Appliance Design - February 2009 - (Page 36)

SHIELDING & EMI filtering uses separate capacitors and inductors, one applied on each +/- line, or between the lines. The wired connections between components and the mismatched component tolerances create an imbalance in the EMI filtering. (See Fig. 7.) The difference in EMI filtering on each power line translates to increased emissions. A single X2Y capacitor properly mounted at the cable I/O provides balanced filtering on both +/- lines while simultaneously minimizing the potential difference to the motor case. Since only one X2Y component is used, imbalances caused by wire connections are minimized in the application. (See Fig. 8.) A single X2Y component has met automotive requirements for CE and RE, transient suppression, and various motor-stall requirements. In appliance applications, a single X2Y filter component can often provide the needed filtering to meet less stringent FCC EMC compliance at a lower cost than conventional EMI filter measures. For AC powered appliances, the advent of more efficient, faster switching power supplies makes meeting agency compliance an increasingly difficult task. Schurter offers an AC powerline filter product with an X2Y capacitor inside that meets IEC and UL agency safety requirements and is designed specifically for high-frequency filtering of radiated emissions [6] to GHz frequencies. Low inductance improves high frequency filtering. Motor or Enclosure Conventional EMI Filter Difference Between Enclosure VCM VDiff VCM Difference Between Cables Difference Between Enclosure Fig. 7. A conventional EMI filter, motor, or enclosure. Motor or Enclosure X2Y® EMI Filter Difference Between Enclosure VCM VDiff VCM Difference Between Cables Difference Between Enclosure Fig. 8. X2Y EMI filter, motor or enclosure. Fig. 9. Schurter 5150 PowerLine Filter. 36 applianceDESIGN February 2009 www.applianceDESIGN.com http://www.appliancedesign.com

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Appliance Design - February 2009 Contents Editorial Shipments/Forecasts News Watch Force-Sensing Technology Offers Designers an Alternative Approach to Creating Touch-Control Interfaces A Flammable Vapor Sensing Technology that was Originally Developed for use in Water Heaters has Evolved for use in a Broader Array of Applications Latches, Hinges, and Slides Must Reliably Secure Parts Together, Sometimes for Hundreds of Thousands of Cycles. Beyond their Utilitarian Functions, They Can Also Change Consumer Perceptions Elastomeric Electrical Connectors Can Solve Space Constraint Problems in Electronic Products and Provide Some Cost Advantages as Well A Multi-Layer Ceramic Capacitor with a Novel Electrode Design Can Suppress Electromagnetic Interference, Improve Circuit Performance, and Reduce the Number of Needed Components Design Marts Association Report: AHRI Advertisers’ Index

Appliance Design - February 2009

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