Re: broadband RE from AC induction motors
Thanks to all who responded to my question about broadband radiation from ac induction motors. -- >From: John Woodgate >To: emc-p...@majordomo.ieee.org >Subject: Re: broadband RE from AC induction motors >Date: Mon, Jan 28, 2002, 2:52 PM > > > I read in !emc-pstc that Price, Ed wrote (in > ) about > 'broadband RE from AC induction motors', on Mon, 28 Jan 2002: > >>Possibly ESD caused by motion of the air over the rotor, with a regular >>discharge from a pole-piece? Can you relate the 10 ms interval to the RPM >>and number of pole-pieces? > > This happens with *non-conducting* fan blades, or a metal fan which is > well insulated from earth, if the blades move near an earthed object > that they can discharge to. > -- > Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk > After swimming across the Hellespont, I felt like a Hero. > PLEASE do NOT copy news posts to me by E-MAIL! > > --- > 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: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Michael Garretson:pstc_ad...@garretson.org > Dave Healddavehe...@mediaone.net > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > 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. > --- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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.
Re: broadband RE from AC induction motors
The need for snubbers on the relays? I dealt with a product which used a 1 1/2 HP motor with arcing visible to the operator and did have any high end emissions. 600 MHz is rather high for a motor. Even 30 MHz. Would have thought problems showing up in the conducted side of things instead. - Doug McKean --- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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.
Re: broadband RE from AC induction motors
I read in !emc-pstc that Price, Ed wrote (in ) about 'broadband RE from AC induction motors', on Mon, 28 Jan 2002: >Possibly ESD caused by motion of the air over the rotor, with a regular >discharge from a pole-piece? Can you relate the 10 ms interval to the RPM >and number of pole-pieces? This happens with *non-conducting* fan blades, or a metal fan which is well insulated from earth, if the blades move near an earthed object that they can discharge to. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. PLEASE do NOT copy news posts to me by E-MAIL! --- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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.
Re: broadband RE from AC induction motors
That crossed my mind but the motors are three phase 400 cycle. 400 cycle is a 2.5 ms period, then you have the three phase and number of poles so the period associated with anything rotationally related to the motor would be much less than a millisecond, or that was my thought process at any rate. -- >From: "Price, Ed" >To: "'Ken Javor'" , emc-p...@majordomo.ieee.org >Subject: RE: broadband RE from AC induction motors >Date: Mon, Jan 28, 2002, 8:45 AM > >>-Original Message- >>From: Ken Javor [mailto:ken.ja...@emccompliance.com] >>Sent: Friday, January 25, 2002 10:09 AM >>To: emc-p...@majordomo.ieee.org >>Subject: broadband RE from AC induction motors >> >> >> >>Do any forum members have knowledge of a mechanism by which ac >>induction >>motors (two are fan motors, one a compressor motor) can >>generate broadband >>RE from 30 - 600 MHz? This is outside my experience. Are >>there perhaps >>degradation modes that result in arcing? The motors run off >>three phase 400 >>cycle power, 115 Volts rms phase to neutral. The control system is >>bang-bang, just mechanical relays making >>connections/disconnections based on >>temperature and pressure inputs. The rep rate of the BB noise >>is variable >>but around 10 milliseconds. >> >>Thank you. > > > Possibly ESD caused by motion of the air over the rotor, with a regular > discharge from a pole-piece? Can you relate the 10 ms interval to the RPM > and number of pole-pieces? > > Ed > > > Ed Price > ed.pr...@cubic.com > Electromagnetic Compatibility Lab > Cubic Defense Systems > San Diego, CA USA > 858-505-2780 (Voice) > 858-505-1583 (Fax) > Military & Avionics EMC Services Is Our Specialty > Shake-Bake-Shock - Metrology - Reliability Analysis > --- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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.
RE: broadband RE from AC induction motors
>-Original Message- >From: Ken Javor [mailto:ken.ja...@emccompliance.com] >Sent: Friday, January 25, 2002 10:09 AM >To: emc-p...@majordomo.ieee.org >Subject: broadband RE from AC induction motors > > > >Do any forum members have knowledge of a mechanism by which ac >induction >motors (two are fan motors, one a compressor motor) can >generate broadband >RE from 30 - 600 MHz? This is outside my experience. Are >there perhaps >degradation modes that result in arcing? The motors run off >three phase 400 >cycle power, 115 Volts rms phase to neutral. The control system is >bang-bang, just mechanical relays making >connections/disconnections based on >temperature and pressure inputs. The rep rate of the BB noise >is variable >but around 10 milliseconds. > >Thank you. Possibly ESD caused by motion of the air over the rotor, with a regular discharge from a pole-piece? Can you relate the 10 ms interval to the RPM and number of pole-pieces? Ed Ed Price ed.pr...@cubic.com Electromagnetic Compatibility Lab Cubic Defense Systems San Diego, CA USA 858-505-2780 (Voice) 858-505-1583 (Fax) Military & Avionics EMC Services Is Our Specialty Shake-Bake-Shock - Metrology - Reliability Analysis --- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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.
