Static Transfer Switch - Toshiba T90S3S08KS6XSN Manual

Toshiba G8000, G8000MM, & G9000 Series UPS
Description of Toshiba Hybrid Static Transfer Switch
The Static Bypass Transfer Switch used in the Toshiba G8000, G8000MM, and G9000 UPS is a
combination of a magnetic contactor and a SCR used in parallel configuration. This hybrid combination
increases the overall reliability of the static bypass device beyond that of an individual SCR while not
jeopardizing the speed or time of static bypass transfer to or from Inverter operation.
The Toshiba Hybrid Transfer Switch needs no cooling fans because the SCR device only conducts the load
for the short time needed for the magnetic contactor to change contact states. The SCR has ample
short-time current and heating rating for this duty. With much less heat produced, and no requirement for
forced cooling, the risk of failure due to excessive heat is drastically reduced.
In addition, the contactor is not required to make or break the load current – which is done by the SCR. The
result is the magnetic contactor experiences much less wear and contact erosion than a typical
load-make/break contactor, resulting in increased reliability and longevity of the contacts.
The main circuit and control circuits are simplified as follows:
Control Circuit
R1 R2
UPS Bypass
SCR
Switch
R1 R2
Doc: G8000 G8000MM G9000 Hybrid Static Transfer Switch 03 02 2009
Route 2
Bypass}
Route 3
R1 R2
83MC1 83MC2
Inverter}
Route 1
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Static Transfer Switch

SCR Switch
83MC2
83MC1
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