Calculating QS205 motor torque vs. speed curves

Electric Motors and Controllers
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jaybee9   1 mW

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Calculating QS205 motor torque vs. speed curves

Post by jaybee9 » Apr 19 2018 9:40am

I have been trying to decide what version of the QS 4000W 205 V3 motor would be best for my EV application. I have gotten a couple data sets from the QS sales guy: 3T- (Fast) @ 72 V and 3T (Balance) @ 72 V. He didn't have 4T (Torque) data. My nominal battery voltage is 88.8 V and I am planning on using an Elmo Gold Drum 100/100 controller.

I am trying to quantify what the motor performance would look like at my nominal voltage level for the 4T (Torque) and 3T (Balance) windings. I plotted the data from QS and my predicted performance (Calc) in the attached file. Below are the main input parameters I used for my calculations.

Parameter Value Unit

4T
Nominal voltage 88.8 V
Max current 70 A
Max torque 190 N-m
Kv 11.5 rpm/V
Max speed 1020 rpm

3T
Nominal voltage 88.8 V
Max current 77 A
Max torque 180 N-m
Kv 15.6 rpm/V
Max speed 1390 rpm

My calculation procedure was basically as follows. First, determine input power (nominal voltage x max current). Then I calculate efficiency as a function of speed from polynomial curve fits (3T data up to 1000 rpm, 3T- curve above 1000 rpm). Then calculate output power (input power x efficiency) and torque (output power / speed).

Do my calculated 3T and 4T torque versus speed curves look right?
Attachments
QS205 Curves.pdf
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flippy   1 MW

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Re: Calculating QS205 motor torque vs. speed curves

Post by flippy » Apr 24 2018 1:06pm

do you have the original datasheets you used? it seems that the blue one lower ceiling is wrong.

i would also not use the - or + types, they have uneven balancing so they dont heat up evenly.
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jaybee9   1 mW

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Re: Calculating QS205 motor torque vs. speed curves

Post by jaybee9 » Apr 26 2018 5:46am

See attached files. The blue curve is straight from the file 10_205_55H_V3_72V_1321RPM.pdf. I only plotted it differently than how it is done in the file to be more useful for my purposes.

I am not planning on using the +/- versions but it was helpful insofar as it gave me more data to work with.
Attachments
10_205_55H_V3_72V_1321RPM.pdf
(187.14 KiB) Downloaded 188 times
4000W Motor Testing Report V3 Balance.pdf
(108.78 KiB) Downloaded 111 times

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teklektik   10 GW

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Re: Calculating QS205 motor torque vs. speed curves

Post by teklektik » Apr 26 2018 1:22pm

jaybee9 wrote:
Apr 19 2018 9:40am
I have been trying to decide what version of the QS 4000W 205 V3 motor would be best for my EV application.
Are you looking for the projected top speed on a bike or motorcycle?

FWIW:
A quick examination of the dyno data (10_205_55H_V3_72V_1321RPM.pdf) shows that the results are limited by the controller and don't actually show the raw motor performance. It looks like the battery current was limited to ~83A and the controller went into phase current limiting at around 105Nm of torque. Depending on your application (controller, etc), this data might be just what you need or may upset other results you derive. For example, different controller current limit settings even at the given 72V level would result in significant power and torque increases.

Also, figuring the Kv from the raw data shows 18.3 (1321rpm/72.17V)...
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jaybee9   1 mW

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Re: Calculating QS205 motor torque vs. speed curves

