BLDC Design 102

[EbikeMaui]

http://ww1.microchip.com/downloads/en/DeviceDoc/93001A.pdf

 

[TylerDurden]

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."

 

[EbikeMaui]

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."

Now that all depends on how many poles and the wave form as well as how the magnetic flux is routed.
http://www.ee.kth.se/php/modules/publications/reports/2004/IR-EE-EME_2004_006.pdf

 

[eP]

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.

 

[EbikeMaui]

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.

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]

That it is and much harder to make.

Why it is 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.

So show me 5 Kw constant power motor 89% efficient at Power_out=300W for $350.
Is it coreless or not ??

instead of $15,000. per copy for the Csiro motor.

I don't propose buying so pricy copy.
What i propose is start to think for do the similar efficient motor for $350 or maybe even a little less.

So what we need: 5kg N50 magnets and few kg copper wires, bearings and the stainless steel case.

The difference for 75% efficiency and 90% efficiency is 20% of battery pack costs.
So if you use $500 pack for 2 years than you can save $50 a year this way.

 

[EbikeMaui]

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.

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.

This motor is a direct replacement for the Etek (Briggs & Stratton) brushed DC motor. It is an Axial Air Gap permanent magnet motor. This technology is very compact. Highest power to weight ratio of any PM motor technology.

Commutation is accomplished with an internal Hall Cell assembly, connected to the 6-pin external wire harness.

Output Power, Torque and RPM:
Voltage Constant: 70 RPM/VDC. Torque Constant: 1.20" lbs/amp. Max Motor Current: 300 A/1min. Weight: 22 Lbs. Dia. 8". Output: 15HP Max. 6HP Cont. Voltage: 24-48 VDC.

This is a Brushless motor and requires a 3 Phase 8 Pole control to operate the motor

 

[eP]

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.

90% efficiency at what Power_out ??
How much is efficiency at 0.2HP power out ?

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.

Low resistance is not the all we need and want.
We also need low idle current.
So tell us: how much is this current at 500rpm for example ?

Cheers

 

[fechter]

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.

 

[eP]

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.

So tell us what is the eff. at 300W at what torque.
And the same at 150W power out.
600W is a lot of power at flat road.

 

[Lowell]

Why would you run a 2500W motor at 150-300W? 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.

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.

 

[TylerDurden]

Why would you run a 2500W motor at 150-300W? And if you really had to go that slow, you could always pedal.

Methinks we're seekin the "best bang / buck"... a system that covers the widest range of application.

Of course, it might not qualify under legal terms (hence the guys in the desert), but I personally would like to see a bike that can offer efficiency at slow speeds and high speed too.

It does bring us back to Safe's pseudo-debate of hubs v. gears, but with the distinction that we are focusing on motor efficiency with a minimum of gearing (1 or 2 gears).

In-town, 23kph could be as fast as cars average, considering traffic. Four or five hours of that speed could be a helluva a messenger/delivery vehicle.

 

[eP]

Why would you run a 2500W motor at 150-300W?

It is a very good question.

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.

I dont need to pedal at power out = 150W at 10 mph.
Even if i had to pedal at that low speed it is no problem at all for me as i all the time pedaling for now ( i have no e-bike yet ) - over 1600 miles by last 12 months.

I don't want battery pack sized to fuel a multi kW motor as i don't need continous multi kW power.
And i care about efficiency all the time at any speed as i don't want spend to much for batteries and i don't want take to much batteries on board.

For temporary multi kW power the supercapacitors bank is the best option for me i'm sure.
That could work nice for regen also.

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.

300W average power at flat is to much for me.
I want 120-150W at flat, and maybe 500W at low grade slope, so 200-250W is the average power i need for trip.

TylerDurden

Methinks we're seekin the "best bang / buck"... a system that covers the widest range of application.

Yes it's true. It is very important especially in poor countries as my.
The shortest way to e-bikes be popular they should be powerful, efficient and cheap at long term of usage.
The less batteries i need the cheaper my vehicle will be.

 

[Lowell]

A small 500W motor would be very efficient at the power levels you're looking for.

 

[eP]

A small 500W motor would be very efficient at the power levels you're looking for.

A small 500W motor have no enough room for fat (efficient - low resistance) windings.
So such motors have poor efficiency at theirs nominal power out when you need great torque.

It could be enough for climbing at very low speed ( 80% efficiency is enough) if geared enough (high ratio).
For flat driving i want efficiency over 90% (95% max.) so it should be gearless.

Universal powerful motor hub should work well at low and high rpm at great efficiency.
Such type a motor is not a toy, so i dont need cheap motor hub. The same motor you can use at any type of light vehicle or you can sell it, so it is good investment.
This way you can subtract the motor's cost and this way your conversion set is cheap enough to be popular.

If you freaquently use inefficient e-bike you lose a lot of money, so low price (small motor) conversion kit is never cheap as you must spend a lot of money for batteries.
If you want use your e-bike occasionally, so it is different story.

I'm looking for motor (or 2 motors set) for daily driving now.

 

[Toorbough ULL-Zeveigh]

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 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. Argueing about a few percentage points difference in efficiency is just argueing how many angels can dance on the head of a pin.

 

[eP]

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.

Sorry man, but i see you completly didn't understand what we taking about.

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.

You talking simply: bla bla bla ...

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.

 

[Lowell]

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.
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.
I guess the question is whether you want to solve real world problems, or climb volcanos in la-la land.

 

[eP]

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.

Dear Lowell
Dont compare aples and oranges.

Try load 200 kg on your 2 wheel vehicle and tell us what is your average speed and efficiency.

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.

So tell us how many times faster you sleep for savings ? 8)
How many times faster you exercising at gym ?

I'm going do drive my e-bike for pleasure not for time savings or speed records.

