[JimDanielson]

Im working on an induction motor and wondered what you guys thought. The past year I have spent working on 3 phase motors, I have built several running motors at a few hundred watts power, most synchronous machines. Currently, I am working on scaling up several of these ideas to a ~30kw motor.

All the parts for this larger prototype are nearly manufactured, waiting on electrical laminations. By the end of the month it should be running on the bench.

A major difference this motor will have is the max rpm. Prototype is a 12pole machine. If I remember the frequency on the Curtis Controller correctly, it will approach 3000rpm top speed. But, this final model may be designed as a 24 pole machine. The main reason I am doing this is for elimination of the transmission. The goal would be to have 2 of these motors directly coupled to the CV joints of a car. It would save on weight and inefficiency of gears.


I am also working on a synchronous rotor for 3 phase machine that will not have permanent magnets or brushes. This works with the small prototypes but I will be holding off for the large motor due to a number or reasons, mainly being time to get it working perfect.


Questions; what do you think of directly coupling to CV joints?
how do you feel about having to deal with 2 motors?
would you buy a motor with 1500rpm top speed?

Ill try to answer any questions, because I am filing provisional patents on some of these features I might not be able to say everything. It would be great to hear if it sounds interesting to you

[somanywelps]

> Questions; what do you think of directly coupling to CV joints?

I don't like it, the torque's going to be too low. The Tesla and others use an 8:1 gearbox for a reason.

See if you can find an ~8:1 diff and link to that.

> how do you feel about having to deal with 2 motors?

up to the software. If they're inline on the same shaft you don't even have to worry about it.

> would you buy a motor with 1500rpm top speed?

Never. 0-1500rpm is a pathetic power band. I wouldn't even do 3000.

6000 is decent with a transmission or very high torque and a 3:1-4:1 diff.

12000 is great with an 8:1 gearing.

Also 35kw is far too low. You're fighting AC-50's and whatnot.

Now if you were making 100kw-200kw motors less than Remy and AC propulsion, well now you've got possible OEMs interested...

[iti_uk]

I am very interested in your work. I have previously expressed my desire to have a motor-per-wheel vehicle (4 motors), using CV jointed half shafts to allow chassis-mounted motors. Since I was looking at motor-per-wheel, I was imagining 15kW or so per motor, which would fit nicely with your proposed two 30kW motors.

To answer your questions;

I can't see any problems coupling directly to CV joints. I have heard about high currents at low motor speed, suggesting that mechanical down-gearing of a faster-spinning motor might eliminate low-RPM current spikes (or at least narrow the range). Of course, having direct drive means low voltage and high current, so you'd have to use heavy cabling. In my head I have a motor driving a planetary reduction gearset, in turn driving the CVJ/halfshaft/wheel.

I think having motor-per-wheel is the way forward (as I see it so far), and opens up fantastic possibilities with traction control and active virtual-differential algorithms. Very exciting.

I certainly would buy a motor as spec'd, especially if it were liquid-cooled. I have been looking into refridgeration as a possible method of cooling while allowing a decent cabin heater - evaporators on the motors and controllers, and condensers in the vehicle's HVAC. I'm not aware of having seen this before.

Do you have any pictures of your prototypes? What are the projected power and torque levels, dimensions and masses?

Chris

[jddcircuit]

I am interested.
If you have a motor that produces the necessary torque within your weight budget without a gear reduction then it would be worth consideration.

I was surprised to see how much losses were attributed to the gear reduction and differential in one of the Prius transaxle studies that I read on line. I can't remember what it was but IIRC it was significant percentage.

However I remember Major stating that torque multiplication using gearing vs. using extra copper can result in a much lighter package. I want to think it was a 4 to 1 weight ratio. But then I see some slick high pole outrunners flying RC airplanes where weight is a premium.

good luck
jeff

[Nathan219]

Please let me know how you motor turns out. You are building a torque motor, like the kind they use in elevators. I have been trying to source a motor like yours, but they are very expensive generally. 1500 RPM is good for well over 100mph depending on tire size.
Good luck keep us posted!

[subcooledheatpump]

Hey, some people aren't reading this correctly. He's making multipole motors to elminate the gearbox. More torque but less speed. That means his power band isn't "pathetic"

The Tesla Roadster has an 8.28:1 gearbox. That means 15,000 RPM goes in but only 1811 RPM comes out.

So if he wants to make a motor with a maximum speed of 1500 RPM and it's 24 poles, That means he'd be getting a ton of torque in exchange for a ton of speed, enough torque to get the wheels turning without a gearbox/transmission

But there are a few problems with that. Multipole motors are alot less efficient, They consume more reactive power. The frequency will also need to be high, more losses. The shafts will need to be extra hard and made with high precision since they are connecting right to the CV shafts. Other than that, sounds good to me.

[peggus]

Torque is a function of fluxdensity in the airgap and the geometry of the airgap (radius, length). Polecount doesn't factor into it much, one might however be mislead by a commonly known equation into thinking that it does.

You want a high torque motor, you end up with a large motor since flux density is limited by the materials used.

[JimDanielson]

subcooledheatpump is right, I have run magnetic simulations on this 12 pole motor and am getting ~200ftlbs peak. The 24 pole motor would have the same slot design and winding pattern so the torque would be about double.

The AC50 peaks at 115 ftlbs of of torque. If you look at a civic ratio for example of about 4:1, you would have under 500ftlbs of wheel torque with the AC50. With the current prototype I would have 400 ftlbs of wheel torque and the 24pole could potentially have nearly 800ftlbs at the wheel.

Also, I have the ability to increase the height of the lamination stack with no change to manufacturing. Right now I am running all my simulations on a short stator stack at a rather large diameter (nearly 14inches on the 24pole). The lam stack can be lengthened to increase both power and torque. These simulations are being run right at the peak flux density of the silicon steel I am using.

Of course, with some inefficiencies and manufacturing tolerances, I do not expect to get the exact numbers in the real world, but thats whay I have a prototype that I will be able to test soon.

[JimDanielson]

jddcircuit mentioned the extra copper requirement. I have designed this motor so the temperature limitations on all the materials are at least 350C (including protective coating on the wires); class H insulation is limited to 180C. Although it would be inefficient to run continuously at this temperature, it would allow bursts of a much higher peak torque and current. I can operate the copper closer to its fusing current.

I am not positive it will give the desired output for long enough, but I am giving it a shot.

The main goal would be to have extra power available for merging onto the highway quickly and then go back to a much lower average power

[JRoque]

Hello Jim, will you be driving the two motors with Curtis controllers? IIRC they can synch both motors and account for speed differentials while turning. Otherwise, the controller coding will be involved, to say the least.

JR