Perhaps problematic is the IEV definition for WV (most TCs appear to have pasted a variation of this into their standards): " ...highest r.m.s. value of the a.c. or d.c. voltage across any particular insulation which can occur when the equipment is supplied at rated voltage"
Methinks 'Operating' V can be relevant: "... voltage under normal conditions, at a given instant and a given point of the system" Brian Note – This value may be expected, estimated or measured -----Original Message----- From: ce-test, qualified testing bv - Gert Gremmen [mailto:[email protected]] Sent: Monday, May 12, 2014 12:07 PM To: Brian Oconnell; [email protected] Subject: RE: [PSES] Creepage and RMS EN 61010-1 states clearly that creepage is based on RMS values of the working voltage of the creepage way. A table is provided. (K13 2010 version) Of course there are multiple columns for OV and CTI and working voltage. The other 2 of your list are ignored in this standard. WV is defined as the measured working voltage over the insulation to be evaluated. I used an oscilloscope and had it calculate the RMS value, with the cursors encompassing 2 entire periods. There is no clear definition of working voltage in the standard. Nor a definition of RMS voltage (although RMS is well defined outside the standard). So to comply with this standard I have no choice but read and obey ;<). Gert -----Oorspronkelijk bericht----- Van: Brian Oconnell [mailto:[email protected]] Verzonden: maandag 12 mei 2014 19:46 Aan: [email protected] Onderwerp: Re: [PSES] Creepage and RMS The issue with some 60664 tables is that it is (for 0 to 2km) based on Paschen's Law, which is for a simple homogenous e-field. So creepage via RMS is an incomplete analysis. As others have stated, spacing should be determined by both peak and RMS. And because too many do not measure WV correctly, I strongly suggest reading papers and articles by P. Perkins and R. Nute on this subject, and ”The physical fundamentals of low-voltage insulation co-ordination” by Klaus Stimper. In a very nutty shell, you need to determine the following for the intended end-use environment: - OV category - CTI of materials - pollution degree - atmospheric chemistry - frequency-based di-electric heating - WV for the complete range of rated operating conditions Have rejected more than one component mfr's CB reports due to incorrect interpretations of IEC60664 and calculations of 'RMS' (am looking at you people in NRTLs/SCCs/NBs). Finally, the OP indicated that "Creepage is based on the RMS value of the voltage so is based on 1120 V", which indicates a reference a particular safety standard. What does that standard say about WV measurements for the determination of spacing and test voltages ? Brian ----- Original Message ----- From: ce-test, qualified testing bv - Gert Gremmen Sent: 05/12/14 03:20 PM To: [email protected] Subject: [PSES] Creepage and RMS I have a question on creepage distances. A product creates a saw tooth High voltage of 2000 Vpeak The VRMS measured on the scope on a full period equals 1120 V Creepage is based on the RMS value of the voltage so is based on 1120 V. Now the frequency of the sawtooth is 3 Hz. Should I still consider the RMS value, and at what frequency should I consider this as a DC value in regard to creepage.... Anyone aware of the IEC 60664 standard in respect to low frequency signals ?? Regards, Ing. Gert Gremmen, BSc - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
