Turnigy Monster 12S 200A ESC

[Burtie]

Today I received the repaired ESC back from Hobby City (Yes -the very same one I sent back in November ).

I tried it out with a 7 turn Astro 3220 in Wye and then in Delta configuration,both at 24v --and this time I remembered the 5 amp fuse .

3220 in Wye configuration

Wye.jpg (98.18 KiB) Viewed 874 times

3220 in Delta configuration

Delta.jpg (90.88 KiB) Viewed 873 times

Now for the suprise.....
No load current in Wye was 0.6 Amps.
No load current in Delta was 3.4 Amps

Why is there such a large difference in current between these two configurations

I would have expected the current to have maybe doubled in Delta, but a factor of six? Am I doing something silly?

Edit- While I was typing this I left the motor running about half speed in Delta with no load and it got very very hot in about 5 minutes -like water boiled off when the outside was made wet! (it is now cooling down wrapped in a wet rag ).

Burtie

[CNCAddict]

Some motors don't like Delta connections. Depends on the internal design of the motor. A Delta motor can suffer from recirculating currents, which can produce higher losses...Wye doesn't suffer from that.

[Burtie]

It sounds like a possibility that Astros don't do Delta?



Edit added later:- Dont panic! all this means is that they are less efficient in delta and this shows up worst when there is no load.

[AussieJester]

It sounds like a possibility that Astros don't do Delta?

Be might bad news for all those that ordered 6 wire Astros recently LoL ...Deec?

Upside the Turnigy ESC nw works...not that you need it haha... Going in the for sale section is it Burtie?

KiM

[12p3phPMDC]

Burtie,

Do you know what the configuration of the Astro is?
i.e. the number of slots and magnets?

[Burtie]

KiM,
always good to have a broad arsenal of tools. I think I might keep it.


12p3
8 Poles 24 slots- I think

[12p3phPMDC]

8 pole, 24 slot...I think that's what was mentioned earlier...
The windings are distributed too, if I remember correctly...

The circulating currents in Delta result in from the type of drive, i.e. trapezoidal. The third harmonic created by
the trapezoidal drive is 22% of the fundamental....that's huge!! The third harmonic currents are the ones that are recirculating in delta.
They increase the current without adding anything to the useful torque. If we can come up with a sinusoidal drive, or a drive that is purely
the fundamental....then the recirculating currents resulting from the third harmonics go away, because you are driving the motor
with a pure tone.

Maybe that'll make the no load situation much better!

[Burtie]

With delta config, trapezoidal drive and distributed windings, does the efficiency situation get worse when the motor is loaded and the stator current rises?

[12p3phPMDC]

I think that it stays proportional....which means yea, it'll get worse...i.e. more wasted currents...
I have no Idea how the distributed affects things...yet...
I don't think it matters loaded or unloaded...But I'm not sure of that.
There are only a few things I am sure of....death, taxes, and I like warm fires...
I'm referencing Dr. D Hanselman's book, BLPM Design, for the 22% figure in the earlier post.
But the recirculating current problem is well known.

Dr. H has some tables in the examples chapter that show "Phase Back EMF HArmonic Amplitudes Relative to the Fundamental".
For the 24 Slot, 8 magnet configuration like the Astro.
The 3rd Harmonic is 22 or 23%
The 5th is ~8%.

For the 12 Slot, 14 magnet configuration of the Turnigy
The 3rd Harmonic is 10%
5th is negligible.

For large slot motors...I'll just pick an example (apparently a good one!)
36 slot, 24 mag,
3rd H, 1%
5th, 3%

THis may be why the Turnigys run pretty good in Delta and probably alot better in Y.
I think I'll convert the Turnigy in Y to eliminate some "dead currents" and get some halls sensors on there as well.
But, you may have to have the Astros in Y and only Y.
If anybody want's me to look up some stuff, just send me the config and I'll reference Dr. H's book.

[AussieJester]

I tried it out with a 7 turn .

