How to decide a suitable contact time from table 23 of IEC 60601-1:2005

[Roland chung]

Hello all,

It is a power adaptor under test. The plastic enclosure of the adaptor is 81[FONT=&#23435]℃ at maximum ambient of 40[FONT=&#23435]℃[/FONT]. Table 23 specifies the maximum limit of 86[FONT=&#23435]℃[/FONT] for t <1s and 71[FONT=&#23435]℃[/FONT] for 1s£ t<10s. [/FONT]

The standard also says the probability of occurrence of contact and of the duration of contact is determined by the RMF. We then documented t < 1s rather than 1s < t< 10s in the RMF just because of we think the power adaptor is not a handle or control panel which in normal use would have a brief or long contact with a user. So, the measured temperature 81[FONT=&#23435]℃ is below the limit 86[FONT=&#23435]℃[/FONT]. Is it reasonable? [/FONT]

In addition, could someone give some examples (equipment parts) for each contact time specified in the table 23 of IEC 60601-1:2005?

Thanks and regards,
Roland

 

[Pads38]

The standard states that the figures in Table 23 are valid for a healthy adult. What is the likelihood of more vulnerable users touching the power supply?

And if the touch was as a result of attempting to pull the power supply from the socket (is it a plug top type?) then t<1 second would not be reasonable estimate.

 

[Roland chung]

The standard states that the figures in Table 23 are valid for a healthy adult. What is the likelihood of more vulnerable users touching the power supply?

I can not get your point. Please be reminded that even limits in Table 24 (applied parts) are derived from healthy adults.

And if the touch was as a result of attempting to pull the power supply from the socket (is it a plug top type?) then t<1 second would not be reasonable estimate.

No, it is desktop adaptor.

 

[Peter Selvey]

I think the figure of 81C is high if it appears in normal use, and advisable to reduce even just from a sales point of view. I would be a worried and potentially complaining user if things are that hot. It's hot enough to damage things that are sitting near it, for example.

But, it's also likely the measurement is made with a bunch of worst case assumptions. For example, 40C ambient + max load + worst case supply voltage, longest use time etc etc.

Statistically, the probability of all parameters being worst case at the same time is usually negligible. That might be a factor in the risk analysis and also the sales issue.

 

[Pads38]

Apologies if I was not clear.

What I was suggesting was that if the person who may touch the hot power supply was, say, a child or a patient with reduced feeling (perhaps a stroke patient) then the 86 C limit would be too high.

However, if the person who is likely to touch the power supply is a healthy operator then it should be valid. And this also applies to the time part. A healthy operator may brush over the power supply without any harm occurring.

 

[Roland chung]

Thank you all!

But, it's also likely the measurement is made with a bunch of worst case assumptions. For example, 40C ambient + max load + worst case supply voltage, longest use time etc etc.

Yes, the test indeed conducted under the conditions as you mentioned and is also a normal heating test.

What I was suggesting was that if the person who may touch the hot power supply was, say, a child or a patient with reduced feeling (perhaps a stroke patient) then the 86 C limit would be too high.

We actually don't know who will touch the power supply. It is up to the intended use of the end products.

The power of general adaptor is about 65W, but our adaptor is 150W, so the temperature is a little bit high.

 

[Roland chung]

Hello,

I would like to ask a question in regard to the temperature limit of enclosure in SINGLE FAULT CONDITION.

According to the clause 13.1.2 of 60601-1:2005, the temperatures of ME EQUIPMENT parts that are not APPLIED PARTS but are likely to be touched shall not exceed the allowable values in Table 23. That means the limits of Table 23 shall apply in both NORMAL CONDITION and SINGLE FAULT CONDITION.

In my case, it is a power supply. The measured temperature of plastic enclosure under overload condition is 90 C, which exceeds the 86 C limit (Table 23, contact time < 1s). Is it clearly a failure? Is there an alternative method to pass the standard?

Thanks
Roland