Don, Until I contested this arrangement, I routinely had 48vdc equipment tested for the conducted emissions on the AC side (input side) of a seperate AC-to-DC power supply (an HP if I remember correctly) that powered the shelf. That HP supply was part of the test equipment setup and not part of the system.
Doug Donald Kimball wrote: > > I work for Qualcomm, and we EMC test -48Vdc powered telecommunications > equipment, especially cellular and PCS base stations. The -48Vdc power is > usually shared with other equipment at the same location (eg. an Alcatel > Switch, Cisco Router, etc.) > > We have always tested for conducted emissions on DC side of the power line, > since we do not control the AC to DC power converter, and we share the DC > power with other equipment. Recently, we integrated another vendor's E1 > inverse multiplexer into our base station controller racks. The vendor > claimed CE mark compliance and sent us a test report. This equipment is > powered by -48Vdc, but they tested for conducted emissions on the AC side > of the AC to DC power supply that powered the E1 inverse multiplexer. When > questioned, they said that the test facility told them they must test on > the AC side of the line, and not the DC side of the line. The test > facility said they would not issue a declaration of conformity based on > testing the DC side of the power line. In fact, they went through several > AC to DC power supplies before they found a power supply that was EN 55022 > compliant by itself. > > This makes no sense, since the DC power is shared, and the choice of AC to > DC power supply cannot be controlled by Qualcomm. Moreover, a well chosen > AC to DC power supply can filter out the noise on the DC side of the line. > In fact, one version of the inverse multiplexer fails on the DC side of the > power line, but passes on the AC side of the line. If the emissions on the > DC side of the power line are compliant with EN 55022 Class A limits, the > those same emissions should be below the limit on the AC side. > > What is the correct answer in this case? Do you test the AC side or the DC > side? > > Don Kimball --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
