If you perform a limited current test on your inverter, as per
IEC 60950 2.4.2, you will probably find it meets these requirements,
which means that theoretically Operator access is allowed - though
you'll definitely feel it if you touch it :( .However, it does mean that
if the invertor output is not hazardous, you don't have to do the steel
ball test on the screen.
Rich, you said below "Assuming you are using IEC 60950, a fire
enclosure is required for any circuit exceeding the limits of ELV,
independent of available current or power."
Why did you mention "exceeding the limits of ELV" ? Surely specific
components require a fire enclosure, regardless of voltage ?
Regards
John Crabb, Development Excellence (Product Safety) ,
NCR Financial Solutions Group Ltd., Kingsway West, Dundee, Scotland. DD2
3XX
E-Mail :[email protected]
Tel: +44 (0)1382-592289 (direct ). Fax +44 (0)1382-622243. VoicePlus
6-341-2289.
> -----Original Message-----
> From: Rich Nute [SMTP:[email protected]]
> Sent: 24 September 1999 19:27
> To: [email protected]
> Cc: [email protected]
> Subject: Re: LCD Displays
> Hi Duncan:
> > I have a product that has an LCD display with an Inverter that
> operates at
> > 100Khz 2KV and I believe is capable of supplying 6.5mA The question is
> does it
> > require a fire enclosure?
>
> Assuming you are using IEC 60950, a fire enclosure is
> required for any circuit exceeding the limits of ELV,
> independent of available current or power.
>
> However, you MAY be able to invoke other requirements
> to avoid a fire enclosure. Here are some of the "outs:"
>
> Sub-clause 4.4.5.2, third dashed paragraph:
>
> Some interpretations of allow that once a limited
> power source has been achieved, ALL circuits down-
> stream from that limited power source are treated
> as limited power even if the voltage is stepped up
> above the limits of limited power.
>
> Sub-clause 4.4.1, method 2.
>
> This allows fault testing in lieu of a fire enclosure.
> Most low-power, high voltage inverters are rather
> simple circuits; extensive fault testing only involves
> a few components, so such testing is feasible and likely
> to result in acceptable results.
>
> > If it does what are the requirements for the flamability of the screen
> and any
> > plastic protective covers fitted to it.
>
> A fire enclosure requires that the plastic materials be
> rated V-1 or better. Note that the fire enclosure need
> not be the overall product enclosure (e.g., screen), but
> can be an inner part designated as the fire enclosure for
> the inverter circuit.
>
> Best regards,
> Richard Nute Product Safety Engineer
> Hewlett-Packard Company Product Regulations Group
> AiO Division Tel : +1 858 655 3329
> 16399 West Bernardo Drive FAX : +1 858 655 4979
> San Diego, California 92127 e-mail: [email protected]
>
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