QS 3000w midmotor

[eee291]

I'm an easygoing guy, but I still feel like you are talking down on me

Anyways...
I have never used Flux weakening so I know little about it. I always just overvolt motors

[wjr]

I normally try to answer peoples questions but I’m out, hopefully someone else finds the patience to answer you - i won’t.

Of course, I respect that. Sorry for asking.

I'm sure, between wikipedia and a full fledged study in electrotechnics, there must be some intermediate way to understand IPM and flux weakening.
Looks like I havent't just looked hardly enough.
I'll leave a note when I found something.
I see that there is a ressources area in the motor forum, so I'll start digging there.

I'm an easygoing guy, but I still feel like you are talking down on me

Do you mean me?
sorry, if so - that was not my intention.
I felt like replying to the forum, not to individual people.
Regarding your proposal of overvolting, I know that this works with DC motors, but for such a complicated thing as an IPM-controller setup with flux weakening at the edge of demagnetization - and in the context of the thread - I actually considered this as a joke - shame on me.

I just wanted to report that cheap ali sprockets might fit where people reported remilling their shafts.
I found myself drawn into a discussion of ratios and the credibility of flux weakening data that fascinated me, but slightly exceeded my horizon. So I wanted - and still want - to expand my knowledge on that issue.

If this thread is the wrong place - no problem, I'll find another one.

[AviatorTrainman]

Hey, so I'm trying to figure out controllers. I'm having trouble finding the Votol 200 for sale anywhere, and the aliexpress QS motor comes with the votol 150sp, if any. So for 100 USD over the price of the motor with a votol 150, I can get the motor with a sabvoton 72200. Is this controller compatible with the throttle assemblies sold at https://www.aliexpress.com/item/3306149 ... TYTYl&mp=1? I'd be more than happy to do some soldering to put on new connectors - my question is more about actual signals and voltages. Also, my understanding is that I may have to do the same for the hall wires. Is this correct? Also also, I would like to know if the votol and/or sabvoton can be run "headless", as in only hooking up the throttle and motor, without any sort of display output. I already have my own meters for voltage, amperage, and speed.

I'd assume based on the conversation here that the 200 amp controller would be a significant improvement, especially if I'm gearing my motor for a top speed around 130 kph. I'm so far ordering the motor with an 11 tooth sprocket, and I have a 14 on hand in case high rpm performance is not where I'd like it to be. The rear wheel is an 18 inch rim with a 2.5 inch 100% tire, and a 49 tooth sprocket.

[minde28383]

Can use sabvoton even though qs does not recommend it for the motor. It will run but I don't know if field weakening will work as good as with votol.
Also I think sabvoton does not run sensroless.

[larsb]

I'm having trouble finding the Votol 200 for sale anywhere

Just send QS sales a question, adress is carrie@tzquanshun.com or judy@tzquanshun.com

I don’t know if anyone here has tried the votol em200, if you want a known option that works well then ask for the em72150S

[wjr]

I think I found a proper place for learning about and maybe discussing the nuts and bolts of "flux weakening":
viewtopic.php?f=30&t=95174&p=1402148&hi ... g#p1393916
so I'll no longer clobber this place here with newbie level thoughts.

Should have searched for "field weakening" instead, looks like this synonym is more common in use.

[minde28383]

You are not clobbering anything. All places are good.

[larsb]

No they’re not. This is a thread about QS 3000w mid drive motor. Better keep field weakening questions where they belong.

[minde28383]

All stuff is related. Have you heard holistick. It's not that but similar.
Look at the topic. It holds so many things mentioned already so it's spoiled already.

[eee291]

@wjr

I'd say that the problem is that there are no people on this thread that are planning (or know enough) to discuss field-weakening in detail.
If you want to discuss with someone more knowledgeable you are better off finding the specific thread or making a new one.

