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Author Topic: Sharing ideas on how to make a more efficent motor using Flyback (MODERATED)  (Read 350085 times)

gyulasun

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Re: Sharing ideas on how to make a more efficent motor using Flyback (MODERATED)
« Reply #585 on: December 26, 2015, 11:41:31 PM »

....
When the I core is in between to two E cores with the same cardboard spacer but now one on each side (so two) the inductance is 16mH. So only a 3 mH increase as appose to E to E with one spacer.
....

Hi Luc,

I must have been in "Xmas mood" and overlooked the cardboard gap for the case when the I core was used, and this is why I did not notice what verpies mentioned, sorry for these mistakes.

Gyula

tinman

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Re: Sharing ideas on how to make a more efficent motor using Flyback (MODERATED)
« Reply #586 on: December 27, 2015, 12:10:07 AM »
Thanks for your brave ;) reply Brad
That's about how I understood it as far as the I core being there in place or not but you would think these Large MOT E cores could store up a little flux of this short pulse, no?   and where does the flux go?   does it just leaks in space?
Did you notice the voltage pretty much fell flat instantly and how can the current instantly go to maximum on an inductor?
What part of a bucking field is Chris suggesting to be used?

Luc

I was thinking the same thing at first,but have a look at your last scope shot's you posted ???
Only one of the four show's near 0 volts across the coil--just a small voltage pulse at the start.
And it just so happens that the one with near 0 volts across the coil is also the only one where the flux path is incomplete for the two coils-->that being E to E with power to both coils. This one with near 0 volts across the coil will be the one that consumes the least amount of power,yet the current tells us that it will also be the one that produces the greatest !!radiant!! magnetic field(field not contained within the core). If this field is used to produce work ,will it reflects on the P/in?-->will it raise the voltage seen across the two coils?. If it dose not raise the voltage,but increases the current-->what happens to the voltage across the coils when the current is increased?-my guess is that the voltage would actually go down as the current increases ;)

I think Luc that you may be on the verge of seeing if what EMJ is saying is actually true.
I would like to see (if you still have them) what a secondary coil (a coil behind one of the primaries)shows across it in this bucking coil mode- E to E,both coils powered.

Brad

tinman

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Re: Sharing ideas on how to make a more efficent motor using Flyback (MODERATED)
« Reply #587 on: December 27, 2015, 12:19:52 AM »
Thanks for your brave ;) reply Brad
That's about how I understood it as far as the I core being there in place or not but you would think these Large MOT E cores could store up a little flux of this short pulse, no?   
Did you notice the voltage pretty much fell flat instantly and how can the current instantly go to maximum on an inductor?
What part of a bucking field is Chris suggesting to be used?

Luc

Quote
and where does the flux go?   does it just leaks in space?

In fact-yes.
But this space is the air gap between the two coils and the outer legs of the E cores that carry the opposite field,as the field must join/merge. It is this field you must tap into,although i dont think you would have the room between the two coils and outer legs of the E core's to place an air core coil.

Brad

gotoluc

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Re: Sharing ideas on how to make a more efficent motor using Flyback (MODERATED)
« Reply #588 on: December 27, 2015, 05:15:45 AM »
Hi Brad

thanks for your additional posts and interest.
I'm away for a day but Monday afternoon I'll be back and can further test this.

In the meantime I've enlarged the pics and added a few notes.

Luc

tinman

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Re: Sharing ideas on how to make a more efficent motor using Flyback (MODERATED)
« Reply #589 on: December 27, 2015, 06:04:25 AM »
Hi Brad

thanks for your additional posts and interest.
I'm away for a day but Monday afternoon I'll be back and can further test this.

In the meantime I've enlarged the pics and added a few notes.

Luc

Mmm-so the voltage drops to near zero,but the current is still strong right until switch off.

When you get back into it Luc,could you try the simple circuit below,so as we can see both the current and voltage across both coils when switch 1 is open and closed--just so as we remove all the caps and diodes. Use a mosfet,and not the transistor i have depicted. Dont take note of coil wind direction,as i just ghosted and flipped one drawing. Just make them bucking as you did before.

