DC Battery amps vs. Motor Amps

General topics and discussions about the VESC and its development.
maxkinz
Posts: 29
Joined: 30 Jun 2017, 14:41

Re: DC Battery amps vs. Motor Amps

Postby maxkinz » 12 Jul 2017, 10:03

@devin - no same as before - my statement about my drill requiring about the same current was based on "before incident" data. The statement about the battery was just concerning the battery that ships with the drill. It seems to disconnect the VESC after the VESC being connected to BLDC tool but idle (no motor current) for a while. I did have no such issues with other batteries or the lab supply so I just asked rew if that behaviour is normal (or at least if he can replicate it with his prob. identical battery). An over discharge protection seems like a reasonable explanation.

I'm still waiting for my new VESC

devin
Posts: 253
Joined: 08 May 2017, 01:55
Location: San Francisco, California, US

Re: DC Battery amps vs. Motor Amps

Postby devin » 12 Jul 2017, 14:30

maxkinz wrote:@devin - no same as before - my statement about my drill requiring about the same current was based on "before incident" data. The statement about the battery was just concerning the battery that ships with the drill. It seems to disconnect the VESC after the VESC being connected to BLDC tool but idle (no motor current) for a while. I did have no such issues with other batteries or the lab supply so I just asked rew if that behaviour is normal (or at least if he can replicate it with his prob. identical battery). An over discharge protection seems like a reasonable explanation.

I'm still waiting for my new VESC


@maxkinz -- I predict that on the original VESC, If the lab supply had been set to 10A current limit at 10V (instead of 3A/10V), then values shown in the 2 graphs would match... in my theory because maybe the reality of what happened after the fact (Realtime Data) would more closely match the predictions/intentions the VESC had made in advance which I think may be displayed in the Current Plot.

I think the Blue line on the current plot are the intended battery amps -- which at the far left side of the plot appears to begin right at 3A which is the same value indicated by KB control.

I think the pink line in the current plot is the intended motor amps.

I think the motor current and battery current plots in the realtime data are likely more accurate but the voltage is wildly inconsistent across the chart.

I think the difference between the 2 graphs' numerical values arises from the VESC intending to draw 8.88 amps, 33.78% of the time averaging to 3 battery amps -- but during the 33.78% of the time 8.88 amps were attempted to be drawn, the voltage of your supply was dipping wildly to only allow 3A during the 33.78% time -- leading to a discrepancy between the VESC's "intentions" and the end result.

This theory would also account for the blue, pink and green lines in the Current Plot appearing so "chaotic."

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devin
Posts: 253
Joined: 08 May 2017, 01:55
Location: San Francisco, California, US

Re: DC Battery amps vs. Motor Amps

Postby devin » 12 Jul 2017, 23:56

...definite correlation between "pink" current plot troughs and "blue" current plot peaks...

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devin
Posts: 253
Joined: 08 May 2017, 01:55
Location: San Francisco, California, US

Re: DC Battery amps vs. Motor Amps

Postby devin » 13 Jul 2017, 14:22

maxkinz wrote:Hello Devin,

Thank you for your answer !
I do get the conservation of power centered argumentation what I do not understand is what element in the VESC is actually able to convert excess voltage into current.


devin wrote:In the example, at 9.29% duty cycle-- during the 90.71% of the second the battery isn't applying voltage to the coil [in the motor], the current generated during the 9.29% time is inductively recirculating through the coil, a fact which simultaneously lowers the "effective voltage" of the current and raises the total number of motor amps above the amount which was "drawn" from the battery.

The amount of inductivity measured in henries in the coil is strongly increased by the presence of ferromagnetic element iron-56 in the stator core of each solenoid. Iron-56 has the least mass per nucleon (nuclear particle "mass defect") and nearly the highest nuclear binding energy, and lowest nuclear "excess energy" of all elements, and I suspect these properties give rise to ferromagnetism itself through correlation of the geometrical alignment of the iron-56 4 unpaired 3-d electron orbitals and the rotational axis of symmetry of the iron-56 nucleus itself, due to the iron-56 protons having the least mass and therefore least kinetic energy of all elements, in my theory giving rise to a similar effect to precession of a rotation axis via tidal locking in planetary orbits (similar to the moon's orbit stabilizing earth's tilted rotation axis with respect to the ecliptic), but at the quantum scale between the unpaired electrons and the symmetry axis of the iron-56 nucleus, leading to ferromagnetism we witness in the world.

