Re: Temperature Measuring of Magnetic Components
Dear Mohajer and all If you are using type K thermocouplers you will have to turn off power to the component before measuring the temp. Since they are sensitive to magnetic fields. Best regards, Mr. Kim Boll Jensen i-data, Denmark Kamran Mohajer kmoha...@cisco.com on 99-08-24 23:50:26 Please respond to Kamran Mohajer kmoha...@cisco.com To: emc-p...@ieee.org cc:(bcc: Kim Boll Jensen/INT) Subject: Temperature Measuring of Magnetic Components Hello EMC-PSTCers, I wonder if anyone knows of the method of measuring temperature limits on magnetic components. I happen to get involved in this and found that my results are different than the vendors result by as much as 10-15 degrees on measuring on a same magnetic component. Even applying the thermocouple to different location on a coil seems to give you different results. Is there a method that I should be following to measure temperature with thermocouples methods, not change of resistance, on magnetic parts such as transformers, coils, etc.? Thanks, *** Kamran Mohajer DSL Compliance Lead Cisco Systems, Inc. Phone(408)-525-6121 Fax(408)527-0495 kmoha...@cisco.com *** - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Temperature Measuring of Magnetic Components
I too, have noticed a variation in temperature, especially when measuring a very hot component with forced air cooling. I usually try to get the highest possible temperature reading by : 1. Use very small thermocouple wire, such as AWG 30. Larger wire sizes can conduct heat away from the tip. 2. Bury the tip of the thermocouple as deep into the winding as possible. If the component comes from a vendor, already varnished, use a tool to try to separate a gap in the center of the winding layers. Then, push the tip of the thermocouple into the gap as far as you can. use epoxy to hold it in and to help couple it thermally to the winding. Use a thermocouple bridge that is isolated from everything else and be aware that the thermocouple wires might be hot. I have seen a switching power supply transformer thermocouple be so noisy that it would not work with an electronic thermocouple bridge without running the wires through ferrite beads. 3. I usually also measure and record the core temperature. The core temp and winding temp do not have to be the same. To measure core temp, again seek the hottest spot which would be deep, away from air and connected with epoxy. 4. If the component is large and has a few ohms of resistance, you can allow the temp to stabilize, quickly make several resistance measurements of the winding and then extrapolate back to the maximum resistance and use the copper law to determine temperature. 5. If you do all this and worry that the readings are inconsistant, only measure it one time! (Joking) Kamran Mohajer wrote: Hello EMC-PSTCers, I wonder if anyone knows of the method of measuring temperature limits on magnetic components. I happen to get involved in this and found that my results are different than the vendors result by as much as 10-15 degrees on measuring on a same magnetic component. Even applying the thermocouple to different location on a coil seems to give you different results. Is there a method that I should be following to measure temperature with thermocouples methods, not change of resistance, on magnetic parts such as transformers, coils, etc.? Thanks, *** Kamran Mohajer DSL Compliance Lead Cisco Systems, Inc. Phone(408)-525-6121 Fax(408)527-0495 kmoha...@cisco.com *** - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Temperature Measuring of Magnetic Components
Hi Kamran, I use both change of resistance and a thermocouple as a check. I would expect the thermocouple to read a little below the resistance method. Some standards require the change of resistance method (not the thermocouple method) to be used for compliance assessment of winding temps. Regards Barry Esmore AUS-TICK Phone: + 61 3 9886 1345 Fax: + 61 3 9884 7272 Email: bar...@melbpc.org.au - Original Message - From: Kamran Mohajer kmoha...@cisco.com To: emc-p...@ieee.org Sent: Wednesday, August 25, 1999 7:50 AM Subject: Temperature Measuring of Magnetic Components Hello EMC-PSTCers, I wonder if anyone knows of the method of measuring temperature limits on magnetic components. I happen to get involved in this and found that my results are different than the vendors result by as much as 10-15 degrees on measuring on a same magnetic component. Even applying the thermocouple to different location on a coil seems to give you different results. Is there a method that I should be following to measure temperature with thermocouples methods, not change of resistance, on magnetic parts such as transformers, coils, etc.? Thanks, *** Kamran Mohajer DSL Compliance Lead Cisco Systems, Inc. Phone(408)-525-6121 Fax(408)527-0495 kmoha...@cisco.com *** - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
