What are the pro's of having a dual motor vs dual stator?

[markz]

Whether it be front wheel and rear wheel, or dual stator in one wheel?

I just came across this, used for motorcycles or a vehicles. And thought it was interesting. I know QS motors does one. Comment Another


https://www.youtube.com/watch?v=BoTfKThTwvU

 

[amberwolf]

independent 2wd gives you good traction control in a lot of situations; if you only have one powered wheel (with twice the power), then in a loss of traction on that wheel, you don't have any power from it at all (or cant' safely use any of it; same thing), while with 2wd you'd at least have half the power, in the wheel that still has traction.


With CrazyBike2's 2wd I've had a number of such situations where being able to cut one motor and still use the toher have saved me from a crash (usually in wet conditions, in a turn, in traffic).

With all of the variations I've had of single-powered-wheel bikes (including pedal bikes) there have been instances where I crashed but probably would not have if I had been able to power out of it with the other wheel.


BTW, since a dual-stator motor has the same end-turn losses as two motors, you would be better off with a single-stator motor that was as wide as the active area of the dual-stator, if you really just want one motor.

It would be lighter, too.

 

[Punx0r]

Heat dissipation is better for dual motors as the external surface area is greater compared to one larger motor.

 

[Voltron]

From some random PDF on dual stators...



The proposed dual stator PMBLDC motor consists of two separate concentric stators having different number of slots with a common rotor on the same shaft. Two stator stampings of different radii are used for design of stators. The rotor is a hollow cylindrical rotor in the space between two stators.


Dual stator topology has been widely used in motors for different applications where power segmentation and reliability are main concern.
Dual stator configurations are already being used in induction, synchronous motors for applications like wind-mill generators, aircrafts, etc.

In these dual stator machines,there are two stator windings which share the same magnetic and mechanical structures. These machines are typically used in high power applications. The stators may consist of two identical windings with or without phase shift.

The two windings may have different number of poles, number of phases and ratings.
In dual stator machine, the output torque corresponds to the algebraic sum of two independent torques. By having two independent torque
components the low frequency operation, including standstill maneuvering can be improved.

To improve the torque density, two air-gaps are combined in a motor to deliver the output torque and then the
electromagnetic torque is produced by the separate currents of both stators. Based on this concept, the double-stator PM motor drive is introduced. It combines the double-stator structure of the PM brushless motor so as to provide high starting torque and good controllability for EV propulsion. Because of its unique configuration the
motor can offer advantages of high torque density and good controllability.


I just looked at the other pictures,,, that one is two side by side stators... the one from the PDF is concentric stators, so not sure the same benefits apply.
One side by side benefit I just read it you can run it on dual controllers, splitting the load and giving redundancy.

 

[macribs]

I like very much the idea of a dual stator, and even if I think QS generally does a great job this motor you link to is a phat pig. 52 kilos, or 114 lbs.
That much weight in the rear wheel would likely generate pendulum effect in the same way old porsche 911 was known for. Come into a turn too hot, and the weight of the engine all the way in the rear would abruptly and quickly send the tail around its axis so fast many are those who recked their new sports car when dueling with the law of physics, or putting the foot the metal a little too early on the exit. If motor could be used as a mid drive like electric scooter or moped and the motor was sprung weight that would be an insane torque monster. And in a scooter the weight wouldn't matter that much as long as it was not in the hub.

Imagine a more sensible e-bike dual stator motor. Maybe a QS 205 with machined outer shell to shave of weight,even thicker phase wires, better and stronger axle yet lighter. Maybe weighing in at say around 15 kilos. Strap on two reasonable priced controllers and it could be the hubmonster take 2. Or maybe we will see a mxus 10K Dual stator at 11-12 kilos? Should make it possible to peak past 20 kw peak for short bursts, or possible even 30 kw without pushing hard. I would say that would put the e-bike grin on peoples faces.

 

[spinningmagnets]

There was a project a while back where two stators had all the wire cut off, and they were pressed together onto a single custom shaft. It was to make a motor of a diameter and width that was not available at the time.

This dual-stator motor would be very hard to wind the coils around the stator-teeth, but not that hard to take two assembly-line stators and mount them side-by-side.

Don't assume that just because China is making it, that it must be a good idea. They are only making it because somebody wants to buy a fatter hubmotor.

 

[macribs]

I think we have seen close to what is possible of power output from those hi powered hubs like mxus and 205's.There are alternatives, joby, astro, various 20+ kilos hubs, and other high roller alternatives. Only price is high. Or weight is high.

A dual stator DD hub if well executed and drawn from the ground up for e-bikes should possible come in with significant less weight then say a 273 motor. Then add the benefits of splitting the load onto two controllers. Not only will each controller see half the load, one would be able to get high power output with a couple of mid range controllers rather then buying one monster controller to feed ie 273. Add in FF and even heat sink if needed.

I really wonder what weight we would see from say a QS 205 dual stator designed from the ground up for e-bikes? Ie Beefier Ti axle, thicker phase, thinner shell. Think it would be possible with a dual 205 <15 kilos? Possible 20+kw for 1.000 - 1500 $ controllers included.

With the MoQ for such a design we won't see that for while. So while waiting maybe a light weight hub for the front like justins 20 mm thru axle, or even mxus up front will have to do. Or sink some serious money into one of the exotic boutique motors.

 

[amberwolf]

There was a project a while back where two stators had all the wire cut off, and they were pressed together onto a single custom shaft. It was to make a motor of a diameter and width that was not available at the time.

That's probably Farfle's dual Magic Pie.

But it was not really a dual stator motor, and that makes it a better motor than one of the side-by-side types pictured in the OP, because it has half the end-turn losses than it would if made that way.