Using PWM from Aux contacts

[ClassicCrazy]

Are the Aux contacts on the Hawkes Bay functional now ?
I would like to try using one for Waste Not pwm .
The HB manual says this
The AUX circuit outputs 10.5VDC at a maximum of 200mA
So I would look for a suitable IGBT Module that can be used.
Looking at spec sheets for IGBT stuff makes my head a bit sluggish since i don't know what everything means to choose one. And I don't know much about the drivers needed.
This is the least expensive one I see on Digikey.
https://www.sanrex.com/wp-content/uploads/2022/06/media.nl-7.pdf
Any suggestions or insights would be appreciated.
I want to share the PV input to HB with a resistive baseboard heater. Right now I have parallel PV connection - goes to both HB and baseboard heater. I have a separate breaker to the baseboard but also the power goes through a contactor that for now is controlled by Classic Aux 1 in waste not. So far this seems to work fine and no problem with HB. So what I wanted to try doing is replace the contactor with IGBT and then try to pwm using Waste-Not ( from HB).
Larry

[Barry Fields]

What is the wattage of the baseboard?  Looks to me like the unit you posted is capable of 100amps times PV of 80v = 8000 watts. What PV current could you expect?

It might be a little overkill. I am not a real engineer but maybe one could assist.

Barry

[ClassicCrazy]

My PV is about 240v 10 amps or less.
The baseboard is rated at 240v 1000 watts I think - I forget the exact  watt figure right now.
If it was lower voltage I could use a relay but that won't work .
I was looking for 600v rated igbt. I guess I could use igbt not in a block but I can't wrap my head around all the specs I need to consider.
Larry

[ClassicCrazy]

I have a bunch of these SKW25N120 igbt that I salvaged and could use one of them if it was suitable.
https://www.infineon.com/dgdl/Infineon-SKW25N120-DS-v02_03-en.pdf?fileId=db3a304412b407950112b427fc7f3d32
Do I need to look at the gate emitter voltage to figure out if it is suitable ? photo of graph below
I just looked up a driver - don't really know what I am doing but would this one work with the above ?
https://www.infineon.com/dgdl/ir2117.pdf?fileId=5546d462533600a4015355c84331168d
Larry

[boB]

I think what you are thinking of doing should basically work.

Be advised that heaters (power resistors) can be very inductive.  So when PWM'ing them fast, they can make lots of voltage spikes.  So don't forget to add a cache diode around the heater element.

This is one of the basic problem with the MidNite DC Clipper where there is no AC zero crossing to switch on or off at.

I stole a picture from your Sanrex data sheet to use as kind of an example.  In this picture, treat the L = 185uH inductor  that I circled as the heater element and the diode as the cache diode.  The 300 V variable as your battery that you are Not-Wasting.

I would say to use the mountable IGBT. Be careful to not ESD the gate !  Maybe it's protected though.
Either IGBT, use 10 to 20 Ohms gate resistor or there-abouts.

I thought the Waste-Not Aux PWM was working but I am not sure.  I don't know how fast or slow it is though.

It is supposed to work like the Classic.  I will dig into this tomorrow.

boB

[ClassicCrazy]

Thanks Bob for the example - now I have something to go from.
I was just checking on internet to see if chatgpt can design circuits and was going to see what it says if I get that far - never used chatgpt before.
Larry