Learning about different Electric motors.

[Arlo1]

So as I look at hi power options for various aplications in my life I need to learn whats happening with all the motors out there.
Here is a page which talks about the tesla and the use of a induction motor. http://www.economist.com/blogs/babbage/2011/04/induction_motors

Overall, the Tesla Roadster is said to achieve a battery-to-wheels efficiency of 88%—three times better than a conventional car.

Thats a big number for eficiency. I wonder what the motor/controller it self can realy be?

 

[Arlo1]

The reason I bring this up Is I keep working on brushless motor stuff and want the best of the best but every time I talk to luke he says go brushed....
And for me that's just a big reason to say nope I will work even harder to find non brushed solutions. But As I work on colossus and other permanent magent brushless motors its good to see what else is out there and how it works. Maybe we can make a hybrid of all the best motors. I figured It is best to look at mission motors and see what they are using. And sure enough its a Asynchronous motor as well.

 

[liveforphysics]

The Tesla's battery sag alone loses more than 12% of the energy stored in the battery if it's moving at a highway speed...


It uses an induction motor (think big junky things you see powering giant industrial equipment), so you have to waste a portion of your energy creating a field in your rotor that resists the stator rotating currents to even make it turn. The big advantage there is that you can roll freely when off-throttle. The power advantage is that you have no magnets to cook, so the hotter you get that thing, the more heat it can shed, and the only real failure mode is melting the insulation off the copper somewhere.


If you're going to make a high performance EV, using a big dumb induction motor starts to make a lot more sense than running a PM motor, because the hit you take in the motors efficiency while driving becomes quite small compared with the reduction in core losses of having a big PMBLDC motor turning anytime the vehicle is moving.

It's actually been nice to get to BS with Tesla drive system engineering team while we both happen to be using the same test lab, hanging out waiting on an monitoring our tests. They have a really dumb battery, which the engineers obviously know but the bean-counters won't let them do anything about it, but they seem to be good guys.

 

[salty9]

The alternator intrigues me. I keep wondering about its potential with a rotor (with no magnets) that didn't look like it was hacked out of the early stone age. I've seen posts that claim the rotor saturates at around 2 amps.

 

[Arlo1]

So I will post a couple links for the NEWBs Here is a site for the brushelss out runner info http://www.aerodesign.de/peter/2001/LRK350/index_eng.html They show this picture to describe how it works.

 

[Arlo1]

Here is the wiki on inductoin motors http://en.wikipedia.org/wiki/Induction_motor

And Brushed motors http://en.wikipedia.org/wiki/Induction_motor

And a Wiki on all electric motors. http://en.wikipedia.org/wiki/Electric_motor

 

[Arlo1]

Now Before this becomes a war lol I must admit some DC brushed motors like the AGNI kick some serious ASS! They have high efficiency and can make some crazy power using Hi amps and relatively low volts (a good safety feature for a race machine) Luke can tel you the numbers but I think it was low 90's for % efficiency!

I just like the ease of a brushless motor and a guy can rewind one in a day it has no moving parts to wear out other then bearings. But the controller needs semiconductors that don't really exist yet for controlling them. There is lots of small brushless motors making some ok power have some good controllers but as we scale it up it becomes a major issue. One reason is inductance and it seems the more powerful and efficient the motor per kg the lower the inductance which KILLS fets!

One thing I have been thinking what about designing a induction motor with some low power magnets on the rotor? Making it a hybrid induction/permanent magnet motor!

 

[bigmoose]

Arlo, I think these guys did the Tesla induction motor and drive. Luke would know for sure. http://www.acpropulsion.com/ It would be good to scour their site. Like you are saying it is about the "system." As batteries get larger and cheaper, one can loose a bit on motor efficiency to make up on cost, and perhaps add a bit more high temperature durability, not to mention leaving the rare earth elements in China... Each vehicle class has an optimum HP/mass that make it fun, cost effective, and capable. There will likely be different options for different classes.

If an Agni run on the performance map will serve your needs, it is likely the best choice. Note the TTXGP guys running two and pushing them are having brush/brush holder failures. So BLDC the weak link is the controller, Agni is the Brush system, Induction... mass?

 

[Arlo1]

Induction... mass?

Lol I may have worded that a bit off. There is still more to know about induction for sure. I am just comparing my X5 @255uH to a small colossus @45uH and a big colossus @8uH. The big colossus is the most HP/kg motor I have.

I will continue working on building an awesome bdlc controller as we are talking on the not simple controller thread. I am not sure but the same controller may work on an induction controller?