Enjoy your time away ;)


Cheers
Brad

verpies

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Re: Sharing ideas on how to make a more efficent motor using Flyback (MODERATED)
« Reply #590 on: December 27, 2015, 01:54:08 PM »
In the meantime I've enlarged the pics and added a few notes.
These notes are correct.
I will not elaborate now...still in Xmas mode
« Last Edit: December 27, 2015, 04:57:06 PM by verpies »

synchro1

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Re: Sharing ideas on how to make a more efficent motor using Flyback (MODERATED)
« Reply #591 on: December 27, 2015, 03:00:53 PM »
Hi Brad

thanks for your additional posts and interest.
I'm away for a day but Monday afternoon I'll be back and can further test this.

In the meantime I've enlarged the pics and added a few notes.

Luc

@Verpies, Tinman and Milehigh:

Luc has a scope shot above labeled "Reverse direction Flyback". How does this equate with your "Same direction" theory for BEMF?

gotoluc

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Re: Sharing ideas on how to make a more efficent motor using Flyback (MODERATED)
« Reply #592 on: December 27, 2015, 09:32:58 PM »
@Verpies, Tinman and Milehigh:

Luc has a scope shot above labeled "Reverse direction Flyback". How does this equate with your "Same direction" theory for BEMF?

Hi synchro1,

you are still under moderation but I will allow your posts as long as they conform to the rules I wrote in my first post of this topic.

It's true I've suggested a reverse flyback on the bucking E cores but with a question mark.  Let's allow the EE to think about it a little and see what they make of it.
I will be performing the test TinMan has suggested to see what other results come of it.

Kind regards

Luc

verpies

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Re: Sharing ideas on how to make a more efficent motor using Flyback (MODERATED)
« Reply #593 on: December 27, 2015, 09:36:24 PM »
Luc has a scope shot above labeled "Reverse direction Flyback". How does this equate with your "Same direction" theory for BEMF?
It would be a violation with one coil, but with two coils one can push flux and current into the other coil.
Without seeing two gate waveforms (or d-s) on the same scopeshot, it is difficult to conclude much more.

Loosely coupled inductors ( a transformer with low k coupling coefficient ) are notoriously hard to analyze when they have capacitors across these inductors on both sides.  Without the diodes in series they behave like a tuned transformer.

itsu

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Re: Sharing ideas on how to make a more efficent motor using Flyback (MODERATED)
« Reply #594 on: December 27, 2015, 11:08:23 PM »
I build the below verpies "C2 discharge" version (so with the MOSFET driver), and found the below screenshot signals.

As normal, blue is across CSR (point A to B)
Purple is across the Q1 MOSFET drain (point C to B)
Yellow is across the C2 cap (point D to B).

C2 cap is a 2.2uF one

2e screenshot is a zoomed in one.

Is this the kind of signal you would expect for the yellow one?

Regards Itsu

verpies

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Re: Sharing ideas on how to make a more efficent motor using Flyback (MODERATED)
« Reply #595 on: December 27, 2015, 11:50:26 PM »
Is this the kind of signal you would expect for the yellow one?
Almost.
Notice that C2 is not discharging all the way down to 0V.

To discharge C2 all the way down to 0V:
- start discharging C2 sooner
or
- discharge C2 longer. (if I knew Q3's gate waveform then I could decide whether increasing L2's inductance is necessary for this).
or
- discharge C2 faster by decreasing R2 (Warning: don't decrease R2 so much that Q3's maximum pulsed drain current is exceeded)
or
...all of the above or combination thereof

Also, put some small but good bypass caps to ground on the source of Q3 and on cathode of D2, because there is an unwanted voltage spike on the purple trace. While you are at it, decrease the inductance of the entire drain circuit of Q3 including C2 (short leads, small loop area, etc...)

Below is a revised schematic with the correct probe placement and countermeasures against the voltage spike form L2.
If C3 and C4 do not help, then adding R4 will slow down the closing of Q3 and its drain current spike that gets converted to a voltage spike by stray inductances in the drain circuit.  For R4 try anything between 0Ω to 1K.

