Eaton PDI WaveStar TFA STS 250-600A, Installation And Operation Manual

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Eaton PDI WaveStar TFA Static Transfer Switch Installation and Operation Manual P-164001113—Rev 01 11
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One of the limiting factors in using an STS in mission critical facilities has been the inability of the electrical
infrastructures to withstand the transformer inrush when switching occurs on the primary side of the
transformer, typically at 480VAC. When downstream transformers saturate, currents can rise to 10-12 times
the transformer rating, creating an outage by tripping circuit breakers and molded case switches in the STS or
in a UPS upstream of the STS.
Eaton’s patented Volt Second Synchronizing (VSS) algorithm solves this problem, dramatically reducing the
current rise or inrush when transferring between sources. Transformer inrush is limited to (1.5) x the
transformer’s full load current rating, but is typically less than (1) x transformer rating.
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Sense algorithms detect that the active power source is going out of specification and that a transfer is
required. Eaton has optimized STS sense algorithms experimentally, but algorithm parameters can be adjusted
by administrators if necessary.
Transfer algorithms move the load to the other source. Transfers are not performed by connecting the two
sources ("Make before Break"), which would cause cross-currents between sources.
Administrators can choose between two transfer algorithms using the front panel touchscreen:
• POG (Power or Gate) (fast) algorithm transfers the load as quickly as possible from one source to another
without connecting the sources together.
– Automatic transfers including sense time are ≤ 1/4 cycle for all phase conditions.
– Manual transfers are ≤ 1/8 cycle for in-phase conditions (phase-synchronized sources).
• VSS (low inrush) algorithm transfers the load in ≤ 3/4 cycle, including sense time, and will balance the
volt seconds of any magnetic load to not draw in-rush current.
– Automatic transfers are ≤ 3/4 cycle for all phase conditions, including sense time.
– Manual transfers are ≤ 1/8 cycle for in-phase conditions.
The TFA STS can successfully switch the load between sources that are 180 ⁰ out-of-phase within the above-
specified cycle times.
VSS is the recommended and default algorithm and should be used whenever there are transformers
downstream of the STS, including small transformers embedded in devices. The POG algorithm can be used
when there are no downstream transformers.
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There are three sets of Molded Case Switches (MCSWs) controlling whether the system is in Normal or
Bypass Mode and two sets of SCRs, which provide power switching for transfers:
• Source 1 MCSW and Source 2 MCSW are switches from the two power sources controlling power flow to
the SCRs.
• SCR 1 and SCR 2 open or close to control which source powers the load.
• Bypass 1 MCSW and Bypass 2 MCSW are used to shunt power around STS logic and power switching
elements for maintenance.
• Isolation 1 MCSW and (optional) Isolation 2 MCSW isolate components for maintenance during Bypass
Mode. The second isolation MCSW provides redundancy and is optional on units ≤ 800A.
System Description