Re: What Makes A Transformer Hum (continued)
David, et al, I just learned that a toroid core is wound from a single strip of metal, like a coiled clock spring, one continuous piece. But whether this one is welded, I cannot say. My guess is probably not. As for impregnation, I do not think so. The construction details I saw describe core, core caps, insulation layers, winding wires, and the core potting material. Nothing at all about varnish or impregnation. The windings are covered with an overall insulation wrap so I cannot see how tight they may be. These are all interesting questions and we will be talking with the vendor after the first of the year to go over these and other construction details. Roger McCoy raises the question of the center bolt being a shorted turn since it passes through the core and electrically connects to the metal box on either side of the transformer. That box surrounds the core just like a winding turn would do. My question is, is it usual practice to isolate this bolt electrically from the metal chassis, say by a fiber or plastic washer? The bolt is certainly isolated electrically from the core and windings by the core potting material. Once again, I am amazed at the depth of the discussion this list can generate. My heartfelt thanks to all participating. Merry Christmas and Happy New Year! Scott David Greig wrote: I should have added that the most probable cause of noise besides lamination, is the mmf between loaded windings. Are the windings tightly constrained or impregnated? Best Regards David Greig -Original Message- From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of David Greig Sent: 22 December 2005 11:58 To: drcuthb...@micron.com; j...@jmwa.demon.co.uk Cc: christopher.col...@harmanpro.com; emc-p...@ieee.org Subject: RE: What Makes A Transformer Hum (continued) Is the lamination stack welded? This could provide a outside rigid axis for the laminations to pivot against, given that any impregnation will be more compressible than the weld. Welds may also distort the stack. Best Regards David Greig __ GigaDyne Ltd Buchan House Carnegie Campus Dunfermline KY11 8PL United Kingdom t: +44 (0)1383 624 975 www.gigadyne.co.uk __ snip snip - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Mains test - India
Hi, Thanks for those that replied. Basically, I would conclude that this test it's not a must requirement. Just an additional test that the customer requires. Regards Koh Koh wrote: Hi group, We had a request from an India customer. They need to have the following test performed on our speaker. The speaker can be mains operated or powered via a external AC/DC power adaptor. Test to perform/meet, 1) Voltage input line shall be able to withstand 300Vac for 30mins 2) Next followed by two 410Vac/1sec surge @ 0.1Hz repetition rate There shall be no permanent damaged to the power supply or the speaker connected to the power supply during or after the test. 3) If the sample pass the above test, continue test with single 1 sec surges at 10V increments from 410Vac until failure and report failure limit. I'm not an safety guys and moreover very puzzle on such test. Could someone advice which standard calls out such test? Is this test a India regulatory requirement to meet this? What is the purpose of this test? Regards Koh - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: What Makes a Transformer Hum in the UK?
In message f72651ec60c2c945878cf1cf6a3e5af401bc8...@ntxboimbx13.micron.com, dated Thu, 22 Dec 2005, drcuthb...@micron.com writes Loading a transformer secondary does absolutely nothing to the magnetic core flux. The core flux is set by the magnetizing current and not the load current. Does this sound correct to the rest of the group? It would be true if the primary winding resistance was zero. In fact, the increased voltage drop across that, under load, reduces the induction and flux a bit - 2.5% in a big transformer and 5% in a small one, typically. -- Due to a virus attack, I've lost all my clever signature tags. Are you sorry? OOO - Own Opinions Only. See http://www.jmwa.demon.co.uk and http://www.isce.org.uk John Woodgate - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: What Makes a Transformer Hum in the UK?
