EMI considerations: emanations relate to amount of energy available, little energy = little emanations 1. voltage surges are usually 'shielded' by metal structures, including the slip ring. 2. current surges are related to the amount of current being carried and area of the loop. Small amount of current in combination with small loop area = little emanations. 3. spectral content - pretty low frequency, in my experience the rise and fall times of mechanical contacts making and breaking are extremely slow, in the audio range. which translates to... * Radiated Emissions above 30MHz is unlikely * Conducted Emissions in the 10kHz to 30MHz range is possible being caused by capacitive coupling of voltage or inductive coupling of CURRENT [the most likely transfer path]. Easy to mitigate with twisted pairs and reduced loops [both source loop *and* receive loop], lowered power, and proximity [move away from each other].
Forgot to add, assume this is in atmosphere, changes if in vacuum. Regards, Robert --- david.car...@plexus.com wrote: From: "David Carney (Neenah)" <david.car...@plexus.com> To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: [PSES] Slip Rings and EMI Date: Thu, 3 May 2012 12:18:48 -0500 We're considering a slip ring in a design to pass some wires through a rotating motor shaft, and we have never used one before. Are there any EMI concerns with this architecture? If there are concerns, what types of mitigations are used for EMI when slip rings are used? If slip rings are to be avoided for certain types of signals due to EMI concerns, what other alternatives should we consider? Thanks. David T. Carney P.E. (WI) Senior Design Engineer Plexus Engineering Solutions Neenah Design Center 920.751.5646 - ---------------------------------------------------------------- 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 <emc-p...@ieee.org> 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://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...@radiusnorth.net> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
