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14.1.6 Electrical Requirements
14.1.7 Surge Suppression
The static transfer switch is equipped with transient voltage surge suppression on each input for
surge suppression. The surge suppression is capable of protecting the static transfer switch from
operating outside of tolerances due to surges as defined by IEC 1000-4-5 (1.2/50uS surge, 2kV CM and
1kV DM) as required under EN 50091-2. Optional surge suppression modules (TVSS) are available
for each input of the STS2/PDU for surge protection of the transformers.
14.1.8 Response Time
A dual level fast/slow transfer threshold is used for under voltage detection to allow the STS2/PDU to
be compatible with UPSs and generators. The voltage thresholds and the slow transfer delay time is
user-adjustable. The fast transfer delay time is less than 4 ms.
The over voltage detection uses a single threshold, with programmable level and delay time. See User
Settings on page 101 for instructions on configuring these settings.
14.1.9 Environmental Requirements
See 3.0 - Locating The STS2/PDU for details concerning environmental requirements for the STS2/
PDU.
14.2 System Components
All STS2/PDU models provide two isolation transformers connected to a solid-state, three-pole dual-
position static transfer switch within one enclosure, with the ability to transfer between two input
sources to a single output.
All STS2/PDUs are configured with an LCD Color Graphical Interface touch screen display for moni-
toring and configuring the unit.
Table 23 Electrical requirements
Item Requirement
Maximum Continuous Current 250, 400, 600, 800 amps
Load Power Factor Range 0.75 to 1.0, leading or lagging
Load Crest Factor Up to 3.5
Source Voltage Distortion Up to 10% THD with notches and ringing transients
Overload Capability
125% for 30 minutes 250A-400A
125% for 10 minutes 600A-800A
150% for 2 minutes
500% for 0.25 sec
Table 24 Unit short circuit withstand capability
Unit Voltage Unit Amps Withstand Capability
208-240V
250A 100kA
400-600A 100kA
800A 100kA
380-480V
250A 65kA
400-600A 100kA
800A 65kA
600V
250A 25kA
400-600A 25kA
800A 42kA