QS motor magnet max temp before demag ?

Doctorbass

100 GW
Joined
Apr 8, 2007
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Location
Quebec, Canada East
I am not sure if i made a mistake about max magnet temp

Yesterday i have painted the magnets of my 4T QS205 50H and baked the paint at 78 celsius for 24h witch is the temp i usually use as it worked nice and i never noticed demag on all my previous motor

I was sure that the operating temp of that QS motor was like 90-100 celsius, however i saw in the spec that QS have that these have workingtemp to 70 celsius and max 120celsius

so i wonder if 78 celsius from a 70 working temp for long period of 24h could have some effect .. well i guess it is not close to the curi point witch i suppose is 120 celsius or maybe 150...

The spec i have found for the QS are these one:


( the temp above are for the stator but the relationship with magnet is uncertain...)


"Note: QS Motor could work 120 ℃ in half an hour without damage.
Conservative Suggestion (Setting of Controller)
When it's 130 ℃ inside of motor (in 30s), the current should be limited 50%.
When it's 150 ℃, the controller shut down.
When it drop down to 110℃, the controller work again."

What do you think?

Doc
 
I'd be surprised if you'd done any damage at 70°C...

Can you check the KV of the motor? It should have risen if the magnets have lost any strength.
 
Punx0r said:
I'd be surprised if you'd done any damage at 70°C...

Can you check the KV of the motor? It should have risen if the magnets have lost any strength.

Yes that's a good point i will check the kv :)

Doc
 
from what i know, the max temperature the magnets can withstand depends also on the return of the magnetic field.
In free air (without any return) it is worst, and in an assembled motor the temperature can be higher.

normally, 70°C should be no problem
measuring kV -> good luck with modern sine wave controllers :p
here it is more the opposite (at least with Adaptto) -> you adjust the controller with manual tuning as close as possible to the motors kV you know from the datasheet (momentan battery voltage minus about 7% for sine wave)

probabaly an old lyen controller is what you need to find it out.
 
I think that neodymium magnets are produced in temperature grades, see this table: http://e-magnetsuk.com/neodymium_magnets/temperature_ratings.aspx and I believe that every "better" PMSM producer is using 150°C grade magnets.
 
I have contacted Vito and he said the magnets of the QS205 50H motor are 35SH type.

I still wonder if the rotor only for 24h period at 78 celsius is still borderline...

I have found this great recommendation too witch correspond with what you also said guys:

" a magnet rated for a recommended maximum working temperature of 150 degrees C may start to demagnetise significantly at 100 degrees C if the design is poor or a magnet rated for a recommended maximum working temperature of 80 degrees C may start to demagnetise significantly at 100 degrees C is the design is really good."
(from http://e-magnetsuk.com)


This is geting confusing as i also found on another website the spec of the 35SH: withc mention max operating temp of 150 celsius.. ( reference: http://www.magnetsales.com/neo/neoprops.htm)
 

Attachments

  • 35SH magnet temp.jpg
    35SH magnet temp.jpg
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I have two brand new QS motor so if i can get a gaussmeter i will measure teh magnetic field and compare...

Doc
 
I also found that info about ferrofluid temperature:

(reference: Wikipedia)

However, ferrofluids lose their magnetic properties at sufficiently high temperatures, known as the Curie temperature.

I also expect to use ferrofluid in the Qs205..

Doc
 
How do you think this will compare vs the x5403?

50mm stator.. nice copper fill from what i've seen.. and it come up the 17.71kv version... and around 29lbs!

i wonder what the efficiency rating of a x5403 was?.. this seems to be around 90%.. .. i know my hub-monster according to johnincr is up to 94% efficient but around 60lbs with tire.

-steveo
 
steveo said:
How do you think this will compare vs the x5403?

50mm stator.. nice copper fill from what i've seen.. and it come up the 17.71kv version... and around 29lbs!

i wonder what the efficiency rating of a x5403 was?.. this seems to be around 90%.. .. i know my hub-monster according to johnincr is up to 94% efficient but around 60lbs with tire.

-steveo


The QS205 is an excellent choice in term of power and continuous power. The 5403 i had was surprizingly a cold motor however i had modified it alot with liquid cooling.

