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Asynchronous motors - is induction the new future?

Deafcat said:
Hey totally! I just watched that video now,

https://www.youtube.com/watch?v=x3brfAEs_RY#t=307

that sure looks like SRM motor...
This is a regular synchronous permanent magnet motor... at 4:00 you can see how the magnets are inserted into the rotor splices... and then at 4:15 you can see the splices slightly repulses each other because magnets are inserted into splices with same polarity.

A SRM motor can't have an absolutely round rotor. The whole idea betwen SRM is that the rotor has a number of salients, which are attracted to fill the respective magnetic gaps when magnetic flux flows in a certain direction through the stator. If the rotor is round, it can't make the flux path energetically more efficient, so it will stay in place.
 
anpaza said:
A SRM motor can't have an absolutely round rotor. The whole idea betwen SRM is that the rotor has a number of salients, which are attracted to fill the respective magnetic gaps when magnetic flux flows in a certain direction through the stator. If the rotor is round, it can't make the flux path energetically more efficient, so it will stay in place.
My understanding is that the magnets themselves act as a flux barrier, creating a reactance differential between the d & q axes so, the torque does (can) have a reluctance component. Most of the IPM rotors are of this hybrid type. Even a surface PM rotor with the magnets inset has some potential for reluctance torque.
 
anpaza said:
This is a regular synchronous permanent magnet motor... at 4:00 you can see how the magnets are inserted into the rotor splices... and then at 4:15 you can see the splices slightly repulses each other because magnets are inserted into splices with same polarity.

A SRM motor can't have an absolutely round rotor. The whole idea betwen SRM is that the rotor has a number of salients, which are attracted to fill the respective magnetic gaps when magnetic flux flows in a certain direction through the stator. If the rotor is round, it can't make the flux path energetically more efficient, so it will stay in place.

all of the latest SRM rotors are machined completely round on the outside, many sources will confirm this. it is the geometry beneath the outside diameter of the rotor which counts. You may also want to consider how many relatively tiny magnets are in that rotor compared to its size... they are there to compliment its performance in addition to reluctance forces. not nearly enough there to provide the necessary density required in an IPM motor of its relative displacement.

most obvious of all: it's clearly configured with concentrated windings, and the magnets are internalized. this would not work as a PM only motor. IPM motors use distributed windings (not concentrated windings, which would be the configuration for an SPM motor)
 
Indeed, at a second sight it looks like an IPM motor.
In any case, IPM is not SRM, it's something like a mix between SPM and SRM.
Tries to take the best of two worlds.
 
Induction motors have better overall efficiency on a typically drive cycle than a bldc motor but lower torque density

still no cogging of the induction motor is a huge advantage on a pedal bike. Ironless bldc motors also have no cogging but power density limited by the mags

Without active cooling an induction motor may have a large power density advantage

ironless induction motors made from superconductors habe a 10x torque density advantage over ironless bldc but are only being used in flying vehicles. Long term hub motors will use the same tech

Switched reluctance is cheap and has a wide speed range but hard to control (non linear) and loud. I would skip it and just go ironless

In any case this motor is an awesome development and I hope to buy one soon if it can wheelie. If a 20kw hub motor cannot wheelie from a standing start without pulling up on the handles it is useless to me. Pretty simple test. I dont care about efficiency or power/torque density that much. The advantage here is being able to pedal a 20kw ebike, given it has at least enough torque to wheelie
 
I have yet to read through this whole thread, but I'm so excited after just discovering this that I have to post now! I have been dreaming of an induction hub motor since I got into ebikes and have spent many hours contemplating on whether such a device would work as a hub motor or outrunner without needing slip rings. Absolutely awesome! cant wait to get my hands on one now!
 
FYI. There was an asynchronous machine being produced a few years ago which was an axial flux machine, I believe. Bigger than needed for a bike, maybe for a motorcycle, might be good for some ideas if you can find one. Several went to auction with Azure Dynamics. Check out Auragen.

http://www.aurasystems.com/documents/906203_AUR_proof07.pdf
 
Is anyone familiar with the company ThinGap? They have made thousands of motors for Industry and the 4 branches of defense service.I emailed them and they replied back stating:

Thanks for your interest in our motors.

The basic reason that our motors are lighter and run cooler than traditional copper wound motors is that ours do not have any iron in the stator. We use a unique design which uses an epoxy fiberglass core around which we wrap copper litz wire. The result is a light weight, high torque motor.

You can read more about the technology on our web site.

I hope this helps.

