AC vs DC amps?

ligwyd
ligwyd Registered Users Posts: 209 ✭✭
If I have a 240 VAC generator that can produce 30 amps continuous, how many DC amps can it produce going through a 48 Volt Inverter/ Charger? I am using the Schneider XW+6848.

From this calculator I get approx 165 amps DC. Is this correct?


Also, if I have 4.7 KW of PV (18 - 265 watt panels hooked up in 6 strings of 3) how many DC amps at 48 Volts can it produce?

Thanks

Comments

  • jonr
    jonr Solar Expert Posts: 1,386 ✭✭✭✭
    edited August 2018 #2
    About 99 amps, not accounting for de-rating, losses and higher voltage needed to charge.

    I am available for custom hardware/firmware development

  • rick
    rick Administrators Posts: 134 admin
    The most basic math for your generator would be the following:
    240V * 30A = 7,200 VA
    7,200VA / 48V = 150 Amps

    That's a pretty rough estimate, but should get you in the ballpark. The XW+ 6848 is only capable of 140 Amps DC output for charging batteries, so your generator will be pretty much maxed out when charging batteries at maximum output.

    For your PV array, it depends on what exactly you're asking. I'm assuming that you're wanting to know how many Amps your MPPT charge controller can produce at 48VDC. If that's what you want to know, here's the math:

    4,700 Watts / 48V = 97.92 Amps
    Website administrator for Northern Arizona Wind & Sun
  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    One potential complication, which doesn't appear to be included in the linked-to calculator, is the power factor of the charger. A power factor corrected charger might produce 30x240/48 x90%pf = 135a. A non corrected charger would produce substantially less (eg 50%pf would be 75a). I think the Schneider is pf corrected, but I'm not sure.

    If 4.7kw is the nameplate (STC) rating, you can expect ~25% less in most climates (~75a) with properly tilted panels around solar noon in most climates.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • jonr
    jonr Solar Expert Posts: 1,386 ✭✭✭✭
    edited August 2018 #5
    Looks like the calculator includes some inefficiencies, so it shouldn't be used in reverse (eg in the case of a generator).

    Say 58V at 140A  = 8120W (more than the generator can produce).

    I am available for custom hardware/firmware development