The 205 is like the famous cormotor. it is heavy yes but it is a perfect match for 5+kW controller.

I bought a 3T and a 4T ( 11.5kv) and (9kv)... and the 9kv is my favorite when used with field weakening to boost speed because it have excellent torque and powerband can be extended with the Field weakening.

the famous 5403 and the 5304 have also the same kv of 9 if i remember correctly.

now let's go back to original subject :(demag and temp) wink:

Doc
 
For future references when painting and curing a motor I would recommend a pid and and old fashion heater, the kind that got analog switch and heat up the elements to glowing red while a fan blast the heated air out to the room. I tried to use my old brewery heater from a water heater but that just tripped the fuses and tempsensors. I did a heating chamber of some old brownstone bricks and some leftover prefab heat resistance sheets to make a "small oven". I used the same pid and temp probe I use for beer brewing. I got a tip from the shop how temperatures came to play for curing, so I sat the temp to max 45 min 44 celsius and closed the heat chamber and left motor for the weekend. Those pids are fairly quick to response to temp changes and turn the heat source on/off to match the set min/max temp. Of course you can choose higher temps to shorten the curing period.

No sticky paint left on my fingers when I closed down the "curing oven" on sunday night. And temps so low it should not affect the magnets. Side covers I forgot in the garage door opening when my cell rang, and one hour later the sun had baked those covers so hot I jerked my arms back when I tried to move them. That mat flat black really can suck up heat from the sun :oops:
 
I wonder what paint you have used. Was ist the krylon deep black? :)

Doc, maybe you remember that i also have painted the entire inner surface of one MXUS 3000 V2 motor and the parts i have also put in the oven for drying. Back on the bike, the motor did overheat quicker than usually (especially when loaded high), because the magnets got weakened.
The temperature was set to 70-80°C, but as mentioned such regualtion is very inaccurate.

Did you have already compared the strength with the gaussmeter?

At that time i used a piece of metal and measured the force it takes to remove it from the magnets with a scale.
It wasn't that accurate, but the results did show reproducible lower strength.

In the end, the dry process in the oven of the rotor did not help anything i believe, because i could chafe off the paint from the magnets easy with my fingers :|
On the other surfaces the paint holds extremely well. I was surprised how well it hold on the strands of the windings.

Did you do any surface preparation on the magnets?
 
madin88 said:
I wonder what paint you have used. Was ist the krylon deep black? :) Simply Krylon ultra mat flat black 1602, 97% absorption on large spectrum

Doc, maybe you remember that i also have painted the entire inner surface of one MXUS 3000 V2 motor and the parts i have also put in the oven for drying. Back on the bike, the motor did overheat quicker than usually (especially when loaded high), because the magnets got weakened.
The temperature was set to 70-80°C, but as mentioned such regualtion is very inaccurate. Well that is sad that yours overheated and that you noticed permanent damage!... On my side, the Oven i have used is a special equippent with very accurate Honewell PID temp controller. The temp remained below 78 degree c ( i had set the shutdown alarm to 80 to be sure )

Did you have already compared the strength with the gaussmeter? not yet , i'm actually looking for a gaussmeter. at work we have one very professional, but i can't locate it

At that time i used a piece of metal and measured the force it takes to remove it from the magnets with a scale.
It wasn't that accurate, but the results did show reproducible lower strength. Yeah that good idea. But i think if i have mathetic field loss it should not be so high as it is right in the knee of the curve according to the 35HS spec sheet at 78 degree C.

In the end, the dry process in the oven of the rotor did not help anything i believe, because i could chafe off the paint from the magnets easy with my fingers :|
On the other surfaces the paint holds extremely well. I was surprised how well it hold on the strands of the windings. Yes you are right, and i remember that last time i painted the magnet on my previous motor, i applied a very thin layer of residual epoxy coming from the excess of sides of the magnet brick, amd applied it on all teh inner surface of the magnet witch helped the paint to stick on these. Then i applied the paint. Yes that paint stick very well on most surface including the winding

Did you do any surface preparation on the magnets?
Yes, i cleaned the magnet with aceton and then isopropylic alcool.

