Now that all depends on how many poles and the wave form as well as how the magnetic flux is routed.TylerDurden said:Nice lead Rando, I can actually wrap my head around some of this stuff...
http://ww1.microchip.com/downloads/en/AppNotes/00857a.pdf
Brushless DC Motor Control Made Easy
"...If voltage were to be applied to an ideal motor from an ideal voltage source, it would draw an infinite amount of current and accelerate instantly to the speed dictated by the applied voltage and KV. Of course no motor is ideal, and the start-up current will be limited by the parasitic resistance and inductance of the motor windings, as well as the current capacity of the power source. Two detrimental effects of unlimited start-up current and voltage are excessive torque and excessive current. Excessive torque can cause gears to strip, shaft couplings to slip, and other undesirable mechanical problems. Excessive current can cause driver MOSFETS to blow out and circuitry to burn.
We can minimize the effects of excessive current and torque by limiting the applied voltage at start-up with pulse width modulation (PWM). Pulse width modulation is effective and fairly simple to do. Two things to consider with PWM are, the MOSFET losses due to switching, and the effect that the PWM rate has on the motor. Higher PWM frequencies mean higher switching losses, but too low of a PWM frequency will mean that the current to the motor will be a series of high current pulses instead of the desired average of the voltage waveform. Averaging is easier to attain at lower frequencies if the parasitic motor inductance is relatively high, but high inductance is an undesirable motor characteristic. The ideal frequency is dependent on the characteristics of your motor and power switches. For this application, the PWM frequency will be approximately 10 kHz."
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That it is and much harder to make. If you could stand using a chain this 89% efficient Axial flux disc motor with 5 Kw of constant power can be baught for $350. instead of $15,000. per copy for the Csiro motor.eP said:Lets look at:
[ url = http://www.cip.csiro.au/Machines/papers/DesignOfAnInWheelMotorForASolarPoweredElectricVehicle(IEE).pdf ]Aurora_pdf [/url]
http://www.cip.csiro.au/Machines/pa...MotorForASolarPoweredElectricVehicle(IEE).pdf
[url = http://216.239.59.104/search?q=cache:vxNsjN1L3KYJ:www.cip.csiro.au/Machines/papers/DesignOfAnInWheelMotorForASolarPoweredElectricVehicle(IEE).pdf+Aurora+axial+flux&hl=pl&ct=clnk&cd=9&gl=pl] Aurora HTML[/url]
Coreless pretty efficient motor.
Why it is much harder to make ?????EbikeMaui said:That it is and much harder to make.
So show me 5 Kw constant power motor 89% efficient at Power_out=300W for $350.EbikeMaui said:If you could stand using a chain this 89% efficient Axial flux disc motor with 5 Kw of constant power can be baught for $350.
I don't propose buying so pricy copy.EbikeMaui said:instead of $15,000. per copy for the Csiro motor.
90% efficiency at what Power_out ??EbikeMaui said:What ever.. These are sold at some places for what I said or occasionaly on ebay for $200.
POWER: 24-48 VDC BRUSHLESS MOTOR. NEW ADVANCED BRUSHLESS DESIGN of the DISCONTINUED B&S ETEK motor. Now back in production. 15HP peak, 6HP cont. 90% EFFICIENCY for much longer battery life. BRUSHLESS DESIGN = 0 maintenance.
Low resistance is not the all we need and want.EbikeMaui said:Originaly designed for B&S 4.5 HP continuous outboard boating applications. Brushless Permanent Magnet Syncronous motor otherwise known as PMAC. Input voltage of 30-56 VDC. 100 amps continuous, up to 300 amps for 30 seconds. The phase resistance is very low at 10 milli-ohms, so it is 90% efficient. This motor has a built-in cooling fan set for a CCW direction, but can be run CW with optional fan. Motor weight is 22 pounds.
eP said:So show me 5 Kw constant power motor 89% efficient at Power_out=300W for $350.
Is it coreless or not ??
fechter said:eP said:So show me 5 Kw constant power motor 89% efficient at Power_out=300W for $350.
Is it coreless or not ??
My modified BMC motor comes pretty close (but it's cheaper). I can get about 2.5kw output for as long as my batteries last (not that long).
It is not coreless, but uses good core material and has minimal wasted copper in the ends. It's around 89% eff at 600w.
Lowell said:Why would you run a 2500W motor at 150-300W? And if you really had to go that slow, you could always pedal.
It is a very good question.Lowell said:Why would you run a 2500W motor at 150-300W?
I dont need to pedal at power out = 150W at 10 mph.Lowell said:And if you really had to go that slow, you could always pedal. Plus if your battery pack was sized to fuel a multi kW motor you wouldn't care about a loss of efficiency at very low power levels.
Lowell said:Just to see, I ran the simulator on my setup, and it comes up with 75% efficiency with 300W power out and 23km/h. My battery would give roughly 4.5 hours at this discharge rate... far longer than I care to ride a bike at that speed.
Methinks we're seekin the "best bang / buck"... a system that covers the widest range of application.
