Author Topic: The theory of possible conversion of an induction motor to BLDC operation.  (Read 20362 times)

Offline arlo1

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On second hand.....I do not think we want a ferrous rotor core to compete with the magnets....do we?

   If you use a ironless core you have to spend a lot of time designing it to work without the iron to direct the flux most of the time it will be easier/faster/cheaper to design it with an iron flux ring behind the magnets.
Quote
The R/C guys use non magnetic materials in their motors...

Miz
Wrong where did you read this?  ALL my rc motors including my big 12kw continuous motor have a iron flux ring all of mine are out runners but it is really easy to make with iron all you do is make a rotor out of pipe the right size and attach the magnets.  If you want lower eddy currents at hi speed you can use lams like the volt and David's motors have.   Start reading here.  http://endless-sphere.com/forums/viewtopic.php?f=30&t=240
I will find more.

PS I tried to respond to this 7 f'n times at work and my phone kept hitting the amazon add even though its not even close.  Then I got a response typed and the amazon link caused me to loose it.   I was so close to saying F this forum.  No offence to you Ivan or Miz but I don't have time for that.

Offline mizlplix

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Ivan needs to be home to work on the server.  He plans to dump Amazon then.

So, I guess the picture of the rotor at the top of this thread has an aluminum (or a steel) hub?

And the magnets need to set directly on it?

This means I could drill the shaft hollow and flow water through it to cool the magnets.

Or do I just lathe turn the original core down a touch to open up the gap and then drill holes for the magnets?

I was wondering if the big iron core would be fighting the magnets somehow?

Thx, Miz
1930 Ford Speedster, AC50, full manual powerglide, 6.14gears, 38-130AH CALBs.

Offline arlo1

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You can see the flux lines in this inner runner simulation using FEMM   http://endless-sphere.com/forums/viewtopic.php?f=30&t=40614&hilit=femm

Offline arlo1

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Offline arlo1

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Another one with lams making up the rotor and a magnet inside the lams with a great picture. http://www.endless-sphere.com/forums/viewtopic.php?f=30&t=41153

Offline piotrsko

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so what arlo is saying is we need to go back to my easy rotor suggestion?  IMHO kinda no reason to use the halbach array with a iron backing

Offline arlo1

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so what arlo is saying is we need to go back to my easy rotor suggestion?  IMHO kinda no reason to use the halbach array with a iron backing
Yes I think that's how it works if you want to build a BLDC (PMAC) motor with no flux ring you should use a hallbach array.   There is always more then one way to skin a cat but for a DIY setup it needs to be cheep and easy to build.

Offline mizlplix

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The only reason I mentioned a hallbach array is this article.


Halbach Array Electric Motor
High-Efficiency, High-Power-Density, Halbach Array Electric Motor


LaunchPoint has completed optimization and initial prototyping for a high efficiency, high power density, Halbach array electric motor. With a total weight of only 1.4 pounds, this motor produces 7 horsepower at 8400 rpm with 95 percent efficiency. At 5 horsepower per pound, this motor has a higher power density than any other motor on the market. The brushless, axial flux permanent magnet design is highly tolerant of temperature and centrifugal effects, and the ironless rotor and stator eliminate iron eddy-current and hysteresis losses. Motor development is ongoing.

It made me wonder. If there weren't some power hiding there.

Miz
1930 Ford Speedster, AC50, full manual powerglide, 6.14gears, 38-130AH CALBs.

Offline arlo1

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Imho the amperage is quite low for that motor on the motor side.  And I think doing something like that with an inner runner would be quite hard.  I think that if you take an induction motor and try to make an ironless rotor you will loose power and low end torque to what you could make with a iron flux ring behind the magnets.

Offline mizlplix

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Some of those with the metal ring under the magnets use a stack of three magnets in each hole too. 

I wonder if the regen would still work?  I dont use it for the power it puts back as I find it nice to drive all day and never touch the brakes...LOL

Miz
1930 Ford Speedster, AC50, full manual powerglide, 6.14gears, 38-130AH CALBs.

Offline arlo1

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Pmac motors are just relay efficient 3 phase generators so yes regen can work very well with a good controller.

Offline arlo1

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Here is a inner runner that has been taken apart.  It looks to be a well designed motor. http://endless-sphere.com/forums/viewtopic.php?f=30&t=50066

Offline arlo1

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Here is variable regen set up on my E-ysr  just working out some bugs before upping the power.

Offline piotrsko

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hate to say it but that looks amazingly like the alternator on my old honda 450

Offline mizlplix

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Hehe, It does look like an alternator.

I had 2 Honda 450's.  An early and a late model.  The early
had a different firing timing than from the later one.

I mostly remember the one because it didn't have any
traditional valve springs. It had torsion bars and forks to
open/shut the valves.  That and the motor looked huge
when set beside a 350.

Arlo:  That was a good looking bike. Could you tell us about it?

Thx, Miz
1930 Ford Speedster, AC50, full manual powerglide, 6.14gears, 38-130AH CALBs.