In recent years, the European electrical and electronics industry has reworked the safety
standards for surge protective devices (SPDs) several times – in some cases with
significant changes: thus the first edition of EN 60950-1 specified the mandatory use of
surge suppressors. They additionally had to satisfy the then applicable UL 1449 standard
on transient voltage surge suppressors (TVSS).
The second edition of EN 60950-1 stipulates that a varistor used in a primary circuit
must satisfy either IEC 61051-2 or the new UL 1449 3rd Edition.
By Wolfgang Dreipelcher, Epcos