Inrush Current Tester Enables More Thorough Validation Of Server Power Supplies

Focus:

Although server power supplies pass extensive qualification tests performed with conventional programmable ac sources, they still have a significant failure rate in the field due overstress of the power factor correction (PFC) stage caused by ac transients known as “re-rush” currents. This overstress is not detected during power supply qualification due to the limited transient current capability of existing ac grid emulating equipment used to qualify server power supplies and the high cost/large size of test equipment with sufficient power capability. This article describes the implementation of a simple, inexpensive test instrument to adequately test power supply vulnerability to re-rush current. Experimental results obtained using this test tool are presented. The article begins by explaining the mechanisms responsible for re-rush current and the associated PFC failures, and describes the calculation of the required test current level.

What you’ll learn:

• How to build a low-cost ac transient test tool for accurate verification of the ac inrush/re-rush current withstand capability of server power supplies
• How to verify the ac inrush current withstand capability of circuitbreakers, LED lighting, power transformers and ac motors
• How to understand the cause and effects of re-rush currents in ac-dc power supplies

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Author & Publication:

Viktor Vogman, Power Conversion Consulting, Olympia, Washington, How2Power Today, Apr 17 2018

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