How Cisco Automated Line/Load Testing of their N+1 Server Power Supplies

Device Under Test

Cisco’s line of AC DC power supplies include dual AC inputs ranging at 110-220VAC and dual 50VDC outputs are capable providing sufficient power in the case of one side power down. Each AC inlet module provides half the output power at high line 220VAC, and is fully isolated from the 2nd AC inlet.

Cisco wanted to be able to test and show that the power supply outputs will remain within the tolerance defined by Cisco specifications under all combinations of line variation and load variation. The power supply is hot swapping and acts as a 2 in 1 PS with I2C communication protocol. The power supplies also have a SMBUS/I2C communication requirement.

Test System

Chroma Systems Solutions - power supply automated test equipmentA C8000 automated test system running on a Power Pro software platform with advanced power and programming capabilities that hit the mark for safety, speed, and efficiency.

Our engineers designed and provided an automated test system with a programmable 480VAC 61612 18kVA AC Source with 3P4W output, where each phase can be programmed and controlled to provide input to the DUT with 110-220VAC variation from a single source. Cisco’s wide range of power supplies required as little as 20A and higher than 1000A in total load output. To meet the wide ranging load requirements, the system was equipped with a 63600 mainframe loaded with a combination of 5 DC electronic load modules for low power and two 63200A DC Loads were integrated for the higher output requirements; each load programmable and efficient. Our 62000P programmable supplies provided ample DC power with transients. Chroma’s Power Pro software program was a huge plus for speeding through all the input and output variations in seconds over hours. To connect the DUT to the system, we custom built an accessible wiring harness that is easily moved from one power supply to the next.


The ATE for Cisco was custom built to have inhibit output for the sources, EPO circuit for safety, quick change connectors, bus bars for higher loads, work surface for convenience, and various communication lines feature to meet programmable instruments or DUT. For the I2C communication from the power supply, we routed the SMBUS/I2C communication card (NI) to the front of the ATE and to the power supply with a custom harness for one time plug in. For safety, our design featured an EPO switch to quickly shutdown to the DUT. Each programmable electronic source is capable of inhibiting the output when EPO switch is pressed. The connection points of the bus bars sit safely inside a housing cover; custom panels with high-grade workmanship.

The test items and program were written with easy drop-down selectors for the user to quickly make changes when navigating from one test to another. We also provided a user friendly, customizable test report that output detailed results.

Cisco was happy with the safety features, abundant power, and that their system was functional, efficient and easy to upgrade. As a result, Cisco quickly upgraded the system by adding a DMM and a low power DC source. Chroma applied the upgrades with short notice to meet the requested quick turnaround.