Sharing ideas on how to make a more efficent motor using Flyback (MODERATED)

[MagnaProp]

...In other words, if a copy of the observed sine wave is shifted to the left, does it match up, is it time continuous, with where the preceding sine wave stops at the beginning of the on time?...

Don't know if this is what you mean as I have no idea where the on and off time is. His image is so small that aligning them isn't very accurate.

From the image resolution accuracy, I could tell no difference in the graph. each blip in the graph looks the same and the space between blips is the same. I would need much larger images or closer views to do a more accurate match up.

The scope is across the emitter/collector junction,so the on time is when you see 0 volt's,and the off time is the rest...

Thanks for the info. Just looked at your thread and I'll check it out some more. Good info in this one and yours.

[tinman]

Don't know if this is what you mean as I have no idea where the on and off time is. His image is so small that aligning them isn't very accurate.

From the image resolution accuracy, I could tell no difference in the graph. each blip in the graph looks the same and the space between blips is the same. I would need much larger images or closer views to do a more accurate match up.

The scope is across the emitter/collector junction,so the on time is when you see 0 volt's,and the off time is the rest. I will continue on my thread,so as not to fill Lucs thread up with a different setup.


Brad

[gotoluc]

Hi everyone and Merry Christmas

I built a flyback test device that consists of two MOT face to face to continue the study of different setups like attraction vs repel (bucking) to see how it  affects the flyback.
I noticed just by changing mosfet's it causes a problem, see first scope shot using a IRF840 (switch) which looks good then the next scope shot is using a IRF3710 for less on time resistance but look at what it does

The input is 12.98vdc through 0.1 Ohm CSR and flyback cap is 57uf
Yellow CH1 is CSR, Blue CH2 is not used, Purple CH3 is Voltage and Green CH4 is Cap charge voltage

Any ideal what causes this and why?

Thanks for your time

Luc

[poynt99]

The slower (and curved) rise time and higher current is likely due to the much lower on resistance of the IRF3710.

The truncated flyback spike might be due to the avalanching of the body diode, but it should tolerate at least 100V, so not sure 100%. The 3710 is a 100V device, while the 840 is a 500V device. The 3710 also requires 5x the gate charge (190nC vs. 38nC).

For the voltage rating alone, I don't think the 3710 is a good choice.

BUT, I am not familiar with your circuit, so if this is with the flyback load connected, then the truncation could be caused by the flyback capacitor absorbing the spike, which is what you want anyway I think, isn't it?

[gotoluc]

The slower (and curved) rise time and higher current is likely due to the much lower on resistance of the IRF3710.

The truncated flyback spike might be due to the avalanching of the body diode, but it should tolerate at least 100V, so not sure 100%. The 3710 is a 100V device, while the 840 is a 500V device. The 3710 also requires 5x the gate charge (190nC vs. 38nC).

For the voltage rating alone, I don't think the 3710 is a good choice.

Thanks for the reply .99

I was thinking it could be caused by the body diode but why is it happening at that low of a voltage, since like you say it should be able to deal with up to 100v.

BUT, I am not familiar with your circuit, so if this is with the flyback load connected, then the truncation could be caused by the flyback capacitor absorbing the spike, which is what you want anyway I think, isn't it?

Yes, we want most absorption of flyback to the cap at off time but the 3710 charging the cap to only 60v when the 840 is charging it to 97v and costing less input current

Oh well, I'll just have to find a better mosfet then the IRF3710 and IRF840

Merry Christmas

Luc