STS/MBS Operation
Copyright © 2008-2010 Eaton Corporation. All Rights Reserved.
IPN 997-00012-68D February 2010
63
Normal Operation (mains priority)
Normal Operation (NORM)
Mains priority:
• Mains AC powers the load
through the static switch
• MBS can be switched to
Mains Static Switch or
Inverter Static Switch
position
• SCR2 open, SCR1 and Back-
feed Relay closed
• If the mains voltage or
frequency is abnormal, but
the inverter is normal, the
STS will transfer to on-line
mode
• If SCR2 is short, the STS
will keep the off-line mode
Normal Operation (NORM) (inverter priority)
Normal Operation (NORM)
Inverter priority:
• Inverters power the load
through the STS
• MBS can be switched to
Mains Static Switch or
Inverter Static Switch
position
• SCR1 open, SCR2 and Back-
feed Relay closed
• If the Inverter’s voltage or
frequency is abnormal, but
the mains is normal, the
STS will transfer to off-line
mode
• If SCR1 is short, the STS
will keep the on-line mode,
and the Back-feed relay will
open
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