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

[gotoluc]

Hi everyone,

sorry for the delay on the replies. Had other things to attend to today.

Below is a new test 2 video of my Bucking Field Reluctance Motor which should address the CSR concerns and issues.
It was late last night (1 am) when I made the first video and today I found the probe X settings in the scope menu were reversed.

Link to test 2 video: https://www.youtube.com/watch?v=TeO9iM2-29o

Post your comments or test suggestions (within reason) of what could be further tested on this (limited) proof of concept.

Luc

[gyulasun]

Hi Luc,

Thanks for the new video, very good, albeit I have two puzzles. The scope still shows a 2.6V drop in the pulse amplitude level across the bucking coils and I wonder why it happens?

My other puzzle is that in case the analog meter shows a 140-150 mA current draw for the 'unloaded' wheel and you mentioned it went up to 200 mA when you loaded the wheel with your hand. Is this not Lenz effect? albeit in a small degree for sure (a normal pulse motor would probably have higher current draw increase than that).   Question is how the input current increases if you load the rotor further down to say 30-40 RPM? 

EDIT:  Of course the wider pulse (longer ON time of the switch) can also increase the input current.

I think the voltage drop in the pulse amplitude may still come from the supply voltage fluctuation when the MOSFET is ON, the voltage drop may mainly be caused  by the added up series inner resistances of the current meters. There may be other cause for it too.  If we could add up all the DC resistances which are in series with the coil (MOSFET r_DS, current meters, shunt, secunder coil of the AC step down transformer), that would help to estimate whether the drop is simply due to by those accumulated drops.

Gyula

[gotoluc]

Hi Luc,

Thanks for the new video, very good, albeit I have two puzzles. The scope still shows a 2.6V drop in the pulse amplitude level across the bucking coils and I wonder why it happens?

Yes I agree!... I'm quite sure it's the Analogue Amp meter, since as soon as I introduced it in series with the positive input terminal its internal resistance caused a decrease in RPM, so I had to incease the input voltage to keep the rotor turning at the same speed.

My other puzzle is that in case the analog meter shows a 140-150 mA current draw for the 'unloaded' wheel and you mentioned it went up to 200 mA when you loaded the wheel with your hand. Is this not Lenz effect? albeit in a small degree for sure (a normal pulse motor would probably have higher current draw increase than that).   Question is how the input current increases if you load the rotor further down to say 30-40 RPM? 

I don't think it is so. When you slow down the rotor the pulse on time gets wider so naturally the current of an analogue (moving coil) meter will have more time to get to its real level, however, the pulses now are less frequent so it should all come to the same vs. many shorter on times. If we could have a continual reading I'm quite sure we would see the input power stays the same no matter what RPM. It's unfortunate I can't raise the RPM of this prototype. The next build won't have this limitation and will also have High Impedance assist coils powered by the flyback of the Low Impedance coils.

EDIT:  Of course the wider pulse (longer ON time of the switch) can also increase the input current.

Yes, correct and what I tried to explain above.

I think the voltage drop in the pulse amplitude may still come from the supply voltage fluctuation when the MOSFET is ON, the voltage drop may mainly be caused  by the added up series inner resistances of the current meters. There may be other cause for it too.  If we could add up all the DC resistances which are in series with the coil (MOSFET r_DS, current meters, shunt, secunder coil of the AC step down transformer), that would help to estimate whether the drop is simply due to by those accumulated drops.

Gyula

Yes, also correct!... the Amp meter is the biggest cause in this case.

Thanks for your input

Luc

[gyulasun]

Yes I agree, I quite sure it the Analogue Amp meter I introduced in series across the positive terminal that is causing the voltage drop across its internal resistance. As soon as I connected it I had to incease the input voltage to keep the rotor turning at the same speed.
....

Luc,  does it mean that in case you short cicuit the analogue Amp meter, the top of the voltage pulse becomes more or less a straight
line instead of the curved sloping one?

Gyula

[gotoluc]

Luc,  does it mean that in case you short cicuit the analogue Amp meter, the top of the voltage pulse becomes more or less a straight
line instead of the curved sloping one?

Gyula

It helped but there is still something else. First scope shot is with Amp meter and motor at 108 RPM and second scope shot is removing the Amp meter and lowering the voltage to maintain the same 108 RPM.

I wonder if the switch could be part of the losses?... it's a dual mosfet (IRFP4310Z) arrangement so current can go either direction?

Let me know what you think

Thanks for your help

Luc