Long distance run

[jrannis]

In my area, DC and solar gates are used mostly and are extremely reliable. Iv'e worked with a gate company, wired quite a few up and their a joy to do. A local sheet metal guy makes these nice SS battery boxes, and the install looks clean. Wish I had pics.

You only need a 15A circuit for a battery trickle charger, and I doubt it ever draws more than 2-3A at a time...

If you did power the gate with AC, how would it work in a power outage?

I agree, I have notice alot of solar units installed in this type of application. Are you in an area where this might be possible?
http://www.mightymule.com/mmguides.htm#solar

 

[kingpb]

Overloading the breaker was not my point. And, no, the current won't "go down" on the secondary. Compared to the primary, yes it will be less, but the load current will be a function of the secondary voltage and the load impedance, as always.

In reference to your first post, you proposed running straight service voltage for the distance, and placing a 240/120v transformer at the end of the run, near the load. That makes the 1000' run the primary circuit, not the secondary.

Therefore, any voltage-drop compensation's effect would be to add current, and thus add voltage drop, to the long run. That's not the end of the world, but it should be taken into account while calculating the best compromise in wire-size selection.

Using 240v instead of 120v is absolutely a good idea, of course, but the "outcome" of using voltage-tap compensation would be slightly more current along the long run, not less, and won't allow "less copper" for the 1000' run. Using 240v will.

The calcs I ran can prove otherwise.

 

[LarryFine]

The calcs I ran can prove otherwise.

"Can", or do? If, for example, you have a transformer at the load end of a 120v run, and the secondary load is, say, 10a @ 120v, and you use, say, a tapped transformer or an autotransformer to compensate for voltage drop, that the primary current won't be higher than 10a?

Power isn't free. If you have to supply the primary of a transformer 100v due to voltage drop, but want 120v out, the primary current must be higher than the secondary current, by the inverse of the voltage ratio. That would mean 12a primary current for 10a on the secondary.

Ignoring losses, VA out must require the same VA in. Raising the primary voltage to 240 of course halves the primary current, but the same otherwise applies. The higher voltage improves the performance, but compensating for voltage drop will still increase the primary current.