Recent content by bdj

Okey, thanks :thumb: Some of these fets and igbts I already ordered and soon they should arrive. I will test and share findings.

Hi, it has been a while and I was testing H bridges(one with with STGAP2 and other with TD350E). I was thinking about some changes of position of gate driver so here is picture. Horizontal board is power stage board. Vertical board is gate driver and it is soldered directly on fet legs. Gate...

Yes, some test are on second page of this thread but it seems that I missed something. I didn't verify blanking time and also went with zener diode witch has no specification for such small amount of current 250uA but it seems to work and reaching 7.2V with enough current through fet. I will...

Looking at original design. Seems that on high fet gate signal passes above power section common node forming S from high fet and D from low fet. On low fet, gate signal passes above - dc bus. Doing double pulse tests separately on high and low fet I noticed little differences in gate signals...

Okey. I turned on again desaturation detection. Seems that fault pin is floating between 5V(fault pin is connected with resistor to opti diode and then to 5V) and 12V( + power supply of TD350E) but no low level output. Here are waveforms on all 4 fets with probes on fault pin and ground). These...

Is it possible to share some of your sim models :)? Yes I read about it among the posts. If this is left unresolved what could be issues? Fet will be in liner mode and heat? Does SOA from datasheet refer to operation limits in this scenario?

If you have a time take a look of this document. https://unbscholar.lib.unb.ca/islandora/object/unbscholar%3A9775/datastream/PDF/view I think it is not issue of switching fets it could be as described here distortion as combination of dead time(during which diodes will conduct) and operating...

Thanks for fast response. I did test as you suggested. Rise time of Vgs from -5V to 8V is 3uS. Changed pwm from 0% to 10% in 2-3 steps, Vds slope is changing significantly. Did test on all 4 fets mostly turn on waveforms. Load was dc motor 1.6R and 1 mH locked rotor with current up to 1A. Light...

I have completed H bridge, final configuration is Ron 27R, Roff 10R and GS caps of 55nF. Gate driver power supply is +12V and -5V. Tested with coil and two different DC motors from 1-2mH inductance with locked rotor scenario. Duty cucle was changed from 0% to 50% and current was from 0- 50A. DC...

I made some measurements in meantime. f0 = 30.49MHz when added 32nF f1 = 5.49MHz Calculated that pcb inductance is 25.4 nH. I was testing and tried different combinations of GS caps, Ron and Roff values. At the end used on both fets Ron = 20R, Roff = 10R and GS caps of 55nF. For a test...

Yes but wouldn’t high inductance motors “eat” these harmonics so they will not reflect current and torque. Currently am buliding this for motors having from 1mH to 2.5mH. So current controller would not have to fight with such disturbances. I see that problem coiuld be with low inductance...

Ok plan is assemble second phase, connect them and test H-bridge with real load. When assembling second phase I will experiment with different gate resistors(SMD) to extend fet switching time and maybe this Vds oscillation with PP caps would be smaller. Concerning testing what would be good...

Here is pic when removed 2.2uF. Graph looks almost same if I try adding 0.1uF PP. Here is added 330uF electrolytic (330uF + 30uF PP). Then removed all caps. Install only electrolytic 330uF and poliester wima 1uF . Here are results.

I saw some of their models on ebay but could not find any info. I tested coil from aliexpress seems that can not hit bandwidth near 100KHz but in specification says that can easily go to 10MHz and factory confirmed :D. Boards arrived and one phase is assembled here are some pictures. I did...

It was about 50-60A. Probes could be even better connected. Currently couldn’t manage to connect them to be at exactly where legs leave package but plan is to test again. Doing measurements I see that every part of mm on a fet legs means a lot concerning quality of results and get a sense if...