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

[verpies]

That's just noise from the mosfet having a hard time switching off. See close up below.

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 D1.

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.

[itsu]

I was trying to adapt to Tinman's design when drawing that diagram, thus it was not optimal.

This circuit^* and probe hookups are much more preferable because:

- it allows the potential of the scope's ground to vary only minimally.
- the CSR also measures the current in the L1,D1,C2 circuit
- it separates I & V signals (Itsu's setup does too)

Anyway, your green current waveform is not showing strong signs of flattening out, so I judge that the pulse width is around 2*Tau.  That's better than most people do but still beyond the break-even point shown here.

Also, what is the current waveform induced in the coil measured in this circuit ...when the rotor is spun by hand (or motor)?
The 22.4V in the recovery cap is about correct.  The Source-Drain voltage waveform shows a peak close to 40V and with 12V power supply that gives 40V - 12V = 28V and the difference from 22.4V is probably wasted between pulses in that resistor in parallel with the cap.


Cheers

^* iso-drivers and double MOSFETs are optional

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.

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

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.).
(unfortunatly the current probe offset is toasted appearently (due to kacher activities), so never mind the green trace offset value)

The coil measures 11 Ohm and 37.8mH @ 100Hz.
Wire is AWG 24 and core is made of cut-up welding rods

Tinman

Itsu

Is it hard to change every second magnet in your rotor to south up ?.

It is good to see that even with the all north up rotor,there was no energy cost to spin your rotor as MH seems to think there should be.


Brad

the magnets are superglued in, so i doubt it, but i will try gently

Itsu

[tinman]

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.

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.

Verpies.

Watching the video,i see Luc was running a brushed DC motor from the flyback- storage cap. Could that noise that is being seen be brush noise from the DC motor ?.


Brad

[verpies]

Watching the video,i see Luc was running a brushed DC motor from the flyback- storage cap. Could that noise that is being seen be brush noise from the DC motor ?.

No, no!
That noise is definitely caused by lack of D1 conduction after switch-off and if  C2 is emptied before the switch-off then the t_OFF time will lengthen and the noise will disappear.
The current waveform, when the coil is not under the influence of the rotor, should look like this:

[gotoluc]

I see you have identified the MW waveform. 

Thanks again for sharing some details.

Let's have a closer look at the MW waveform you have identified that my current 2 pole magnet rotor is producing.
It looks quite different then the one in your picture, so I was wondering if that has to do that mine is produced using strictly a magnet and yours may be a magnet and iron rotor combination?

Thanks for sharing

Luc