QS 205 vs 273

[Doctorbass]

From my understanding, the max power the stator can do is limited my the copper amount the winding is made of.

The more copper of winding the more power you can pump into these.

I tought it woudl be interestign to determine how much more copepr is in the 273 compare to the 205(3000W rated)

I have calculated the copper amount between the 205 24x5 and the 273 65x3.
Unless i am wrong, these calculations should give a greast comparaison between the 205 and the 273 max power.


First we have to calculate the difference of strands lengh between both motor.

The 273 is 0.013ohm phase to phase resistance and that is representing 65 strands so we can calculate using the parallel ohms law that every strands is 0.866ohms

The 205 is 0.065ohm phase to phase resistance and that is representing 24 strands so we can calculate using the parallel ohms law that every strands is 1.56ohms

Now that we have the single strands resistance of each motor and that the strands of the 205 and the 273 are the same size, we know the lenght ratio between both.

The 205 is (1.56/0.866)= 1.8 time longer strands than the 273

The 273 is (65/24) = 2.7times more strands than the 205.

The 273 have more strands but they are shorter... let's calculate witch win

The ratio of copper of the 273 is (2.7/1.8) = 1.5 times higher than the 205.

So we could conclude that in term of copper amount and max winding power, the 273 is 1.5 time the 205 = 1.5 x 3000W = 4500w of power

According to the copper amount the 273 should be rated 4500W?

Doc

 

[Doctorbass]

Luke have bring a great additional information about these:

Let me quote his explanation:

It's precisely about more copper fill % alone for comparing the same stator with various winding options.
For different stators, it's about the Km of the motor to make apples to apples comparison.
When the motor diameter grows, think of it has the length of the motor when unrolled into a linear motor increasing at the same rate the lever arm length the linear motor is acting on to make a torque growing with it.
Essentially, the larger the radius of the motor the less stator materials (and tooth flux density) it requires to make a given sustained torque.
Big diameter motors are ideal for making big torque due to the ability to make torque growing at the square of the diameter. For a smaller diameter motor to make the same torque it needs to be very much wider.

Doc

 

[Emoto]

Good idea doc im assuming your comparing the 50mm stator 273, How about including the 40mm stator 273 as well , as its a bit lighter than the 50mm 273.
Would be intriguing to see how the larger diameter compares torque wise to the 205 even though its 40mm ...

 

[gensem]

Good idea doc im assuming your comparing the 50mm stator 273, How about including the 40mm stator 273 as well , as its a bit lighter than the 50mm 273.
Would be intriguing to see how the larger diameter compares torque wise to the 205 even though its 40mm ...

To me it looks like Doc is comparing 273 40h to 205 50h.

 

[cal3thousand]

I thought I read somewhere that a couple measurements (including phase resistance) is all that is needed to get the motors on the Ebikes.ca Simulator. How about we get Vito to do some those measurements and ask Justin to put this motor up?

 

[Doctorbass]

Vito already provided the info for the 205.

I asked hem to send me these info fo rthe 273 and he did. He sent me a link to vide showing him mkinh phase to phase resistance measurement. I have posted the results on the top post.

Doc

 

[John in CR]

I was running one of their earliest versions of the 273 back in 2011 and 2012, a 1.5 turn 50x273 with a Kv of just over 18. Be careful of what controller you use, because it will eat your Russian controllers as a snack if you lean on the current. I push mine past 30kw peak input at 74V nominal with the limit being the controller, not the motor. It was the motor I originally dubbed Hubmonster...that was until I got my hands on the real deal in mid 2012.

It's not just about the copper. Copper determines the current limits and the larger diameter can make more copper fit on motor designs where low cost is the driving factor. ie big hollow motors with as little expensive steel as possible at the perimeter of the stator. The steel and magnets determine the torque potential of the current flowing through the copper. More copper working with more steel and magnets at the greater radius means more torque potential, so you can push bigger loads (more weight and/or bigger diameter wheels), which is why big heavy scooters with DD hubbies are going that route.