Post by jaybee9 » May 01 2018 8:27am

teklektik wrote:
Apr 26 2018 1:22pm
jaybee9 wrote:
Apr 19 2018 9:40am
I have been trying to decide what version of the QS 4000W 205 V3 motor would be best for my EV application.
Are you looking for the projected top speed on a bike or motorcycle?
My application is a multi-axle electric vehicle, to be specific. I have a good handle on the top speed. My question was more geared towards understanding the entire torque vs. speed envelope, especially the low speed torque.
teklektik wrote:
Apr 26 2018 1:22pm
jaybee9 wrote:
Apr 19 2018 9:40am
I have been trying to decide what version of the QS 4000W 205 V3 motor would be best for my EV application.
FWIW:
A quick examination of the dyno data (10_205_55H_V3_72V_1321RPM.pdf) shows that the results are limited by the controller and don't actually show the raw motor performance. It looks like the battery current was limited to ~83A and the controller went into phase current limiting at around 105Nm of torque. Depending on your application (controller, etc), this data might be just what you need or may upset other results you derive. For example, different controller current limit settings even at the given 72V level would result in significant power and torque increases.
Great point! That had not occurred to me that it was not raw motor performance. I will check with the sales person I have been talking to and update based on what I find out.
teklektik wrote:
Apr 26 2018 1:22pm
Also, figuring the Kv from the raw data shows 18.3 (1321rpm/72.17V)...
Yes, roughly. QS told me Kv = 19 for 3T-. The data shows at 1321 rpm it not quite a no-load speed, close though, so somewhere between 18.3 and 19.

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spinningmagnets   100 GW

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Re: Calculating QS205 motor torque vs. speed curves

Post by spinningmagnets » May 01 2018 8:35am

It's my understanding that at very low speeds, a wide open throttle (WOT) will signal the controller to provide as many amps as possible. Then, as the RPM's rise closer to the top theoretical RPM, the amps will proportionately taper off, resulting in less "felt" torque.

I think this is part of the reason Luke is so enamored of low turn count motors. Even if he is riding along at 30-MPH, he doesn't want to be "topped out", he wants a build capable of 60-MPH...even if he never rides at 60-MPH.

The fact that the lower turn count versions of a motor have thicker wire means that the windings have a lower resistance (less watts wasted as heat in heating up higher resistance coils), is just icing on the cake.

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Re: Calculating QS205 motor torque vs. speed curves

Post by Bullfrog » Mar 17 2020 9:55am

Gentlemen (and ladies if there are any :)),

This is a little off topic but I am trying to understand the QS205 and QS273 motors better so I can make an intelligent decision on my motor selection/winding. My overall objective is top speed in a straight line while running a 52.8 volt battery or 79.2 volt battery. I''d like to investigate the top speed capabilities for both voltages for a 80A controller (if I use an 18650 cell based battery) and if amperage was not a limitation (if I use LiPo packs) and see how everything would theoretically affect my top speed. I plan to use the Grin Tech Motor Simulator and the Trip Simulator for my modeling.

Two concepts where I need a little better understanding please....

A. What physically happens inside a motor when it is a "3T+" winding or a "3T-" winding as opposed to 3T? Is the "+" somewhere between 3 full turns and 4 full turns and the "-" somewhere less than 3 full turns but more than 2 full turns...I am guessing. I may have it backwards. Just need someone to verify exactly what is meant by the "+" and the "-".

B. Is there an advantage or disadvantage to having a partial turn? I have read that a partial turn tends to run hotter/overheat more than a full turn but I don't see why it would matter besides slightly less or more copper mass, assuming I understand the +/- concept correctly. If anybody could clarify this, I sure would appreciate it.

Thank You Thank You Thank You

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Re: Calculating QS205 motor torque vs. speed curves

