In a message dated 8/30/2002, Chris Maxwell writes:
> Most "isolation" transformers have a non-magnetic, metal shield between the > primary and secondary. The shield does not appreciably degrade the > transformer's magnetic coupling at 60Hz; however, it does attenuate the > high frequency differential noise passed from primary to secondary. > Hi Chris: Thanks for your response. This transformer does indeed have a grounded shield between the primary and secondary. I guess I don't know enough about transformer design to understand why the shield would attenuate differential noise. I can certainly see how it would reduce common mode coupling at high frequencies, since the grounded shield will reduce the inter-winding capacitance. Do you know of some typical applications for this type of "isolation" transformer? There must be enough demand for them, since Tripp-Lite and a few other manufacturers offer them as a catalog item. In the mean time, I plan to modify the wiring as I described previously to obtain a floating, ungrounded AC supply. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 http://www.randolph-telecom.com
