Generator Pickup and Drop out

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jes25

Senior Member
Location
Midwest
Can someone help me understand what this means. If I have a 80% pickup and a 60% drop out setting on a transfer switch, when exactly will the genset turn on and take the load, and when will it accept utility again?
 
ATSman

ATSman

ATSman
Location
San Francisco Bay Area
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Electrical Engineer/ Electrical Testing & Controls
Basic ATS Sequence of Events

Basic ATS Sequence of Events

jes25 said:
Can someone help me understand what this means. If I have a 80% pickup and a 60% drop out setting on a transfer switch, when exactly will the genset turn on and take the load, and when will it accept utility again?
Click to expand...

I will try to be simple here and based on the info you gave, I will state the obvious.
Transfer switches monitor voltage and frequency of the sources that are connected to them. The sensing you are describing I am assuming refers to the normal source voltage sensing. This means that when the nominal voltage on the normal source (usually utility) drops below 60% the transfer sequence of events starts: engine start time delay, V & F accepted by ATS, load transfer to genset. All of these settings are adjustable to fit the application.
When the normal source voltage reaches 80% of nominal (208, 240, 480V etc) a timer starts and after time out the ATS transfer the load back to the normal source. This is true of single phase or 3 phase systems. Aside from voltage monitoring ATS's can monitor frequency and voltage phase imbalance. The application all has to do with the nature of the load and how critical it is to sustain continuous, clean power.
 
J

jes25

Senior Member
Location
Midwest
ATSman said:
I will try to be simple here and based on the info you gave, I will state the obvious.
Transfer switches monitor voltage and frequency of the sources that are connected to them. The sensing you are describing I am assuming refers to the normal source voltage sensing. This means that when the nominal voltage on the normal source (usually utility) drops below 60% the transfer sequence of events starts: engine start time delay, V & F accepted by ATS, load transfer to genset. All of these settings are adjustable to fit the application.
When the normal source voltage reaches 80% of nominal (208, 240, 480V etc) a timer starts and after time out the ATS transfer the load back to the normal source. This is true of single phase or 3 phase systems. Aside from voltage monitoring ATS's can monitor frequency and voltage phase imbalance. The application all has to do with the nature of the load and how critical it is to sustain continuous, clean power.
Click to expand...

Simple, clear answer. I appreciate that. I was having trouble understanding why there was two percentages listed, but I get it now. Thanks
 
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