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Power Supplies Benefit From Complementary EMC Filters

Posted : 17 Mar 2014

TDK Corporation announces that in addition to its own range of two-line filters for its power supplies, TDK-Lambda is offering complementary EPCOS two-line EMC filters of the SIFI® series and EPCOS IEC inlet filters manufactured by EPCOS, a TDK group company.

“Even if a power supply is compliant with EMC norms, EMC filters are needed when the load produces additional disturbances, for example from electric motors and variable speed drives,” maintains Martin Southam, Director of Marketing at TDK-Lambda EMEA.

“Often those disturbances are in a high and/or different frequency range from that of the filter inside the power supply itself. Some applications also involve more than one power supply and their conducted electrical noise can cause failure in EMC tests. Furthermore, long cabling looms in the application can cause an ‘antenna effect’, creating radiated noise disturbances both externally and within the application itself.”

Professional high-end EPCOS EMC filters include the SIFI product line, a standardised modular system based on five product lines with different insertion loss characteristics and terminal styles, including a medical version with low leakage current. These filters offer very good suppression of symmetrical and asymmetrical interference and come in F, G and H variants for normal, enhanced and very high insertion loss characteristics at 50 Ω impedance. The medical versions also boast extremely low leakage current of 2 μA for applications such as ultrasound devices, X-ray systems, or other medical diagnostic devices where low leakage current is a critical factor. Applications for all three of the important approvals, namely UL, cUL and ENEC, have been submitted.

Also offered is the proven B84771 series of EPCOS IEC inlet filters with two new series. The B84773 series features an integrated fuse, while the B84776 series has both a switch and a fuse. The power switch of the B84776 series is of bipolar design and thus separates the phase and the neutral conductor. The three series offer an extended range of rated current from 1-20 A at 250 V DC/AC and a climatic category (IEC 60068-1) of 25/85/21. Additionally, the new IEC inlet filters are available in a medical version with low leakage current of 2 μA. Designed for a maximum ambient temperature of 85 °C, all IEC and SIFI filters are RoHS-compatible with UL/CSA approval. ENEC approval is already available on the B84771, and pending on the B84773 and B84776