X-File - The "Is My Math Right?!" Thread
#21
devin, post:35, topic:17037 Wrote:1440w electrical @ 95% duty = 6718.93 rpm

@Ackmaniac I'll go so far as to say I'm still quite (95%) confident that:

1440w electrical @ 100% duty = 6718.93 rpm

I'm still not so sure yet about:

1440w electrical @ 95% duty = XXXX.XX rpm

",0,3,http://www.electric-skateboard.builders/t/the-is-my-math-right-thread/17037/37,2017-02-02 21:46:38 UTC
Reply
#22
devin, post:37, topic:17037 Wrote:I'm still not so sure yet about:

1440w electrical @ 95% duty = XXXX.XX rpm

@Ackmaniac

Speculation: to solve this might require knowing motor H - Inductance.

",0,1,http://www.electric-skateboard.builders/t/the-is-my-math-right-thread/17037/38,2017-02-02 22:00:01 UTC
Reply
#23
ajaynagra, post:39, topic:17037, full:true Wrote:Are you some mathematician, whats your job lol?

@ajaynagra Photography, design, business marketing, front & back end web coding

Artist, musician (drumset & n'goni)

[Image: stairs.jpg]


[Image: dinosaur.jpg]
[Image: people.jpg]


",1,1,http://www.electric-skateboard.builders/t/the-is-my-math-right-thread/17037/40,2017-02-02 23:37:48 UTC
Reply
#24
Ackmaniac, post:10, topic:17037, full:true Wrote:Correct. But lets imagine that the motor spins at no load with 94 % duty cycle. And now we want full power and feed the motor with 95% duty cycle. So my question is at which no load can i still achieve 1440 watts when i fed the motor with 95% duty cycle.

Ackmaniac, post:14, topic:17037 Wrote:Pack V = 36V, Ohm Resistance = 0.016, Batt = 1000 /Motor = 1000 /Absolute Max = 2000 Amp Limit Settings, and Motor KV = 190

devin, post:37, topic:17037 Wrote:@Ackmaniac I'll go so far as to say I'm still quite (95%) confident that:

1440w electrical @ 100% duty = 6718.93 rpm

I'm still not so sure yet about:

1440w electrical @ 95% duty = XXXX.XX rpm

devin, post:38, topic:17037 Wrote:Speculation: to solve this might require knowing motor H - Inductance.

@Ackmaniac

what is H?

",0,1,http://www.electric-skateboard.builders/t/the-is-my-math-right-thread/17037/42,2017-02-03 03:14:07 UTC
Reply
#25
psychotiller, post:43, topic:17037, full:true Wrote:What is the answer to the Ultimate Question of Life, The Universe, and Everything?

@psychotiller 56 -- but what is the question? :innocent:

",1,2,http://www.electric-skateboard.builders/t/the-is-my-math-right-thread/17037/44,2017-02-03 03:29:15 UTC
Reply
#26
psychotiller, post:43, topic:17037, full:true Wrote:What is the answer to the Ultimate Question of Life, The Universe, and Everything?

devin, post:44, topic:17037 Wrote:@psychotiller 56 -- but what is the question? :innocent:

psychotiller, post:45, topic:17037, full:true Wrote:Really it's 42 lol

@psychotiller I wouldn't be so sure.... :nomouth:

[Image: upsidedown.jpg]

[Image: maxresdefault.jpg]


Neodymium "Magnet": Nd Fe B

"Electrical" Stator Steel: Si:5 Fe

Fe: Iron 56





",0,0,http://www.electric-skateboard.builders/t/the-is-my-math-right-thread/17037/46,2017-02-03 03:35:16 UTC
Reply
#27
psychotiller, post:43, topic:17037, full:true Wrote:What is the answer to the Ultimate Question of Life, The Universe, and Everything?

@psychotiller Iron-56 is considered "spontaneously" - lol - ferromagnetic, but interestingly it has also has  4 unpaired electron orbitals, and least mass per nuclear particle of all the elements,  and is also produced in mind boggling quantities as the final end product of certain types of supernova explosions... :thinking:

My theory is that only in "ferromagnetic materials" Iron-56, Cobalt, Nickel and Gadolinium below 68F are the "unpaired electron orbitals" "stongly coupled" with the "spin axis of rotation" of the atomic nuclei themselves due to the Iron-56 protons, which are attracted to the orbiting electrons, having the least mass, and therefor least energy and therefor least momentum of all elements.

