Inrush Current Tester Enables More Thorough Validation Of Server Power Supplies
by Viktor Vogman, Power Conversion Consulting, Olympia, Washington, How2Power Today, Apr 17 2018
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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