Safety of power transformers, power supply units and similar — Part 1: General requirements The European Standard EN 61558-1:1997, with the incorporation of amendments A1:1998 and A11:2003, 

CONTENTS Page INTRODUCTION..............................................................................................................5 Clause 1 Scope........................................................................................................................6 2 Normative references.................................................................................................7 3 Definitions .................................................................................................................10 4 General requirements ................................................................................................17 5 General notes on tests ...............................................................................................18 6 Ratings ......................................................................................................................20 7 Classification .............................................................................................................20 8 Marking and other information....................................................................................21 9 Protection against accessibility to hazardous live parts ...............................................26 10 Change of input voltage setting ..................................................................................27 11 Output voltage and output current under load .............................................................27 12 No-load output voltage ...............................................................................................28 13 Short-circuit voltage ...................................................................................................28 14 Heating......................................................................................................................28 15 Short circuit and overload protection ..........................................................................34 16 Mechanical strength...................................................................................................38 17 Protection against harmful ingress of dust, solid objects and moisture........................39 18 Insulation resistance and dielectric strength ...............................................................42 19 Construction ..............................................................................................................44 20 Components ..............................................................................................................51 21 Internal wiring ............................................................................................................56 22 Supply connection and other external flexible cables or cords.....................................57 23 Terminals for external conductors ..............................................................................63 24 Provision for protective earthing.................................................................................65 25 Screws and connections ............................................................................................66 26 Creepage distances, clearances and distances through insulation ..............................69 27 Resistance to heat, abnormal heat, fire and tracking ..................................................76 28 Resistance to rusting .................................................................................................78