edition of IEC 62040-3 is adopted in its entirety with certain differences described in the Amendments clause. As these differences could@ in the future@ be a contribution to a revision of IEC 62040-3 or a related IEC standard@ this publication has been prepared in accordance with ISO/IEC Directives Part 2@ Rules for the structure and drafting of International Standards. The purpose of this publication is to provide guidance to manufacturers and users on specifying and verifying the performance of Uninterruptible Power Systems. This publication covers both installation and manufacturing criteria obtained from manufacturers and users. This publication represents the technical judgment of the NEMA Power Electronics Section with respect to the performance and construction of Uninterruptible Power Systems. This judgment is based on sound engineering principles@ research tests@ manufacturers' records@ and field experience.