Does a 6T only handle half the watts of a 3T?

[DogDipstick]

I have a friend. he is telling me that if you have two identical motors.. but different turn counts... The higher turn count , a 6T, ( lower RPM @ V) will only handle " half the wattage" of a 3T or similar.

I dont think this is true, so I figured i would ask others. I am going so far to say I know its not true.. but I figured i would ask if there is any truth in this statement.


Friend says:

(SIC)
yeah turn count does make a huge difference though. Literally a 6T can only handle half the watts of a 3T. So if you have people posting QS205 50H can handle 20,000 or 25,000 watts (which it can in certain circumstances) and some noob goes and buys a 6T motor and runs it at 25,000 watts up a hill or without a temp sensor, that fvcker is gonna melt. Poor guy. Lol.

( END QUOTE SIC)


So who is right here?
probally wont believe what I say.. but he might hear what some other(s) ( expert) says.

Thanks. Jp.

Now.... some of yall know who I work for, and why I might know a little here or there... but.. when it comes to these hubbies...


..... Hills. Reaching loaded RPM. Bogging vs power. ya know. Lol. IDKY this kiddo thinks this.. maybe he hasnt datalogged enough QS205 motors under high power. I have not seen much difference in the current data or temperature data I store.

 

[bengxe]

Your friend's right. For the same total copper fill, the 3t will have twice as much in parallel.

 

[DogDipstick]

Your friend's right. For the same total copper fill, the 3t will have twice as much in parallel.

I dont think this is true. I dont think he is right... and what effect would " twice as much in parralel" have to do the millihenery inductance ( you should know this? explain it to me like Im five pls if you can...... ) ?

How does that affect the power handling ( and where do the magnets field strength come into play? )

could you explain more? I see you are new here... 15 posts total in two years but you might have some credential and knowhow I dont have.

how can you exemplify? I do not think this is true, i might be wrong. IDK. I know the names of a few real experts here.. and you might be one, but not the one I was looking for.. but you have credential in the power engineering field? Where does your knowledge come from.

can you tell me more rather a one sentence reply? Greatly appreciate it.

 

[bengxe]

I have no credentials you'd be interested in, but twice as much copper = half the resistance = half the heat. You're hinting at some kind of expertise, so why don't you share.

 

[ebike4healthandfitness]

Power potential is exactly the same but the 6T gets there at twice the voltage and half the amps.

 

[Chalo]

If the motor can withstand higher RPM, then the low turn count motor can be turned faster, but still has the same maximum torque. Each motor architecture regardless of turn count makes the same heat to produce the same torque. So the motor that makes the same torque (max heat rejection) at higher RPM can make more power.

 

[Portugaline]

Hello sir,

I don't know if it would be exactly half, but yes will make a big difference
- 6t will have copper phase windings twice the length of the 3T motor
- 6t will have less strands per phase than the 3t motor.

The info bellow was provided by QS motors, maybe it will help out.

Phase amps recommendations and info​

strand cross section – 0,2mm²

Phase cross section inside motor
6T 20x0,2= 4 mm²
5T 24×0,2= 4,8 mm²
4T 30×0.2= 6.0 mm²

“For QS 3000W 205 50H V3 Spoke Hub Motor, 24X5T Winding.
Phase current, we suggest to set 200A (10s), 220-240A (1-2s).
For battery current, it could be 150A (72V).
For other winding motor, we suggest to set max phase current 40 Time of Wire cross-sectional area (10s).
E.g. 24X5T winding, the wire cross-sectional area is 24X0.204=4.896mm²
Peak Phase Current 4.896*40=195.84A.”

 

[Portugaline]

This doesn't mean the 6T will not outperform the 3T in the real world!

The 6T will need much less phase amps to get to full speed and will get there faster.

It all depends on the application, if you try to simulate the 2 motors in ebike.ca hub motor simulator probably the 6T will have a better temperature.

