hi, i need some help with ideas on this one, and please remember that i dont have an electronics store nearby, am on a budget, and need to use the materials i already have. also i am experienced working high voltages, and live working.

I just received some really nice fuji fwave solar rolls that put out about 400vdc and they easily feed a standard smps to give 12vdc but i already have oodles of 12v, 24v, 240v power in my off grid systems and i want to use these new panels to run a submerged well pump that requires 220vac sine. there will be no battery on the system so it just needs pump non stop whenever there is sun and water.

the materials i have and want to use are salvaged ferrite transformers if needed, and a box of very chunky igbt modules from littelfuse that are capable of huge voltage and current switching. as controllers i have a box of pics in many types and also an olinuxino imx233 single board linux computer running arch, and sporting many gpio.

the pump is 500w and solar is 600w, but i would like to keep it expandable for more pumps and solar in future as i intend a big irrigation system and also a gravity hydro energy store.

i want to keep it simple, so i thought maybe use a pic or olinuxino to create a pwm sine and phase switching signal that switches the igbts direct in a big fat bridge.

my skills are minimal in software and i have never used igbts. but the job needs doing and i have all this expensive stuff gathering dust. so what say guys?

 

oh yeah, and i have any bits i can rip from an old russian telly (exept the pl805 wich is earmarked with one solar roll as an hf linear!)

 

The simplest thing would be to buy a off the shelf sine wave inverter and hack into the HV DC circuitry between the step up stage and the secondary power inversion stage.

 

i just managed to get a pic programmed with linux after years trying. i used the hex file from http://www.instructables.com/id/Adaptable-24vDC220vAC-Pure-Sinewave-Inverter-1/ and it flickers the outputs at 8hz because of my only xtal being 3.57 instead of 20mhz. so i can use the pic to switch the igbt modules in a bridge. i think the igbt are 400A 600V so well within tolerance. i will get the correct crystal somehow, which leads me to ask; what happens if i run that type of ac pump motor on a higher or lower frequency? could i vary the power of the pump, or water flow? or speed it up and have it pump more (it will run nowhere near its maximum head). but back to the design: can i feed igbt modules direct from the pic, or will it need buffering? there wont be a transformer as i am just taking 320v from the input and modulating it with a bridge of igbt. as that is around the rectified mains the rms filtered output should be close to 220v unless i missed something. i have never used igbts before but believe they can run direct from logic levels and only need heavy drive currents at higher frequency.

 

The simplest thing would be to buy a off the shelf sine wave inverter and hack into the HV DC circuitry between the step up stage and the secondary power inversion stage.

i never realised they did it in 2 stages. i thought it would just hit a transformer and come out. i have a 3kw peak 24v inverter but that is a critical system that i live from. i have an old ups but thats not a double conversion.
i have a box of old pc atx supplies that can step it down but i dont want to waste the power. buying stuff is not possible at the moment. i have 4 half bridge igbt and 2 tripples for 3 phase which may be the next project

 

i just discovered vfd's. i assume a vfd will do exactly the job? maybe better?

 

http://www.littelfuse.com/products/power-semiconductors/igbt-module/mg06400d-bn1mm.aspx

thats what i have to use,

 

Yes a VFD will do exactly what you want and the vast majority of them can be cheated internally to run on a line voltage DC input. Especially the smaller single phase input capable ones.

 

buying is still not an option but at least it gives more scope to find schemas and ideas to adapt. the vfd would also help starting the pumps although they are currently single phase so lossy. the next project can be 3 phase ready for when i can find a bigger pump.

so anyway......... i have a pic generating 2 phases of pwm (assume because i have no scope) and i have the igbt modules. the modules are very expensive so i want to drive them safely.

is it ok to go pic to igbt direct or do i need current limiting resistors or will i need current buffers to get into full saturation?

also i am considering using the solar in 2x3 series parallel with centre tap instead of a full bridge or transformer, then keep adding capacitors to the input until i get maximum power out. i would only need a single igbt half bridge would this have any disadvantages?

 

is it ok to go pic to igbt direct or do i need current limiting resistors or will i need current buffers to get into full saturation?

I would recomend running things through dedicated purpose built driver IC's like IR2110 or IR2113 or similar.

As for those IGBT block units other than blowing out the gates, even that's surprisingly hard compared to a standard mosfet, they are darn near indestructible in normal applications. Especially so if you are only trying to run a 500 watt motor with them.

I have used them for the primary switching devices to run junk yard crane electromagnets which can push the 100+ amps and 300+ volts levels when the operators turn the generators up all the way and they handle that like it's nothing.

 

whats confusing me is the wiring from the gate/emitter, the gate being kind of floating but the emitters are going to be at vastly different potentials and cant just go to a 0v line. does this mean i have to drive the gates with an isolating transformer? what do those driver chips do that is special? i thought they would just be for high frequency work.

 

Read the data sheets and study their schematics.

There's a reason they are called high side/low side drivers.

 

this is getting interesting now.

 

datasheets used to have application schemas in the back.. seems out of fashion now. hope i can build a driver from discretes.

 

http://www.mitsubishielectric.com/semiconductors/files/manuals/powermos4_0.pdf

this is a good bit of info for anyone reading this thread with similar questions.

big question is the worth it factor: i could probably sell these igbt modules for enough cash to buy several vfd's.
however i do want to use this as a learning platform as i have 4 more way larger igbt earmarked for ev use that will really dig in to that 1600v/1000A rating ;-)
I tested out the first solar roll yesterday, great output and worked fine into a junk box smps.

heres a short vid i made:

 

Same problem here..thanks for the infos!

 

Same problem here..thanks for the infos!

hi, whats your application?

 

Found these on Ebay some time ago & purchased them to make pure sine wave inverter. The intention was to build it to replace a burnt out one on a Inverter Generator. Havent got around to it yet, but it was relatively cheep.

 

thanks for posting that schema, the ic ir2110 certainly takes a lot of work out of the job. the only way i see to bodge around it is to have a separate supply for each igbt driver board, which is something i can do, being that its a solar system and i also have about 50 mini solar 6v panels. 3 of those for each igbt driver board and 18v (15v with a little load) is spot on.
it seems that they drive more like a triode and there will not be any static current flowing but to overcome the junction capacitance its necessary to have current available to keep the junction in the saturated zone, and that current will increase as the switching frequency increases.
this worries me because i dont know what the pwm frequency is for the hex file i blew to the pic and i would like to try and calculate.
also realised that i need 6 mini panels per gate driver as the junction likes a hefty negative pull down to switch off.
it sounds feasible to etch a bunch of cards, they will all get used and i can post the pdf so anyone can do the dirty laser printer transfer.
any ideas of either:
the pwm frequency the posted hex file generates (i dont have a scope and im not a programmer)
or, what size transistors shall i pull out my squirrel nut stash of components (please say bc548)
i can make optoisolators from leds and heat shrink and then it can be logic driven.
possibly could get away with 2x -+ floating supplies, one for high side and one for low.
i will drag my junk bin and draw a schema for the bits i have got, and maybe one of you guys can look it over before i commit to copper, or trust it to my beloved igbt modules because every time i fry a new component the baby jesus cries.

 

looking at the above circuit again, they can't take that much drive or those charge pump capacitors wouldn't hold up. i feel a max232 could help me here. google confirms it has been tried.