I don't know who to ask about this. I know it works, but don't know if it's a good idea or a safe idea.
I have 3 solar panels, 240W each.
I have a need for 720W max and 60V.
I thought. hmmmmm, put 2 panels in parallel, and then put that "parallel group of 2 panels" in series with the 3rd panel.
This gives me my required voltage, and watts but is this a really bad idea or is it perfectly safe.
All panels are the same type, model manufacturer etc.
You will be current-limited by the 3rd panel (that doesn't have a series twin). Your maximum output would be 2x 240W, the same as two series panels.
I'd recommend buying a 4th panel to run 2 series - 2 parallel or finding a way to run the 3 panels in series while still meeting the needs of your load.
@Deanb is correct - the maximum current that a PV panel will pass is proportional to its illumination level. So, you can't make one panel pass the current from two panels if all are identical and equally illuminated.
A MPPT controller (in this case effectively a buck converter) will allow you to put 3 panels in series and to output some lower voltage.
1 or 2 or 3 grid tie inverters will allow you to make "mains" voltages and then to convert that to 60V.
