I never made any claims about power.serious_sam said:Power.
In fact, I've explained higher kV at equal torque = more power.
I never made any claims about power.serious_sam said:Power.
Motor winding is not independent of supply voltage and current. It is the thing that determines the relationship between the two.fatty said:This is nonsensical. Motor winding is independent of supply voltage and current. As explained above, rewinding only exchanges kV for kT.BobBob said:To be clear, you are not rewinding the motor to be more "powerful" unless you achieve more copper density but you are changing the amount of voltage and current to suit your power supply
This is where the simulator might help you, the power curve is different - the bit in the middle not the bit at either endfatty said:Read my post again -- I address both these points. You continue confusing two different procedures/mechanisms:BobBob said:If you want more current you need thicker wire, not thinner wire, you need to go to a 3T from a 4T or 5T.
Gotta go, will re-edit later but you've got your calcs the wrong way round.
Rewinding for higher kT = lower kV, requires more turns, and possibly thinner wire with side effect of higher electrical losses -- relevant only at maximum motor torque (not maximum controller current)
Rewinding for higher kV = lower kT, requires less turns, can possibly use thicker wire with side effect of lower electrical losses -- relevant only at maximum motor torque (not maximum controller current)
1. He didn't burn out his old windingsfatty said:Distinct from
Rewiring with thicker wires because you burned out your old windings with too much current in a current/temperature-limited (not flux-limited) motor design. Thicker wires fit less turns, with side effect of reducing kT, thus requiring more current for the same (previous) torque, thus requiring much thicker wires to increase current capacity to result in net torque increase. Much thicker wires decrease electrical fill factor.
I'm using Grin simulations and simple examples to illustrate a fundamental of motors.fatty said:Please take a second to re-read through this carefully, so we don't continue to talk past each other. You are overgeneralizing a rare corner case (rewiring) and thus missing the big (motor constant) picture.
Exactly :thumb:fatty said:markz said:https://youtu.be/c96n0Ma2rLY?t=8174
Here's your original - you have the 3T motor running at half throttle but are trying to say that the 6T one at full throttle is faster to make them look the same but they're not.fatty said:markz said:https://ebikes.ca/tools/simulator.html?motor=MX4506&batt=B7208_DT&cont=cust_21_42_0.035_V&hp=50&cont_b=cust_40.5_81_0.035_V&motor_b=MX4503&batt_b=cust_45_0.1_8&hp_b=50&bopen=true&throt_b=92&throt=100&grade_b=0&autothrot=true&autothrot_b=true
**********Range is different because the batteries are different total Wh.
Exactly :thumb:
Here is a customized chart with the OP's fatbike and battery pack.
It's just not clear why. Perhaps for efficiency at a target speed but ignoring power in mid range.fatty said:This is why I always recommend selecting the lowest kV suitable to reach desired maximum speed:
Yeah but we don't want to use the same current, we have 350A available and youve limited it to 40 A LMAOfatty said:lower kV = higher kT
= lower current for same torque = lower electrical losses = higher efficiency (as seen in simulator above)
AND
= higher torque from same current
fatty said:I never made any claims about power.serious_sam said:Power.
In fact, I've explained higher kV at equal torque = more power.
Your answer was incorrect, the key word is "effectively"fatty said:No, as was correctly posted above, you can only trade speed for torque.EpicShelter said:If I'm not mistaken, I should be able to rewind the hub motor to draw more current at 72V effectively making it more powerful (increasing its wattage).
Does anyone have any resources on how to rewind a motor for increased current draw?
He's blown his controller and has a 25Kw capable battery at 72V so 350A available apparentlyneptronix said:You want more torque, why not set the controller for higher amps? what is your current maximum amperage?
John in CR said:You can't rewind a motor to make it able to make more torque at any voltage. A rewind accomplishes nothing that you can't accomplish by changing the voltage and current, unless you are able to fit more total copper around the stator teeth than the factory.
If you want better performance from the same motor, the best way to accomplish that is increasing voltage and decreasing wheel diameter.
If you never admit when you've put your foot in your mouth (and you never do), you'll never get rid of that bad breath.fatty said:I never made any claims about power.serious_sam said:Power.
I think we disagree enough not to add your lack of reading comprehension to the list:serious_sam said:If you never admit when you've put your foot in your mouth (and you never do), you'll never get rid of that bad breath.
