Brian, Thank you very much for your exhaustive answer. I should have been more clear; in our medical devices we usually design the SMPS by ourselves, and we don't want to have a separate certification for the supply unit, but just one for the system as a whole.
I was just wondering if, according to IEC 60601-1, we ought to test the SMPS for overload and shortcircuit or not, as I don't find such requirements in the standard (neither do you...). As per Douglas Adams, Root Beer and Cheetos ....touchè Paolo Peruzzi From: "Brian O'Connell" <[email protected]> To: <[email protected]> Sent: Fri, 23 Mar 2007 06:41:12 -0800 Subject: RE: SMPS test according to IEC 60601-1 > Mr. Peruzzi, > > With the exception of certain ECMA safety standards and the IEC > safety standard for power supplies (61204), I am not aware of any IEC/harmonized > safety standards that contain special clauses for the consideration > of the power supply's performance and construction as a special type > of component; i.e., there are no "a component power supply shall > ..." statements. > > In fact, most safety standards will have a statement in the scope > that says that if the power supply is not installed within the end- > use system, it is not covered; e.g., > > "power supply systems which are not an integral part of the equipment...". > > AND > > "Where a separate power supply (such as those containing transformer > and dc conversion in a separate package and feeding dc directly into > the equipment) is required, the supply shall be identified in the instructions > for use as: 1) part of the equipment (the requirements of this standard > apply to it also) OR 2) part of an ME System (meaning the supply can > comply to another IEC standard but with appropriate isolation in the > ME equipment). The supply must be specified in adequate detail to assure > continuing compliance to this standard." > > The 3d ed of 60601-1 says this about power supplies: > 4.8 *Power supply > 4.8.1 Source of power for ME EQUIPMENT > ME EQUIPMENT shall either be powered by an INTERNAL ELECTRICAL POWER > SOURCE, be specified for connection to a separate power supply, or be > suitable for connection to a SUPPLY MAINS. > 5.5 Supply voltages, type of current, nature of supply, frequency > a) Where test results are influenced by deviations of the supply voltage > from its RATED value, the effect of such deviations shall be taken into > account. The supply voltage during tests shall be according to 4.8 or > according to that specified by the MANUFACTURER, whichever is least > favourable. > b) ME EQUIPMENT for a.c. only shall be tested with a.c. at RATED frequency > (if marked) ± 1 Hz between 0 and 100 Hz and ± 1 % above 100 Hz. ME > EQUIPMENT marked with a RATED frequency range shall be tested at the > least favourable frequency within that range. c) ME EQUIPMENT > designed for more than one RATED voltage, or for both a.c. and d.c., > shall be tested in conditions (described in 5.4) related to the > least favourable voltage and nature of supply, for example, number > of phases (except for single-phase supply) and type of current. It > may be necessary to perform some tests more than once in order to establish > which supply configuration is least favourable. > 16.3 *Power supply > If ME EQUIPMENT is intended to receive its power from other > equipment in an ME SYSTEM, the instructions for use shall specify > such other equipment sufficiently to ensure compliance with the > requirements of this standard > (see 4.8.1, 5.5 g) and 7.10.2.3). > > Most SMPS are certified as 'components', so you will probably be limited > to applying the requirements for components of the end-use standard. > And this is why the conditions of acceptability and the Type Test conditions > for the SMPS are so very very important. > > As the regulatory honcho for your company, you must insist the the vendor > provide a CB test report for the unit. And you must study and understand > whether the vendor's type test conditions can apply to both normal > and abnormal operating conditions of your end-use box. Because the > new IEC medical standard has complex risk-analysis requirements, you > will need a direct safety contact at your power supply vendor. > > No one can hand this to you in neatly packaged standard that also > has the added bonus of an additional clause explaining the meaning > of life (this was, in fact, clearly defined by Douglas Adams...). > Ultimately, I can only offer this advise - Root Beer and Cheetos are > very effective compliance-requirement analysis tools. > > luck, > Brian > > > -----Original Message----- > > From: [email protected] [mailto:[email protected]]On Behalf Of Paolo > > Peruzzi > > Sent: Friday, March 23, 2007 1:32 AM > > To: [email protected] > > Subject: RE: SMPS test according to IEC 60601-1 > > > > > > Brian, > > Could you please give me ONE example of a specific > > requirement on a POWER > > SUPPLY (not on a single component) in IEC 60601-1? > > > > Thanks, > > Paolo Peruzzi > > > > ---------- Original Message ----------- > > From: "Brian O'Connell" <[email protected]> > > To: <[email protected]> > > Sent: Thu, 22 Mar 2007 08:10:13 -0800 > > Subject: RE: SMPS test according to IEC 60601-1 > > > > > Although, the 3d edition of IEC 60601-1 'appears' to relax test > > > requirements for a component P.S. (and explicityly allows > > the use of > > > I.T. approved units), and I recommend that you avoid the temptation > > > to reduce these tests to that of 'transformer'. > > > > > > My employer makes many custom and off-the-shelf power > > supply models that > > > are certified to medical standards, and we encourage our > > customers to > > > repeat certain SFC tests and abnormal operating conditions in the > > > end-use installation. > > > > > > Also, try to get a copy of the CB Test Report. Carefully review the > > > tests, test conditions, and what failed as a result of the > > test. The > > > performance of the P.S. during abnormal operating conditions should > > > drive the conditions of acceptability for the end-use installation. > > > > > > Requirements for SFC test and abnormal operating conditions will be > > > dependent on the affect of the end-unit installation has on > > the component > > > power supply. And yes there are, in fact, specific requirements in > > > 601-1 that would apply to a component power supply. Read the > > > standard again. No, again. > > > > > > luck, > > > Brian > > > > > > > -----Original Message----- > > > > From: [email protected] [mailto:[email protected]]On > > Behalf Of Paolo > > > > Peruzzi > > > > Sent: Thursday, March 22, 2007 7:25 AM > > > > To: [email protected] > > > > Subject: SMPS test according to IEC 60601-1 > > > > > > > > Dear group, > > > > > > > > I would like to gather some opinions about safety tests on > > > > switch mode power > > > > supplies within medical devices, according to IEC 60601-1. > > > > My question arises because a test house technician told me he > > > > used to test > > > > power supplies as they were transformers, for what concerns > > > > short circuit > > > > and overload tests, on each dc output. > > > > I couldn't find such requirements for power supplies in the > > > > standard (I > > > > couldn't find any!!!), but I think it would be at least wise > > > > to do these > > > > tests. > > > > Do you think they should be included as single fault > > > > condition tests, even > > > > if not mentioned? > > > > Any other thoughts? > > > > > > > > Thanks, > > > > > > > > Paolo Peruzzi > > - > ---------------------------------------------------------------- > This message is from the IEEE Product Safety Engineering Society > emc-pstc discussion list. Website: http://www.ieee-pses.org/ > > To post a message to the list, send your e-mail to [email protected] > > Instructions: http://listserv.ieee.org/request/user-guide.html > > 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] > > All emc-pstc postings are archived and searchable on the web at: > > http://www.ieeecommunities.org/emc-pstc - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html 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] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________
