Hello from San Diego (y buenas dias de San Diego):
The intent of the EN 61000-3-2 requirement to measure at rated current is just that: rated current. The objective of EN 61000-3-2 is to minimize the effects of harmonic current on the public network. To this end, the worst- case harmonic current emissions is when the load is operating at maximum current. Hence, the requirement that testing be performed at rated current. For rectifier-capacitor loads such as linear or switching electronic power supplies, worst-case harmonic emissions occurs at maximum dc load at the output of the power supply. It was the intent of the authors of IEC 1000-3-2 that products such as PCs be loaded, artificially if necessary, to the point where the input current is the maximum rated current at the nominal rated voltage. When I measure a product for harmonic current emissions, I measure the power supply by itself with an electronic load set such that the input current is the maximum rated input current. In practice, one need not measure harmonic currents. If the power supply is a linear or switcher rated more than 75 watts, then it fails -- unless it is a switcher with a PFC front-end. If it is less than 75 watts, then it is acceptable. (Even though there are limits for 75 watts and less, the limits are so high that it is not possible for the emissions to exceed the limits.) (I grant that there may be some exceptions to the above rules- of-thumb, but they are relatively rare and unusual.) For example, we have a 220-watt power supply operating in an application where the maximum rated input is less than 75 watts. Therefore, it does not need a PFC front-end. (The power supply is common to other products which are sold outside the EU and do not need the PFC.) Best regards (y saludos), Rich ------------------------------------------------------------- Richard Nute Quality Department Hewlett-Packard Company Product Regulations Group San Diego Division (SDD) Tel : 619 655 3329 16399 West Bernardo Drive FAX : 619 655 4979 San Diego, California 92127 e-mail: [email protected] -------------------------------------------------------------