And your breath stinks bad.
fatty said:Again, I'm not disputing that higher kV = more power at fixed maximum motor torque (obviously, power = torque * rpm). But nobody asking such beginner questions is holding their motor at the ragged edge of burning up.
But it was you that were wrong on many of the points you made, specifically the one that Serious_Sam picked you up on - power.fatty said:I think we disagree enough not to add your lack of reading comprehension to the list:serious_sam said:If you never admit when you've put your foot in your mouth (and you never do), you'll never get rid of that bad breath.
And your breath stinks bad.
1. yes that is exactly what you started by disputing and got it wrong.fatty said:Again, I'm not disputing that higher kV = more power at fixed maximum motor torque (obviously, power = torque * rpm). But nobody asking such beginner questions is holding their motor at the ragged edge of burning up.
fatty said:Rewinding a motor for more torque (higher kT) in the direct, textbook meaning of "rewind" is simply increasing turn count to trade kV for kT.
fatty said:Rewinding for higher kT = lower kV, requires more turns, and possibly thinner wire with side effect of higher electrical losses
I have you on ignore but keep getting repetitive notifications that I'm wrong "in several ways", without explaining (or indeed, understanding) why.BobBob said:[repetitive]
This is precisely my point. He's not limited by maximum motor current/temperature, but rather some lower controller current limit. If not limited by ultimate motor current/temperature, what determines motor torque? kT, right? Higher kT = more torque, right?BobBob said:4. He's planning on putting 2-3 Kw through a 1.5 Kw motor. How is this not "holding their motor at the ragged edge of burning up", thus you appear to be incorrect in this point as well, at least from my reading of the question.
Thus it appears that yes, the OP was asking whether he could get his motor to 3 KW by using thicker windings
Actually, this conversation is probably pointless. If you keep arguing this point without understanding it, you're beyond reason:BobBob said:For your subsequent answers you have confused increased windings with increased KT - you got the relationship the wrong way round which may be causing your confusion - suggest re-reading your own posts:
fatty said:Rewinding a motor for more torque (higher kT) in the direct, textbook meaning of "rewind" is simply increasing turn count to trade kV for kT.
Turn Count
The more turns a motor has, the slower it will spin. Turn count is how many times the wire is wound around the tooth of a stator. It is inversely proportional to the Kv of the motor. For instance, a 3210 4T has a Kv of 339 RPM/V. From this, it can be determined that the Kv of a 3210 8T is 165 RPM/V (339 RPM/V * 4T / 8T = 165 RPM/V). Further, the turn count is also directly proportional to the Kt of the motor. Using the same example, a 3210 4T has a Kt of 4 Inch*Ounce/Amp, which means the 3210 8T has a Kt of 8 Inch*Ounce/Amp.
There is an common misconception that increasing the turn count is the same as gearing down. It is true that by doubling the turn count while maintaining the same input voltage and current yields half the RPM and double the torque, which is the same result as using a 2:1 gear ratio. However, spinning the motor at half the RPM will also half the maximum output power of the motor. This is because the maximum torque of all motors of a specific motor size (eg. 3210) is the same and unaffected by turn count (the reason they're all the same is because there is the same amount of copper loss).
For example, the 3210 4T has a Kv of 339 RPM/V. We have a 50V power supply to use and would expect to get about 17,000 RPM (339 x 50 = 16,950). However, 17,000 RPM is too fast for our application. We want to run our at half that speed, 8,500 RPM. To achieve this, we have 3 options: we can use a power supply of half the voltage (25V), we can apply a 2:1 gear reduction, or we can use a 3210 8T. We opt for the 3210 8T to avoid having to buy a new power supply and to avoid having to add a reduction system, but after looking at the application specs, we realize that we need 500 Inch*Ounce of torque for the product to work correctly. The 3210 series, however, can only supply 375 Inch*Ounces (any more and the excessive copper loss would cause the motor to overheat). The only option that will fit our needs is to use a 2:1 reduction on the 3210 4T. By doing so, we've achieved our desired RPM and also can afford a bit of overhead in torque (the reduction allows us to have a maximum torque of 750 Inch*Ounces).
