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

[verpies]

I believe the general consensus at the time tho was the capturing of the flyback was what made it so efficient.

It is still true that "capturing of the flyback" makes a motor more efficient.

The Ossie motor is basically a couple of reeds and a FWBR. Certainly no caps, ...

The lack of caps is a problem, because the most efficient way to transfer energy between two coils is:
Coil1 --> Cap -->Coil2

Transferring directly Coil1 --> Coil2 is a most inefficient scheme.

[verpies]

Before somebody asks whether S2 is absolutely necessary to maintain high efficiency:
The answer is "no".
S2 can be deleted but then L2 will be energized soon after S1 opens and this will constitute the loss of precise control over L2 timing.

Also, the purpose of D2 is to prevent the energy in L2 from returning back to C1 and L1. 
If D2 is deleted then energy will slosh back and forth between L2 and C1 (as a decaying sinewave oscillation with the max p-p amplitude equal to the forward voltage drop of D3, which is not much for a Schottky diode) and the L2 energy will return to L1 if the forward voltage drop of D3 is larger than forward voltage drop of D1.
If S2 is opened as soon as the voltage across C1 falls to zero, then D2 becomes completely unnecessary and can be deleted, leading to increased circuit efficiency.
The purpose of D3 is to maintain current flowing through L2 once it becomes energized.  Without it, the energy will escape from L2 very quickly (as soon as C1 discharges to zero).

BTW: All diodes should be Synchronous Rectifiers or Schottky diodes with low forward voltage drops (that means no SiC diodes!) because these voltage drops cause the majority of electric energy losses.
The capacitor does not have to be bipolar, but it should have a low ESR - unfortunately electrolytics are not known for their low ESR.



P.S.
Since capacitors store energy as voltage and coils store energy as current, if you are interested in measuring their energy content, then capacitors should have their voltages measured across them and coils should have their currents measured through them.

[shylo]

When the caps are full just discharge them into the drive? No?
artv

[verpies]

When the caps are full just discharge them into the drive? No?
artv

If by "drive" coil you mean L2, then yes.
...but remember, that if you do not have D3 (and D2 possibly) then the energy will go from C1 to L2 and then later it will return from L2 to C1 and L1.  Would you want that ?

[Magluvin]

Before somebody asks whether S2 is absolutely necessary to maintain high efficiency:
The answer is "no".
S2 can be deleted but then L2 will be energized soon after S1 opens and this will constitute the loss of precise control over L2 timing.

Also, the purpose of D2 is to prevent the energy in L2 from returning back to C1 and L1. 
If D2 is deleted then energy will slosh back and forth between L2 and C1 (as a decaying sinewave oscillation with the max p-p amplitude equal to the forward voltage drop of D3, which is not much for a Schottky diode) and the L2 energy will return to L1 if the forward voltage drop of D3 is larger than forward voltage drop of D1.
If S2 is opened as soon as the voltage across C1 falls to zero, then D2 becomes completely unnecessary and can be deleted, leading to increased circuit efficiency.
The purpose of D3 is to maintain current flowing through L2 once it becomes energized.  Without it, the energy will escape from L2 very quickly (as soon as C1 discharges to zero).

BTW: All diodes should be Synchronous Rectifiers or Schottky diodes with low forward voltage drops (that means no SiC diodes!) because these voltage drops cause the majority of electric energy losses.
The capacitor does not have to be bipolar, but it should have a low ESR - unfortunately electrolytics are not known for their low ESR.



P.S.
Since capacitors store energy as voltage and coils store energy as current, if you are interested in measuring their energy content, then capacitors should have their voltages measured across them and coils should have their currents measured through them.

If you use a lot of little electrolytic caps in parallel the esr is lowered considerably.  Plus, smaller caps have lower esr compared to larger ones, so the gain of a lower esr is even better than just the paralleling of larger caps.


Mags