Hello folks, I'd like to elaborate onto this former September_2024 Topic,
Hi intabits, nice work in reverse engineering a partial schematic, thanx, great job,
I to am busy on such thrown-away still good operational R3000h Transformerless UPS.
Just thrown away wuth the dead batteries, just for the sake of operational guarantee, . . .
Good for us, electronics enthousiasts.
However, no original schematic to be found yet, bummer ;-?
I am into the idea of converting this excellent pure-sine inverter for more-or-less
sustained use, so specifically the cooling needs upgrading, etc . . .
I enjoyed reading the actual forums Q&A,
however it seems nobody really understands AC ? ? ?
To try understand, one needs to get out of this simple DC-thinking,
each half~cycle, the upper and lower rails change in polarity,
but the Batteries string, still needs to receive only DC ;-?
Now some thoughts of mine: ofcourse you need thick gauge wires in the power lines,
whether they are receiving or delivering power, that should be obvious.
Hence also something I never read on any forums:
There is NO power gain, only conversions of Voltages & Currents.
So there is no such thing as Free energy !
If it states 3000Watts, that means max. current of 12,5Amps (for 240Vac)
<without taking into count for all the losses and inefficiencies>
Moreover, this also implies that the same 3000Watts desired output power needs to come from its input source !
The Batteries. Hence the higher the voltage of the Batt-string, the 'Lower' the currents in those Batteries leads.
Lets again count plain simple, for a 240Vac out, with a 120Vdc in, Currents will already double !
Over 24 Amps at Max. power output.
And three wires, because one remains common, the other two serve the in & output going of the AC~.
To my limited knowledge: inline coils L1 & L3 serve the sine shaping towards the Load.
Two coils in each line one, because of the Alternating Current ;-?
One half cycle L1 is positive seen from L3-side,
than the other alternation it goes opposite, . . .
L2 imho serves [together with Q7 & Q8] for the alternated Buck/Boosting the Batts 120Vdc upwards in amplitude,
alternating in polarity with both transistors.
The coils inductance serves the swinging effect of an AC~voltage.
But L2 is never the same polarity continious.
To get for lets say EU 240Vac, out of a 120Vdc batt.string, it needs to get doubled.
Hence L2, together with Q7 & Q8 , doubling the Amplitude of each AC~cycle ;-?
Both beefy counter polarised 3x Diodes couples D22 & D23 are just to avoid damaging the H-bridged Tors Q5---Q10
against the Fly-back Voltage spikes from alternating L2 voltage swings ;-?
But to go really into deep theory, I have to admit, we need explications from an electronics developper of this
Transfromerless UPS-inverter design.
These principles yet exists for more than 10 years, so patents & such are obsolete I'd guess.
They could yet provide us enthousiast from a decent circuit schematic drawing, I'd pressume ;-?
Hope to get this Topic back on track, a Happy NewYear, Harry - Belgium.