 

[scianiac]

Yes the 6T can only take half the amps assuming the same total copper fill but at half the amps it will generate the same magnetic field strength as the 3T because there is twice the numbers of turns. You just need more voltage to do it, lots more when you start having to fight the back EMF. So basically you put the same power in and get the same out in an ideal world you just have to put more amps and less voltage or more voltage and less amps. That is an oversimplification just to prove the power of a 6T is not half of course, in the real world there are pros and cons to both and one will be able to output a bit more power than the other depending on the circumstances.

 

[gromike]

It's just Ohm's "law", although you need to calculate the counter emf to figure out your amp draw. I don't know how.

 

[Chalo]

Yes, if low turn count were an absolute advantage, all motors would be 1T. There is always an advantage in matching available power, load, speed, efficiency, and equipment limitations . I generally use high turn count motors for that exact reason.

 

[DogDipstick]

It's just Ohm's "law", although you need to calculate the counter emf to figure out your amp draw. I don't know how.

Ohms law depends on the voltage? The current too? Correct? V=IR? That?

How does this apply to the bucked voltage a phase line winding with a turn count .. sees? Its kW1 + kW2 = kWtotal and its Ph1 to GND ( or ph2) kW = W1 and kW2 = ph3 to GND ( or ph2) and they add for kW (total in the motor)?

something like that?

counter EMF yes I would suppose that feeds into the eq. too.

 

[DogDipstick]

If the motor can withstand higher RPM, then the low turn count motor can be turned faster, but still has the same maximum torque. Each motor architecture regardless of turn count makes the same heat to produce the same torque. So the motor that makes the same torque (max heat rejection) at higher RPM can make more power.



Yes, if low turn count were an absolute advantage, all motors would be 1T. There is always an advantage in matching available power, load, speed, efficiency, and equipment limitations . I generally use high turn count motors for that exact reason.

This right here makes me REALLy understand, Chalo! Thankyou for the education. you are an absolute goldmine in info sometimes. Key understanding of the word " overheat" when it comes to a motor... ( capabilities)... hence the physical limit to the application specific.

yeah I asked about ' power " handling, and some are hung up on thinking both motors have to be the same V.. running on the same bike? or something.. No.. I did not ask about that... Or about the cross sections or copper fill.. Just a simple... Power. Tork and rads per second squared around a diameter I can understand. Rpms matter here. yes. tuned loading of a winding and why they would not just " have all motors be 1T windings"... yet its the tork that is taken and resultant heat.

I didn't say both motors have to be on the same voltage... I didnt say the same current, or even the same diameter prop, wheel, or wing... I didnt say anything about all of that and you put the simple answer out there... Just the power consumed vs the power output... and how much different each would be compared.

 

[DogDipstick]

Yes the 6T can only take half the amps assuming the same total copper fill but at half the amps it will generate the same magnetic field strength as the 3T because there is twice the numbers of turns. You just need more voltage to do it, lots more when you start having to fight the back EMF. So basically you put the same power in and get the same out in an ideal world you just have to put more amps and less voltage or more voltage and less amps. That is an oversimplification just to prove the power of a 6T is not half of course, in the real world there are pros and cons to both and one will be able to output a bit more power than the other depending on the circumstances.

Thankyou for this detailed reply: yes this is a school of thought I follow: The application of the power to the loading... can be facilitated in many ways, to take advantage of the maximum effective efficiency. Hence the usefulness of different voltages, wheel diameters, and RPM/V (kV) numbers. For the tork per amp to make the magnetic flux necessary to produce the motion pole to pole.


So there are certainly differences but the end product is the magnetic flux generations. Not 50% or greater than, difference, is a consensus I am accepting, but a 5-10% difference in outputs for the different turn counts... On the same loading.

 

[DogDipstick]

So do wanna say thanks yall.

I have gotten alot of replies over at Facebook ES forum... . too. Here are some of them provided by my friends over there...

MarcOliver wrote:
Half the amps, roughly yes so if same voltage then half the power. Talking about peak power only. Continuous is the opposite, the high turn count can handle a little bit more because it produces more torque with less amps.

