Hello Rich, I understand your point.
Unit is DC/DC converter supplied from generator or windmill. There is a 3 phase rectifier in front of the unit. Wind mild has rated phase voltage 230V tolerances of -15%/+30% (e.g. 195,5-299V). For short period (at start) output voltage can achieve 343V~ (up to 1 min). When you rectify this values you get rated voltage 563Vdc and with considered ac tolerances 480-730Vdc. If you check IEC 60950-1 standard, it says you need to consider for dc mains tolerances of -15%/+20% unless otherwise specified by the manufacturer. For clearances and creepage distances you only need to consider rated voltage (not tolerances) of the product (only 560VDC will be marked on the unit). In this particular case manufacturer specified a bit higher tolerances. There is nothing mention about value of tolerances. I know many products have rated voltage 220-240V and operational voltage range 180-276V. For clearances and creepage distances only 240V was considered. Therefore I am a bit confused what should we consider for determination of working voltage. Is it rated voltage (marked on the unit) or we need to consider also tolerances or even short-term voltage? Best regards, Bostjan -----Original Message----- From: Richard Nute [mailto:[email protected]] Sent: Thursday, September 10, 2015 12:28 AM To: [email protected] Subject: Re: [PSES] requirement for spacings > I can't understand how a 'rated voltage' can be 560 V > +30%/-15%. It must > mean something other than what is normally understood as 'rated > voltage' > in safety standards. In the IEC, rated voltage is a value assigned by the manufacturer. For years, standards committees have attempted to specify one or more formats for the voltage rating. Each standard is different, and sometimes each edition is different. The problem is when a manufacturer uses a single, nominal value. We know that line voltages vary, so standards committees choose, say, +6%, -10%. We have commonly seen wide-ranging power supplies rated 90-250 volts. But, we cannot fault a manufacturer for rating his wide-ranging product as 150 volts, +166%, -60%. With your i-Phone, you can easily calculate whether the equipment will operate on your power line! In this case, the manufacturer has rated his product to operate from 470 to 728 volts. What is wrong? Best regards, Rich - ---------------------------------------------------------------- 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]>
