200mph what to use AC or DC??

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200mph what to use AC or DC??

Post by Catavolt » Tue, 21 Dec 2010, 17:38

What do you guys think should be used AC or DC?

Time to build the new Catavolt with the aim of 200mph 320kph ish,
We have a new bike frame the aim is to build a custom swing arm and mount a motor or two on the swing arm. eg two 8inch motors.
So the bike revert back to somthing more usefull after the event.
Image
We feel it will take 150kw for 2-3mins to reach this speed.

2010 Catavolt was 144v DC 8 inch motor it took aprox 40kw to do 110mph
keen to hear any suggestions.

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200mph what to use AC or DC??

Post by acmotor » Tue, 21 Dec 2010, 18:05

What weight of motor are you considering ?
What drive are you planning, chain, belt, direct gear ?
What shaft/sprocket/pulley RPM does that give you at 320kmph ?
Have you a torque profile of the desired drive system for the full 320kmph ?
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200mph what to use AC or DC??

Post by Catavolt » Tue, 21 Dec 2010, 18:28

There is no real weight limmit for the motor two 8inch motors would be around 90kg,or a 160 frame AC alloy would be around the same.

The drive can be belt but I was thinking 520 chain.

320kph at 2-1 is around 6500rpm last year we ran 1.65-1

The approx torque at the wheel needed is 450nm 3200rpm


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200mph what to use AC or DC??

Post by Richo » Tue, 21 Dec 2010, 20:46

A tesla kit Image

Hard to say with off the shelf Industrial motors.
2-3min of peak is uncharted territory.
minimum would be 2 x 5.5kW 4-pole (good ones). [112 frame?!?]
And I would think this would be around the 90kg mark.
1 x 160 alloy frame will be harder to get.

An AC motor usually isn't so much the problem it's the driving it.
Do you have an AC controller planned for such a beast?

And batteries for that matter!
Add 150kg of batteries for around 150kW

That's one heavy monster bike!

So the short answer is NO but the long answer is YES.
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200mph what to use AC or DC??

Post by Johny » Tue, 21 Dec 2010, 20:51

Wavesculptor controller and a very carefully balanced SEW copper rotor 3 phase 132 frame 7.5kW motor running around 12K RPM.
TJ may even be able to provide peak torque figures up to around 6000 RPM.
The motor frame should absorb 3 minutes of mistreatment - probably won't even need a fan as the heat won't make it out in time - just some subtle ducting for airflow.

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200mph what to use AC or DC??

Post by EV2Go » Tue, 21 Dec 2010, 21:24

Completely different approach... What can you fit in that meets your needs?

320kph is pretty damn fast, I have done high 200's and that nearly blew me off the back of the bike.

Anything sitting out in the wind is going to act like a big parachute and steering device, so while it might be great to say I want this controller, or that motor, it comes down to what you can get in the frame that wont hinder the top end speed.

Also who ever rides it is going to have to have massive kahunas if you don't get the weight balance just right. Those kinds of speeds won't tolerate much weight inbalance.

There is a huge difference between 180kph and 320kph, the first 180 will be a walk in the park compared to the next 140.

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200mph what to use AC or DC??

Post by acmotor » Tue, 21 Dec 2010, 21:40

That's along the line of what I was thinking.
Wavesculptor + induction motor.
4 pole 6000RPM 200Hz (2:1 drive) or
2 pole at 12000RPM 200Hz (4:1) for the 320kmph. The latter will be lighter but with higher drive losses.

Motor torque would need to be 225+Nm at the motor for the 6000RPM+ 4 pole or 112+Nm for the 12000PRM 2 pole so 15kW range motor.
Quite doable. The WS controller (presently 150kW ?) would be the limiting factor though could be modified for short term extra !)

Efficiency is a big factor.
Was the 40kW at 110mph was the DC power input to the 8" motor ? Probably off any published data but likely to be 60% or so overall efficiency inc. controller and chain loss so around 50% to the wheel.

Double speed would need 8x power so 40kW x 50% x 8 = 160kW at the wheel.
I can see where your 150kW comes from. But that would be the rear wheel power ? Going DC with present efficiencies would require a DC input power of 300++kW ? Big battery demand ! Its been done but with almost unobtainium batteries.

