UNDERSTANDING AND CONTROLLING COMMON …

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Henry W. OttHOCELECTROMAGNETICCOMPATIBILITY2001By Henry W. OttHenry Ott ConsultantsLivingston, NJ 07039(973) AND CONTROLLINGCOMMON-MODE EMISSIONSIN HIGH-POWER ELECTRONICSPage 1 Henry W. OttHOCELECTROMAGNETICCOMPATIBILITYTHE BASIC PROBLEM!Switching Power Supplies and Variable Speed Motor DrivesProduce Large Noise Currents Which are Conducted Out tothe Load, as Well as Conducted Back to The Power Source!These COMMON -Mode Noise Currents are the Cause of: Low Frequency Conducted Emission, and High Frequency Radiated Emission!Once One Has an UNDERSTANDING of the Noise Source andCoupling Mechanism, a Solution Can be Determined!Power Line Filters in Combination With Proper Load SideFiltering, Grounding, and/or Shielding Will Usually SolveMost COMMON -Mode Emission 22001 Henry W. OttHOCELECTROMAGNETICCOMPATIBILITYBASIC PRINCIPLE OF EMCReturn Current to its Source as Locallyand Compactly as PossiblePage 32001Minimize the Loop Area Henry W.

©Henry W. Ott HOC ELECTROMAGNETIC COMPATIBILITY COMMON-MODE & DIFFERENTIAL MODE NOISE! Differential-Mode Noise — Involves the Normal Operation of the Circuit — Currents Flowing Around

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