To first order it is true that the magnetic flux in the core does not change with load current. It would be exactly true if the permeability of the core were infinite. For real materials with finite permeability, a load current on the secondary does force some flux out of the core into the air. One can confirm this empirically by holding a permanent magnet near a transformer, and then loading and unloading the secondary. This flux going into the air causes the coupling coefficient to come up just short of 1. Perhaps the flux in the air is interacting with some other nearby metal (magnetic or not). Going back to the start of this discussion: The inner diameter of the transformer was reduced. There is something in the back of my head telling me that perhaps the part of the core at the inner diameter is going into saturation. Maybe someone with a field solving engine could give this a go. If this is so, could this cause more hum via magnetostriction? The transformer overall would not exhibit saturation effects due to a sufficient amount of unsaturated core material at the outer diameters. Don Borowski Schweitzer Engineering Labs Pullman, WA drcuthbert@micron .com Sent by: To emc-p...@ieee.org peter.tar...@sanmina-sci.com, emc-p...@ieee.org cc 12/22/2005 08:54 AMSubject RE: What Makes a Transformer Hum in the UK? Peter, When John Woodgate said that secondary current does not change the core flux I went back to the books to see where I went wrong. Here is what I think is going on: The primary current that is caused by the secondary load creates a magnetic flux in the core. The secondary current creates a magnetic flux in the core. These magnetic fields are equal and opposite and therefore they cancel. Loading a transformer secondary does absolutely nothing to the magnetic core flux. The core flux is set by the magnetizing current and not the load current. Does this sound correct to the rest of the group? This has come as a revelation to me, I must say. But, it is intuitively obvious. The formulas support this but none of the papers I read pointed out why, or if they did, I missed it. Dave Cuthbert Micron Technology, Inc. From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Peter Tarver Sent: Tuesday, December 20, 2005 10:43 AM To: emc-p...@ieee.org Subject: RE: What Makes a Transformer Hum in the UK? Dave - Removing the load removes flux from the core. My experience has shown that some transformers vibrate only for higher current load conditions (not necessarily at saturation) and there's negligible or no vibration with only magnetization current supporting flux in the core. Replacing the in situ load with a resistive load would demonstrate if the phenomenon John is describing is the root cause. This is more seat-of-the pants than your method but could be more direct with regard to effects load type. Regards, Peter L. Tarver, PE ptar...@ieee.org From: drcuthb...@micron.com Sent: Tuesday, December 20, 2005 9:01 AM John, You have helped me to think about this differently. To tell if it is the transformer secondary load that is the culprit one can disconnect the load. If it still hums then the load is not the problem. _ Scanned by Sanmina-SCI eShield _ - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For
RE: What Makes a Transformer Hum in the UK?
Peter, When John Woodgate said that secondary current does not change the core flux I went back to the books to see where I went wrong. Here is what I think is going on: The primary current that is caused by the secondary load creates a magnetic flux in the core. The secondary current creates a magnetic flux in the core. These magnetic fields are equal and opposite and therefore they cancel. Loading a transformer secondary does absolutely nothing to the magnetic core flux. The core flux is set by the magnetizing current and not the load current. Does this sound correct to the rest of the group? This has come as a revelation to me, I must say. But, it is intuitively obvious. The formulas support this but none of the papers I read pointed out why, or if they did, I missed it. Dave Cuthbert Micron Technology, Inc. From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Peter Tarver Sent: Tuesday, December 20, 2005 10:43 AM To: emc-p...@ieee.org Subject: RE: What Makes a Transformer Hum in the UK? Dave - Removing the load removes flux from the core. My experience has shown that some transformers vibrate only for higher current load conditions (not necessarily at saturation) and there's negligible or no vibration with only magnetization current supporting flux in the core. Replacing the in situ load with a resistive load would demonstrate if the phenomenon John is describing is the root cause. This is more seat-of-the pants than your method but could be more direct with regard to effects load type. Regards, Peter L. Tarver, PE ptar...@ieee.org From: drcuthb...@micron.com Sent: Tuesday, December 20, 2005 9:01 AM John, You have helped me to think about this differently. To tell if it is the transformer secondary load that is the culprit one can disconnect the load. If it still hums then the load is not the problem. _ Scanned by Sanmina-SCI eShield _ - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: What Makes A Transformer Hum (continued)
