DC load on PV side [RE-wrenches]

[Windy Dankoff, Dankoff Solar]

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>Yo sunwise,
>
>It's interesting that Todd was the only respondent to your question. Maybe
>most wrenches are just in it for the grid connect topics? I sure hope not.
>Maybe everybody on the list is at the MWREF? Except us, that is.

I just was. Actually, there were very few dealers there this year. 
You guys must be busy!    :-)

>I just went through a "thing" with an ETA pump and a Wattsun tracker (which
>could have been avoided by actually reading the instructions from Dankoff!);
>every time the tracker motor started the pump stopped. There was seemingly
>plenty of extra Wattage to go around, but the ETA controller didn't like the
>action one bit.

Right Matt. the ETAPUMP  has a synchronous motor, rather like a 
stepper motor. If there is a very sudden drop in the input voltage 
(not a normal occurrence) it will can go out of synch and de-couple. 
The controller senses the loss of synch and loss of load, and shuts 
off. To avoid frequent stop/starts, it waits about a minute before 
restarting. The Wattsun tracker represented a motor starting on the 
array circuit. No wonder you were not happy!

Thanks for acknowledging the instructions. I added a warning about 
putting loads (like an electric fencer or something) on the array 
side after the electronic designer saw some similar experience. I 
suppose a tiny steady load would be fine, but not a sudden surge load.

This is a case where there is no way to put a DC load on the output 
side. the output is 3-phase AC.

>  I also ran a circuit from the batteries (a twelve volt bank
>with a DC/DC converter) to the tracker, which is something I usually do
>anyway, but the previous Sunrise pump ran fine (until it broke of course)
>with the array powered tracker. Who knew?
>
>This is why Dankoff is selling their "ETA Track" system with a passive
>tracker.
>
>Matt T

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