I guess the question is whether you want to solve real world problems, or climb volcanos in la-la land.

You don't solve traffic/transport problems by 2 wheel vehicles.
This way you go maybe you add extra work for surgeons. Btw how much charge 1 day at good hospital ?

 

[Lowell]

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?

If you're going to ride for pleasure only, why go electric? That would imply the whole bike is an extra expense. 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...

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]

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?

So all or most cars in Canada are only 1 seat place ?
How do you think: why people (abroad of Canada) driving 4-5 seat autos mostly ?
Or didn't you know that ?

If you're going to ride for pleasure only, why go electric? That would imply the whole bike is an extra expense.

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 ).

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...

Yeah i see the best way is working in Canada at $60 per hour

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

Yours cementary system is very good too i suppose
Churchyards have enough area. We all going to that place at the end, but i see you want to go there a little bit faster (+50 mph ) :lol:

 

[safe]

200 MPH Or Bust
Super Streetbike's Neale Bayly blazes his way into the East Coast Timing Association's exclusive 200-mph club--and takes us along for the ride

By Neale Bayly
Photography: Scott F. Odell

"First gear...second gear...third gear...fourth"--this is my mantra, my song, my sole, slim grasp on reality as I hurtle headlong down the crumbling runway surface at the Maxton airstrip. Like a metronome I mutter the word "fifth" and push the button telling the air shifter to jam home another gear on the big, black 'Busa I'm borrowing for the weekend. As I edge up against 170 mph, I hope to hell I haven't miscounted before I depress the button on the left bar that activates the nitrous-oxide system. I punch the button and an additional 100 horsepower suddenly materializes, noticeably accelerating the bike even at this insane speed. The shift light comes up quicker than I expect, and keeping the throttle pinned, I hit sixth and get back into the giggle gas--again.

Staring through the curved windscreen at 180 mph is a lot like looking down the wrong end of a telescope, which is hell on my nerves. All I can do is follow the white line down the center of the airstrip and force myself to accept that it continues though the rapidly approaching timing lights at the other end. Everything else is a blur, and I try to make myself as small as possible to get under the paint, looking for every possible advantage to get me beyond 200 mph. I twist the throttle hard against the stop and push the nitrous button forcefully, as if the extra pressure will somehow give me more power--and more speed.

At Maxton you break two timing lights approximately 100 yards apart--your average speed between these two lights is considered your official speed. Breaking the first light, I fight the overwhelming urge to shut the throttle and instead keep it pinned until I'm sure I pass the second light. Now comes the hardest part--slowing back down to zero in the too-short runoff area. My heart is pounding. I sit up too soon, and the wall of air almost rips me off the bike. But none of this matters right now--all I care about is this: "Did I go 200?"

What Am I Doing Here?
"Are you effin' crazy?" As a motorcyclist, I'm used to this question, of course, but this time even those inside my close circle of riding buddies expressed concern after I shared my plans to join the East Coast Timing Association's exclusive 200-mph Club. "Have you lost it?" they asked. "You're a street rider--what do you know about land-speed racing?"

I didn't need to know anything, I told them. I'd be operating under the strict supervision of two of the most accomplished names in land-speed motorcycle racing. They'd take care of preparation and instructions--all I had to do was sit in the saddle and twist the go-handle. Even a monkey could do that, right? "Besides, these guys go 200 mph all the time--how hard can it be?" This was my primary line of defense--this and just not thinking about it. But as I drive into Maxton under a cold and gloomy North Carolina-in-October sky and come face to face with the 200-mph 'Busa, I'm not even convincing myself.

The whole funny business started this past summer when I made my maiden voyage to Maxton, investigating tales of 240-mph streetbikes for a story that appeared in the last issue of Super Streetbike. I was introduced to Scott Guthrie, known in land-speed circles as the "Sultan of Speed." With a personal best of 241 mph on a motorcycle at Maxton (and 256 mph in a car at Bonneville) and not one but four 200-plus-mph streetbikes in his garage, Guthrie knows plenty about going fast. It was during this initial meeting that Guthrie came up with the idea for me to come back to Maxton and make an attempt to join the ECTA 200-mph Club, which at the time numbered just 42 members. A brilliant story idea when I was sitting on the sidelines a few months back, but now, as I make the long and lonely drive to Maxton, I'm having my doubts.

...

http://www.superstreetbike.com/features/122_0444_200_mph_club/

A 50 mph crash will hurt, but you will most likely live... 100 mph is probably deadly... 200 mph might rip your limbs from your body... (and without leathers chucks of meat would fly off)

 

[Toorbough ULL-Zeveigh]

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.

Sorry man, but i see you completly didn't understand what we taking about.

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.

You talking simply: bla bla bla ...

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.

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, 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. 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:

 

[eP]

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,

Yeah 110 thousand dollars or 10 dumbtrucks full of bullshit as you writen above.
You forget to mention about platinum resistors for that mistery AC power inverter - 2 kW - $5 per watt.

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.

5kg magnets for the Halbach array must cost next few dumbtrucks full of dumb and full of bullshit like you give us above.

5kg magnets for $50 per gram it is $250 000.
So any dumb could buy your story.

Wires for windings are also prohibitive expensive 1kg of copper windings is another $10 000 or more isn't it ?

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:

I see you are pretty clever jew :lol:
I nie masz sraki zamiast mozgu :lol:

 

[TylerDurden]

I'm getting more intrigued by the thought of dual or multiple outrunner motors:

More power on demand
Less mass
More cooling
Higher efficiencies
Off-the-shelf availability

The more this gets "discussed", the more it seems like one motor trying to do the job that two can do better is a waste of resources.

Yes, we are coming back to eP's earlier proposal: one motor with high efficiency at high-loading, another motor with high efficiency for the flats.

Use one, the other or both...