I should have added that the most probable cause of noise besides lamination, is the mmf between loaded windings. Are the windings tightly constrained or impregnated? Best Regards David Greig From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of David Greig Sent: 22 December 2005 11:58 To: drcuthb...@micron.com; j...@jmwa.demon.co.uk Cc: christopher.col...@harmanpro.com; emc-p...@ieee.org Subject: RE: What Makes A Transformer Hum (continued) Is the lamination stack welded? This could provide a outside rigid axis for the laminations to pivot against, given that any impregnation will be more compressible than the weld. Welds may also distort the stack. Best Regards David Greig __ GigaDyne Ltd Buchan House Carnegie Campus Dunfermline KY11 8PL United Kingdom t: +44 (0)1383 624 975 www.gigadyne.co.uk __ From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of drcuthb...@micron.com Sent: 22 December 2005 00:34 To: j...@jmwa.demon.co.uk Cc: christopher.col...@harmanpro.com; emc-p...@ieee.org Subject: RE: What Makes A Transformer Hum (continued) John, You are correct. The load current does not change the core flux density. The two transformer scheme can eliminate core saturation only if the transformers are series connected. That will cut the flux density in half while also cutting the total system core loss in half. The total system copper losses are doubled. Dave Cuthbert Micron Technology, Inc. From: John Woodgate [mailto:j...@jmwa.demon.co.uk] Sent: Wednesday, December 21, 2005 10:42 AM To: drcuthbert Cc: christopher.col...@harmanpro.com; emc-p...@ieee.org Subject: Re: What Makes A Transformer Hum (continued) In message f72651ec60c2c945878cf1cf6a3e5af401bc8...@ntxboimbx13.micron.com, dated Wed, 21 Dec 2005, drcuthb...@micron.com writes The consensus is that the core is saturating. This sounds like the best hypothesis. A quick fix is to parallel another transformer if there is room for it. Just make sure that the turns ratios is exactly the same. I don't see how that would work. The induction is determined by the supply voltage, not the load current. -- Due to a virus attack, I've lost all my clever signature tags. Are you sorry? OOO - Own Opinions Only. See http://www.jmwa.demon.co.uk and http://www.isce.org.uk John Woodgate - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc -- Virus scanned by Lumison. - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc -- Virus scanned by Lumison. - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: What Makes A Transformer Hum (continued)
Is the lamination stack welded? This could provide a outside rigid axis for the laminations to pivot against, given that any impregnation will be more compressible than the weld. Welds may also distort the stack. Best Regards David Greig __ GigaDyne Ltd Buchan House Carnegie Campus Dunfermline KY11 8PL United Kingdom t: +44 (0)1383 624 975 www.gigadyne.co.uk __ From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of drcuthb...@micron.com Sent: 22 December 2005 00:34 To: j...@jmwa.demon.co.uk Cc: christopher.col...@harmanpro.com; emc-p...@ieee.org Subject: RE: What Makes A Transformer Hum (continued) John, You are correct. The load current does not change the core flux density. The two transformer scheme can eliminate core saturation only if the transformers are series connected. That will cut the flux density in half while also cutting the total system core loss in half. The total system copper losses are doubled. Dave Cuthbert Micron Technology, Inc. From: John Woodgate [mailto:j...@jmwa.demon.co.uk] Sent: Wednesday, December 21, 2005 10:42 AM To: drcuthbert Cc: christopher.col...@harmanpro.com; emc-p...@ieee.org Subject: Re: What Makes A Transformer Hum (continued) In message f72651ec60c2c945878cf1cf6a3e5af401bc8...@ntxboimbx13.micron.com, dated Wed, 21 Dec 2005, drcuthb...@micron.com writes The consensus is that the core is saturating. This sounds like the best hypothesis. A quick fix is to parallel another transformer if there is room for it. Just make sure that the turns ratios is exactly the same. I don't see how that would work. The induction is determined by the supply voltage, not the load current. -- Due to a virus attack, I've lost all my clever signature tags. Are you sorry? OOO - Own Opinions Only. See http://www.jmwa.demon.co.uk and http://www.isce.org.uk John Woodgate - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc -- Virus scanned by Lumison. - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Mains test - India
I don't see any contradiction here. Step 3 clearly states that if the sample passes the earlier test, then keep increasing the voltage until the sample fails. Regards, Ravinder Server PCB Development Hitachi Global Storage Technologies Email: ravinder.ajm...@hitachigst.com Robert A. Macy m...@california.com Sent by: emc-p...@ieee.org 12/21/2005 08:11 AM To Koh koh...@singnet.com.sg cc emc-p...@ieee.org Subject Re: Mains test - India Interesting wording. Make it fail with permanent damage to the supply, then repeat the test. Hmmmam I the only one to see a failure in this logic? - Robert - On Wed, 21 Dec 2005 23:15:19 +0800 Koh koh...@singnet.com.sg wrote: There shall be no permanent damaged to the power supply or the speaker connected to the power supply during or after the test. 3) If the sample pass the above test, continue test with single 1 sec surges at 10V increments from 410Vac until failure and report failure limit. - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