What are you using for U2 ?  Do you use its inverting input or non-inverting?

tinman

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Re: Sharing ideas on how to make a more efficent motor using Flyback (MODERATED)
« Reply #596 on: December 28, 2015, 02:11:25 AM »
@Verpies, Tinman and Milehigh:

Luc has a scope shot above labeled "Reverse direction Flyback". How does this equate with your "Same direction" theory for BEMF?

Because you need to understand the circuit,scope probe placement,and the way the two inductors are coupled to each other.


Brad

gotoluc

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Re: Sharing ideas on how to make a more efficent motor using Flyback (MODERATED)
« Reply #597 on: December 28, 2015, 03:11:44 AM »
It would be a violation with one coil, but with two coils one can push flux and current into the other coil.
Without seeing two gate waveforms (or d-s) on the same scopeshot, it is difficult to conclude much more.

Loosely coupled inductors ( a transformer with low k coupling coefficient ) are notoriously hard to analyze when they have capacitors across these inductors on both sides.  Without the diodes in series they behave like a tuned transformer.

Good point verpies!... I can confirm even thought both E cores are very close to being identical I noticed one is using a little more current then the other and I'm quite sure it's the one I didn't provide the scope shots.

Luc

sm0ky2

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Re: Sharing ideas on how to make a more efficent motor using Flyback (MODERATED)
« Reply #598 on: December 28, 2015, 06:22:21 AM »
I'm a little confused about the premise here....

We are trying to improve efficiency of an electric motor,... by adding losses to the system adding a transformer???

my experience with this matter has led me to believe the "most efficient" motor that mankind has so far created
is the one we use in nearly every electric device that has a motor in it....
like a stand-alone fan, or a vaporizer, im sure you've seen these things, they are brushless A/C motors, just an inductor, with two large copper links,
and an aluminum rotor with arc-shaped grooves in it.

when these are operated at a frequency that is compatible (multiple, divisor, or octave of) with the self resonant frequency of the inductive core.
they run at 95+ % efficiency. That means if you have a supercapacitor storing an hours worth of run-energy,
you can cycle back and forth a "q-Mogen" of two of these motors for 54 minutes, (minus heat losses in your circuit)
before the energy is depleted.

We have no better motor than that.(except some magnetically suspended stuff NASA did in space...)
 So it seems like a good place to start.
What I don't get, is how adding something that increases losses is supposed to raise efficiency?? like a flyback transformer?

Flybacks are notoriously sources of system losses. They are discontinuous by nature, and generally over-tax the maximum frequency of the inductor.
This is because of the high conversion ratio, I.E. # of turns on the primary compared to secondary. The voltage has to step-up faster than the induction time factor.
When the timing of the inductive core is faster than the time it takes for the signal to circle around all those turns in the secondary coil,
it has to "skip a beat" to re-synch. That sounds weired, but that's what happens inside the inductor. When the flux is saturated, and has not gone down yet, and it switches again, the inductor can't keep up. so lets say you run a fly-back for 100 cycles.
there will be a number of these cycles where the energy is unrecoverable, because it switched faster than the secondary coil could dump its energy.
it will depend of course on the ratio of turns, and the operating frequency, but lets just for example assume it's 3 out of 100.
so you're flyback runs at 97% efficiency before you attach it to the motor. that's - 3% just by adding a flyback
This effect is well known in the television industry, and is calculated into the total energy consumption of devices, as displayed on the FCC tag.

if you have a flyback of X ratio, operating at frequency Y, you will have Z losses.



verpies

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Re: Sharing ideas on how to make a more efficent motor using Flyback (MODERATED)
« Reply #599 on: December 28, 2015, 10:11:15 AM »
We are trying to improve efficiency of an electric motor,... by adding losses to the system adding a transformer???
No, I think this is an experimental tangent that investigates the simulation of a rotor by a transformer

Flybacks are notoriously sources of system losses. They are discontinuous by nature, and generally over-tax the maximum frequency of the inductor.
No, "flybacks" last as long as the engineer wants. Precisely t=½π(LC)½
In circuits like this the "flyback" current is not discontinuous but quarter-sinusoidal.

What is the maximum frequency of the inductor, anyway ?