Post by Bullfrog » Mar 17 2020 10:03am

jaybee9 wrote:
May 01 2018 8:27am
teklektik wrote:
Apr 26 2018 1:22pm
jaybee9 wrote:
Apr 19 2018 9:40am
I have been trying to decide what version of the QS 4000W 205 V3 motor would be best for my EV application.
Are you looking for the projected top speed on a bike or motorcycle?
My application is a multi-axle electric vehicle, to be specific. I have a good handle on the top speed. My question was more geared towards understanding the entire torque vs. speed envelope, especially the low speed torque.
teklektik wrote:
Apr 26 2018 1:22pm
jaybee9 wrote:
Apr 19 2018 9:40am
I have been trying to decide what version of the QS 4000W 205 V3 motor would be best for my EV application.
FWIW:
A quick examination of the dyno data (10_205_55H_V3_72V_1321RPM.pdf) shows that the results are limited by the controller and don't actually show the raw motor performance. It looks like the battery current was limited to ~83A and the controller went into phase current limiting at around 105Nm of torque. Depending on your application (controller, etc), this data might be just what you need or may upset other results you derive. For example, different controller current limit settings even at the given 72V level would result in significant power and torque increases.
Great point! That had not occurred to me that it was not raw motor performance. I will check with the sales person I have been talking to and update based on what I find out.
teklektik wrote:
Apr 26 2018 1:22pm
Also, figuring the Kv from the raw data shows 18.3 (1321rpm/72.17V)...
Yes, roughly. QS told me Kv = 19 for 3T-. The data shows at 1321 rpm it not quite a no-load speed, close though, so somewhere between 18.3 and 19.
Damon at QS told me the highest actual Kv available for the 205 V3 motor was 18.50 and the highest Kv available for the 273 V3 is 17.64. I found it interesting that the 205 has a slightly higher rpm potential than the 273 motor. So that spurred me to start investigating which one could actually be faster for my application. Before getting the Kv data, I planned to go with the 273 motor but now I need the motor parameters so I can see if the 205 can supply enough torque to actually reach a higher top speed based on the voltage/amperage supply I plan to run.

I have asked QS for the parameters required in the Grin Tech Motor Simulator to build a "Custom Motor" so I can vary the voltage/amperage supplied and compare the performance of a QS205/273 V3 motors. If anyone has the parameters listed below for a QS205 V3 motor with Kv=18.50 or a QS273 V3 motor with Kv=17.64, I sure would appreciate you passing along the info. Communicating with QS is fairly challenging :) .

Rmotor: Room-temperature phase-to-phase winding resistance (Ω)

Lmotor: Phase-to-phase winding inductance (mH)

Poles: Effective magnetic pole pairs, ie motor pole pairs times the gear ratio to the wheel

Hysteresis torque of the motor in Nm.

Eddie current torque of the motor, (N-m/(Rad/sec)).

Thanks

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flippy   1 MW

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Re: Calculating QS205 motor torque vs. speed curves

Post by flippy » Mar 18 2020 7:04am

Bullfrog wrote:
Mar 17 2020 10:03am
Communicating with QS is fairly challenging :)
depends on how many motors you order... :roll:

that said, they are are a fuckton better then sevcon for example. they wont even respond a email unless you order a pallet of the things.
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Re: Calculating QS205 motor torque vs. speed curves

Post by DogDipstick » Mar 18 2020 8:07am

flippy wrote:
Mar 18 2020 7:04am
Bullfrog wrote:
Mar 17 2020 10:03am
Communicating with QS is fairly challenging :)
depends on how many motors you order... :roll:

that said, they are are a fuckton better then sevcon for example. they wont even respond a email unless you order a pallet of the things.
... I would say this is true. I have a friend who ordered 60. They were ordered pre-pandemic, and will still be showing up in the 120 day window.. as of right now.
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Re: Calculating QS205 motor torque vs. speed curves

Post by amberwolf » Mar 19 2020 12:15am

Bullfrog wrote:
Mar 17 2020 10:03am

I have asked QS for the parameters required in the Grin Tech Motor Simulator to build a "Custom Motor" so I can vary the voltage/amperage supplied and compare the performance of a QS205/273 V3 motors.
it's pretty unlikely that they will give you the info, even if they have it. they either prefer to keep necessary technical info about their stuff secret, or they have no clue to what you are asking them about (more likely) and have no way of testing for it.

they have actually told some people that even their engineers cannot test for various motor parameters, which seems strange for a company that designs and builds motors.

