Ladies and Gentlemen
Richard Huges commented that 60950-1 had changed to absolute temperatures
rather than a delta above ambient. I checked in CSA60950-1 and this is
indeed the case. Personally I preferred the delta measurement, as it was
easier to measure in the lab. The implications on testing are that the
heating test has to be done at the highest rated ambient temperature, e.g.
if the equipment is rated to operate at +5 to +30 Deg C, the heating test
has to be carried out at at an ambient of +30DegC. This now complicates the
thermals testing somewhat, in that it now has to be done in an oven,
instead of on the bench in the lab which is temperature controlled at
around 23deg C. Is this assumption correct?
A second question is does anyone know why the limits were changed from a
delta K to absolute degreesC?
Regards
Doug Beckwith
Rich Nute
<[email protected]> To: [email protected]
Sent by: cc:
[email protected]
owner-emc-pstc@majordom Subject: Re: Surface
Temperature Limits
o.ieee.org
04/25/03 12:47 PM
Please respond to Rich
Nute
Hi Brian:
> In EN61010-1 section 10 and EN60950 safety standards, there are surface
> temperature limits specification for Normal Condition based on an
Ambient
> Temperature of 40ºC. Our company makes analytical instrumentation and a
new
No, this is not true for IEC 60950.
The temperature limits in IEC 60950 are temperature RISE
limits, not absolute limits.
> product we are working on is functionally very susceptible to room
temperatures.
> So, the operational specification in our manual says it must be in a
room no
> warmer than 30ºC.
If you use IEC 60950, you would place the equipment in a
30 C ambient, and then measure the temperatures of the
parts in question, and then subtract the ambient to get
the temperature rise.
> Question is, is it proper to consider surface temperatures for safety
based on
> a 30ºC ambient which would give us 10º more range to work with?
Someone told
The operating ambient temperature range is a manufacturer's
spec. The safety standard does not tell you what ambient
temperature your equipment must operate in.
> me you could do this but it doesn't seem right to me. You are relying
on the
> building's air conditioning as a level of protection. Then I was told
that if
> the AC broke down it would be considered a Fault and then the 105ºC
limit would
> be applied.
No.
Ambient temperature outside the manufacturer's spec is
not a fault condition. The user's responsibility is to
operate the product within the manufacturer's temperature
spec just as it is the user's responsibility to connect
the equipment to the correct supply voltage.
If the AC broke down, what would be the ambient
temperature? The temperature is indeterminant, so no
meaningful measurements could be made, and, likewise, no
meaningful temperature limits could be set.
Best regards,
Rich
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