Wiseguy New Inverter Build Nano R6

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Joined: 21/06/2018
Location: Australia
Posts: 1088
Posted: 11:46am 05 Mar 2024      

To begin, I propose to start at the end. The finish build major parts are a 100mm square controller PCB and a Power PCB 260mm x 108mm and a couple of Bulk Capacitor boards also 100 x 100mm. The controller connects to a 20 character x 4 line display with a 3 wire interface. The inverter can read out VIN, VAC, AAC, temperature of toroid and heatsink and if the 2 associated fans are running.

These nifty LCD features and Nano programming are all made possible by none other than the generous and gifted Poida !! In a weak moment he offered to help we with a few lines of code that grew somewhat in the process.

Now that maybe I have gained interest from some BS artists - we are though, did you see the artwork of RogerDWs inverter on his wall - just brilliant.

So now for some boring background info on what and how the design evolved.

The evolution of my inverter has been somewhat spasmodic and slow due to many asynchronous external interrupts.  The inverse opto-coupled high/low side drive topology has proven to be successful.  A few users are using this topology in their power section, KeepIS is using my Power PCB & EG8010 controller design and has given his creation some real-world scary peak power loads exceeding 20kW.

I do advocate the use of HY5608s for the Power PCB’s, they have proven to be extremely robust, each FET is roughly equivalent to two HY4008’s in parallel.  My Power PCB designs all incorporate 3 low cost Isolated DC-DC converters, two 12 to 12V @ 1W modules for the upper LHS & RHS gate drives. The third 12 to 12V or 12 to 15V @ 1or2W type powers both low sides of the H Bridge.

A 12V output DC-DC converter for lower side FET gate drives works fine, but I prefer and use a 15V output which creates a -3V bias on the lower FETs giving another 3V of protection against glitches from the high side exceeding a lower FETs turn on threshold, causing it to conduct when it should be off.

The opto-couplers and gate drivers are FOD3182s, outputs buffered by an NPN/PNP bipolar transistor totem pole stage which initially used small TO251 packages.  The TO251’s types are now very hard to find but there are some similarly rated SOT223 surface mount transistors that use the same pin spacing as the TO251s and so can have the 3 (short) legs inserted into the existing PCB pad holes and soldered.

LCSC has the SOT223 PNP and NPN versions for the buffers which are ~30c ea and have continuous current ratings of ~5A and peak current ratings of ~ 15/20A so the overall cost is low and the peak current drive worked fine during some testing at 50kHz SPWM.

My latest Nano controller uses a precision rectifier, followed by an adjustable gain section and then an opamp Bessel filter, before the Nano feedback input. On the bench the output voltage is very stable from no load to 50% load (1.5KW) within 0.2V.

The control card can sense 48V low input voltage and the pre-charge capacitor voltage, to hold off Nano start. If the battery voltage falls below low voltage set point (software user setup value) the inverter shuts down, if the pre-charge power bridge capacitors are below the battery voltage by a few percent the inverter running is also inhibited.  These inputs allow an automated High current contactor to automatically bypass the pre-charge resistor and apply full current to the inverter.

There is more to the story but maybe tomorrow. Meanwhile I will post a pdf here of the overview of the inverters main parts.
4KW Nano R6 AutoStart.pdf
If at first you dont succeed, I suggest you avoid sky diving....
Cheers Mike