Lowell said:A small 500W motor would be very efficient at the power levels you're looking for.
Sorry man, but i see you completly didn't understand what we taking about.Toorbough ULL-Zeveigh said:A BLDC hub motor is not as bad as you think.
In fact a hub motor is about as close as your going to come to a universal motor (IMO) because of it's wide efficiency bandwidth. It has reasonable efficiency over a wide range of rpm.
You talking simply: bla bla bla ...Toorbough ULL-Zeveigh said:You can't have it both ways. Something that's specialized will always work better in its designed bandwidth, but then you can't expect it to have the same efficiency outside of the parameters it was specially designed for. A hub motor is a generalist type of motor, but it's not far off the mark & the penalty in efficiency for that general purpose is rather small.
Toorbough ULL-Zeveigh said:Argueing about a few percentage points difference in efficiency is just argueing how many angels can dance on the head of a pin.
Dear LowellLowell said:A good battery pack is small change compared to the cost of owning cars. Just by purchasing 2 instead of 3 insurance policies this year pays for most of my ebike parts. When you factor in gas, tires (and I go through a lot of tires) and other maintenance, the savings are significant.
Lowell said:Another thing to consider is how much is your time worth? My battery pack might cost me $2/cycle, but I charge out $60/hr at work which means if I even save 2 minutes on my trip, I'm breaking even. In reality the time savings add up to quite a bit more than that.
You don't solve traffic/transport problems by 2 wheel vehicles.Lowell said:I guess the question is whether you want to solve real world problems, or climb volcanos in la-la land.
So all or most cars in Canada are only 1 seat place ?Lowell said:200kg? Plus rider, or including rider? I don't think there's anywhere to put so much weight. I weigh about 80kg... why do you need to carry so much? 2 people on 1 bike?
For longer range, for health (easy high grade climbing ), for pleasure again, for more independence on the road (high power always ready - human power is far less than horse power ).Lowell said:If you're going to ride for pleasure only, why go electric? That would imply the whole bike is an extra expense.
Yeah i see the best way is working in Canada at $60 per hourLowell said:If money is tight, spending $ on putting an electric motor on a bicycle doesn't make much sense. I'd be figuring out ways to make more money...
Lowell said:Two wheel vehicles don't solve traffic problems? That's news to me, because if I'm on my bike, that means one car is parked in the garage. As for hospital stays, I don't know how much they cost per day as Canada has a very good health care system. $54/mo covers 1 person.
http://www.health.gov.bc.ca/msp/infoben/premium.html
eP said:Sorry man, but i see you completly didn't understand what we taking about.Toorbough ULL-Zeveigh said:A BLDC hub motor is not as bad as you think.
In fact a hub motor is about as close as your going to come to a universal motor (IMO) because of it's wide efficiency bandwidth. It has reasonable efficiency over a wide range of rpm.
You talking simply: bla bla bla ...Toorbough ULL-Zeveigh said:You can't have it both ways. Something that's specialized will always work better in its designed bandwidth, but then you can't expect it to have the same efficiency outside of the parameters it was specially designed for. A hub motor is a generalist type of motor, but it's not far off the mark & the penalty in efficiency for that general purpose is rather small.
Toorbough ULL-Zeveigh said:Argueing about a few percentage points difference in efficiency is just argueing how many angels can dance on the head of a pin.
A few percentage points difference in efficiency at nominal power is key difference !!
For example Aurora's efficiency at Power out=1800W is over 97.5% , so at 8 times less rpm and the same current Power out =225W at 82.5% efficiency.
For other BLDC hub (good iron core) 90% efficiency at 1000 rpm (nominal power out) and 53% efficiency at 125 rpm (at 1/8 nominal power out).
So you need put 1.6 times more power in to this well efficient (iron core stator) BLDC hub than to sligtly more efficient coreless hub.
1.6 times is enough difference for me to looking for more efficient motors.
You dont have to care about efficiency as you have a lot of money to waste, or you dont have to use your brain i suppose.
So you have completly no idea what you taking about.
Yeah 110 thousand dollars or 10 dumbtrucks full of bullshit as you writen above.Toorbough ULL-Zeveigh said:Are you aware that the Aurora design has been abandoned for being no longer competative?
Are you aware that the Aurora requires an AC power
inverter that costs 10 thousand dollars,
5kg magnets for the Halbach array must cost next few dumbtrucks full of dumb and full of bullshit like you give us above.Toorbough ULL-Zeveigh said:or a dumptruck full of zloty. Add the cost of Litz wire in the windings & the expensive Halbach winding pattern then that is the price to be paid on the altar of efficiency when you are doing solar racing which is what the Aurora was designed for, not for leisure riding.
Toorbough ULL-Zeveigh said:If you're talking about money efficiency which you claim you are, that kind of scratch will buy a whole lot of batteries for a slightly less efficient but whole lot cheaper hub motor.
It is obvious that you don't know what you're talking about.
What's also obvious is that your are a Pedal dupek & masz srake amiast mc'zgu.
Hope this helps. :lol: