Hi Joe:
Electric shock requires both voltage and current. If the voltage exceeds the specified limit, the current must not exceed its specified limit. The 60335 standard as well as the 60950 standard concentrated on voltage. But, there was some recognition that if the voltage was too high but if the current was low, the construction was acceptable, hence the requirements for limited current circuits. See attached discussion of how some standards addressed this reality. As I mentioned, I am guessing that your 60-volts is a limited current circuit. You can easily test this with a 1500-ohm resistor across the 60 volts and measure the voltage. My guess is that it will be near zero. More later, Rich From: Joe Randolph <[email protected]> Sent: Friday, January 10, 2020 10:07 AM To: [email protected] Subject: Re: [PSES] Touch current in IEC 60335-1 for Household Appliances I agree that there are several opportunities to add some interlocks (physical or electrical) that would power down the high voltage circuit under certain conditions. If that were all that is necessary to comply with 60335-1, it would probably be quite manageable. i The main problem I'm concerned about is the apparent requirement in a Class 2 appliance to provide double insulation between the high voltage circuit and accessible parts. In particular, the creepage and clearance distances required for the double insulation would be a challenge to achieve without major changes to the physical design. Presumably, with a sufficient number of interlocks, it would be possible to ensure that the high voltage circuit is disabled under certain circumstances, and this might possibly help to avoid double insulation in certain areas. However, the fact remains that when this handheld product is actually in use (no battery charger connected, battery compartment closed, and user-replaceable module installed), there is a non-SELV voltage being generated within the device, and 60335-1 seems determined to require a double-insulation barrier around that circuit. In other standards such as 60950-1 and 62368-1, circuits with non-SELV voltage but limited current can be classified as a "limited-current circuit" (60950-1) or "ES2 circuit" (62368-1). Circuits that qualify have no accessibility restrictions whatsoever. In terms of accessibility, they are treated like SELV. For the product in question, this would be a much easier way to demonstrate compliance. I think that clause 8.1.4 in 60335-1 is intended to provide this option, but the unusual wording of clause 3.3.12 appears to prevent this option. I agree that it can take a very long time to get an official interpretation issued or, worse yet, get a standard changed. Fortunately for me, the product in question is not my product and I was not involved in designing it. I've simply been asked to evaluate the product for compliance with 60335-1. When I made my initial post on this topic, I was just trying to find out if clause 3.3.12 had been (or might soon be) revised to remove the apparent contradiction in the 2009 edition. From some preliminary feedback I have received, it sounds like the answer is "no." In the meantime, the responses I have received here have identified some useful approaches for trying to demonstrate compliance as a Class 2 appliance per 60335-1, and I plan to think carefully about those approaches. Right now, the main sticking point is the apparent requirement to provide double insulation, with its attendant creepage and clearance distances. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) [email protected] <mailto:[email protected]> http://www.randolph-telecom.com <http://www.randolph-telecom.com/> From: John Woodgate [ <mailto:[email protected]> mailto:[email protected]] Sent: Friday, January 10, 2020 11:43 AM To: Joe Randolph < <mailto:[email protected]> [email protected]> Subject: Re: [PSES] Touch current in IEC 60335-1 for Household Appliances Can that be done while the product is powered-up? If not, how long does it take after power-down for the 60 V to disappear from the accessible poles? Can you cover up the accessible poles? Basic insulation might be enough, but reinforced insulation might not be too bulky. It would almost certainly take years to get 60335-1 modified. There is a very small chance of an Interpretation Sheet being agreed, but even that takes about 18 months minimum. I suppose you are in USA. If so, go to this page on the IEC web site and send an email explaining your problem to Ms R K Myers and ask for advice how to try to get a clarification: <https://www.iec.ch/dyn/www/f?p=103:29:13970009729823::::FSP_ORG_ID,FSP_LANG _ID:1236,25#3> https://www.iec.ch/dyn/www/f?p=103:29:13970009729823::::FSP_ORG_ID,FSP_LANG_ ID:1236,25#3 You will probably be referred to the chair of the ANSI committee. You can still do that if you are not in the USA. but there is a different path if you are not. On 2020-01-10 16:03, Joe Randolph wrote: 4) Lastly, there is a user-replaceable module that, when removed, allows both poles of the high voltage supply to be accessible. - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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elv-selv-es1-es2_rev-b.docx
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