Vasilisk, seems to have a lot experience with this motor and field-weakening.
https://www.youtube.com/user/realcrafts/videos
memberlist.php?mode=viewprofile&u=37468


Madin88 also seems very interested in filed-weakening with this motor, you might have a fruitful conversation with him.
+ You both know German so win-win

[Torti]

with kelly controller one must specify the polpaare are the 5 polpaare?

[eee291]

with kelly controller one must specify the polpaare are the 5 polpaare?

I'm pretty sure you don't have to unless you want an accurate rpm reading.
You just need to do the ''Identfy angle'' thing and it should run fine.

[ZERONEST]

I recently received the 2000w motor, I noticed someone had water in the hall sensor, is there a gasket on the plate? or only silicone? I'm wondering if its possible to place a paper gasket to stop water getting in..

would there be any other areas on the motor which might need protecting?

Thanks

[eee291]

You could add some oil to the motor so it has some protection against water.
I used a really thick engine oil additive, about 100ml, then sealed the cover with some engine gasket silicone.
The Hall PCB seems to be very water sensitive so I also dipped it in some glue.

[wjr]

I think this is the essence from the flux weakening thread as it relate to my QS 3000w - gear ratio design decision:
viewtopic.php?f=30&t=95174&p=1402148&hi ... g#p1402148


With FW, I can optimize my ratio for mid speed (~ 60 km/h) and still have some nice performance above the motor's designed base speed with close to constant power till 100 km/h and maybe even above.

Stuff is complicated and has to be done by the controller.
There is risk of demagnitizing the motor, and maybe burning motor and/or controller if it's done the wrong way.
It's quite challenging to do it perfectly right, and as far as the QS datasheet promises, the appear to have done it right.
I'll not going to try to top them, just gain the performance their datasheet promises.

What worries me a little bit is the sometimes fuzzy language in the controller manual, in the light of those risk.
But no risk no fun, it's a hobby project, neither motor nor controller are that expensive.
It's just a matter of patience to wait for shipment, if I misunderstood some manual clause and accidentially burn my stuff by trial-erroring out the semantics.

[DanGT86]

I was under the impression you cant demagnetize a motor unless you heat the magnets past a specific temp. While its believable that poorly calibrated field weakening could heat your motor I think you'd notice on the temp gauge before hurting the magnets.

[minde28383]

Current floods motor with more current when field weakening kicks; motor does not converts it to mechanical energy and more heat is happening. If temp is not monitored that something will burn. At least with cheap controllers it is. Just poor controller design.

[wjr]

I think this is one, but not the only thermal death scenarios.

Just consider what the Votol Controller manual says:
(since in the end, the motor is broken, please allow me to consider this not as off-topic )

3.4.4 Attention
...
3.4.4.5 Weak magnetic failure: The flux weakening value exceeds the motor and controller parameter values, causing the motor to demagnetize and the controller to burn MOS.

By educated guess:
The flux is weakend by applying some external field across the permanent magnets opposite to their own permanent magnetic field.
While those are supposed to be strong magnets, they display some magnetic hysteresis nevertheless, which means they may be demagnetized if this counter field exceeds their hysteresis level.
Maybe stuff get's quite inhomogenous there, and demagnetization initially only occurs in some corners - who knows....

Anyway, if this happens, rotary field strength further decreases, counter-EMF decreases, current increases.
Maybe we even get a runaway condition that exceeds the controll loop time constant?
Thus this may "burn MOS" much faster as a thermal overload by excess current?

This may harder to be avoided by controller design than the much slower process of pure overcurrent overheating.
Even if the controller is fast enough to switch off before MOS burning, the magnets remain irreversibly damaged.
You end up with a motor in "permanent flux weakened condition", means you loose torque and power at low speed, including rated speed.

[DanGT86]

I think you are worried about it for no reason. As with most things in the EV world the goal is to get away with the maximum current you can before the temp gauge tells you to stop or until you stop making more power.

What you are reading is likely poorly translated instructions trying to warn you that field weakening will heat your motor faster than the same amount of input current without field weakening.

