Automatic transfer to generator switch

[stevenal]

So I understand that low voltage will cause a transfer, but now it's been suggested that high voltage will also. Web searches indicate "power quality" issues will cause a transfer. Pretty non-specific. I finally found a device that was a little more specific: low, high, and unbalance voltage are listed. Still no thresholds given, though. What can folks tell me about these things? Are they set to ANSI range A or B or other limits? How much unbalance? Are they user settable? And if they transfer, do they indicate why? Thanks.

 

[itsmoked]

Make and Model number?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[stevenal]

Thanks for responding, Keith. No access to that information from where I sit. Hoping to find general information on these devices. The device gave three parameters via a search was the Eaton ATS-PWR.

 

[wroggent]

After a quick look it seems like the ATC-300 and 900 have adjustable overvoltage settings of off and 105 to 120 and it looks like the unbalance is adjustable to 105 to 120%, or off. I'm guessing nominal is based on what you order.

http://www.eaton.com/ecm/idcplg?Idc...veAs=0&Rendition=Primary&dDocName=VOL02_TAB05

 

[DanEE]

Best answered by narrowing down to specific make/model/application given the wide range of transfer switches available to meet specific needs with many being programmable for coordination with the overall power back up system design.

https://power.cummins.com/system/files/literature/brochures/PT-7012-ATSselection-en.pdf

For critical applications there will likely be a UPS behind the switch for more effective handling of power quality issues and of course keeping power up during the transition. ATS settings are likely to be coordinated with the UPS characteristics and capacity. Specific programming may take into account generator longevity considerations e.g. delays to avoid gen starts on short term outages and running for some minimum time to get the genset fully up to operating temperatures.

With make and model info the manufacturers website should give some insight on the range of settings available e.g.

https://power.cummins.com/transfer-switches

to get some feel

Example setting of one automatic transfer switch.

https://powersuite.cummins.com/PS5/...et/pdf/Commercial/Transferproducts/s-1601.pdf

 

[stevenal]

DanEE and wroggent,
Thanks. Looks like wide ranges are available. Probably most are set to whatever comes as default.

 

[waross]

This is ATS specific.
A basic transfer switch will have a relay that drops out when the line voltage drops below the hold-in voltage of the relay.
You can add features until the money runs out. A common economy switch will have an adjustable transfer voltage and an adjustable re-transfer voltage.
A re-transfer delay is quite common. Many economy models have a cool-down timer.
As the price goes up add an over-voltage transfer, an unbalance transfer and under/over frequency transfers.
As technology changes from relay based to processor based, features that were once rare are becoming more economical and more common.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[waross]

The settings are chosen to avoid nuisance transfers.
Ride through on a severe voltage dip may be preferable to a transfer.
I have had to tweak default settings to live with the sites normal voltage profile.
I have also had issues with re-transfer. One grid phase was chronically low. When grid power returned, the set would refuse to re-transfer due to one low phase voltage. A little tweaking of the default re-transfer setting and the problem went away.

Bill
--------------------
"Why not the best?"
Jimmy Carter