Source 1 is available
Is Source 2
available?
Close Source 2 contactor
(Momentarily energize K4)
N
Utility - Generator Transfer Switch
Close Source 1 contactor
(Momentarily energize K3)
Source 1 becomes unavailable
(or Engine Test, Plant Exerciser, Go To Emergency)
TDES timer times out
Send “Engine Start” signal
(Energize Gen Start relay)
TDNE timer times out
Open Source 1 contactor
(Energize K2)
Y
Source 2 is powering the load
TDEN timer times out
Open Source 2 contactor
(Energize K1)
Close Source 1 contactor
(Momentarily energize K3)
N
Is Source 1
available yet?
Y
Source 1 is powering the load
TDN timer times out
(if Option 32A is enabled)
TDN timer times out
(if Option 32A is enabled)
Source 1 is powering the load
TDEC timer times out
Remove “Engine Start” signal
(De-energize Gen Start relay)
Send Pretransfer signal. TPRE times out.
(if Pretransfer enabled)
Send Pretransfer signal. TPRE times out.
(if Pretransfer enabled)
For more information visit: www.eaton.com
IB140036EN
Instruction Booklet
Page
30
Effective: October 2014
O&M Manual for 40-1200A (480/600 Vac) ATC-900 3-Position,
Open/Closed Transition Contactor Based Transfer Switch
Figure 20. Utility - Generator Transfer Switch.
