UPS for 208 Vac Grid, B120US Installation Guide, doc. rel. 3.0
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8.
Using the UPS with a Generator
At many sites a generator is used as a reserve source for feeding the UPS during mains power
failure.
8.1.
The Automatic Transfer Switch (ATS)
At many sites a generator is used as a reserve source for feeding the UPS during mains power
failure. In such cases, the switching between the two sources (the mains and the generator) is
performed by an Automatic Transfer Switch (ATS). Because these two sources are not usually
synchronized, switching between them requires an interval of at least 10 seconds.
Figure 63 illustrates the timing factors involved when using an ATS. For proper functioning of the
UPS, the values used for T3 and T4 must be greater than 10 seconds.
Figure 63: Timing variables when using a generator and an ATS
