Prototype water heater - direct DC and AC using Classic PWM

[ClassicCrazy]

I got the IGBT power block installed to control the DC input .
It is working as planned so far.
I did have to put on a larger heatsink because the one I had it on initially was getting too hot.
Here is a short video of it installed and working .
https://youtu.be/j9B9mOV-YLQ

Larry

[ClassicCrazy]

If you want even a faster pulldown, to help the IGBT's or FET's gate, you can do something like this quick LTspice simulation...

You don't want the gate turning off too slowly otherwise it can get hot from staying in that linear region too long.

I have been watching this guy talk about IGBT driver - I can halfway follow what he explains too !  His other videos are fun where he tears things apart and explains circuits. Pretty interesting was how magnetron on microwave oven works.

https://youtu.be/w1PUG_8AsOc

Larry

[boB]

I have been watching this guy talk about IGBT driver - I can halfway follow what he explains too !  His other videos are fun where he tears things apart and explains circuits. Pretty interesting was how magnetron on microwave oven works.

https://youtu.be/w1PUG_8AsOc

Larry

Glad you are dabbling in this stuff, Larry.

Yes, that guy has it right !  Turns out I subscribe to his channel too.  He is very good but I probably couldn't stand to listen to his voice all day

The IGBTs he shows has internal diodes across Collector-Emitter.  Beware that you can get IGBTs with or without that diode.  They are not intrinsic like in MOSFETs.   What I find is that IGBTs that do have the added diode, have smaller transistor and smaller diode in order to fit both of them in the package.

That is fine as long as the part is big enough for the job.  Otherwise you may rather use a separate diode, external to the IGBT.  A FAST diode.  Maybe even a silicon carbide diode if you can and if the voltage you are dumping is high enough.

With the inductance of the load resistance, you can get some nasty voltage spikes that may require a snubber circuit or may be OK by switching the PWM at a low enough speed.   

We have been through this with our DC clipper designs....    Same with all of the drive circuits and capacitance and Miller issues the DiodeGoneWild talked about.

[ClassicCrazy]

I have been watching this guy talk about IGBT driver - I can halfway follow what he explains too !  His other videos are fun where he tears things apart and explains circuits. Pretty interesting was how magnetron on microwave oven works.

https://youtu.be/w1PUG_8AsOc

Larry

Glad you are dabbling in this stuff, Larry.

Yes, that guy has it right !  Turns out I subscribe to his channel too.  He is very good but I probably couldn't stand to listen to his voice all day

The IGBTs he shows has internal diodes across Collector-Emitter.  Beware that you can get IGBTs with or without that diode.  They are not intrinsic like in MOSFETs.   What I find is that IGBTs that do have the added diode, have smaller transistor and smaller diode in order to fit both of them in the package.

That is fine as long as the part is big enough for the job.  Otherwise you may rather use a separate diode, external to the IGBT.  A FAST diode.  Maybe even a silicon carbide diode if you can and if the voltage you are dumping is high enough.

With the inductance of the load resistance, you can get some nasty voltage spikes that may require a snubber circuit or may be OK by switching the PWM at a low enough speed.   

We have been through this with our DC clipper designs....    Same with all of the drive circuits and capacitance and Miller issues the DiodeGoneWild talked about.

yes it is fun to tinker and experiment .
Since watching DiodesGoneWild now I can understand what you are talking about Bob !
I think I will just be dabbling in the easy PWM stuff like I have been doing so far.
What I may work on is having the water temperature control the PWM rate to the IGBT to maintain water temperature - instead of the on and off like I have now.
Roy told me that if I keep the PWM rate low like the Classic does on Aux I probably don't have to worry about making a special gate drive circuit for the IGBT blocks I am using.

My next project after the water heater will probably be to put the direct PV DC into a resistance baseboard heater in my shop.

Larry