WaveStar Static Transfer Switch 2000A 3-Pole
46
Ctrl Nr: PM375118-004
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Excessive load current.
If the load current exceeds an adjustable preset level, automatic
transfers are disabled until load current falls below that level, even if the voltage on the selected
source exceeds the transfer limits.
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Shorted power switching element.
Shorted SCRs cannot be opened and the load must remain
on or be transferred to the side with the shorted SCR to avoid cross-currents. Hence,
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If there is a shorted SCR on the non-conducting side, the load is transferred to the non-
conducting side and retransfer is inhibited. The input switch or circuit breaker on the
previously conducting side is opened. An alarm is sounded and recorded with a date-and-
time stamp in the Event Log.
•
If there is a shorted SCR on the conducting side, transfer is inhibited and the input switch or
circuit breaker on the non-conducting side is opened. An alarm is sounded and recorded with
a time/date stamp in the event log.
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Open power switching element.
If there is an open SCR on the preferred or alternate side, the
load will either remain or transfer to
the “good” side, and retransfer is inhibited.
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Cross currents.
If cross currents between sources are detected, the STS logic will transfer the
load to the non-conducting side and lock on that source.
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Failure of both sources.
If both sources fail, the logic locks on the last available source for 100
ms. After 100 ms, the logic will transfer the load to the first available source that returns to
acceptable operating limits.
Example A:
1. Source 1 is the preferred source and supporting the load.
2. Source 1 experiences an outage.
3. The load is transferred to Source 2.
4. The current inrush reduces voltage to Source 2 for 2 cycles.
5. This causes the internal voltage monitors to detect an outage on both sources.
6. The logic locks the load on Source 2 for 100 ms, allowing the source voltage to stabilize, and
the load is not dropped.
Example B:
1. Source 1 is the preferred source and supporting the load.
2. Source 2 experiences an outage (load remains on Source 1).
3. While Source 2 is unavailable, Source 1 experiences an 8 ms transient outage.
4. The load remains connected to Source 1 even though both sources experience outages for 8
ms.
7.2
Redundant Mode Operation
Redundant Mode is entered when the
MODE OF OPERATION
toggle switch is set to
REDUNDANT
.
In Redundant Mode:
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The SAS board controls transfers and Monitor logic is bypassed.