RE: Temperature Measuring of Magnetic Components
Hi Kamran, I've run into this problem myself. Usually, it is because the test conditions you use are different from what the vendor is using. They may be loading the EUT to full capacity and/or using a thermocouple attachment method different from yours. In the case where your product's configuration is not identical to the vendor, you can expect some discrepancy. Compliance agencies such as UL understand that your conditions of applicability are different from the vendor's and thus your data will be unique. If you wish to minimize the discrepancy, load the EUT to maximum rating and use a similar probing scheme as the vendor. In some cases, magnetic flux can be so great that it induces an undesirable EMF and reading error in which case you might have to run the EUT until thermal equilibrium occurs then, cut power and take a measurement sweep immediately afterward. UL for example, demands that the thermocouple probe be attached to the windings of the coil -with the thermocouple junction in direct contact with the wiring and NOT through core, ferrite or tape insulation (if the conductors are coated there is no need to remove the coating). I was just audited a couple weeks ago for COMPASS FUS and was reminded that the use of cyanoacrylate glue or thermal conductive epoxy to attach a thermocouple to a coil was entirely acceptable. Here's a tip in using thermocouples: It is best to force the junction wires of the thermocouple to fuse into a single point and to avoid using a junction made of twisted bare wires (which forms several thermocouple contact junctions and can cause errors). In the fabrication of the junction, I use a microtorch to fuse type 'J' thermocouples. Twist the wires together, but clip the excess off and leave enough that when you hit it with the torch a 'ball' fuses from the wires and consumes all the twists. This takes a little practice but works much better than using a zapper to 'arc' weld thin 30 to 36ga. wires (IMHO). I then check each channel for accuracy before attachment and test. On most thermocouple types the red wires are negative polarity, white is positive. The thinner the wires, the better ease in accessing tight spots and getting a good contact. Kyle Ehler kyle.eh...@lsil.com mailto:kyle.eh...@lsil.com Assistant Design Engineer LSI Logic Corporation 3718 N. Rock Road U.S.A. Wichita, Kansas 67226 Ph. 316 636 8657 Fax 316 636 8889 Fax 316 636 8315 -Original Message- From: Kamran Mohajer [SMTP:kmoha...@cisco.com] Sent: Tuesday, August 24, 1999 4:50 PM To: emc-p...@ieee.org Subject:Temperature Measuring of Magnetic Components Hello EMC-PSTCers, I wonder if anyone knows of the method of measuring temperature limits on magnetic components. I happen to get involved in this and found that my results are different than the vendors result by as much as 10-15 degrees on measuring on a same magnetic component. Even applying the thermocouple to different location on a coil seems to give you different results. Is there a method that I should be following to measure temperature with thermocouples methods, not change of resistance, on magnetic parts such as transformers, coils, etc.? Thanks, *** Kamran Mohajer DSL Compliance Lead Cisco Systems, Inc. Phone(408)-525-6121 Fax(408)527-0495 kmoha...@cisco.com *** - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Temperature Measuring of Magnetic Components
Dear Kamran, Obtaining a temperature test results that is 10-15 degrees higher or lower than your vendor is not unusual at all. We experience this all the time with major test houses. I have had many cases where an experience test engineer in a test house measures as much as 20 degrees lower or higher than our in-house measurements. This is because there are many variable/uncontrolable factors involved when measuring thermals. Thanks H.Ahmadi - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Temperature Measuring of Magnetic Components