Sam says:

No. Not half. The motor simulator on ebikes.ca can confirm what i am about to say. It all comes down to copper density (ignoring everything else).
So for example if you weigh a 3T, 4T , 5T and 6T mxus 45mm with identical magnets and stators, the heavier will be slightly more power dense because m ore copper makes more flux. With only certain strand and turn counts possible each of the different variants have slightly different weights due to different amounts of copper fitting inside.
From memory for this specific example the 4T motor variant was about 5 percent more power dense due to having more copper.
But thats not 50 percent.

Ray the admin over at EMBuilds writes:

Yes. That's not true at all ..
So here's Ray's2Cents . And it's just my opinion..
And I do realise that pretty much everyone sees things differently and has their own opinions..
And more that open for a debate..
The wattage stays the same no matter what , especially if we have the same controller..
if it's the same copper fill and identical motor phase cables cross section and we can upgrade the controller then it's possible to up the wattage but it should always be proportional to the peak power with battery Amp's..
Do in essence the motor RPM and torque changes , everything else stats the same .
But efficiency might change due to eddy currents at higher RPM
I believe he's mixing up motor phase Amp's with battery Amp's and after doing his calculations he ends up with these conclusions..
Motor phase Amp's should never ever be used to calculate raw power output of the motor power , unless if we can measure the voltage and Amp's at that given moment.
Motor phase Amp's are instantenious - very short when compared to peak or even continuous power output which is battery Amp's..
And most likely he doesn't know that the voltage at 1RPM from the controller can fall below 30% nominal .
And sometimes it might even go as low as 50% below the nominal..
That's if the controller can deliver , let's say 3X phase Amp's when compared to battery Amp's .



Bryce writes:

Lower windings (higher kV) will run cooler, but I don't think twice as cool. Think it can really depend on riding conditions and phase amp requirements. Controller will need to feed significantly more phase amps to a 3T to have it keep up with a 6T through the acceleration range. Changing wheel size can account for it though. For example, a 3T 20" will run much cooler than a 6T 29" despite the top speed being nearly identical. I would also recommend checking out the grin tech simulator to mess around with parameters.

Mike the EEngineer wrote:
This is why "Phase amps" is a gimmick term.. line amps (battery) is what a real engineer would use, 2nd n 3rd calculation would be controller efficiency and motor efficiency...

Daniel wrote:

I would say your friend is largely wrong, the motors can put out roughly the same watts if they have the same amount of copper, the number of turns instead affect how different amp and voltage levels affect the motor.
But as the constant voltage scenario above shows, there is a common real world scenario in which your friend is right.

Pingwing wrote: ( before getting scolded by another electronics hobbyist for not speaking in Polish)...

there is no point in comparing motors with different windings because in the same situation each of them will have different efficiency and power consumption. So example:
3T motor - 6000W
6T motor - 3000W
riding uphill
3T consumes 5000W
6T consumes 2000W
so this comparison doesnt make any sense, because of coarse 6T will handle less current thus power, but it also would be consuming less.

 

[Hummina Shadeeba]

As said regardless of how many turns and the subsequent kv and kt the heat to torque produced will be the same if same amount of copper. Double the speed will produce double the power but will be x2 the hysteresis and ^2 eddy currents and ^2 windage losses

 

[Boosted]

Lots of good info on this thread.

Both motors are capable of producing the same torque, however the 6T will produce the same torque at half the watts/amps. Therefore given a fixed voltage (72v or 84v or whatever) the 6T would only be able to handle half the watts/amps/phase amps, if it were to be consuming the same wattage, it would be producing twice the torque and therefore overheating faster.

Theres 3 reasons I dont like using a fixed statement of how many "maximum watts" a motor is good for.

1. Turn count, as described.

2. Type of riding: Phase amps are what overheat a motor. So riding on pavement/street generally max phase amps are only used for a couple seconds, then at operating speed the amps are much lower, allowing you to use "20KW" or whatever without blowing the motor. But steep hill climbs, deep sand, offroad riding, towing a trailer, using the motor on an electric golf cart, or something, where you are under high load and low RPM, the motor is stuck in a high phase amp environment. This can overheat a motor in a matter of seconds. Using a QS205 as an example you may be able to get away with 20kw or whatever without overheating a motor on the street, but if you took that bike to the sand dunes (deep sand) its possible to blow the motor on the first hill climb. Type of riding makes a big difference. Offroad (dirtbike style) riding is much harder on motors than the pavement.