[Image: upsidedown.jpg]


Inside the Iron-56 atom (found in stators & magnets):

[Image: magnet-electron-shell.gif]

[Image: 8aDOv.jpg]

[Image: 21a-periodic-table-ferromagnetic-paramag...gnetic.jpg]

^^ Light Blue Color = Ferromagnetic ^^

[Image: tycho_chandra.jpg]

(tycho's "supernova remnant:" each pixel is much larger than the diameter of pluto's orbit around the sun (entire solar system), and material velocity = ~5000km/s)

wiki (pair instability supernova):

"In addition to the immediate energy release, a large fraction of the star's core is transformed to nickel-56, a radioactive isotope which decays with a half-life of 6.1 days into cobalt-56. Cobalt-56 has a half-life of 77 days and then further decays to the stable isotope iron-56 (see Supernova nucleosynthesis). For the hypernova SN 2006gy, studies indicate that perhaps 40 solar masses of the original star were released as Ni-56, almost the entire mass of the star's core regions.[5] Collision between the exploding star core and gas it ejected earlier, and radioactive decay, release most of the visible light."

",0,0,http://www.electric-skateboard.builders/t/the-is-my-math-right-thread/17037/47,2017-02-03 07:21:27 UTC
Reply
#28
^^i think it's the only theory that properly explains the cause for the H - Inductance property of Iron.

devin, post:42, topic:17037 Wrote:@Ackmaniac

what is H?

@Ackmaniac so what should we assume is Motor H for the 1440 W @ 95% duty = XXXX.XX rpm problem?

",1,1,http://www.electric-skateboard.builders/t/the-is-my-math-right-thread/17037/48,2017-02-03 08:08:18 UTC
Reply
#29
Ackmaniac, post:49, topic:17037, full:true Wrote:I thought
36 V at 95% DC = 34,2 V
1440 W / 34.2V = 42.105 A
42.105 A * 0.016 Ohm = 0.674 V
34,2 V - 0.674 V = 33,53 V
33,53 V * 190kv = 6370 RPM
6370 RPM / 60 seconds = 106.17 RPM/s106.17 RPM/s / (36 Wheelteeth/14 Motor Teeth) = 41.29 Wheel RPM/s
41.29 * (0.097 wheelsize in meter * 3.14159265359) = 12.58 m/s
12.58 m/s * 3.6 = 45.29 km/h

So at 45 km/h i should still be able to reach a power of 1440 W. But in reality it happens earlier. So something is missing. Maybe the Motor H but my undertanding ends here.

@Ackmaniac

"36 V at 95% DC = 34,2 V" <<--- only true @ 0rpm

Essentially:

Effective PWM Voltage @ 0rpm: 34.2V = Pack Voltage @ 0rpm: 36V x (95% duty / 100)

or simply @ 0rpm:

36V x (95% / 100) = 34.2V

but once the wheel starts to rotate, this is no longer true because of Back EMF V.

via Ohm's Law @ 0rpm

34.2V Effective PWM @ 0.016ohm gives:

2137.5 motor amps @ 73102.5 W

2030.625 battery amps = 2137.5 motor amps x (%95 duty / 100)

Ackmaniac, post:14, topic:17037 Wrote:Pack V = 36V, Ohm Resistance = 0.016, Batt = 1000 /Motor = 1000 /Absolute Max = 2000 Amp Limit Settings, and Motor KV = 190

so:

36V @ 95% duty @ 0rpm gives:

2030.625 battery amps @ 73102.5 W

and i think:

36V @ 100% duty @ 6718.93rpm gives:

40 battery amps @ 1440 W

[Image: 20120716-18349-01-2.jpg]

",0,0,http://www.electric-skateboard.builders/t/the-is-my-math-right-thread/17037/50,2017-02-03 15:07:35 UTC
Reply
#30
@Ackmaniac

fortunately the VESC itself provides a simple way to detect both "H" and "Ohm":

[Image: h.jpg]
[Image: 48-200-200-1.png]
[Image: 48-200-200-2.png]





",0,0,http://www.electric-skateboard.builders/t/the-is-my-math-right-thread/17037/51,2017-02-03 15:36:11 UTC
Reply


Forum Jump: