This part of IEC 61204 specifies electromagnetic compatibility EMC requirements for power supply units PSUs providing d.c. outputs up to 200 V at a power level of up to 30 kW, operating from a.c. or d.c. source voltages of up to 600 V. The devices are for free-standing operation or for use in other equipment when used with adequate electrical and mechanical protection. For certain specialized industrial PSUs, for example in the chemical and metallurgical industry, other product EMC standards may exist. In this case these standards can be used as an other alternative. Since many PSUs are used as components of lager units which are covered by different EMC standards, a classification of power supplies and the applicability of the relevant EMC standards is given in items a) and b) below. a) Power supplies intended for free-standing operation (individual apparatus). This part is applicable to PSUs developed as a unit with a direct function and sold on the market as a stand-alone unit. b) Component power supplies. These can be devided into two categories: 1) Component power supplies considered as equivalent to apparatus. 2) Component power supplies intended for a professional assembler/installer. The object of this part is to define EMC limits and test methods for PSUs. It includes limits for electromagnetic emissions which may cause interference to other electronic equipment (e.g. radio receivers, measuring and computer devices), as well as electromagnetic immunity limits for continuous and transient conducted and radiated disturbances incl. electrostatic discharge.