3. Flux weakening: Without flux weakening, running 72v (84v peak) at 300 amps (20kw+) at full speed the motor would plateau at say 70-150 phase amps (depending on turn count). Not too far in the danger zone. So more or less you could ride on the freeway to work at full speed without worrying as much about a motor overheating. But if you were to run MAX flux weakening instead of plateauing, it could draw 150-300+ phase amps to the motor allowing full speed runs to overheat the motor.

So one guy who rides on the street running 20kw through a 3T QS205 might be fine, but another guy running a 6T in the sand dunes, with max flux weakening would be doomed. You could blow a QS205 at <3000w riding in the sand dunes. For this reason I run temp sensors, problem solved!

 

[Hummina Shadeeba]

however the 6T will produce the same torque at half the watts/amps

The 6t will produce the same torque at half the amps but double the voltage and ultimately be the same wattage

 

[Boosted]

The 6t will produce the same torque at half the amps but double the voltage and ultimately be the same wattage

Absolutely, those are output watts though. I believe the OP was referring to input watts (battery/controller watts).

If the motor is consuming the same wattage (or amps or phase amps) the higher turn will overheat faster.

 

[G8trwood]

All these conversations over the years and the different camps, lol

Seems often apples and oranges get compared, mid drive against hub, different tires sizes, voltages, etc. In that light

say 48v, 20” wheel front hub
5Kv
10Kv

you end up with two very different applications, slower with low power band vs faster with a higher power band. Now you can always just throw power at the 10Kv, it is the way, right?

 

[Hummina Shadeeba]

Absolutely, those are output watts though. I believe the OP was referring to input watts (battery/controller watts).

If the motor is consuming the same wattage (or amps or phase amps) the higher turn will overheat faster.

If it’s double the kv it will be double the amps to produce the same torque but half the resistance and end up same torque to heat. The low turn motor needing double the amps does it with half the voltage and it’s the same wattage.

 

[Portugaline]

Absolutely, those are output watts though. I believe the OP was referring to input watts (battery/controller watts).

If the motor is consuming the same wattage (or amps or phase amps) the higher turn will overheat faster.

Hello,

I think what he is trying to explain is that the motors will have a different voltage at the same speed and this in most cases will make the 6t drop phase amps sooner even at the same wattage because the motor voltage will be higher at the same speed.

 

[Boosted]

If it’s double the kv it will be double the amps to produce the same torque but half the resistance and end up same torque to heat.

I agree with this.

After further review, I concede, in regards to total wattage you are correct a 6T will not overheat quicker than a 3T.

It should be noted however when you are controller limited (as most builds often are) the 6T would overheat sooner. In regards to the OP original post, on a QS205 50H whether you are running what most people run (72450, or even the larger 72680) you could still overheat faster on the 6T in the real world, specifically at low rpm or during flux weakening.

 

[99zip99]

If you can get the motor that does the speed you want with the voltage you want to use. If it is the 6T that hits 30 mph and tops out with the type of controller you're using at 40 amps then keeps that 30 mph and only uses 1/3 watts for 30 miles an hour you won't have to carry the same amount of amp hours to get the distance you want to travel.
The three turn won't saturate to higher speed and because you want to you're going to waste more amps and battery end up going faster mean more expensive battery to keep in line with your 3T
Bigger wires for the 3T to be more effective.
Do you want something for your huge battery electric motorcycle with pedals 3T.
Do you have a heavy family or grocery getter going up a hill for a long period of time for more of a long distance commuter. That's my general recap.
3T with the high amps is more prone to melt melt wires melt solder on the connections.
I have a Mxus 3,000 4t as I melted a 5t first gen Mxus on a hill with speed bumps the stop and Go melted the motor with the hill.

 

[AdR]

At the same phase/motor current, the 6T produce half the of torque as the 3T.
The 6T will be running at 2X the rpm of the 3T while producing that torque
Mechanical power=torque X rpm.
6T: 1/2(torque) X 2(rpm) = 3T: torque X rpm=same mechanical power.