Targetting a motor/controller/drive efficiency of 80% would reduce this DC power requirement by maybe 100kW. Not to be scoffed at ! The AC drive will help in the efficiency game.

Using dual motors may not help with the economy and efficiency of scale.

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200mph what to use AC or DC??

Post by Catavolt » Wed, 22 Dec 2010, 01:11

The problem with the Wavesculptor controller is delivery before March might be dificult Image .
So might need to use cut down industrial controller for AC
What about a drip proof open winding AC motor frame 22kw 4p 160 frame? Teco still sell them.

For batteries we can fit 300-400 headway/Lifetech LifePo4 style power cells in the bike. 8ah 10-15C each.

Somthing like this if we go DC two by 80kw 300vdc motors.
Image

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200mph what to use AC or DC??

Post by acmotor » Wed, 22 Dec 2010, 04:43

22kW 4 pole would deliver 12 x 22kW (264kW) at more than 80% efficiency reliably at 6000RPM but offering a VFD up to it in a bike may be a challenge.
You'd need a 180kW VFD with 160% overload rating.
A re-housed VFD could be the answer.
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200mph what to use AC or DC??

Post by Electrocycle » Wed, 22 Dec 2010, 05:35

make the massive swingarm a heatsink to mount the IGBTs on :)
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200mph what to use AC or DC??

Post by Johny » Wed, 22 Dec 2010, 14:40

Electrocycle wrote: make the massive swingarm a heatsink to mount the IGBTs on :)
Nah - use an industrial sized AC controller and mount the wheels and motor on it.

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200mph what to use AC or DC??

Post by Electrocycle » Wed, 22 Dec 2010, 14:44

hehe, I wonder what the chassis rigidity is like on your average industrial VFD?
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200mph what to use AC or DC??

Post by Catavolt » Wed, 22 Dec 2010, 16:39


Another option could be 4 x double brushless Mars motors run at 144v with two Kelly controllers.
http://www.marselectricllc.com/me0913.html

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200mph what to use AC or DC??

Post by EV2Go » Wed, 22 Dec 2010, 16:43

Driving both sides of the rear wheel?

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200mph what to use AC or DC??

Post by acmotor » Wed, 22 Dec 2010, 17:25

Possible combination :-
Remember the focus is the top speed, so target max power at max speed.

15kW nom.(50Hz) 92% eff. <<100kg induction motor
4 pole
running at 200Hz
6000RPM motor
(180kW before pullout at 6000RPM at 80+% eff.)

3200RPM wheel
(1.875:1 subject to sprocket options)
98 x 3 = 294 Nm motor (conservative Tmax before pullout)
551 x .95 = 523Nm at wheel (450 required)
chain eff. <95% at those revs

VFD selection depends on battery voltage.
If motor wound for 100V at 50Hz (2V/Hz) then 400VAC required at 200Hz.
This would require some 560VDC (under load) at 180kW/.8 (eff.) = 400A
Or wind motor for 50V would require some 280VDC under load (at twice the current, 800A)
The VFD would be a 200VAC say 120kW with 160% overload or 400VAC with similar power. The 200VAC version will of course be twice the current and larger than the 400VAC version. Or use a 400VAC version of 240kW nom. for either system.

edit: or just fit a tesla emotor ! but where's the challenge ?

In a way, that is the easy bit. Now comes the battery pack.
(the higher voltage is more efficient due to I2R/weight and IGBT switching losses, however that aside)
560VDC under load at 400A
or
280VDC under load at 800A
Say allow for 6 minutes at these loads, so 40 and 80Ah
mmmm, looking big. Maybe 4 minutes ? Image

Any suggestions on battery pack options ?

edit: some units for clarity
Last edited by acmotor on Wed, 22 Dec 2010, 08:22, edited 1 time in total.
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200mph what to use AC or DC??

Post by Catavolt » Wed, 22 Dec 2010, 20:01

looks like its possible with AC induction if a controller can be found.

The power wont be a problem with the batteries we can fit 300-400 headway/Lifetech LifePo4 style power cells in the bike and possibly more on the swing arm maybe a couple in the riders pocketImage. 8-10ah 10-15C each.

The track has a 3 mile(4.8km) run up and 3 miles of timing gates.
The speed recorded is an average speed over a flying mile (1.609km).
Image

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200mph what to use AC or DC??

