How the InfraStruXure Power Generation System Operates
8 InfraStruXure Power Generation System
Open and closed transfers
When transfers are not occurring, one switch is ON and one switch is OFF.
During a closed transfer, the second switch will turn ON before the first switch turns OFF, creating a
brief period of time when both switches are ON.
During an open transfer, the first switch will turn OFF before the second switch turns ON, creating a
period of time when neither source is connected. This period is commonly referred to as neutral time.
Neutral time is defined by the configurable Open Xfer Time.
You can set whether or not to Allow Closed transfers under the Transfer Setup item on the ATS
Setup menu on the display interface (see page 35 for details about these settings). If the Allow
Closed setting is Yes, the ATS will always seek to perform closed transfers. In order for a closed
transfer to occur, the voltage and frequency for both sources must be acceptable and both sources
must be synchronized. The ATS monitors both sources for synchronization before transferring. If the
time it takes for the sources to become synchronized exceeds the configured Max Sync Time, the
ATS will perform an open transfer instead. During a closed transfer, the ATS also takes into account
the time it takes for the switch to actuate. This results in a seamless transfer in which non-UPS-
protected equipment is uninterrupted and the UPS time on battery is reduced or even eliminated.
If the Allow Closed setting is No, the ATS will never perform closed transfers; it will only perform
open transfers (see page 35 for details about these settings).
Closed Transfer
Source 1 Source 1 Source 2
Source 2
t=miliseconds
Open Transfer
Source 1 Neutral Source 2
t=seconds