 

[Arlo1]

http://www.acpropulsion.com/

This charging system is sweet!

tzero™ technology includes patented control and construction techniques that allow the power electronics and motor windings to be re-configured as a high-rate Reductive™ battery charger. Using existing componentry, the Reductive™ Charger reduces vehicle cost and weight. By allowing safe charging from existing 110V to 240V outlets at rates as high as 18 kW, the Reductive™ Charger reduces infrastructure installation requirements and costs, and its innovative bi-directional power capability allows self contained vehicle battery diagnostics and standby power generation.

 

[strantor]

It uses an induction motor (think big junky things you see powering giant industrial equipment

speaking of big dumb induction motors & industrial equipment, check out this piece:


Last night I pulled it out of a big cable machine capstan (as 3"O.D. cable is having polymer extruded onto it, this thing pulls it through the extruder). When I first saw it, I though it must be 40hp or better, but it's only 15hp (11KW)!
It must weigh over 500lbs, and it has less than half the power of my weak mars motor (abt 40lbs).

All that being said, I'm sure the ones used in the tesla are much lighter & better suited for an EV.

 

[Miles]

Last night I pulled it out of a big cable machine capstan (as 3"O.D. cable is having polymer extruded onto it, this thing pulls it through the extruder). When I first saw it, I though it must be 40hp or better, but it's only 15hp (11KW)!
It must weigh over 500lbs, and it has less than half the power of my weak mars motor (abt 40lbs).

How do the specific torque values compare, though...?

 

[strantor]

Well, mars says for the ME0708 the toque constant is .13nm/Amp. Figure 300A, that's 29ft lbs peak stall torque.
The nameplate of the big dumb induction motor says 6.86ft lbs. I assume that 6.86 ft lbs is rated @ 60Hz mith max slip, so not really apples to apples comparing to stall torque of a DC brushed motor.
if the mars motor was ran at 1100RPM (the rated speed of the induction motor @ 60hz) I am going to guess that it would have less torque, but I have no idea how much.

 

[rhitee05]

The nameplate of the big dumb induction motor says 6.86ft lbs.

The nameplate says 6.86 ft-lbs^2, which if you look it up is the rotor inertia. If you do the math for power = torque * speed, you get around 91 N-m, which is about 67 ft-lbs of torque. Also remember that's a continuous, run-it-all-day at 40C specification.

One thing I have been thinking what about designing a induction motor with some low power magnets on the rotor? Making it a hybrid induction/permanent magnet motor!

Not possible. BLDC are synchronous motors, induction are asynchronous motors. They would just end up fighting each other.

 

[Miles]

The nameplate of the big dumb induction motor says 6.86ft lbs.

The nameplate says 6.86 ft-lbs^2, which if you look it up is the rotor inertia. If you do the math for power = torque * speed, you get around 91 N-m, which is about 67 ft-lbs of torque. Also remember that's a continuous, run-it-all-day at 40C specification.

And the Mars is rated at 100 Amps cont. which gives 13Nm or 9.7 ft-lbs.

 

[strantor]

The nameplate says 6.86 ft-lbs^2, which if you look it up is the rotor inertia. If you do the math for power = torque * speed, you get around 91 N-m, which is about 67 ft-lbs of torque. Also remember that's a continuous, run-it-all-day at 40C specification.

Ok, well I guess that makes the 2" output shaft a little more reasonable (by a factor of 10), but still, that 15hp motor weighs more than a GM big block.

Thanks for clearing that up about the torque, I really didn't know about that torque number; seemed pretty low.

so how do you figure they came up with the numbers for the mars motor, if it's torque is 7 times less than the induction number, and its RPM is only 4X greater than the induction motor? The mars motor is frequently advertised as 8hp continuous, 18hp peak.

 

[Arlo1]

Not possible. BLDC are synchronous motors, induction are asynchronous motors. They would just end up fighting each other.

Ok so this is new to me. A induction motor is out of sync you meen the rpm of the rotor is not what the rpm the stator is trying to get it to spin to? Or is the rotor just always chasing the magnetic feild the stator is producing and only off by a number of electrical deg.?

 

[strantor]

Not possible. BLDC are synchronous motors, induction are asynchronous motors. They would just end up fighting each other.

Ok so this is new to me. A induction motor is out of sync you meen the rpm of the rotor is not what the rpm the stator is trying to get it to spin to? Or is the rotor just always chasing the magnetic feild the stator is producing and only off by a number of electrical deg.?

Theres always "slip" with an induction motor. I thought for a long time that that meant the rotor just lagged behind the magnetic field, but its a real difference in rpm. for example a motor might have a synchronous speed of 3600rpm, but a rated speed of 3450; the missing 150rpm is the slip. The rotor has to "slip" behind the magnetic field to induce current in the rotor. if the motor went 3600rpm, there would be no current induced into the windings because no magnetic lines of flux would be cut.

http://www.wisc-online.com/objects/ViewObject.aspx?ID=IAU10108

 

[Arlo1]

Hey thanks for the very clear answer! That link is cool and good to have on this thread.