Kamran, As John Crabb pointed out, making measurements at different points will give you some variation due to hot spots etc. What most people miss is that thermocouple readings are affected by magnetic fields. To get a correct reading, turn power off and take a reading immidiately after the reading stabilizes. I have seen the reading change as much as 10-15 degrees when the power is turned off. Usually the reading jumps higher. I also noticed that how much the reading changes depends on where I placed the thermocouple. Usually the biggest change is when the thermocouple is placed between the core and the coil. When trying to correlate your readings with your vendor's make sure you're using the same type of thermocouple and measure at the same point. Find out if they made the measurement with power on or off. Several years ago I had the same problem. I called the manufacturer of the thermocouple I was using. They could not tell me how much my reading would change but recommended taking the reading with power off. Hope this helps. Regards, Fred Waechter Kamran Mohajer wrote: Hello EMC-PSTCers, I wonder if anyone knows of the method of measuring temperature limits on magnetic components. I happen to get involved in this and found that my results are different than the vendors result by as much as 10-15 degrees on measuring on a same magnetic component. Even applying the thermocouple to different location on a coil seems to give you different results. Is there a method that I should be following to measure temperature with thermocouples methods, not change of resistance, on magnetic parts such as transformers, coils, etc.? Thanks, *** Kamran Mohajer DSL Compliance Lead Cisco Systems, Inc. Phone(408)-525-6121 Fax(408)527-0495 kmoha...@cisco.com *** - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). -- Fred Waechter Sr. Applications Engr. SMPS Consulting w...@skybest.com Phone/FAX: 336-246-5236 - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Temperature Measuring of Magnetic Components
Hello Kamran, I have been faced with this problem many times in the (nearly 35) years that I have been involved with such measurements. In my experience, this is the major and problematic correlation factor (in the product safety domain). It is the one that stands out above all others, when faced with correlation difficulties (especially when the tests are conducted on different continents as they were in my situation :-) Very slight changes in the immediate-area ambient temperatures and the electrical service where you are making the measurements can drastically affect the temperature readings as can the location of the thermocouples on the transformer under test (as you already noted). Consider the following possiblilites (not in any particular order) ; A) Be certain that there is no extraneous air-flow over the trafo (from a room-fan, people constantly walking by in the adjacent aisles, or room air-conditioning drafts. ( I believe ambient air-flow to be a major factor when you are faced with correlation difficulties) B) Be certain your input voltage is a clean sine-wave. Distortions in the input voltage waveshape will affect your data. (At one time we tried to use a low-distortion/low harmonics constant-voltage transformer to keep the line voltage constant during temperature tests - even that small amount of input distortion was sufficient to affect our results). C) If the trafo is in a switching-mode power supply, the currents being switched will likely be affecting the indicated temperatures. D) Why do you discount rise-of resistance ? I believe this technique integrates the temperature differences across a transformer and yields a more repeatable result (in my humble experience). E) One problem I've found in transformer construction is that air can become entrapped, by the impregnating materia, between the outer-wrap layers. This effects the temperatures measured on the outer surfaces (again, a thermocouple location problem). F) Another problem is the heating effect on the trafo of adjacent hot components (cold ones or sinks too, I suppose) when transformers are evaluated in an end-product. Be certain that you and your vendors (and your test agency) apply thermocouples in the same location/s. Consider submitting a transformer, with thermocouples attached by you, to your vendor/s and test agency/ies. This will, at the least, rule out thermocouple location (and its attachment) as a variable. G) Be certain that you are using high-grade (low error) thermocouples and calibrated equipment. Good Luck! Regards, Art Michael Int'l Product Safety News A.E. Michael, Editor P.O. Box 1561 Middletown CT 06457-8061 U.S.A. Phone : (860) 344-1651 Fax: (860) 346-9066 Email : i...@connix.com Website: http://www.safetylink.com ISSN : 1040-7529 - On Tue, 24 Aug 1999, Kamran Mohajer wrote: Hello EMC-PSTCers, I wonder if anyone knows of the method of measuring temperature limits on magnetic components. I happen to get involved in this and found that my results are different than the vendors result by as much as 10-15 degrees on measuring on a same magnetic component. Even applying the thermocouple to different location on a coil seems to give you different results. Is there a method that I should be following to measure temperature with thermocouples methods, not change of resistance, on magnetic parts such as transformers, coils, etc.? Thanks, *** Kamran Mohajer DSL Compliance Lead Cisco Systems, Inc. Phone(408)-525-6121 Fax(408)527-0495 kmoha...@cisco.com *** - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
