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Common Rack Automatic Transfer Switch Scenarios and Questions
This article discusses common Rack Automatic Transfer Switch (ATS) Scenarios and Questions and provides configuration recommendations.
Rack Automatic Transfer Switches including the following models only:
- All firmware versions
- All Rack ATS models listed above
As the Rack Automatic Transfer Switches are complicated and involved products, we have provided some common scenarios and questions along with recommendations and general information on functionality.
With these models, please ensure that after analyzing the situation, the latest available ATS firmware has been applied and instructions followed - .
INFORMATION BULLETIN - Upgrading Rack ATS Firmware (AP77XX) - potential to permanently damage ATS during download
Please review the scenarios and questions below for additional information.
When both sources are available and stable, the ATS will switch back to its preferred source after a 30 second wait period. Attempts to continually switch the unit prior to the completion of the 30 second period could result in loss of load or damage to the ATS. Anytime an anomaly is detected within this sampling period, the 30 second timer will be reset.
The following is a list of potential causes of ATS to source switching when the upstream UPS goes to battery or when power appears to be present at the ATS input:
- Switching of the ATS when the UPS goes to or from "on battery" mode
- Dropping the load when the ATS switches sources while both appear to have power
Here are some recommended actions that can be put into place to reduce the probability of the ATS switching when the UPS transfers to battery mode:
- Revise the voltage transfer range from medium to wide, revise frequency deviation from +/-2 Hz to +/-3 Hz on the ATS:
- Set the sensitivity preference from high to low:
- Set the source preference from source A to none on the ATS:
Using the Rack ATS with a Generator
APC recommends placing a UPS between the generator and the ATS input. The UPS will condition the input voltage to the ATS to prevent thrashing. A second UPS should be used between the power utility and the other input of the ATS. This UPS will power the load while the generator starts and stabilizes. The UPS should be sized to allow time for the generator to be started and the time needed for the UPS attached to the generator to operate normally. While the generator is starting, the generator voltage and frequency are not stable. If the ATS is connected directly to the generator, the ATS can switch to the generator input before the generator has stabilized. The load of the ATS will cause the generator voltage to dip. This dip can also shift the frequency of the voltage. Either of these issues can cause the ATS to switch to the other input.
Publié pour:APC Canada (French)
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