Simply if you want to change the orbit axis of the 4 unpaired 3-d electron orbitals on an iron-56 nucleus with a nearby EM field, you have to change the rotational symmetry axis of the whole nucleus which has much more mass, leading to a delay in changing the axis, and requirement of additional energy above what it would otherwise require to change the electrons' orbits themselves compared to a non-ferromagnetic material, and this "tidal locking" between the electron orbitals and nucleus is due to the iron-56 protons having the least mass and therefore lowest kinetic energy of all elements, I think.


To illustrate, I visually imagine that the 56 protons and neutrons in the Iron-56 nucleus are arranged as optimally close-packed magnetized spheres cumulatively taking up the least possible total volume (though current scientific consensus is each proton & neutron is further subdivided into 3 quarks):

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When viewed from the top-down, it becomes clear that the close-packing of 56 magnetized spheres has a single axis of rotational symmetry, and has "3 sides" radiating from this axis:

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If one considers the number and geometrical arrangement of the hybridized probability lobes of the 4 unpaired 3-d shell electron orbitals, each unpaired electron has 2 probability lobes for a total of 8 probability lobes surrounding the nucleus within the 3-d electron shell. I also visually imagine these 8 lobes as 8 optimally close packed magnetized spheres:

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^When viewed corner-on, this 8-lobed "cube of spheres" also has an axis of rotational symmetry with "3 sides" radiating from the axis.

I believe in an Iron-56 atom, below the curie temperature, the hybridized 3-d electron shell unpaired orbitals' axis of symmetry is "tidally locked" and therefore correlated with nuclear axis of rotational symmetry, a result of Iron-56's "mass defect" -- Iron-56 nuclear protons have the lowest mass and therefore lowest kinetic energy of all elements. As previously mentioned I believe this "tidal locking" between the orbitals and nuclear axis of rotational symmetry results in ferromagnetism and inductance.

devin wrote:Simply if you want to change the orbit axis of the 4 unpaired 3-d electron orbitals on an iron-56 nucleus with a nearby EM field, you have to change the rotational symmetry axis of the whole nucleus which has much more mass, leading to a delay in changing the axis, and requirement of additional energy above what it would otherwise require to change the electrons' orbits themselves compared to a non-ferromagnetic material, and this "tidal locking" between the electron orbitals and nucleus is due to the iron-56 protons having the least mass and therefore lowest kinetic energy of all elements, I think.


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Image Source: https://dashboard.dublinschools.net/lessons/?id=fe4368151f953fa93fb839172a66352e&v=5
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Image Source: https://dashboard.dublinschools.net/lessons/?id=fe4368151f953fa93fb839172a66352e&v=5

devin
Posts: 253
Joined: 08 May 2017, 01:55
Location: San Francisco, California, US

Re: DC Battery amps vs. Motor Amps

Postby devin » 01 Aug 2017, 17:20

maxkinz wrote:Hello Devin,

Thank you for your answer !
I do get the conservation of power centered argumentation what I do not understand is what element in the VESC is actually able to convert excess voltage into current.


Here is an interesting graph. I asked an anonymous rider to send me an acceleration log documenting loaded full throttle acceleration from standstill on an electric skateboard using a vesc. I'm not sure exactly which motor type was used or the motor amp limit and battery amp limit settings used, but it clearly shows around 90a motor amps produced in the motor from only 10a battery amps close to full throttle standstill:

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This second graph taken by the same rider on the same board clearly shows (@ log 48 sec) that at about 28mph, the same 10a battery amps produces only about 28a motor amps instead of about 90a as in the 1st graph, a result of back emf voltage opposing the battery voltage more and more at faster and faster speeds.

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The electrical wattage in both cases -- the 90a motor amps @ 10a battery amps -- and the 28a motor amps @ 10 battery amps -- is the same.

Simply if he wants to draw 500w electrical (10a battery amps x 50v) full throttle at all physically possible speeds including close to standstill, his motor amp limit setting needs to be at least about 90a motor amps.


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