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Chapter 12 Helpful information
Date: Monday, February 8, 2021
To:
Lenovo and valued partners
From: Lee Nino, Eaton DPQ Engineering Manager
Subject UPS Leakage current and Residual Current Devices
There have been on-going questions regarding the use of Residual current devices upstream from
an Eaton UPS for applications. This document also applies to any Lenovo 5594 and IBM 5594
hardwired UPS unit. The intent of this letter is to clearly state Eaton s recommendation for such
application requests.
Residual Current Devices (RCD) provide protection from electric shock. An RCD works on the
principle of comparing currents in live conductors passing through a current transformer and
determining the amount of current imbalance.
Uninterruptable Power Supplies (UPS) have an ordinary leakage current due to the hardware
architecture, the internal battery and input filtering required for signal noise cancellation. This
leakage current is typically < 3.5mA. However, for fixed higher power systems over 3kVA the
leakage current allowed in the IEC-62040 specification Touch Current and Protective Conductor
Current can be up to 5% of the input current. Such UPS systems with a leakage current over
3.5mA have a warning label cautioning that the ground connection is essential before connecting
the other conductors.
Eaton does not recommend the placement of RCD upstream from UPS systems with a leakage
current higher than 3.5mA. There are RCDs available with sensitivity up to 420mA but will still
not meet the 5% input current limit allowed by IEC-62040 section 5.1.
Best regards
Lee Nino
Engineering Manager DPQ
Eaton Corporation Power Quality
8609 Six Forks Road
Raleigh, NC 27615
More information concerning UPS systems can be found at http://www.eaton.com/UPS,
RCD application guide:
circuit-protection/circuit-breakers/xeffect-rccb/eaton-rcd-application-guide-
br019003en-en-us.pdf
6U Rack or Tower UPS RT8kVA and RT11kVA IUOMG
https://www.eaton.com/content/dam/eaton/products/electrical-
Eaton Corporation
8609 Six Forks
Road Raleigh, NC
27615
197
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