if you increased the kv and copper fill with a hub then the heating in the motor will be less but the heating in the controller will be more for the same constant speed.
with a 220kv motor and 15t motor pulley I would need a 150T wheel pulley. That’s also not practicable. I could do 12S1P 100kv and 16T/72T with belt.
You think this would give me more range thank 6S2P 50kv DD?
What’s the relation to usable torque?
twice the kv is half the torque per motor amp… if the copper fill stayed the same the motor heat would stay the same at the same constant speed, but since you increased the copper fill the motor heat would decrease for the same constant speed… but since it takes more motor amps for constant speed with higher the controller heat would increase.
I guess drones are the most efficient?
Super high propeller kv speeds. No gear reduction required
So if I doubled the kv but were able to double the amp capabilities of the motor I would have the same torque?
doubling the kv at the same copper fill automatically doubles the amp capabilities of the motor because twice the amps produces the same heat… the resistance is 1/4th… half the winding length and twice the thickness. so for the same heating you get the same torque either way (in the motor - but controller heating is quadrupled with the doubled kv for the same torque).
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in setups, is it usually overheating motors or controllers that’s the bottleneck?
well if you overheat the controller it thermal throttles, but if you overheat the motor it gets an internal short and the wheel locks up while you’re at speed… so in my opinion, overheating the motor is more… dangerous?
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Over-heating a motor Is vague. If it’s a one time high temp ur more likely to lose synch w the esc as the resistance and inductance of the motor changes w heat. You could demagnetize the common magnets too. a breakdown of the winding insulation and a shorting happens only after many hours of sustained heat. First likely will cook out the bearing grease.
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If someone can spin their motors to top speed and see the current draw we can find the iron losses, and if you take the same setup n spin to the same top speed w the belt on maybe that would give a good idea of the drive system loss
I somebody able to answer this question?
if they’re geared to the same top speed with the same voltage the higher kv same size (same copper fill) motor is more efficient. for the same top speed (via gearing) higher voltage is more efficient.
It depends on the motor size and how many poles it has and the stator lamination thickness and what ur doing among other things. Going to a bigger gearing doesn’t always make things more efficient and the faster the motor spins the greater iron losses. Also running high voltage creates wasted pulses in the motor as it’s harder to get a smooth current wave
but this doesn’t become a *edit: significant factor till the kv or voltage is much higher than is being discussed
but these losses are insignificant when the higher voltage motor is geared to the same top speed as the lower voltage motor
No depends on the motor and how many poles and how used ( what current and speed driven)
I’m sorry, I can’t follow both of you.
If someone could like me a motor which can provide more than 20km of range with 20km/h on 12x 50E cells I would be very thankful.
you’ll have a practical limit in terms of gearing reduction so use the highest kv, lowest electrical resistance, largest size motor and highest battery voltage that allows the lowest adequate no load speed and practical gearing ratio for your tire diameter if you care mostly about efficiency.
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@Chricious-- i ran a simulation for you comparing a 50kv (0.32ohm) direct drive vs a 200kv (0.02ohm) motor with 4:1 gear reduction (same battery voltage, same motor current), both sustaining 25mph on a 10% slope…
^notice:
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the same size same copper fill 200kv motor has 1/16th the electrical resistance of the 50kv direct drive motor (200kv has 1/4x fewer turns and 4x greater cross section wire than the 50kv)
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in the bottom left chart, purple line – vehicle thrust is the same for both vehicles
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in the bottom middle chart, green line – ohmic motor heating drops from about 250w total with the 50kv DD to around 16w with the 200kv 4:1 reduction
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in the top left chart, green line – electrical to mechanical efficiency is far higher with the 200kv
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top left chart, blue line – motor current is the same – 20a with both motors
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top middle chart, yellow line – electrical wattage is far lower with the 200kv motor than the 50kv direct drive motor for the same mechanical wattage output (red line, same chart)
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top right chart, yellow line – the 200kv motor torque at the same motor current is 1/4th the torque of the 50kv motor, but the 200kv motor is spinning 4 times faster with 4 times the gear reduction, so you get the same mechanical power to the wheels either way
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bottom right chart, purple line – battery current is less with the 200kv 4:1 reduction than the 50kv direct drive
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graphs
I’m just going to drop this conversation here… discuss