Doc
 
GOT MY GAUSSMETER!! :mrgreen:

made in china but very impressive and give repeatable measurement value.

It have 4 effectives digits so it is accurate.

I have measured the only rotor i have at the moment as my two personnla rotor from the 205 are at IREQ lab for 2 days at the moment.

That rotor was damaged by rust and might be also damaged by heat but this is impossible to tell as that motor was on a adaptto at 12kw but WITHOUt temp sensor connected by the user :lol:

once i get the rotor of my 4T motor that got 78 celsius fgor 12 hours i wil test and post results, but from now let see what a 4T motor stator and damaged 5T motor can get as magnetic field!

go to this link! : https://endless-sphere.com/forums/viewtopic.php?f=30&t=87751&p=1281093#p1281093

or see the video directly: :wink:

[youtube]hub6ZQ0uB7E[/youtube]


Doc
Doc
 
@Doc, could you please explain me why you have put that brown paper between your stator and the side plate of your motor? It looks like some classic baking paper which is used for making pizza.. :roll: :D
 
My guess is that he has been masking up the motor before he sprayed the motor. I am sure the paper was removed before he assembled the motor.
 
DasDouble said:
@Doc, could you please explain me why you have put that brown paper between your stator and the side plate of your motor? It looks like some classic baking paper which is used for making pizza.. :roll: :D

Ah excellent question!

in fact that,s the residual brown paper that i used for painting.. however that part is the negative part of the paper i used to protect the rest of the motor outside when painting the magnet. I used the paper disk to protect the magnet from dust and magnetic particle while waiting to receive my gaussmeter.

Doc
 
I wonder if iron saturation can be measured with such gaussmeter?

About the magnetic field i always was the meaning it is strongest above the middle of the magnets, since between the magnets the fields are canceling out and doing not much (or nothing?) in view of torque.
Thats why weight optimized motors have a gap between the magents.
 
spinningmagnets said:
Doc, you have tried several coatings inside the motor to protect from rust. what brand of coating do you use now as the best?
Really good question. +1 Im interested too
 
madin88 said:
I wonder if iron saturation can be measured with such gaussmeter?

About the magnetic field i always was the meaning it is strongest above the middle of the magnets, since between the magnets the fields are canceling out and doing not much (or nothing?) in view of torque.
Thats why weight optimized motors have a gap between the magents.


That's a good point!

In fact i have remeasured the mag field and it appear that if i place the probe 90 degree ( perpendicular) to the magnet exactly while between at the intersection of two consecutive magnets, the magnetic field reach 5000 gauss.
That's the closer point where the magnet field lines ( WITHOUT being affected by the stator witch is absent) are the most dense since this is the point where N and S are the closest. However when the stator is present the core make the mag filed to modify their path and from now i have no way to measure it as the room between rotor and stator is too thin. But if you look at this drawing you can see that the fied seem to have a better distribution than the 3400Gauss to 5000 gauss i measure on the rotor only.

Lite+FEMM1.png


Doc
 
DasDouble said:
spinningmagnets said:
Doc, you have tried several coatings inside the motor to protect from rust. what brand of coating do you use now as the best?
Really good question. +1 Im interested too


I only use one brand as this is the most popular and professional product i have acces to. It is SPECIALY made for that purpose and is specialy formuled to wistand the worst environment. In Canada we develop and produce alot of motor and transformer in different brands and the Sprayon is the product the most availlable/popular. The actual version i use is the EL601. It is a epoxy based coating.



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Dielectric Strength: 2,600 Volts per Meter

NEMA & UL Temperature Class

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Nozzle Type: EZ-Touch™ for superior coverage and control with a conical spray

HMIS Rating: 2,4,0

Hazardous Materials Identification System (HMIS) Rating: Health - 2, Flammability - 4, Reactivity - 0


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Resists oil, moisture, acids and alkalis
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Propellant = Hydrocarbon
Sheen = Semi-Gloss
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Doc
 
Thanks a lot! As always, really detailed information about that spray. I wonder where I could get that in Germany.... :roll:
 
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