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

[tinman]

Hey Brad



The 24 coils on my lasersaber motor are in series. each are 42 awg 3200 turns at 15k ohm all in series. Seems like a large inductance would be had having a high rise time, but due to the high resistance the rise time seems almost instantaneous. Strange to experience.

They do make square enameled magnet wire.  Would probably do wonders for the capacitance of a bifi coil.

Mags

I suppose the idea of having 2 coils of the same dimensions and volume of copper but each having 2 diff sizes of wire, that they could produce the same field strength as long as the (P)ower dissipated into each is the same, where the smaller wire coil gets higher voltage input to overcome higher resistance and the larger wire coil gets less voltage to calculate the power as the same.  Makes sense.

Yes,it dose in that situation. But we dont have that situation with Woopy's DUT. The load resistance determines the voltage,current,and time base for the available flyback energy. There is also the matter of the power being generated by the rotating magnets.

Anyway,i will have my motor up and running by tonight. I have mounted my rotor onto a PM stator motor that i will be using as a generator i can load to variable resistive loads.

Brad

[tinman]

Well the motor is up and running.
First i will show a scope shot of both the voltage across the primary coil,and the current flowing through it. The flyback current is being sent to a resistive load ATM. As you can see,the current flow from the flyback is not quite as linear as Woopy's is,but not to bad.

[Magluvin]

Dont know if this thread has died out or not. Been thinking on it.

First thought is we have shown a couple ways to accomplish what is stated in the topic.  But they only show that there can be an advantage to using bemf, as most call it.
So from there one needs to build a motor that is very efficient to begin with. The output of the mechanical part is not in any of the equations so far. Rotors are not loaded and just free spinning.

When building a motor that is very efficient, meaning input compared to loaded output, the time frame for capturing collapse and reusing it has to be instilled into the design.  Pwm drive comes to mind where the coils are pulsed multiple times during a push and pull cycle and bemf is captured multiple times.
When we look at a chart curve of a coil building a field and taking on more current, as the curve just starts to level out, then we begin to input more and more as the curve flattens and the bemf becomes less and less as compared to the input total. So in my opinion it is best to cut the input while the current and field build is still on a strong vertical climb. Thats when the bemf will be closest to equaling the input of the cycle. For example, you could leave the input on for min or even hours, but still only get a very short period of bemf that does not build over that period of time.

My other thoughts on this are that the cap across the second coil design will be freq dependent in a much stronger way than using a switch or reed to fire the second coil from a precharged bank of caps charged by bemf. Just from studying the circuit in circuit sim with different freq inputs.

I have an electric bike that has an asymmetrical brushless motor where only 1 coil is switched to opposite polarity at a time, while all the others are on push or pull mode. A very smooth near zero cogging operation. The controller uses pwm to power the coils with varying pulses depending on the throttle input. The coils of that motor have thicker wire and less turns than the coils shown in my earlier vid. Possibly a virtual farm for capturing bemf.

If we were to try and capture bemf from say a standard dc, 2 brush, multiple commutator/winding motor, most of the windings for each com switch are in a steady on state and only one winding 'might' produce some bemf out. And a study of that is that there may not be much due to when the brushes are making a switch, they are contacting 2 commutator tabs at the same time, thus actually shorting a winding while the motor is running, causing large inefficiency in the motor to begin with. Big loss there, especially when the shorted windings are in the middle of the stator pole field, where pole switching generally happens.


So a particular motor design will have to be decided on in order to take the most advantage of bemf in my honest opinion. And if the initial motor design is up in the 90%, while being able to secure high amounts of bemf to recycle back into the motor function, I believe it can go over 100%

Mags

[MoRo]

Pwm drive comes to mind where the coils are pulsed multiple times during a push and pull cycle and bemf is captured multiple times.
When we look at a chart curve of a coil building a field and taking on more current, as the curve just starts to level out, then we begin to input more and more as the curve flattens and the bemf becomes less and less as compared to the input total. So in my opinion it is best to cut the input while the current and field build is still on a strong vertical climb. Thats when the bemf will be closest to equaling the input of the cycle. For example, you could leave the input on for min or even hours, but still only get a very short period of bemf that does not build over that period of time.

Magluvin,

All of your points are spot on! But, I really like the point above. It is well within the point Newman stated in his book on firing a coil multiple times.

Of importance too, and I don't know if this was mentioned with regard to this possible build, but, we should keep in mind that Newman started with 'higher voltages' to begin with. It becomes obviously important when you consider the advantages we receive due to the kick-back being of such high voltage.

Regarding the point mentioned earlier on same-time-frame-fired series reed switches. I understand the possible inconsistencies. Yet, a commutator is a terrible source of friction. So, maybe a an optical switch (for even greater efficiency) can act as a relay to fire the series switches that open and close in the correct time frame.

MagnaMoRo
I just enjoy siting back and thinking about this stuff!

[Magluvin]

Magluvin,

All of your points are spot on! But, I really like the point above. It is well within the point Newman stated in his book on firing a coil multiple times.

Of importance too, and I don't know if this was mentioned with regard to this possible build, but, we should keep in mind that Newman started with 'higher voltages' to begin with. It becomes obviously important when you consider the advantages we receive due to the kick-back being of such high voltage.

Regarding the point mentioned earlier on same-time-frame-fired series reed switches. I understand the possible inconsistencies. Yet, a commutator is a terrible source of friction. So, maybe a an optical switch (for even greater efficiency) can act as a relay to fire the series switches that open and close in the correct time frame.

MagnaMoRo
I just enjoy siting back and thinking about this stuff!

Thanks MoRo

The point of the series mechanical switches is the possibility of opening the switch fast enough to beat the collapse and resist possibly thousands of volts of potential crossing the gap. Like making an ideal high voltage switch, when  it comes to the off cycle.

Can transistors be set up in series to do that? Havnt looked yet to see if that is being done out there.

As for the friction, if we are dealing with higher voltage and lower currents, the brushes dont need to be as tight against the commutator as a high current motor would.

Mags