Gert, A low current fuse is necessary to protect the instrumentation transformer from voltage swells above the rated voltage and a couple other conditions. It has nothing to do with the transient protection. A customer would be very unhappy to have to replace a $500 transformer instead of two $8 fuses. BTW, in our application you do not want fuses in the current measurement.
The problem with replacing all components is that the standard specifically states you must repeat the surge within one minute. For the fuses this might barely be possible, but is definitely not possible for the other components. Of course as always, there is what the standard requires and what good engineering requires. I'm asking about the standard; I've already done what testing I can (and am arranging further testing) doing what you suggest in replacing components as needed to ensure good engineering. My guess is that the standard-writers wished to stress a MOV into failure by not allowing it to fully cool between surges. Regards, Rob From: ce-test, qualified testing bv - Gert Gremmen [mailto:[email protected]] Sent: Wednesday, August 05, 2015 2:43 PM To: Rob Oglesbee <[email protected]>; [email protected] Subject: RE: [PSES] IEC 61010-2-030 Transient Overvoltage Testing I do not understand all of it. Why using a low current fuse here ??? If this is a voltage measurement terminal, why should it be protected by a fast fuse ? Fast fuses are used in current measurement circuits, not voltage measurement circuits as these are high impedance by nature. As they seem connected to the mains, I am sure they are high impedance enough ! Unless you are doing something very special, you might just insert a slow fuse at a higher value (say 4A slow-blow). The fuse has no role in the OV IV to OV II reduction, and is there only to prevent hazards if the protection circuit fails. Some testing should show if a shorted MOV would lead to a safe fuse blow. I second the other remarks made by Barry. I would replace all components (fuse MOV GTD) on each voltage step. This is a type test not a duration test, and test should be carried out on non-weared out components. Gert Gremmen ce-test qualified testing bv - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
