Mounting Bridge Rectifiers: Compliance Needs Make It Complicated

Focus:

Bridge rectifiers are subject to safety agency certifications such as UL because in their applications they often connect to the ac mains and may be mounted on a chassis or heatsink, making them part of the isolation safety barrier and therefore subject to creepage and clearance considerations. There are also maximum touch temperatures that affect rectifier usage. The requirements for isolation and heat removal are often in conflict. This article discusses real world best practices for balancing these requirements. The article begins by discussing how to determine spacing and cooling requirements. It then explains factors that must be considered in selecting thermal interface materials, washers (Belville or conical) and screws, and how much torque to apply. It also discusses the importance of consulting with suppliers and safety certification agencies.

What you’ll learn:

• How to satisfy safety and thermal requirements when mounting bridge rectifiers
• How to select fasteners and thermal interface materials when mounting bridge rectifiers to heatsinks and chassis

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Author & Publication:

Kevin Parmenter, Chair, and James Spangler, Co-chair, PSMA Safety and Compliance Committee , How2Power Today, Jul 15 2020

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