EBME Forums Forums Free discussion Free discussion IEC 62353 - MISSED OPPORTUNITY?

I think the tables giving 60601-1:2005 limits in Annex E and multiple references to IEC60601-1:2005 give it away somewhat. No dc or SFC measurements but generally limits appear to follow the 2nd edition 60601-1 standard.

Dear Mr Ling

Why do we believe that IEC 60601 is better then IEC 62353?
More often than not people pick and mix from IEC 60601 (see previous forums), make there own tests up (within the limits of safety analysers), do not test on TN systems (mainly outside UK) or power the safety analyser from an isolated supply.

For this reason, IEC 62353 does not follow the new limit in IEC 60601 3rd for earth leakage. This is a safety concern with the 3rd edition when the test is not performed as per the standard conditions.

IEC 62353 refers to the enclosure / touch leakage (for Direct and Diff. method);

The 3rd edition Earth Leakage limit of 5mA (NC) and 10mA (SFC) are potentially dangerous and can only be tested safely on an isolated supply. This is not always possible when testing “on location” as carrying such transformer would require a decent trolley. The new pass/fail limits on normal non-isolated supplies are potentially fatal (macroshock) within the limits of IEC 60601.

The European Directive EN 50191 (guideline for test environment) calls for maximum leakage to earth of 3.5mA. Any potential greater leakage must be supplied through an isolated supply.

I would like to know why the limit went from 0.5 and 1mA (SFC) to 5 and 10mA (SFC)??, when enclosure leakage open earth is still at the 2nd edition limit. Surely in those cases where this is possible and acceptable, you would handle this under a specific standard (ie 601-2) rather than under the general?

The IEC 62353 specifies direct leakage (as per IEC 609601) current limits under SFC only (open earth and mains in applied parts) and are identical to IEC 60601 2nd and 3rd edition.

Equipment leakage (Direct method) is equal to enclosure leakage open earth (SFC) and Applied Part leakage is equal to Mains on Applied Parts and has equal limits to 2nd and 3rd edition.

Only differences are;

o The way in which the current is limited (3ma in IEC 62353 vs 5mA in 60601)
o Compensation of measurement; ie no compensation in 60601 for voltage drop over current limiting resistor which causes the actual voltage on the Applied PArt to drop significant.
o Mains on Applied Part Voltage is 230V vs 253V in 60601.
o CF Patient connections are shortened instead of measured individually.

I am interested in your views on this.

Those interested in EN 50191 guidelines, email me for a free booklet. (same for IEC 62353)

Thanks
John

It just "appears" to follow. As the test methods are different (for example, not using the +10 % voltage) it means that, even if numerically equal to SOME of the values of the second edition, the resulting value will have a different meaning.

The standard let´s you use the values of the second edition, but just if the measurements are done according to the second edition, not this standard.

Also, as the rationale states for the alternative method:



So, disregarding the values for the alternative method, there´s just the EQUIPMENT LEAKAGE CURRENT and the PATIENT LEAKAGE CURRENT in the differential. But the equipment leakage current dos not have the same values as the earth leakage current of the second edition, so we disregard this too. This means that the only values that "follow" the second edition are for patient leakage current.

Hello Mr. Ling, you asked in some previous post why the UK experts voted against the standards, i finally found the voting document. FYI:



Sounds a lot like your vision. Are you sure you´re not one of these experts? :-)))

Never seen that documment Mantunes - must admit I worked it all out by myself - I'm not any any expert panels.

Thanks for that JB,

As you've indicated 62353 uses the same leakage limits but there are important deviations from the standard that can cause confusion when moving between 60601-1 and 62353.

I think it's useful to discuss the real issues rather than just skirt around them. I think I have an idea why the UK experts were unhappy with 62353 - and that's my opinion coming from a hands-on perspective and not academic or regulatory.


I don't believe I've ever made that comment. Neither have I suggested that there isn't a place for 62353. All I want is less confusion RE: safety testing standards, not more. Actually I think the introduction of explicit IR testing is a good idea for workers at the coalface like myself.

I think the changes you've described are significant RE: patient safety, however I'll need time to have a think about it. Remember I'm not involved with developing standards just trying to apply them to my day job in the real-world, rather than voting on my preferences.


I notice the Rigel 288s I've seen are enabled for 3rd edition 60601-1 limits for 62353 direct tests 1). does this mean that unsafe practices are being encouraged when using this device 2). does this device then comply with the 62353 standard itself?


Users like myself are somewhat captive when considering the tests that manufacturers of electrical safety testers provide built into their devices. The majority of operators probably just use automated tests built-in by the tester manufacturer. Are you saying that Rigel, for example, have previously manufactured testers that are not up to routine testing or that they perform non 60601-1 compliant tests?

I think you're forgetting that we do not aim to type-test devices and this is not what medical electrical safety testers on the general market try to achieve - we are looking for reassurance that safety of devices we tests after repairs/routinely, whatever, is acceptable.

Irrespective of this, however, we need to ensure that routine safety testing methods ensure an equivalent level of safety for the patient. That's why I'm reticent about endorsing a method that doesn't necesarily agree with the general standards RE: basic leakage limits (forget the relatively insignificant variations in mains that are required during some type-testing activities) nevermind the more complex stuff.

You came to an interesting point. What is or would be an equivalent level of safety?

I'll leave that to the experts.

Hum, but that´s the whole point of this discussion, isn´t it? As the example from the UK comment shows, it seems that the UK experts think that an "equivalent level of safety" would just be met if the tests and limits were the same as the standard the products "were" based (by the way, this opinion was also shared by the Italian NC).

My view is that the problem with this argument is that equipment are not obliged to comply to IEC 60601-1, or any standards for that matter, in most of the regulatory schemes (CE Mark and FDA for example - strange enough, here in Brazil the IEC 60601 series is obligatory). They have, in fact, to comply with the Essential Principles of Safety and Performance Of Medical Devices,and the principles can be resumed as: the risks related to the device must be managed and kept acceptable. In this case, the equivalent safety can only me defined by the manufacturer, as the equipment can use other forms of construction different from the standards (and altought people use the standards, as they´re the easiest mean of demonstrating compliance to some of the essential principles, they usually use just parts of standards).

Dear Mr Ling,

I respect your opinion (and that of others). Especially on the subject of electrical safety. Judging by your posts, you obviously know what you are talking about. Never the less, I have different views on some matters which are based on spending lost of time in continental Europe, where people also know what is best, based on years of experience. There will always be a difference in opinion between parties who have developed their own best. All, I am sure are in the best interest of the end-user, the patient, employee, member of the public etc.

Perhaps, we can drive the forum to suggestions on how to make the IEC 62353 better than it currently is (to this who have their concerns).


In answer to your question 1) and 2)
1) Default limits are set to the latest standard applicable. We do advocate safe practises hence we are (as a group) actively involved in safety standards committees. Limits can be set by users to reflect other standards or requirement (ie set a limit at 90% or much lower typical value or as per 2nd edition).
2) IEC 62353 and IEC 60601 are treated separately in terms of measurements. Following IEC 60601 limits does not impact on the IEC 62353 tests (or did I misread your question?)

A note on the Alternative Method(main reason for UK to vote against); This test is identical to the dielectric Strength test in IEC 60601 however at a saver voltage (ie 230V instead of 1500V)

By using mains (current limited), a better indication is provided at the insulation at the expected frequency rather than the 500VDC which might give readings subject to caps. Perhaps those who were against this test could see it as a quick (and save) pre test prior to switching on the EUT instead of an insulation test.

regards,
john