I hesitate to give an interpretation on the legal meaning of 'public low voltage supply' although I suspect the interpretation your customer would put on it would be described 'domestic low voltage supply'. I don't see from the view point of common speech why 'public' excludes commercial and don't see in any other European standards or guidance notes any formal interpretation this way.
However, I can certainly confirm that it is common for light industrial premises not to have individual transformers. Close to our factory is a set of 10 small industrial units with a common supply at 240V. 240V (Phase to neutral), three phase at 150A per phase gives 108kW, plenty for many commercial premises and much greater than it is possible to draw from the domestic supply in many cases in America. Also near here is a small commercial pathology lab run upstairs from a shop. Next door in the block, the upstairs rooms provide living accommodation for the family of the owner of the shop below. The whole block of shops, together with some purely domestic premises, is supplied like most urban domestic premises in the UK by a three phase and neutral cable buried in the road with each shop being connected between one phase and neutral, each third shop being connected to the same phase (U.K. 3 phase supply is always balanced about neutral) Such arrangements are common here in the UK and from what I have seen of places like Italy even more common over there. As for marketing only to industrial locations, even if you could get by on the supply not being 'public' this would surely depend on how much control your customer had over its location. If each unit were installed and maintained by them only in premises with their own supply transformer they might claim it was buffered by the transformer. However if they are selling them through distributors or trade paper adverts the authorities are likely to form a judgement as to the likelihood of it being connected to unbuffered supplies, either new or second hand. Hope this helps Nick Rouse ----- Original Message ----- From: <[email protected]> To: <[email protected]> Sent: Sunday, December 03, 2000 11:03 PM Subject: EN 61000-3-3 Flicker Tests > > > Hello group! > > I've got a customer in our EMC lab that makes a laboratory instrument > incorporating heaters with a typical 3-4 amp input current at 230vac. He > is failing the flicker test due to the design of the heater control. They > are undertaking a redesign but would like to keep selling product in the > interim. > > They have come up with an interesting interpretation of the scope of EN > 61000-3-3: the standard specifies that the tests are applicable to > products connected to the "public low voltage distribution systems" but if > you take a typical industrial location or even a typical commercial > location, isn't it true that these locations are fed by a dedicated > transformer at the building that isolates them from the public network? I > guess the question becomes - what is considered the public network? What > if the marketing of the product was restricted to "industrial" locations? > > My initial reaction to the question was that anyplace you can plug or wire > into at typical 230vac is considered the "public network", especially > considering the mixed residential / commercial buildings common in Europe. > > Anyone care to comment? > > Bruce Fagley > Sr. Specialist, EMC > Industrial Products > TUV Rheinland > 12 Commerce Rd. > Newtown CT. 06470 > 203-426-0888 ext 119 > 203-426-4009 fax > > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Jim Bacher: [email protected] > Michael Garretson: [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected]