Regards,David.

http://www.thingap.com/

Their non traditional copper wound motors seem to out excel any others by big strides.It seems like an untapped source for e-bike motors.Maybe it takes big money to go from Thin Gaps tech to an e-bike motor?? That some rich individual investor would be needed??

Tim.
 
Hi Tim,

A continuous torque density of 1.4Nm/kg is really not very much........ For comparison, even an Astro 3210, which is not at all optimised for torque density, is capable of 2.6Nm/kg and for power density, well.............
 
The little I have found on the subject, this SRM setup looks very promising for transport applications. Do any smaller (e-bike suitable) stock affordable motors exist that we could get data on for the motor spread sheet for comparison purposes. Does this switched reluctance motor also require a more complex / expensive controller technology that may put it out of reach in this price point without some significant investment?
 
Coreless motors are low-inductance and, as such, they provide lower torque than traditional motors.
To compensate for that, coreless motors are very high frequency (they don't suffer the Eddy current & other loses in core).
But this means you'll have to add a two-step reductor, so you'll have both weight & loses at this stage.
All in all, it doesn't look like coreless motors are suited for electric vehicles.
Here you need high torque and low speed, the opposite of what coreless can propose.
 
I talked with an engineer at thingap many years ago, about using them in "traction" vehicles. His suggestion was that I look elsewhere, because of the low torque density and low thermal mass of their motors. They can go from good to smoked too fast. Fine platform for positioning and robotics use, but not for variable loads pushing a ground vehicle.
 
Hm. At first it looked so promising. Let's hope luke's russian brother is on to something.
 
macribs said:
Hm. At first it looked so promising. Let's hope luke's russian brother is on to something.
They are indeed, they made second proto motor on bicycle for 20kw max last year and presented new controller for testing, 2 week ago, about 9 fet Infinion in physical size(it has allu plate as heat out), then made announce last week about the sizes of production motors and they are looking for series manufacturer (I believe locally) Will post a link to the youtube chanel, when I get to my account (only Russian language)
 
Russian is beyond me, don't understand a single word. :(
If russian speaking members are aware of any news regarding this matter pls write in english here.
 
First, please understand, I have nothing in common and no direct contact with those guys, info is taken from the YouTube videos with my limited Russian language skills. Channel seems not to be directly involved in the development and more like interviewing those guys. I am sorry, in advance, if some info is given wrong.

Here you can see the experimental controller that passed static testing 90v at 50A and is waiting for road tests, from what I can understand it has only few Fets mounted at 2:36 you can see empty space for missing Fets
[youtube]kIZRnr4D7hA[/youtube]
Here is the motor open, I believe this is 20kW capable version and it can be taken apart with 1 nut. Stator is wound in Y and D pattern at once with different wire gauges You can hear plasma welder in the background at 4:20 :twisted: They use Curtis controller in their testing
[youtube]7PKFYAv3UsQ[/youtube]
Their plan is to make 96 tooth line for 1.5kW, 3kW, 7kW and 10kW by varying stator width and 72 tooth smaller diameter line for under 1.5 kW
[youtube]nodNqJnG4Bk[/youtube]
There is a ton of related road test videos and interviews in Youtube.
 
I wish I could master Russian language. Is there any smart translating online tools that can translate audio from a video? I really would like to know what they are saying in those vids.
 
Some update.

While motor number one (body from Magic Pie I, new stator and rotor) left to Germany for testing in some labs, and the 20 kW motor is waiting for the new controller to finish, they're doing a third motor, which is more of what we call a "bike motor" :-D

Stator width 55mm
Spoke hole diameter 186mm
Expected peak power 10 kW

1.png
2.png

Ongoing buildup:

3.jpg
4.jpg

By the way, with the motor that used Magic Pie body they managed to accelerate over 100 km/h. That was about 6-7kW power. Not bad, counting that original Magic Pie was rated at 750W, if I'm not mistaken. All in all, the mileage from a single charge seems similar to traditional bikes with a comparable battery, so effectivity at cruising speeds seems close to traditional hub motors.

With the first two motors, there are problems with the Curtis controller at low speeds (up to about 150 RPM) - it's not going to field-oriented control at low RPMs, runs in scalar mode (50Hz). Unfortunately, that limits the traction at start, and runs at low effectivity at low speeds. The new motor should be better suited for Curtis' quirks (don't ask how, that's what the engineers says). Besides, they're communicating with Curtis developers, trying to solve some of the problems (there weren't too many asynchronous motors with a large pole number, so that's the cause...).
 
I wonder what that tiny motor weighs?
And how far off are we before someone start taking name for first production run?
 
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