Electronics > Projects, Designs, and Technical Stuff
Operating a CE marked power supply out of spec
Mark:
Hi SiliconWizard,
We are designing a product which will be CE marked and using a CE marked power supply module internally to our unit.
My worry is that this power supply is not just a component of our product, but a safety critical component.
It is my understanding that safety critical components MUST be CE marked on their own, by their manufacturer.
http://www.tracglobal.com/sites/tracglobal.com/files/pdfs/componentacceptabilityforceproductsafety.pdf
The above PDF "Guidelines for selection of safety critical components " says:
--- Quote from: tracglobal ---An approved component is normally marked with the “mark” of the third party certification body.
In addition there will be a certificate detailing the limits of the approval (e.g. voltage. temperature, etc) and a full supporting test report. In some cases the component may not be marked but will be supported by a certificate or report.
It is essential that you obtain the approval certificate to ensure that the parameters of the approval are suitable for your application. You cannot assume that the “mark” covers all of the rated values of the component nor that the component standard encompasses all of the requirement of the equipment standard.
--- End quote ---
So my question would be, if the PSU needs to be CE marked, but it has only been rated for use at 120VDC, wouldn't it invalidate the CE mark if we use it outside the ratings? In other words, what's the point of requiring a CE marked safety critical component if it is allowable to use it way out of spec?
Is there a definitive (legal) answer on whether safety critical components can be used out-of-spec in normal operation?
ogden:
--- Quote from: Mark on February 26, 2019, 04:51:14 pm ---So my question would be, if the PSU needs to be CE marked, but it has only been rated for use at 120VDC, wouldn't it invalidate the CE mark if we use it outside the ratings?
--- End quote ---
It would not invalidate CE marking if you operate supply *below* it's input voltage specs. Anyway you are advised to ask manufacturer, not public forum where anybody can say anything. If current supplier/manufacturer do not talk to you - better find one who does.
Siwastaja:
There's a lot of myth on "safety critical components", like they come from the Heaven as-is, and your product magically becomes compliant by installing them.
In reality, someone makes these "safety critical components" from non-safety critical components! You can be this party. And, if you use a product outside of it's intended parameters, you already are in this position: you need to make a compliant product to whatever requirements are relevant to your product segment; including the internals of this power supply. If you cant't find a more suitable one, then you do what you need to do. The options are, do thorough evaluation and testing (including documentation) for the product to actually prove it works with the reduced voltage; or design your own ground-up. It's hard to say which one is harder - both require a lot of work and understanding about SMPS design.
You say this is a "safety critical component". Why do you think so, are you sure it is? Is a 80VDC system such? (Asking because I don't know.)
Gyro:
That document you linked is a pretty good summary, but as it states normally refers to discrete safety critical components - X and Y caps, Optos, detailed construction and insulation used in the transformer, etc. If you are the power supply manufacturer, to obtain the safety approval documentation for all of these all these from the component manufacturer and include them in your Technical Construction file - the test house... and anyone challenging your CE certification will want to see them. BTW as the customer of the PSU manufacturer you are entitled to ask for copies of them.
It is for you to determine whether the PSU is a safety critical component in your system - I note that you indicated DC input. This implies that it is not directly mains connected and that you may have other safety components in place to mitigate the effects of its failure.
--- Quote from: Mark on February 26, 2019, 04:51:14 pm ---Is there a definitive (legal) answer on whether safety critical components can be used out-of-spec in normal operation?
--- End quote ---
That's the killer. The definitive legally responsible entity for the safety of your product is YOU, in association with your overall 'Design Authority' (but individual engineers can still be held liable). It is you (collectively) who decide what components you put in your product and how you use them. It doesn't matter whether you use a CE marked PSU or not. The only thing the Law is concerned about is who puts the final product on the market, which is you (or the importer if bringing in from abroad).
You might have a secondary case against the PSU manufacturer if your product kills someone (though not likely if you used it out of spec) but that is entirely a separate matter. All the law is interested in is the final product and whether you acted wilfully or negligently, in its design and manufacture, including your choice, sourcing, and usage of components.
Eric_the_EE:
With which EU directives and standards are you trying to declare conformity regarding your unit? I assume you want to conform with EMC and LVD directives. If so, there isn't anything in the EMC directive to my knowledge that would cause a conformity issue with your scenario. But the LVD probably will. You first should identify which applicable standards in the LVD you want to evaluate your unit against. I've only tested against EN61010. IIRC there were some sections in the EN61010 that addressed this very topic. Essentially, improperly use of certain components inside a product would not allow you to pass evaluation against EN61010 (thus rendering your unit non conformal to CE marking requirements). But this was just my experience with a specific product.
But this CE marking process all begins with identifying which EU directives are applicable to your device, then choosing which standards you want to be tested/evaluated against. Those standards will explicitly answer these types of questions.
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