Abstract: Differential mode rejection networks and their use in measuring and limiting electromagnetic interference such as is conducted back into power transmission lines by noise-generating electrical equipment powered from such lines. Both single-phase and three-phase embodiments are specified. Improvement in filter design is enabled.

Abstract: Selectable mode rejection network (SMRN) for electromagnetic interference (EMI) excludes common mode (CM) and, alternatively, differential mode (DM) conducted emissions (CE) from entering power transmission lines from electrical equipment powered from such lines and producing such unwanted electrical noise. Phase-switching the SMRN determines whether CM or DM is so excluded, thereby facilitating measurement of the unexcluded type of CE. So used in measuring EMI, such SMRN enables improved filter design for the respective types of CE and composite filters for limiting both CM and DM CE.

Abstract: Measurement of electromagnetic interference (EMI), especially conducted emissions from electrical equipment under test (EUT) to transmission lines powering the EUT; and then limiting such EMI. Differential mode (as distinguished from common mode) EMI conducted emissions are excluded temporarily from measurement by interposing a differential mode rejection network (DMRN) between the EUT and an EMI-sensitive receiver, and such common mode EMI is measured. A filter against such common mode conducted emissions is designed and is interposed between the EUT and the EMI receiver, and such differential mode EMI is then measured--with the DMRN removed. A filter against the differential mode conductive emissions is also designed and interposed between the EUT and the receiver, and the total conducted emissions are rechecked. The respective filters are combined into a composite filter for the EUT to prevent such EMI conductive emissions from entering power transmission lines.