It is much more expensive with square wire and i think it takes a lot more time to wind it. the thin wires can probably just be wrapped around easily vs the thick wire that needs to be formed, radius by radius, turn by turn
The 6x10 winding won't really have any more torque than the 7x9 or 9x7 windings. You'll only get marginally more torque off the line and at a stall because the controller and phase lead losses will be somewhat less, but the effect is going to be pretty small, and can be negated with the faster winds by using heavy 10 or 12 AWG phase wire between your controller and the motor. As soon as you reach any appreciable speeds, then the slow 6x10 winding would have LESS torque than the faster windings for a given controller/battery combo.
The myth that more turns = more torque is deeply pervasive in this industry. I blame some well intended but ill-informed Crystalyte salesmen in the early 2000's for entrenching the entire ebike community with this falsehood, and it's forever an uphill battle to set the record straight.
Justin
Happy enough with motor constansts but the reason you keep getting this wrong it you rely on simple one dimeinsional retaionships too much rather than looking at the interaction between motor, controller and batteryfatty said:Read my post again and learn motor constants.
You have no idea what you're talking about.
If I have repeated myself several times and yet you still don't understand the difference between thick wire and thin wire it is becomming increaasingly difficult to explain to you.fatty said:I have you on ignore but keep getting repetitive notifications that I'm wrong "in several ways", without explaining (or indeed, understanding) why.BobBob said:[repetitive yet stilll not getting through ]
I do understand your confusion. You tend to try to optimise for efficiency by aiming for 85% of unloaded speed for a target speed.fatty said:I'll try one last time. Read this carefully and think about it, and you might actually learn something. If you don't understand it, ask a specific question where you're getting lost. Isn't the chance to learn something worth at least a try?
He doesn't have a controller, that's why your chart was BS, as I explained before with picturesfatty said:This is precisely my point. He's not limited by maximum motor current/temperature, but rather some lower controller current limit.BobBob said:4. He's planning on putting 2-3 Kw through a 1.5 Kw motor. How is this not "holding their motor at the ragged edge of burning up", thus you appear to be incorrect in this point as well, at least from my reading of the question.
Thus it appears that yes, the OP was asking whether he could get his motor to 3 KW by using thicker windings
You got the first bit wrong so this is all waffle, you didn't read the question but also no, at the same voltage, higher kT will result in lower torque due to the lower current (more turns of longer thinner wire)fatty said:If not limited by ultimate motor current/temperature, what determines motor torque? kT, right? Higher kT = more torque, right?
Either, more current or more volts. You haven't got more volts and you're proposing a solution to get fewer amps = failfatty said:And what is power? torque x rpm, right? So what gives more power at the same speed, low kT or high kT?
He doesn't have a controller, he's going to buy one to suffice so that will not be the limiting factorfatty said:Where are you getting confused? Make sure you differentiate between maximum motor current/temperature limited intrinsically by the motor, and operating current/torque as determined by the controller.
I only reply to the stuff you say, I'm pefectly happy if you don't say itfatty said:I'm unsubscribed and turned off notifications,
lolfatty said:so PM if you actually want to learn motor constants.
Yeah, I know how you feelfatty said:Actually, this conversation is probably pointless. If you keep arguing this point without understanding it, you're beyond reason:BobBob said:For your subsequent answers you have confused increased windings with increased KT - you got the relationship the wrong way round which may be causing your confusion - suggest re-reading your own posts:
fatty said:Rewinding a motor for more torque (higher kT) in the direct, textbook meaning of "rewind" is simply increasing turn count to trade kV for kT.
Yeah, you're right, that bit was right, the next bit was the wrong way roundfatty said:I don't have the motor constant relationship "the wrong way round". Trade means to give up one thing for another.
As you quoted me above: Increase turn count = decrease kV = increase kT
lol - was this all a wind up? if so, good onefatty said:
lolTurn Count
The more turns a motor has, the slower it will spin.
Yup 2S is double 1S etcfatty said:Turn Count
Turn count is how many times the wire is wound around the tooth of a stator. It is inversely proportional to the Kv of the motor. For instance, a 3210 4T has a Kv of 339 RPM/V. From this, it can be determined that the Kv of a 3210 8T is 165 RPM/V (339 RPM/V * 4T / 8T = 165 RPM/V). Further, the turn count is also directly proportional to the Kt of the motor. Using the same example, a 3210 4T has a Kt of 4 Inch*Ounce/Amp, which means the 3210 8T has a Kt of 8 Inch*Ounce/Amp.