FW causes inefficiency > inefficiency causes heat > heat can demagnetize a motor

I would be willing to bet its impossible to demagnetize a motor without it getting hot first.

As for the controller blowing before the control logic can catch it, that is always a problem with any system. You do have to exercise some level of common sense when applying settings. If you pick a controller that is way under spec for your application and program it to apply way too much phase current then you will probably kill it. That goes without saying.

As for this motor, I don't find it that hard to believe that it maxes out somewhere in the 3000 rpm range without FW and can be run to 5-6k rpm with FW. I don't think there is some magic FW value that destroys your motor without warning. If you have a temp gauge and you are using the controller reasonably within its specs from QS it will be fine.

[larsb]

Why not just google the field strength and conditions needed to demagnetize a neodym magnet. I bet it would take less time than writing the speculations.

Apart from that i'm with danGT86.

I calculated the extra torque that this motor could give in field weakening because of the reluctance in IPM design, it was very small. I consider it as a normal bldc in this regard.

[sn0wchyld]

Why not just google the field strength and conditions needed to demagnetize a neodym magnet. I bet it would take less time than writing the speculations.

Apart from that i'm with danGT86.

I calculated the extra torque that this motor could give in field weakening because of the reluctance in IPM design, it was very small. I consider it as a normal bldc in this regard.

could you share the calcs for this?

[larsb]

I’ll have to dig a bit, it was some time ago.

[larsb]

viewtopic.php?f=30&t=97880#p1433805

My experience with field weakening with votol em72150 controller and this motor supports that the reluctance torque is not large -it doesn’t show any large increase of torque or even a larger field weakening capability.

[larsb]

All stuff is related. Have you heard holistick. It's not that but similar.

Is this the one you mean?

77C1C021-FE07-4F52-B0A9-2107D7ADAF60.jpeg (86.63 KiB) Viewed 2511 times

Seriously, all threads get derailed eventually. I bet it can be proven that there’s a threshold around 100 posts or so where threads always go down in quality. Still it’d be better if they kept a good level.

[wjr]

Thanks for adjusting the quality level.
So it's easier for me to provide a positive contribution - I'll dare again

Why not just google the field strength and conditions needed to demagnetize a neodym magnet.

Google'ing the coercivity of Nd Magnets yields somewhere between 600 and 1200 kA/m.
For Sa-Co I found values as low as 80 kA/m

I bet it would take less time than writing the speculations.

Whats our field?
can still only speculate.
I remember a figure of some forty windings for a custom make, so 50 might be a reasonable order of magnitude.
People (larsb?) have reported 500 phase amps.
And we need some geometry factor (coil length?), for which I'd throw up 50 mm

200 A - 50 turns / 0,05m = 500 kA/m
So we are in the magnitude of Nd coercivity, and taking inhomogenous flux intoaccount, i still see a risk.

Loooks like I did'nt manage to shift the borderline of speculation that far

I calculated the extra torque that this motor could give in field weakening because of the reluctance in IPM design, it was very small. I consider it as a normal bldc in this regard.

But as i've got it, reluctance torque and field weakening are different concepts?
Maybe both are utilized by the same sihft of current phase angle, but a motor w/o reluctance can still use field weakening - OK?

The rotor image here
viewtopic.php?f=30&t=93627#p1376479
shows nearly no gap between magnets, which I have learned were relevant for reluctance torque, OK?

Anyway, I'll not dig into all details of motor design.
I just would like to program my controller so that I can get out the torque curve QS labelled "with flux weakening" in their ads .
Unfortunately, the Votol controller figures are not comprehensible in terms of physical meaning - at least not for me.

The best point to start with I found is this file
QSMOTOR SPEC for VECTOR Dirt Bike V1.2.pdf
download/file.php?id=251220
in this post
viewtopic.php?f=30&t=93627&start=175#p1461316
from QS Judy.