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

[gotoluc]

That should not be happening because D1 should maintain the current at the same level as before.
Of course, when C2 is charged up then not much current can flow through D2.

You must mean "not much current can flow through D1" and not D2 as you wrote above right?

Please disconnect R2 and try to manually discharge C2 and catch it on the scope when C2 is charging up from 0V, for the first time.  The upward current ramp should be followed by a downward ramp and there should be no oscillations.  That downward ramp can tell us a lot about the maximum efficiency of the energy recovery possible.

Would a low value resistor across C2 not do the same?

Luc

[verpies]

I will change my circuit to the one which is preferable, including a 555 timer for the 50 Hz signal as to be able to place my scopes ground probes anywhere in the circuit.

If you have four of these cheap HEF4047B  chips (CD4047) then a universal motor sequencer can be built that will have the capability of positioning the ON-pulse anywhere and have an additional output for emptying C2 before each "flyback" pulse, for accurate recovered energy measurement..

The pulse width was 31%, see earlier blue gate signal, lowering it even 1% made the rotor loose sync with the SG.

Yup, you have to compensate lower pulse width with higher amplitude (supply voltage).

The current waveform in that circuit is as in the screenshot below, where blue is the signal across a 0.1 ohm 1% CSR, and green my current probe signal (100mA/div.).
(unfortunately the current probe offset is toasted apparently (due to Kacher activities), so never mind the green trace offset value)

Was that current waveform obtained from this trivial circuit?
It is the induced current  waveform shape that matters the most anyway - with alternating N, S magnet poles (like Gotoluc suggests) this waveform will appear significantly different.

[verpies]

You must mean "not much current can flow through D1" and not D2 as you wrote above right?

Right. That's what happens when I'm writing in a hurry.
I corrected it already.

Would a low value resistor across C2 not do the same?

No, because the transfer of energy from a coil to a cap is much more efficient than from a coil to the resistor.
With a low value resistor the T_OFF time will be very long. With a small capacitor it will be short and the final voltage across the capacitor will be an accurate measure of the recovered energy (minus diode losses)

...but you can try a low value resistor (or even a 0Ω short) to see that the noise at switch-OFF really disappears.  If it does, then emptying C2 will accomplish the same feat and more.

[gotoluc]

with alternating N, S magnet poles (like Gotoluc suggests) this waveform will appear significantly different.

Sorry verpies but I would like to clear up the way you wrote the above.

I don't consider my rotor to be Alternating magnets.  The magnets are rotated 90 degrees from the conventional way and all oriented the same way.
So each magnets give you instantaneous N/S which produces the unusual waveform below.
You simply power (TDC) at the peaks

Luc

[verpies]

Sorry verpies but I would like to clear up the way you wrote the above.

Don't be sorry.  The devil is in the details.
With your  rotor polarization the coil will see bidirectional flux.  In Tinman's case the flux will be bidirectional, too but the flux amplitude should be larger.
With Itsu's rotor polarization the coil will see unidirectional flux (unipolar) with the smallest flux amplitude of the three cases.