Torque is only part of the equation, but if you're short on torque the larger diameter is one solution. It comes with a cost though, and that is high rpm requires more energy just to spin the motor...higher no load current. Just like in the 205 size QS is going to somewhat lower slot and pole count to reduce the waste heat at cruise. When mine got hottest was simply cruising on flat ground at 60mph (1000rpm). That's because it makes well over 500W of heat just to spin the motor even when you're coasting. My ventilation approach easily solves that, but trying to go to high speed gets too wasteful.

That's why I instantly fell in love and moved the name to my next motor. The 273 motor had more torque than I could put to use, but the far lower slot and pole count of the high efficiency 6 phase now called HubMonster, with better materials and design, makes less than 400W of heat to spin at 2000 rpm, and only 133W at 1000rpm ! It has roughly the same Kv, so same torque per amp, and overall phase-to-phase resistance of 0.016 ohm, so same low heat in the copper you're looking at. Sure it's torque potential is probably lower with a lower point of saturation, but it's still more than I can safely use without getting close to saturation, but opening the door for over 100mph speeds and far greater efficiency at highway cruising speeds is more useful to me, especially while I'm still legal as a bicycle.

With a 273, I'd suggest a 24fet with irfp4468 or 4568 controller at a minimum, though the 36 fet is more recommended. My fan blown 36fet with 4110's was tortured within an inch of it's life every time I twisted the throttle. If you can tune a big Sevcon, that's an option too.

How can eastern Canada be advanced enough to make carbon fiber ebikes, but still be 4 years behind in terms of hubmotors? :lol: I guess you got complacent after leading the pack with X5's when chinese controllers were first getting pushed to 100A with 4110's. I got an X5 way back when and used it a few times before parking it. I used my 273 for longer, but it's been parked and unused for 4 years, and will eventually go a cargo bike when I replace my first scooter hubbied grocery getter built in 2008.

 

[ridethelightning]

subscribe

 

[liveforphysics]

The unit Km defines the amount of heat produced in the windings to make a given amount of torque.

It only takes motor kV/kT and winding resistance to calculate it.

 

[John in CR]

They just notified me that they are coming out with a 273 x 80 motor.

 

[liveforphysics]

They just notified me that they are coming out with a 273 x 80 motor.

I may have to get one of those.

 

[markz]

Very informative thread.
I too have subscribed.
These QS motors have been catching my eye a lot lately.
When I check out the price, it seems a little high for my liking.
I'd jump on them if they were a couple hundred bucks cheaper.
I need to look into the hub size difference between the QS motors and my MXUS 3KW V2 motor.

http://www.aliexpress.com/store/product/273-Rated-8000W-8000W-Spoke-Hub-Motor-Dual-Double-Stator-Hub-Motor-For-Electric-Scooter-Bike/1389549_32304102934.html

 

[Ohbse]

Very informative thread.
I too have subscribed.
These QS motors have been catching my eye a lot lately.
When I check out the price, it seems a little high for my liking.
I'd jump on them if they were a couple hundred bucks cheaper.
I need to look into the hub size difference between the QS motors and my MXUS 3KW V2 motor.

lol, what? You'd buy them if they were $100 instead of $300? You don't say?

These are substantially cheaper, substantially more powerful and better put together than the Cromotors were. They're incrementally more expensive than the MXUS. You could have found the dimension differences quicker than typing this post!

 

[markz]

From what I saw, arent they around $750?
So $500 then yeah I'd buy one.

Their 8k+8k dual motor is only $1900.

 

[Ohbse]

From what I saw, arent they around $750?
So $500 then yeah I'd buy one.

Their 8k+8k dual motor is only $1900.

Group buy here had bare motors for $325 USD.

 

[liveforphysics]

From what I saw, arent they around $750?
So $500 then yeah I'd buy one.

Their 8k+8k dual motor is only $1900.

If the dual stator is made with 205mm not 273mm, then it's a bunch more motor width and bulk for less performance than the 80mm x 273mm.

 

[naujasacc1]

I have calculated the copper amount between the 205 24x5 and the 273 65x3.
Unless i am wrong, these calculations should give a greast comparaison between the 205 and the 273 max power.

...

The ratio of copper of the 273 is (2.7/1.8) = 1.5 times higher than the 205.



Doc

I'm wrong or you just compare different winding hubs (3-T and 5T) with complete different power?