Post by Richo » Wed, 22 Dec 2010, 20:23

acmotor wrote: ...or just fit a tesla emotor ! but where's the challenge ?

The challenge is actually buying one!
acmotor wrote:Any suggestions on battery pack options ?


The bike will need at least 500 Headway cells for that power.
Even 300W/cell is omptomistic for the 10Ah.
And that is only rated for 10-30secs not 2-3min.

I would probably suggest something more like 50C lipo's
So the short answer is NO but the long answer is YES.
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200mph what to use AC or DC??

Post by antiscab » Wed, 22 Dec 2010, 21:49

Catavolt wrote: The power wont be a problem with the batteries we can fit 300-400 headway/Lifetech LifePo4 style power cells in the bike and possibly more on the swing arm maybe a couple in the riders


Its kinda like the supercaps problem, you can get the power, but not enough energy.

6 minutes @ 400A really is 40Ah Image
where as 400 x 10Ah cells only gives you 20Ah at 560v.

I wonder how much of the full 10Ah/cell is usable at 10C?

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200mph what to use AC or DC??

Post by Johny » Wed, 22 Dec 2010, 22:06

antiscab wrote:I wonder how much of the full 10Ah/cell is usable at 10C?
Matt
Tests that I've seen on the 38140 10Ah headways appear to indicate just shy of 8Ah at 10C.

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200mph what to use AC or DC??

Post by jonescg » Wed, 22 Dec 2010, 23:49

I'm with Richo. Go for those NanoTech 90 C LiPos. You should be able to fit 10 kWh on the bike somehow.
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200mph what to use AC or DC??

Post by acmotor » Thu, 23 Dec 2010, 03:20

To help with establishing the battery capacity we need to examine the battery DC load profile during acceleration as the x minutes will only be at the full 400/800A battery load when reaching 300+kmph. i.e. motor current will be at or near max current (3+ x nominal) (depending on wheel spin at <200kmph !) but battery current will ramp up to full over the acceleration time.

e.g. at start (assuming enough traction) induction motor slip will be say 120RPM. This is only 4 Hz of 200Hz so 2% of the voltage as well (no torque boost is likely to be applied as the bike will be a handful enough). Thus only 2% of the final battery current. OK optomistic !

This will ramp up to full voltage at 200Hz (300+kmph) as will the battery current. i.e. power (kW) is a linear ramp

So basically, if the acceleration time is 30 seconds then the average current will only be 1/2 the 400/800A over that time.

We need a woody spreadsheet to graph this for real given the dominating aerodynamic drag component. You there woody ???

Yes, Lithium polymer cells with their 20 to 50 C rating would perhaps best suit. The cycle life of even 50 cycles would be sufficient for the job.

I think that the practicallity of this project will depend on a close understanding of the actual Ah required and a deliberate attention to minimising losses.
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200mph what to use AC or DC??

Post by acmotor » Thu, 23 Dec 2010, 03:38

We need a time line of the 13km of track with target speeds and battery kW / current and cumulative Ah plotted so the battery capacity can be fine tuned.   Image

Come to think of it, I'd be hoping the 320kmph came up early so there was sufficient stopping distance. Image
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200mph what to use AC or DC??

Post by woody » Thu, 23 Dec 2010, 14:22

Always here :-) Mainlining the forum via email.
Spreadsheet isn't geared up for gentle accelleration, but could be modified.
What's the frontal area, weight and Cd for the bike?
Just a hunch that Cd will be the dominant factor - not sure if you have the time to improve that - it's not clear from "The World's Fastest Indian" what timespan that montage represented...
I'll google up some numbers and see what spits out...

I think you could make a nice electric salt flat racer staring with 3 44 Gallon drums, a diff and a nosecone. Or a formula V :-)
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200mph what to use AC or DC??

Post by Catavolt » Thu, 23 Dec 2010, 14:45

The frontal area is between .7 and .8m
The cd is around .4

Last time with the old bike we didnt accelerate hard until the 2.5mile marker.



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200mph what to use AC or DC??

Post by Johny » Thu, 23 Dec 2010, 15:00

woody wrote:.... - it's not clear from "The World's Fastest Indian" what timespan that montage represented...
Note that Burt's Indian was modified to seat the rider a lot lower (kneeling) to reduce drag. He kind of stretched the bike out.
Image

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