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

[tinman]

Hi Jimboot,

One question:  why is your multimeter in the AC voltage mode?? 

It should be in DC voltage mode, no?

Gyula

Also i seen a 30uF cap-->is that not to large?,as i think woopy was using only a 1uF cap from a microwave oven ?.

[picowatt]

It has quite a lot to do with it as far as Lus DUT go's.
Do you know the resistance of the two drive coils?
Dose he have them hooked in series or parallel ?.

Regarding the CVR wattage rating, it doesn't matter.

Only the resistance of the CVR, the voltage across the CVR, and the applied duty cycle, determine the wattage requirement of the CVR, which was and remains the point I was making.

Did you read my reply to you a few post back?

Yes, I read your posts, and although you originally had it right, you drifted off onto a wrong track and started equating power dissipated somewhere else in the circuit as somehow determining the required CVR wattage rating, hence my original post regarding your "84 watts" comment.

PW

[gyulasun]

Also i seen a 30uF cap-->is that not to large?,as i think woopy was using only a 1uF cap from a microwave oven ?.

Yes, it may be a large value. Woopy used first a 1 uF, then tested 2 uF but finally found 0.3 uF as the best fit for giving highest RPM for his 5 mH (and 0.5 Ohm) drive coil.  Jim may have to test several cap values for his drive coil (which may have higher inductance and definetely higher DC resistance) plus for his 'assistant' coil.

Gyula

[gyulasun]

Hi Luc,

Good "detective" work to explore the resistive losses in the circuit.  Now the voltage pulse across the bucking coils has an almost straight top line, albeit it slopes towards the switch-off edge of the pulse but then the voltage across the coils at the moment of switch-off goes below zero to a negative value (cca to -2V),  and then in cca 15 ms time goes up to zero (I judged this from earlier zoom-out time base settings), well before the next ON-pulse comes.
I think this negative amplitude 'excursion' is due to the flyback diode in parallel with the paralleled bucking coils. It is interesting the parallel coils extend the field collapse time beyond to the ON time of the input pulse.  Also, the long collapse time is helped maintained by the increasing inductance value of the paralleled coils as the rotor I core moves across them.

Thanks for showing this interesting test.

Gyula

Here is the best scope shot after removing all the alligator clip and replacing it with no. 12 AWG.
I also added two 0.1 Ohms in parallel as CSR, so it's now a 0.05 Ohms CSR.

It makes quite the difference to reduce accumulated resistive losses. I've also included the original scope shot (last one) of before I started to reduce circuit losses so you can compare the difference of before and after.
Now the most resistive losses in the circuit now the two primary coils which are 0.4 Ohms connected in parallel bucking fields.
The parallel Inductance is 1.05mH with no I core, 1.18mH with I core at switch on position, 2.38mH with I core at switch off position and 4.85 with I core fully in between E cores.


Luc

[MileHigh]

When you think about all of these ideas about using the flyback pulse, perhaps the simplest way of using the flyback pulse would be the best.  That would be to have your decreasing recirculating current during the field collapse be used as part of the initial propulsion pulse.  In other words, no secondary coil at all.

One more time, this is all just an exercise in the proper timing of the energizing of the drive pulse, and the proper timing of the cutting off of the voltage to the drive coil so that the field collapse is part of the drive pulse itself.  Let's call that a "unified drive pulse."

Note, there would be no excess energy from the drive coil discharge going into a charging battery, all of the energy from the drive coil discharge would be used to push on the rotor.

Now, the start and stop timing of the unified drive pulse could be put into a sweet spot where you get the maximum possible usable torque on the rotor to give you the maximum possible energy impulse to make the rotor turn faster.

Nothing is stopping you from measuring the usable torque that this timing system would generate also:  Using a separate pickup-coil and load resistor, measure the electrical power that you can draw off of the spinning rotor and convert that into a torque measurement.

Will the strategy of using a unified drive pulse give you a higher RPM rotor for the same input power as compared to any other strategy, as in using a secondary drive coil?  I am willing to bet you it will.

All of this would be an interesting investigation doing precise measurements on your favourite pulse motor.  However, you need completely flexible timing and that rules out the good old extremely limited pickup coil wound coaxial with the drive coil.  Either go with the MHOP pickup coil design or at least have a separate conventional pickup coil that is movable, or use an optical timing system so that you have the flexibility you need to play with the pulse timing.

In my opinion, trying to measure the theoretical usable torque from your pulse motor makes all the difference in the world in terms of getting some tangible satisfaction from what you are building.  You can finally make a real-world efficiency measurement:  rotary mechanical power out vs. electrical power in.  Just like a real motor in the real world!

Just watching a pulse motor spin and measuring the RPM gets boring after a while.  When you do that you are looking at a device with no useful output at all.  People might not like this way of looking at it but a pulse motor just spinning there and doing nothing with no useful output is just a glorified resistor.  That's why adding the separate pickup coil and load resistor and then converting the electrical dissipation into mechanical power and torque is so much more interesting.