Si Fet, Sic Fet or IGBT?

Thread Starter

Roswell Bob

Joined Apr 14, 2021
6
Greetings. My first post here.

I am doing a single phase inverter for 5kw/120vac. I'm interested to know what group thinks best switch would be at 20kHz carrier.

I'm leaning towards a CREE or ST Micro 650v SiC Fet, but curious as to what the feeling is I have board setup for a pair of TO-247 parts on each corner. I'm thinking I can squeek 5kW out with one SiC part on each corner. With two parts maybe 10kW Power board is 75mm x 125mm. Layout is almost done and looks like it might grow to 75mm x 150mm. Design is open source if anybody is interested.

Thanks
Roswell Bob
 

Solar Mike

Joined Apr 26, 2018
30
In order to help, please post a block dia of what you are building, ie are you converting a DC source to 120vac, using an H-Hridge circuit, or something else, your description doesnt have enough information to give any guidance.

Cheers
Mike
 

Thread Starter

Roswell Bob

Joined Apr 14, 2021
6
In order to help, please post a block dia of what you are building, ie are you converting a DC source to 120vac, using an H-Hridge circuit, or something else, your description doesnt have enough information to give any guidance.

Cheers
Mike
It's an H bridge with 170vdc input 120vac out 20kHz carrier. I think that covers it Mike.
 

Solar Mike

Joined Apr 26, 2018
30
170 vdc peak /1.414 is 120 so that is about right, you may want to go a bit higher to allow some overhead for input and output voltage regulation.
5kw @ 170v = 29.4 A rms, 41A peak so at a minimum the switching devices will want to be rated quite a lot higher in current, a pair will just do it. If you are powering any inductive loads like motors you need a high overload current margin.

For lowest losses (heat), I would use standard 300V mosfets rather than SIC versions, reason being more readily available at a much lower cost and have a lower RDSon value. SIC types are all >600V and to get low on resistance cost a fortune, as you will probably blow some up in getting it working. IGBT's whilst very robust wont be as efficient at those voltages and getting up there at 20 Khz.

Transformer less ?, or are you putting some isolation between your 170v and the AC

Would be interested in looking at the schematic.

Cheers
Mike
 

Thread Starter

Roswell Bob

Joined Apr 14, 2021
6
170 vdc peak /1.414 is 120 so that is about right, you may want to go a bit higher to allow some overhead for input and output voltage regulation.
5kw @ 170v = 29.4 A rms, 41A peak so at a minimum the switching devices will want to be rated quite a lot higher in current, a pair will just do it. If you are powering any inductive loads like motors you need a high overload current margin.

For lowest losses (heat), I would use standard 300V mosfets rather than SIC versions, reason being more readily available at a much lower cost and have a lower RDSon value. SIC types are all >600V and to get low on resistance cost a fortune, as you will probably blow some up in getting it working. IGBT's whilst very robust wont be as efficient at those voltages and getting up there at 20 Khz.

Transformer less ?, or are you putting some isolation between your 170v and the AC

Would be interested in looking at the schematic.

Thank you for thoughtful response Mike. Would you like to pick out a mosfet? I will run loss calculations with your mosfet and a SiC part.

I will make schematic available soon. The project is a 5kW open source HF inverter. Ultimately 48vdc in 120vac out. There are some who would like to run power boards in a LF topology so that is just a first goal-of course mosfets for that. I have power board about 60% done. I have a control board I did with a PIC ready to go. Other boards are out there that I could use as well.

I have a push-pull resonant converter simulation in LT spice that looks very nice. That will drive the inverter (I hope)

I designed industrial inverters for 30 years. I left that market and have been doing R&D for military and aerospace for last 10 years. I was with ABB back in 91 when we teamed up with IXYS and developed an IGBT drive. (WOW 30 years ago) I am giving my website a spring cleaning and will drop off the files there next week. www.veritypower.com will get you there. Just ignore the mess.

thanks
Roswell Bob
 

Thread Starter

Roswell Bob

Joined Apr 14, 2021
6
170 vdc peak /1.414 is 120 so that is about right, you may want to go a bit higher to allow some overhead for input and output voltage regulation.
5kw @ 170v = 29.4 A rms, 41A peak so at a minimum the switching devices will want to be rated quite a lot higher in current, a pair will just do it. If you are powering any inductive loads like motors you need a high overload current margin.

For lowest losses (heat), I would use standard 300V mosfets rather than SIC versions, reason being more readily available at a much lower cost and have a lower RDSon value. SIC types are all >600V and to get low on resistance cost a fortune, as you will probably blow some up in getting it working. IGBT's whilst very robust wont be as efficient at those voltages and getting up there at 20 Khz.

Transformer less ?, or are you putting some isolation between your 170v and the AC

Would be interested in looking at the schematic.

Cheers
Mike
 

Attachments

Solar Mike

Joined Apr 26, 2018
30
Sorry for the delay, here are a couple of mosfets that I have used recently various high voltage projects.
IPB200N25N3 G, D2Pac, not TO-247 though, used in a PV to Hot water element load diverter.
IRFP4768PBF, use these in various PV controllers with 200 Vdc inputs.
IRF300P226; as above with 250 Vdc PV.
FCH029N65S3; used in a PV 320 Vdc to 230 Vac direct inverter for powering a hot water heater element, working on this design now.
Some of these are in short supply with waiting times until 2022 before new stock arrives, shortages are getting serious.

Here are a couple of links to some of my recent projects 60A Mppt Charger; PV Load Diversion Controller

I used to work as an electronics tech 24years on high power AM radio, TV, FM, digital microwave transmitters and all associated control systems, then I moved on to software development for 17 years or so, now retired I can spend a lot more time continuing with my hobby, electronics and software, micro-controllers, I just don't get paid to do it.

Cheers
Mike
 

Solar Mike

Joined Apr 26, 2018
30
Cool the Push-pull design; I have never used LTspice, probably because I have never had the time to sit down and learn about it, there is just too much to learn in current electronics now; cannot say I would have used it anyway, I find building this sort of high power electronics is not too difficult as I can fall back on past experience to work out a design.
 

Thread Starter

Roswell Bob

Joined Apr 14, 2021
6
Thanks for parts. I will take a look. I did look at a few 250v/300v silicon parts yesterday. I think they will work fine and probably save a few bucks.

I was involved with 75m AM phone a few years back - N9NEO. I did a full bridge modulator and then spun a full-bridge at 160m and used phase shift angle to modulate the carrier. Got some nice audio reports. Almost went to work for Harris doing transmitters, but decided to work for their military radio group.

I am now retired too. Just a few projects here and there to buy test gear and software. Looks like you keep busy yourself. You put out some nice work.

regards,
Bob
 
Top