A higher current rated CDN can be used, but only if it meets the lower current CDN's waveform requirements. From the quoted section:
"Any higher current rated CDN can be used if it meets the specification requirements in Table 4 for the relevant lower current rating of the EUT (for example: a CDN rated 64 A can be used for testing an EUT rated at 5 A, if it meets the specification requirements of a 16 A rated CDN)." The reason for this is higher current CDNs are allowed to have pulse widths significantly shorter than lower ratings. Check out Table 4 of the 2014 edition. A 16 amp CDN differential mode pulse width is required to be 50 us +/- 10 us. A 125 Amp CDN is 50 us +10 us/-30 us. So yes, a 64 amp CDN can be used with a 5 amp product, if it meets the 50 us +/- 10 us requirement. Thanks, David Schaefer Department Manager, EMC Element Materials Technology 9349 W Broadway Ave Brooklyn Park, MN 55445, United States O +1 612 638 5136 ext. 4003 [email protected] www.element.com From: John Woodgate [mailto:[email protected]] Sent: Tuesday, April 2, 2019 2:12 PM To: [email protected] Subject: Re: [PSES] IEC 61000-4-5:2014/AMD1:2017 - Using the correct CDN for AC mains testing I think you did (answer your own question). The text you quote seems surprisingly (and gratifyingly) lucid. Under 16 A use a 16 A CDN. Over 16 A up to 32 A, use a 32 A CDN. Best wishes John Woodgate OOO-Own Opinions Only J M Woodgate and Associates www.woodjohn.uk<http://www.woodjohn.uk> Rayleigh, Essex UK On 2019-04-02 19:14, Richard Georgerian wrote: Greeting colleagues, Hopefully, someone in the PSTC group can correct my rational below and enlighten me on the finer points of CDNs. The discussion within our applications group is, shall the EUT current rating be correctly matched to the CDN current rating? For example, don't use a CDN rated for 32 A for a EUT that is rated for 2 A, to ensure that the correct Surge waveform will be applied to the EUT. I cannot think of a good rational why a CDN rated for 32 A cannot be used for a EUT rated for 2 A. We do understand that for the different current ratings of CDNs, 16 A, 32 A, 63A and 125 A, the internal components must have different values to meet the Surge waveform, for Open circuit and Short circuit. However, testing Open circuit and Short circuit on a CDN is without applying any currrent through the CDN, so in effect, the Surge waveform for a 16 A CDN and a Surge waveform for a 32 A CDN should have the same effect on a EUT drawing only 2 A of current. Probably two questions would help in trying to explain what our discussion is about. Must we use a CDN rated for 32 A, for products with a current rating between 16 A and 32 A, to be considered being compliant to IEC 61000-4-5, for AC mains surge testing? Must we use a CDN rated for 16 A, for products with a current rating less than or equal to 16 A, to be considered being compliant to IEC 61000-4-5, for AC mains surge testing? In the IEC 61000-4-5:2014, Section 7.3 Test setup for surges applied to EUT power ports - "The selection of the CDN specification from Table 4 shall be made to match the current rating of the EUT (for example: an EUT rated at 5 A shall be tested using a CDN complying with the specifications of a 16 A rated CDN). Any higher current rated CDN can be used if it meets the specification requirements in Table 4 for the relevant lower current rating of the EUT (for example: a CDN rated 64 A can be used for testing an EUT rated at 5 A, if it meets the specification requirements of a 16 A rated CDN)." So maybe I answered my questions. Thank-you, Richard Georgerian Applications Engineer - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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