What is Outrunner Mode and who needs it?

[scallybert]

I'd be interested in a moderately technical description of what 'Outrunner Mode' is, what (kind of) motors need it, etc.

[By way of background, I'm running Outrage 1700kV 6 pole outrunner motors in 2 Outrage G5 helis, 6S, CCHV45, V2.0, heli fixed RPM governor mode. 12T/150T, 2450 RPM, IIRC.

Motors run happilly & reliably. I've got a slight tail twitch which may be down to governor pulsing or such.

A 3rd G5 is on V2.161 . Doesn't seem to have the tail twitch :) , but has had various firmware upgrade issues, and doesn't seem quite right. (Start-up is unavoidably harsh. Running seems somehow noisier/harsher than those on V2.0)

Eagerly awaiting the version beyond 2.18 ; but I'd like to go for the cautious setings with that.]

[scallybert]

'Similar threads' pointed me at the answers I was too dumb to find myself... :o

http://www.rcgroups.com/forums/showpost.php?p=12856464&postcount=2

http://www.rcgroups.com/forums/showpost.php?p=12858455&postcount=4

http://www.rcgroups.com/forums/showpost.php?p=12909253&postcount=14

[RC Man]

Patrick says that it has a variable PWM frequency but he did not say if it starts at 8KHz or something higher.

I wonder if the variable PWM could be part of the loosing sync problem with the latest firmware?


?

[nsg]

Could well be the case.

I had one of those sync problems yesterday, on takeoff, twice in a row. That was a maiden, too, of a fairly nice plane. I then ran the motor through the whole RPM range, changing the throttle slowly, and it went away. If this were my code, I'd be looking for an uninitialized variable somewhere..

[Patrick del Castillo]

Could well be the case.

I had one of those sync problems yesterday, on takeoff, twice in a row. That was a maiden, too, of a fairly nice plane. I then ran the motor through the whole RPM range, changing the throttle slowly, and it went away. If this were my code, I'd be looking for an uninitialized variable somewhere..

It's actually an issue with high current changes -- so if you throttle very quickly you can see the issue much more often than if you throttle slowly.

Patrick

[RC Man]

It's actually an issue with high current changes -- so if you throttle very quickly you can see the issue much more often than if you throttle slowly.

Patrick
So that explains why the governor won’t work as it is continually making large and very fast throttle changes.
:eek:

[scallybert]

So that explains why the governor won’t work as it is continually making large and very fast throttle changes.

That's exactly what occurred to me.

That aside, are there problems with older outrunner motors ?

[eg 1700kV, 6 pole Outrage, running at ~30kRPM on 6S.]

I must admit, I'd also like to see something describing how the PWM pulses relate to the ideal sine waveform going to the stator coils.

[jsmith285]

Hovering a plane requires fast throttle response. So new version of
the software is not working for me/us that require a fast throttle response.

[nsg]

I was hovering a 3DHS Vyper, ICE ESC, firmware 2.16 running a Torque 2818/900 for about 2 hours yesterday, landing every 8 minutes or so to change batteries. Having to change batteries every 8 minutes or so is, obviously, an ICE problem. It is totally unacceptable to me/us. I want my two hours of air time on a single AAA battery.

:rolleyes:

[scallybert]

Since I was getting nowhere with the 2.161/2.18 HV45, I've swapped it for one with 2.0 fw.

Definitely seeing the tail twitch again (so it seems likely the 2.16 governor improvements had fixed this), but at least 2.0 is a known quantity.

I'm looking forward to a version with the 2.16 governor improvements that I can trust to actually use.

[mjbennett9]

3.00 firmware is out as of last night :-)

Since I was getting nowhere with the 2.161/2.18 HV45, I've swapped it for one with 2.0 fw.

Definitely seeing the tail twitch again (so it seems likely the 2.16 governor improvements had fixed this), but at least 2.0 is a known quantity.

I'm looking forward to a version with the 2.16 governor improvements that I can trust to actually use.

[scallybert]

3.00 firmware is out as of last night :-)

Yes. Must have a play sometime.

Having said, I seem to be getting on ok with 2.161 right now http://www.rcgroups.com/forums/showpost.php?p=13567183&postcount=2 . I suspect the 'problems' I had with 2.161 were mostly down to paranoia because of the scare stories.

[mjbennett9]

3.00 works great!

[scallybert]

3.00 works great!

Cool!

Do you want to post what your application/set-up is, and what settings you're using ?

[e30ernest]

For a Scoprion HK2221-6 should I be running in Outrunner Mode? The motor is an outrunner as far as I know but if I remember right the manufacturer recommends 8khz.

[nsg]

I'd start with 8KHz and might experiment with 12.

[RC Man]

From my experience 8 Khz makes a lot more power and runs smoother and cooler than the outrunner mode. That’s always my first choice when truing a new setup.

[e30ernest]

Thanks so much for your replies! I'll stay in 8khz then.

Off topic:
I asked this question elsewhere and I hope it's ok to ask it here as well. For you who have a Scorpion -6, what timing are you running the motor at? Thanks!

[RC Man]

Thanks so much for your replies! I'll stay in 8khz then.

Off topic:
I asked this question elsewhere and I hope it's ok to ask it here as well. For you who have a Scorpion -6, what timing are you running the motor at? Thanks!

Let us know how that works out for you.


:) :cool:

[gerard71]

Is this true only for Scorpion motors or should I use 8kHz also for my Align 500L?

[scallybert]

I think that Outrunner Mode only helps if the commutation frequency gets close to the PWM frequency. I think that if these are close, but not synchronised in some way, interactions (such as timing issues, beat frequencies, etc) mght be possible.

AIUI, the commutation frequency is the frequency at which the power is switched from one set of coils to the next. I make that (RPM/60)*(pole count) in Hz.

So, I make it that a 6 pole motor at 20kRPM would give a commutation frequency of 2kHz.

My 6 pole Outrage 1700kV motor is governed to 2450*12.5 RPM (30625 RPM) and I run with the default 12kHz PWM frequency. This seems to work fine, with neither motor nor ESC getting hot.

The formula above suggests this has a commutation frequency of 3.063kHz. ie about 1/4 the PWM frequency I'm using.

[Patrick del Castillo]

I think that Outrunner Mode only helps if the commutation frequency gets close to the PWM frequency. I think that if these are close, but not synchronised in some way, interactions (such as timing issues, beat frequencies, etc) mght be possible.

AIUI, the commutation frequency is the frequency at which the power is switched from one set of coils to the next. I make that (RPM/60)*(pole count) in Hz.

So, I make it that a 6 pole motor at 20kRPM would give a commutation frequency of 2kHz.

My 6 pole Outrage 1700kV motor is governed to 2450*12.5 RPM (30625 RPM) and I run with the default 12kHz PWM frequency. This seems to work fine, with neither motor nor ESC getting hot.

The formula above suggests this has a commutation frequency of 3.063kHz. ie about 1/4 the PWM frequency I'm using.

That's correct. We are planning on adding a calculator to the Castle Link software to help determine if outrunner mode or standard mode is more appropriate for a given setup.