RE: Temperature Measuring of Magnetic Components
Kamran, The method used by most of the better magnetics houses is to embed thermocouples into the transformer during construction of a sample. The resulting temperatures will be higher than external measurements. Scott Lacey -Original Message- From: Kamran Mohajer [SMTP:kmoha...@cisco.com] Sent: Tuesday, August 24, 1999 5:50 PM To: emc-p...@ieee.org Subject:Temperature Measuring of Magnetic Components Hello EMC-PSTCers, I wonder if anyone knows of the method of measuring temperature limits on magnetic components. I happen to get involved in this and found that my results are different than the vendors result by as much as 10-15 degrees on measuring on a same magnetic component. Even applying the thermocouple to different location on a coil seems to give you different results. Is there a method that I should be following to measure temperature with thermocouples methods, not change of resistance, on magnetic parts such as transformers, coils, etc.? Thanks, *** Kamran Mohajer DSL Compliance Lead Cisco Systems, Inc. Phone(408)-525-6121 Fax(408)527-0495 kmoha...@cisco.com *** - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
RE: Temperature Measuring of Magnetic Components
Kamran, When UL or Intertek does safety testing (UL 1950, IEC 60950) on one of our units that has coils or transformers in it they apply the thermocouples to the top (highest) horizontal surface of the coil or transformer for their temperature rise (heating) tests. I can usually find the remnants of the glue they use to attach the thermocouples on the top of the parts. On a recent unit from UL with a transformer comprised of two coils standing on end side by side, they placed thermocouples on the top horizontal surface of both coils. The magnetic parts in our equipment are rather small, less than two inches on a side. I would imagine larger magnetic components may require more thermocouples. I figure they use the top surface since heat rises it is likely to be the hottest spot. In my opinion it would make sense to use whatever method the NRTLs use and not worry too much about how the vendors do it. Although not definitive I hope this offers some insight. Kurt Andrews Compliance Engineer Tracewell Systems, Inc. 567 Enterprise Dr. Westerville, OH 43081 Ph. 614-846-6175 Fax 614-846-7791 Email: kandr...@tracewell.com -Original Message- From: Kamran Mohajer [SMTP:kmoha...@cisco.com] Sent: Tuesday, August 24, 1999 5:50 PM To: emc-p...@ieee.org Subject:Temperature Measuring of Magnetic Components Hello EMC-PSTCers, I wonder if anyone knows of the method of measuring temperature limits on magnetic components. I happen to get involved in this and found that my results are different than the vendors result by as much as 10-15 degrees on measuring on a same magnetic component. Even applying the thermocouple to different location on a coil seems to give you different results. Is there a method that I should be following to measure temperature with thermocouples methods, not change of resistance, on magnetic parts such as transformers, coils, etc.? Thanks, *** Kamran Mohajer DSL Compliance Lead Cisco Systems, Inc. Phone(408)-525-6121 Fax(408)527-0495 kmoha...@cisco.com *** - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Temperature Measuring of Magnetic Components
Hello EMC-PSTCers, I wonder if anyone knows of the method of measuring temperature limits on magnetic components. I happen to get involved in this and found that my results are different than the vendors result by as much as 10-15 degrees on measuring on a same magnetic component. Even applying the thermocouple to different location on a coil seems to give you different results. Is there a method that I should be following to measure temperature with thermocouples methods, not change of resistance, on magnetic parts such as transformers, coils, etc.? Thanks, *** Kamran Mohajer DSL Compliance Lead Cisco Systems, Inc. Phone(408)-525-6121 Fax(408)527-0495 kmoha...@cisco.com *** - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
