APC Automatic Disconnect Switch Specifications download pdf (Page 18)

Overview: How the InfraStruXure Power Generation System Operates

8 Automatic Transfer Switch with Power Distribution

Open and closed transfers

When a transfer is not occurring, one switch is ON and the second 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 the neutral

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 on 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 has to be good; in addition, a closed transfer cannot

occur if the two sources are not synchronized. The ATS monitors for both sources to be synchronized

before transferring. If the time it takes for the sources to be 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, which creates a seamless transfer—

non-UPS-protected equipment will not be interrupted and the UPS time on battery will be reduced,

and in some cases, eliminated.

If the Allow Closed setting is No, the ATS will never perform closed transfers—it will always

perform open transfers. (See page 35 for details on these settings.) 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 the neutral time. The neutral time is

defined by the configurable Open Xfer Time.

Closed Transfer

Source 1 Source 1 Source 2

Source 2

t=miliseconds

Open Transfer

Source 1 Neutral Source 2

t=seconds

1 2 ... 13 14 15 16 17 18 19 20 21 22 23 ... 101 102

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APC Automatic Disconnect Switch Specifications Page 18