BLDC motor shaky at high RPM?

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I have a car alternator converted into a BLDC motor. It gets jittery at high RPM, around 3500-3800. Is that the controller not able to output correctly to it? Like it's not reading the back-EMF correctly and feeding it the wrong voltage slightly? Is there anything I can do to fix that, or do I just have to stay below that RPM to avoid it? That's a no-load RPM figure, so under load would it behave differently, or maybe just not even reach that high of RPM with a 350lb or higher load?

EDIT: Would field weakening (reducing commutator power) fix that?

EDIT2: I tried lowing the field voltage from 12.6 to 10, no apparent effect. It seems like it might be in the controller. It only seems to jitter for a moment, then it's fine. Almost like it's switching something internally and it's a rough transition.
 
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SymonLie

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Hi....simply firing up the engine with no heap does it do something very similar?

When driving and it begins doing it, what happens when you let off the quickening agent, does it promptly stop the protest or does the rpm need to drop (leaving it in stuff so the energy of the vehicle keeps rpm up a couple of moments)?

In the event that its not mechanical, some out of equilibrium thing, flash or fuel is pretty much all that is left.

turnkey assembly services
 
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Messages
72
Reaction score
4
Location
Albany, OR
Hi....simply firing up the engine with no heap does it do something very similar?

When driving and it begins doing it, what happens when you let off the quickening agent, does it promptly stop the protest or does the rpm need to drop (leaving it in stuff so the energy of the vehicle keeps rpm up a couple of moments)?

In the event that its not mechanical, some out of equilibrium thing, flash or fuel is pretty much all that is left.
Haven't actually driven it yet (almost done, but not quite), that shake/stutter is at no load. Also it's electric. And since it's only at very high rpm, I'm wondering if it'll even happen when driving. Under load, it may not be able to hit that many rpms.
 
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ShadowNightmares

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Goiania, Goias, Brazil
I have a car alternator converted into a BLDC motor. It gets jittery at high RPM, around 3500-3800. Is that the controller not able to output correctly to it? Like it's not reading the back-EMF correctly and feeding it the wrong voltage slightly? Is there anything I can do to fix that, or do I just have to stay below that RPM to avoid it? That's a no-load RPM figure, so under load would it behave differently, or maybe just not even reach that high of RPM with a 350lb or higher load?

EDIT: Would field weakening (reducing commutator power) fix that?

EDIT2: I tried lowing the field voltage from 12.6 to 10, no apparent effect. It seems like it might be in the controller. It only seems to jitter for a moment, then it's fine. Almost like it's switching something internally and it's a rough transition.
Hello.
You didn't said what voltage are you applying for the stator, that is important.
 
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