V=IRfatty said:Turn Count
There is an common misconception that increasing the turn count is the same as gearing down. It is true that by doubling the turn count while maintaining the same input voltage and current yields half the RPM and double the torque,
No, the slower spinning motor will have higher copper losses and so will be less efficientfatty said:Turn Count
which is the same result as using a 2:1 gear ratio.
it's also less efficient at the lower speed so a little worse than half the powerfatty said:Turn Count
However, spinning the motor at half the RPM will also half the maximum output power of the motor. This is because the maximum torque of all motors of a specific motor size (eg. 3210) is the same and unaffected by turn count (the reason they're all the same is because there is the same amount of copper loss).
So the example application starting point is at no load? That's daftfatty said:Turn Count
For example, the 3210 4T has a Kv of 339 RPM/V. We have a 50V power supply to use and would expect to get about 17,000 RPM (339 x 50 = 16,950). However, 17,000 RPM is too fast for our application.
LMAO, not only will it not spin at the unloaded speed when loaded but it won't spin at allfatty said:Turn Count
We want to run our at half that speed, 8,500 RPM. To achieve this, we have 3 options: we can use a power supply of half the voltage (25V), we can apply a 2:1 gear reduction, or we can use a 3210 8T. We opt for the 3210 8T to avoid having to buy a new power supply and to avoid having to add a reduction system, but after looking at the application specs, we realize that we need 500 Inch*Ounce of torque for the product to work correctly.
That's great, in this example of how to use motor turns we will show you how you use a gearbox instead and the motor turns won't help.fatty said:Turn Count
The 3210 series, however, can only supply 375 Inch*Ounces (any more and the excessive copper loss would cause the motor to overheat). The only option that will fit our needs is to use a 2:1 reduction on the 3210 4T. By doing so, we've achieved our desired RPM and also can afford a bit of overhead in torque (the reduction allows us to have a maximum torque of 750 Inch*Ounces).
Nooooooo - don't do it, well, I mean, ok, go for it, if you're even more brave than a simple re-wind lolmarkz said:Don't forget about COPPER FILL.
There was a post on using squared windings, I should try and find it after this zoom mtg I am on.
Wasnt long to find something.
https://endless-sphere.com/forums/viewtopic.php?f=30&t=103212&p=1541928&hilit=square+winding#p1541928
https://endless-sphere.com/forums/viewtopic.php?f=30&t=103212&p=1541928&hilit=square+winding#p1547731
It is much more expensive with square wire and i think it takes a lot more time to wind it. the thin wires can probably just be wrapped around easily vs the thick wire that needs to be formed, radius by radius, turn by turn
Yeah, wow, I was expecting a "whoops, my bad"markz said:Ah yes, dont forget the wire gauge used
https://endless-sphere.com/forums/viewtopic.php?f=2&t=14482&p=218275&hilit=winding#p218275
The 6x10 winding won't really have any more torque than the 7x9 or 9x7 windings. You'll only get marginally more torque off the line and at a stall because the controller and phase lead losses will be somewhat less, but the effect is going to be pretty small, and can be negated with the faster winds by using heavy 10 or 12 AWG phase wire between your controller and the motor. As soon as you reach any appreciable speeds, then the slow 6x10 winding would have LESS torque than the faster windings for a given controller/battery combo.
The myth that more turns = more torque is deeply pervasive in this industry.
Always sanity check with a Grin simmarkz said:I blame some well intended but ill-informed Crystalyte salesmen in the early 2000's for entrenching the entire ebike community with this falsehood, and it's forever an uphill battle to set the record straight.
Justin
A bit on copper fill, but its all within the Big Myth Thread
https://endless-sphere.com/forums/viewtopic.php?f=2&t=64907&p=984783&hilit=myth#p984783
https://endless-sphere.com/forums/viewtopic.php?f=2&t=24593&p=381600&hilit=myth#p381600
Read on
https://endless-sphere.com/forums/search.php?keywords=myth&terms=all&author=justin_le&sc=1&sf=all&sr=posts&sk=t&sd=d&st=0&ch=300&t=0&submit=Search
I have to admit I had no idea this was contentious, I'm new to this ebike business.markz said:https://endless-sphere.com/forums/viewtopic.php?f=2&t=64907&p=984783&hilit=myth#p984783