Our company manufactures switching power supplies to EN60950 and EN60601-1 standards, and our safety group looks for these issues. In fact, I got 'bit' by that same problem last week. Spacing was OK when the PWB was mounted in the chassis, but when the cover was installed, it failed primary-ground spacing. I had to fix it.
As far as the sample power supplies you have: - What safety standard does the manufacturer claim? - What are the installation instructions, or 'conditions of acceptability'? - Did they look as if they had been modified or installed in another chassis assembly after it was manufactured? On Wed, 24 Oct 2001 15:38:19 +0200, Peter Merguerian <[email protected]> wrote: >I have submitted an ac input to dc output switching power supply for NRTL >approval. One deviation is that the primary ac insulated capacitor is too >close to the earthed chassis and that the insulation cannot be relied to >provide the required basic insulation. > >1. What is the group's opinion regarding this point? I have personally seen >many Listed/Recognized units with clearance distance less than 2.0 mm to the >earthed chassis without any additional insulation to provide the required >insulation. In fact, I am holding a switching power supply by a reputable >manufacturer with only approx. 0.7 mm between the primary and earthed >chassis. This power supply is UL Recognized and TUV approved. > >2. There is a UL Pag 156002 regarding this issue, but it seems that some >NRTL engineers are using their own judgement and approving units at their >own discretion. ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: [email protected] Dave Heald [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
