How should the VESC "feel" on a board?

General topics and discussions about the VESC and its development.
devin
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Re: How should the VESC "feel" on a board?

Postby devin » 09 May 2017, 18:48

i don't think the motor behaves as an inductor circuit during the "off" portion of the duty cycle.

i think there is an amp "cliff" effectively to 0a immediately after each pulse.

benjamin
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Re: How should the VESC "feel" on a board?

Postby benjamin » 09 May 2017, 19:08

What a waste of time... I have no idea what you are trying to prove.

Hummie
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Re: How should the VESC "feel" on a board?

Postby Hummie » 09 May 2017, 19:34

Maybe the current and magnetic field don't colapse as fast as the frequency?

benjamin
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Re: How should the VESC "feel" on a board?

Postby benjamin » 09 May 2017, 20:10


Hummie
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Re: How should the VESC "feel" on a board?

Postby Hummie » 09 May 2017, 20:51

I changed my post earlier, can we simplify and say the magnetic field colapses slower than the frequency as it's shorted and not disconnecting the circuit?
Facinating yet confusing and have no background. Much appreciated. The vesc on foc is a dream come true.

benjamin
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Re: How should the VESC "feel" on a board?

Postby benjamin » 09 May 2017, 21:27

Yes, the field collapses much slower when shorting than it would with an open circuit. Also keep in mind that there is no way to create an open circuit as the induced voltage over an inductor can rise to thousands of volts to maintain the current if it gets disconnected, and well before voltage something will start conducting on the power stage: namely the body diodes in the FETs. The body diodes have some voltage drop and generate heat when conducting, so it is better to switch on the FET with the body diode that would conduct to get less losses (and a bit different behaviour when thinking in terms of BLDC and regenerative braking, but that's a different story).

devin
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Re: How should the VESC "feel" on a board?

Postby devin » 09 May 2017, 22:43

benjamin, trying my best to understand.

i'd like to be able to write an equation to predict which amp limit settings will give a predictable wattage as close as possible to 0rpm full throttle.

i've had trouble locating documentation on the topic of predictable motor amp limit effects on acceleration characteristics.

if the vesc detects 0.0415 ohm winding and expected pack volts with sag is 46v, is there any way to adjust the settings for full throttle = 1000w electrical as close as possible to 0rpm?

Hummie
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Re: How should the VESC "feel" on a board?

Postby Hummie » 10 May 2017, 03:28

Vedder are you saying that if I were to disconnect or break my phase wire while the motor was given a lot of current,
there would be a huge onrush of voltage building throughout the circuit, but before there would be a high voltage last spark through the air there at the break of the circuit, the high voltage would bust through the fet so no spark? So you could break your esc with a high powered broken motor wire if it was broken at the wrong time?

rew
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Re: How should the VESC "feel" on a board?

Postby rew » 10 May 2017, 06:41


rew
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Re: How should the VESC "feel" on a board?

Postby rew » 10 May 2017, 06:52



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