so, speculation based on such things, is that these places don't likely "design" these motors, so much as just incrementally change new versions from previous designs (which themselves probably come from yet older designs, that come from someone elses's designs, etc.). then they probably build one and test it under a few specific conditions, perhaps even on a dyno of sorts. maybe on a "test bed" bike or something, with various "butt dynos" and speedometer readings. ;) (kinda like many es builds)

once upon a time there probably was a motor engineer that designed something, on purpose, to do a specific job, in a company far far away and long long ago. ;) since then, the design has been copied and mutated, for better or worse, into thousands of different versions by dozens to hundreds of companies. :oops:

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Re: Calculating QS205 motor torque vs. speed curves

Post by Bullfrog » Mar 19 2020 5:47am

amberwolf wrote:
Mar 19 2020 12:15am
Bullfrog wrote:
Mar 17 2020 10:03am

I have asked QS for the parameters required in the Grin Tech Motor Simulator to build a "Custom Motor" so I can vary the voltage/amperage supplied and compare the performance of a QS205/273 V3 motors.
it's pretty unlikely that they will give you the info, even if they have it. they either prefer to keep necessary technical info about their stuff secret, or they have no clue to what you are asking them about (more likely) and have no way of testing for it.

they have actually told some people that even their engineers cannot test for various motor parameters, which seems strange for a company that designs and builds motors.

so, speculation based on such things, is that these places don't likely "design" these motors, so much as just incrementally change new versions from previous designs (which themselves probably come from yet older designs, that come from someone elses's designs, etc.). then they probably build one and test it under a few specific conditions, perhaps even on a dyno of sorts. maybe on a "test bed" bike or something, with various "butt dynos" and speedometer readings. ;) (kinda like many es builds)

once upon a time there probably was a motor engineer that designed something, on purpose, to do a specific job, in a company far far away and long long ago. ;) since then, the design has been copied and mutated, for better or worse, into thousands of different versions by dozens to hundreds of companies. :oops:
I am afraid you may be correct...and that original design they started with probably came by copying something from another country. But that is OK and smart on their part...let somebody else pay for the R&D/nonrecurring engineering cost and then just copy what works and punch them out with cheap labor. I guess it doesn't hurt to ask.

Arthritis is flaring up again so all I have been doing is watching TV and sitting on the couch. When it isn't too bad, I get all these grandiose ideas and make huge plans I can't complete. For all you young pups out there...if you have thoughts of doing something...do it now...before you get old and can't. No complaints, I am blessed but I never had a clue getting old would be so challenging :) .

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Re: Calculating QS205 motor torque vs. speed curves

Post by markz » Mar 19 2020 2:14pm

Why not just install and ride and see how it goes with the perfect controller match for your needs.

Otherwise if it under performs, get a bigger motor.
And if it over performs, get a smaller motor or keep it and limit it.

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Re: Calculating QS205 motor torque vs. speed curves

Post by amberwolf » Mar 19 2020 11:07pm

Bullfrog wrote:
Mar 19 2020 5:47am
Arthritis is flaring up again so all I have been doing is watching TV and sitting on the couch. When it isn't too bad, I get all these grandiose ideas and make huge plans I can't complete. For all you young pups out there...if you have thoughts of doing something...do it now...before you get old and can't. No complaints, I am blessed but I never had a clue getting old would be so challenging :) .
i had a really clever line i was going to say, but by the time the page loaded i forgot what it was. :( :oops:

so i'll just have to go with: you have my sympathy here; especially in rainy weather like we've had. :/


and one thing i've found is that if i keep moving, even a little, it helps a lot with being *able* to move at all when i have to. the more i don't move, the less i'm able to. :(

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Re: Calculating QS205 motor torque vs. speed curves

Post by sohamd31 » Jun 02 2020 4:58am

Hi,
I read the complete thread. I am new to EV's and their design. I have similar datsheet as you have posted.
According to my understanding,
the given datasheet is a load dyno test data. Testing sequence is like, full wide open throttle is given at all time and continuously the motor is loaded. Hence initially we get max rpm and low torque but as the loading begins motor draws more current and rpm decreases. It is done until the motor stalls and rpm is almost 0.
So the data presents the maximum possible rpm at a certain torque (not the vice versa). Hence we can't use this for calculating the vehicle propulsion force.
Am I right?

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