Eaton Energy Saver System: Facts and Principles

Overview

In ESS mode the load is fed through static bypass while rectifier and inverter control remain active but gated off. DSPs in each module monitor mains quality and trigger the transfer. Transfer from ESS to double conversion is guaranteed within 2 ms. Double conversion typically reaches 94-95% at loads of 40% or more, whereas ESS mode reaches around or above 99%, cutting losses by over 80%. The control circuitry of each power module consumes about 200 W while gated off.

Storm detection is a configurable criterion: after multiple transitions within a preset period the UPS stays in double conversion, typically for one hour. The paper argues reliability from state diagrams and reduced component stress, and also covers surge suppression.

The mode is not suitable everywhere: it may be unsuitable with poorly maintained generators, overloaded public supplies, or where cooling compressors share the IT supply transformer and cause transients. Cooling plant cannot be downsized, because UPS heat in double-conversion mode must still be removed.

In the example, a 1 MW load moving from 94% to 99% efficiency saves about EUR 50,000 per year and about 195 t CO2 per year.

Key points

1. Double conversion reaches 94-95% at 40% load or more; ESS reaches around or above 99%, cutting losses by over 80%.
2. Transfer from ESS to double conversion is guaranteed within 2 ms.
3. Each power module's control circuitry consumes about 200 W while gated off in ESS mode.
4. Storm detection: after multiple transitions in a preset period the UPS stays in double conversion, typically for one hour.
5. ESS may be unsuitable with poorly maintained generators, overloaded public supplies, or compressors sharing the IT transformer.
6. Cooling plant cannot be downsized because double-conversion UPS heat must still be removed.
7. Example: a 1 MW load moving from 94% to 99% saves about EUR 50,000 and ~195 t CO2 per year.

Using it in design

• Keep an efficiency curve per mode (double conversion versus eco/ESS) and the transfer time in the catalogue.
• In the energy model allow a percentage of time in eco mode, but size UPS room cooling on double-conversion losses.
• Warn on eco mode where IT and mechanical loads share a transformer or where the source is generator-only.
• Show the IEC 62040-3 classification change when eco mode is active.

Who should read it

Energy and electrical designers weighing UPS efficiency gains against eco-mode risks.

Related standards

• IEC 62040-3
• ITI (CBEMA) curve

Publication details

Authors

Janne Paananen

Publisher

Eaton

Year

2015

Document language

English

Source type

Manufacturer

Access

Free to read

Licence

Copyright retained; citation only — the publisher’s terms apply to the original document

Citation