Re: broadband RE from AC induction motors
I read in !emc-pstc that Ken Javor wrote (in <20020125180848.LRWV20810.femail29.sdc1.sfba.home.com@[65.11.150.27] >) about 'broadband RE from AC induction motors', on Fri, 25 Jan 2002: >Do any forum members have knowledge of a mechanism by which ac induction >motors (two are fan motors, one a compressor motor) can generate broadband >RE from 30 - 600 MHz? This is outside my experience. Are there perhaps >degradation modes that result in arcing? The motors run off three phase 400 >cycle power, 115 Volts rms phase to neutral. Yes, marginal breakdown of insulation, or loose connections, can generate broadband r.f. emission. To eliminate the control equipment, temporarily run one of the motors straight from the mains. Don't forget to *switch off* the control equipment and the other motors during this test -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. PLEASE do NOT copy news posts to me by E-MAIL! --- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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.
RE: broadband RE from AC induction motors
Ken, The situation you describe sure sounds like the result of arcing. I would normally suspect that the relay contacts were the culprit if not for the repetition. If the noise is variable it may be caused by vibration. If possible, try to physically isolate the relays from the chassis to see if it goes away. A compressor can generate enough vibration to bounce some relay contacts. It is even possible that the vibration is causing some arcing problems inside of one of the motors. Scott Lacey -Original Message- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Ken Javor Sent: Friday, January 25, 2002 1:09 PM To: emc-p...@majordomo.ieee.org Subject: broadband RE from AC induction motors Do any forum members have knowledge of a mechanism by which ac induction motors (two are fan motors, one a compressor motor) can generate broadband RE from 30 - 600 MHz? This is outside my experience. Are there perhaps degradation modes that result in arcing? The motors run off three phase 400 cycle power, 115 Volts rms phase to neutral. The control system is bang-bang, just mechanical relays making connections/disconnections based on temperature and pressure inputs. The rep rate of the BB noise is variable but around 10 milliseconds. Thank you. --- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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. --- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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.
Re: broadband RE from AC induction motors
Corona discharge can occur when air is electrically stressed near its break down limit and this will generate broadband RF energy. If you have small bubbles of air in a insulator with a fairly high dielectric constant in an electrical field it produces an effect known as dielectric focusing and produces a electric field strength in the air in the bubble many times that given by the voltage across the insulator divided by the thickness of the insulator. If this field strength is strong enough to cause any ionised air molecules that are around (and there always a few from the effects of cosmic rays if nothing else) to be accelerated to sufficient velocity before they bump into other molecules for them to ionise them then this can lead to a cascade. Eventually at high enough fields this can lead to full blown arcing but before that there is a region before that where only the statistically rare long free paths will give enough energy to produce many generations and the cascades the result is eventually peter out. The result is a bubble of highly ionised gas that emits RF energy as the electrical current that movement of the ions varies randomly. . Increasing the frequency of the AC supply makes things worse. A shorter time between cycles leaves less time for the ions to be neutralised after the field strength dies before the next peak comes leaving a greater seed population of ions to start the next cycle. This is one of the reasons it is common when impregnating transformers and other electrical equipment to do so in a vacuum Although this effect can take some time to produce complete failure it will very likely do so in the end Nick Rouse - Original Message - From: "Ken Javor" To: Sent: Friday, January 25, 2002 6:08 PM Subject: broadband RE from AC induction motors > > Do any forum members have knowledge of a mechanism by which ac induction > motors (two are fan motors, one a compressor motor) can generate broadband > RE from 30 - 600 MHz? This is outside my experience. Are there perhaps > degradation modes that result in arcing? The motors run off three phase 400 > cycle power, 115 Volts rms phase to neutral. The control system is > bang-bang, just mechanical relays making connections/disconnections based on > temperature and pressure inputs. The rep rate of the BB noise is variable > but around 10 milliseconds. > > Thank you. > > --- > 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: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Michael Garretson:pstc_ad...@garretson.org > Dave Healddavehe...@mediaone.net > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > 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. > --- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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.
broadband RE from AC induction motors
Do any forum members have knowledge of a mechanism by which ac induction motors (two are fan motors, one a compressor motor) can generate broadband RE from 30 - 600 MHz? This is outside my experience. Are there perhaps degradation modes that result in arcing? The motors run off three phase 400 cycle power, 115 Volts rms phase to neutral. The control system is bang-bang, just mechanical relays making connections/disconnections based on temperature and pressure inputs. The rep rate of the BB noise is variable but around 10 milliseconds. Thank you. --- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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.