Forgotz to ask to Burtie, the Astro motor, is isn't/wasn't going to replace the Turnigy was it mate? it is/was for another build right?
Surely you wouldn't replace the Turnigy!#@?!?@!?$%!? BE a step backwards in power would it not? Maybe the Astro is
for the little ladies build your secretly working on and havn't showed us yet hrmz ? hehe

KiM

[drewjet]

The Astro definately works Delta and Wye. And yes the no load current is higher in Delta. I spoke with Bob at Astro and he explained, I can't recall what it was. Under load the effency of Delta was 91% and in Y 94%. It may be as load goes up that the no load has less effect.

[12p3phPMDC]

Yea, Thanks Drew Jet,

It's not that it won't work, it's a matter of efficiency...
I'm curious about the loaded situation now...

Under load, the BEMF is less, that's why it draws more current
So, if the harmonic currents are proportional to BEMF per the tables, but the BEMF is less under load, then
it seems like the effect on efficiency would drop... not increase like I first thought.
Does that make sense to anyone else?

Didn't think that through before....

[Burtie]

Sounds very plausible.
So the energy wasted in the bad harmonics goes up with speed, not with load.
Meaning the efficiency hit in delta is worst at no-load, the losses become less significant as the motor is loaded.




KiM
The Astro is for my 'steath drive', it is a lot quieter than the outrunner. Not sure what it will end up on yet.

[AussieJester]

KiM
The Astro is for my 'steath drive', it is a lot quieter than the outrunner. Not sure what it will end up on yet.

ahhh gotcha...for those 'stealth trips' back from the Pub on Friday night so you don't wake the missus and the neighbours sneaking in late hehe :: wink ::

KiM

[etard]

Mount a prop on that thing Burtie!! I'm sure e few people are holding thier breath in anticipation. Also, I don't think Bob would send out six wire units if the effects were THAT bad. But maybe he is tired of all the delta/ wye biz from us small timers.

[damcard]

I was counting on the delta/wye on my 6 wire 3220 I have ordered for my current build. You guys have got me very nervous. -David

[12p3phPMDC]

I don't think there's anything to worry about, just a loss of efficiency in Delta of ~3% according to an earlier post.

[swbluto]

I don't think there's anything to worry about, just a loss of efficiency in Delta of ~3% according to an earlier post.

I think this part of Burtie's post is the part he's worried about:

Edit- While I was typing this I left the motor running about half speed in Delta with no load and it got very very hot in about 5 minutes -like water boiled off when the outside was made wet! (it is now cooling down wrapped in a wet rag ).

[nieles]

(sensorless) brushless motors do not like running at no-load.
atleast that is my experience with these motors when i was playing with rc cars

[CNCAddict]

(sensorless) brushless motors do not like running at no-load.
atleast that is my experience with these motors when i was playing with rc cars

I test all my motors at no load before shipping them out. They are quite happy to spin all day doing nothing at all. If the motor is getting to 212F at half throttle with no load...something is wrong or the motor does not like being wired in Delta.
www.xeramotors.com

[nieles]

I test all my motors at no load before shipping them out. They are quite happy to spin all day doing nothing at all. If the motor is getting to 212F at half throttle with no load...something is wrong or the motor does not like being wired in Delta.
http://www.xeramotors.com

my experience is with inrunner motors... they tend to get hot with no-load. i don't know if this is only a problem for inrunner motor and not for outrunners?

Niels

[CNCAddict]

The heat output of a freespinning motor is no load current * voltage. So if the motor is pulling 5A no load at 50V you have 250W of heat generated. The lower the no load current the cooler the motor runs at no load. Inrunner/outrunner doesn't matter.

[johnrobholmes]

Your motors have centrifugal fans on the end, whereas many inrunners do not. With proper cooling any motor can run no load all day. Many motors will indeed overheat just running them on the bench, from lack of airflow.

[CNCAddict]

Many motors will indeed overheat just running them on the bench, from lack of airflow.

Not if it's a good motor (or running at too high a voltage)

[AussieJester]

Guys check the adding halls sensors to Astro motor thread there more on the wye delta scenario Burtie discovered
doesn't look encouraging unfortunately.

"The no-load current was 3.5 amps in delta, as opposed to 0.6 amp in wye, even after the timing had been adjusted."

Burtie was unable to find a 'compromise' with hall sensor placement so both wye and delta worked efficiently. Hall sensors needed to be moved for wye and delta operation to get max efficiency in both modes.

Full thread

http://endless-sphere.com/forums/viewto ... 17#p247917

KiM