 

[bearing]

Arlo, I think these guys did the Tesla induction motor and drive

I used to think that too, but then i found this blog http://www.teslamotors.com/blog/motor-city
They make their own motors.

...
We’ve studied the EV-1 motor carefully. The technique they used to construct their copper rotor was not great, resulting in suboptimal efficiency, and (I suspect) low manufacturing yield.

We have studied AC Propulsion’s rotor manufacturing technique. Their process creates a motor with much better efficiency. But there is quite a bit of hand labor and tweekmanship in the process, and it would not work for the production volumes we forecast at Tesla.

We studied other companies who cast copper rotors like Favi. But their process yielded rotors with lower efficiency than AC Propulsion’s.

The first Tesla Motors prototype motor

So we set out to create our own copper rotor fabrication process. It took us a few years, but it worked: our rotors are readily mass produced in our own factory in Taiwan, and their performance is quite nice. (How we do it is a secret. I don’t keep a lot of things secret from you, but this is some of our secret sauce! That’s why we didn’t outsource the construction of this piece.)

Here’s the cool thing: if you handed one of our motors to Nikola Tesla, he’d recognize it immediately as his own invention. Nice job of optimization, but clearly his.

That’s why we’re Tesla Motors.

 

[Arlo1]

...
We’ve studied the EV-1 motor carefully. The technique they used to construct their copper rotor was not great, resulting in suboptimal efficiency, and (I suspect) low manufacturing yield.

We have studied AC Propulsion’s rotor manufacturing technique. Their process creates a motor with much better efficiency. But there is quite a bit of hand labor and tweekmanship in the process, and it would not work for the production volumes we forecast at Tesla.

We studied other companies who cast copper rotors like Favi. But their process yielded rotors with lower efficiency than AC Propulsion’s.

The first Tesla Motors prototype motor

So we set out to create our own copper rotor fabrication process. It took us a few years, but it worked: our rotors are readily mass produced in our own factory in Taiwan, and their performance is quite nice. (How we do it is a secret. I don’t keep a lot of things secret from you, but this is some of our secret sauce! That’s why we didn’t outsource the construction of this piece.)

Here’s the cool thing: if you handed one of our motors to Nikola Tesla, he’d recognize it immediately as his own invention. Nice job of optimization, but clearly his.

That’s why we’re Tesla Motors.

The link you posted Talks about a copper rotor. But they keep it as a secrate sauce... I am realy thinking about getting one or more of the Azure Ac24LS motors from Remotecontact but I wont waste my time unless I can get them to produce >100hp The motor on the Model S looks small. Now is only one side the motor? That means one little thing the size of a pumpkin can make 400+hp?
Anyone know how to make this Copper rotor? From the looks of things Tesla is approaching BLDC or PMAC motor power density with a motor with 0 drag when coasting and lower materials cost!

 

[Arlo1]

Look what I scored for free today! Now to mod this mofo into a real motor!

 

[Lebowski]

I once thought about a copper rotor.

If you look at my triple stator axial flux motor build, I would go that route but use copper plates instead
of the magnet plates. I would drill holes in the copper plate (25mm, like the magnets) and fill those
with an isolated, wound iron wire. This will be the iron core, the copper plate is the rotor winding.
I would also add iron cores to the stator plates. Basically this gets you an axial flux induction motor...

 

[Arlo1]

I once thought about a copper rotor.

If you look at my triple stator axial flux motor build, I would go that route but use copper plates instead
of the magnet plates. I would drill holes in the copper plate (25mm, like the magnets) and fill those
with an isolated, wound iron wire. This will be the iron core, the copper plate is the rotor winding.
I would also add iron cores to the stator plates. Basically this gets you an axial flux induction motor...

Im more interested in some code....?
There is a good market for Powerfull induction motor controllers, This is the one thing holding back the whole DIY car crowd from doing it. There is a few using induction motors but most just use brushed motors.

If I can mod this motor enough I will put it in the Honda CRX and give er a go! I can do anything to this motor. What do you guys think about silver coating the rotor?? I have some silver Gordo give me to experimant with I will get some mesurements but how do I determin the max speed for the rotor?

 

[Arlo1]

So it turns out the Rotor is made up of lamination's... Proly has a core made from iron and the end look like aluminum. Don't know much about the rotors but from what I have read it will saturate at a point and adding more power to the motor will not make more power so this is why you want to use something that conducts really well for the rotor like Tesla with the copper in the rotor. I would like to know how its made but that's one of their secrets....

Looks like I can get the stator out of the Iron housing... Can you say big aluminum water cooled housing and end caps? Shoud be able to knock 50-75lbs off this thing!
The lams in the stator mesure .012inches
I have the motor shop holding a stator off for me to build a DIY brushless innerrunner!