ACIM, PMAC, PMDC motor efficiency and EVs

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Johny
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ACIM, PMAC, PMDC motor efficiency and EVs

Post by Johny » Wed, 17 Aug 2011, 23:15

I stumbled across this article comparing AC type EV motors - a good, short read.
http://www.4evriders.org/2010/01/usa-ac ... tric-cars/
What is also interesting if you want some Toyota reading material is the link he points to at the end of the fifth paragraph. Type Toyota then hit search.
http://www.osti.gov/bridge/basicsearch.jsp

Edit: Fixed first link, changed 'really' to 'also'
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Richo
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ACIM, PMAC, PMDC motor efficiency and EVs

Post by Richo » Fri, 19 Aug 2011, 20:57

Interesting read.

Actually the idea of shoving a PMAC on the back of an ACIM sounds feasable.

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ACIM, PMAC, PMDC motor efficiency and EVs

Post by Johny » Fri, 19 Aug 2011, 21:15

You would have to wonder if the marginal efficiency gain is worth the weight. Then again the article on the Prius motors and higher voltage advantages making a 200 to 500 VDC boost convertor a reasonable addition defies my natural intuition too! We (AC folk on forum) have tended to bias toward the idea that a rewind solves everything.

Edit: 200 not 100
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Post by coulomb » Sat, 20 Aug 2011, 02:10

Richo wrote: Actually the idea of shoving a PMAC on the back of an ACIM sounds feasible.
Well, but if you only have one controller (which makes most sense to me), you couldn't run both at once. The PMAC part would need synchronous drive (with respect to the driveshaft, considering pole pairs), while the ACIM part will need slip to develop any torque.

So one rotor (and that part of the stator nearest it) would always be dead weight. I guess that's the problem with any hybrid system; at any point some part of the hybrid isn't pulling its weight. Even so, it still may come out ahead, if enough of the advantages of each part of the hybrid shine through.

Hmmm. I'm assuming here that you would have one stator and a kind of split rotor, with permanent magnets at one end and a squirrel cage at the other. But I think that the permanent magnet, which you can't turn off, would stuff up induction into the squirrel cage. So you'd have to separate the stators, effectively having two separate motors. Unless you had changeover contactors, I don't see how you could run with one inverter. I suppose you could have one front end, and two back ends (IGBTs and their driver chips), but that isn't saving very much. At least the two controllers (or back ends) could share the same cooling.

An IPM (Interior Permanent Magnet) motor makes more sense, since in effect it's a hybrid between a standard PMAC motor and a reluctance motor; you just get some of your torque from reluctance. Both of these are synchronous motors, so you can combine them with the same drive. You can even vary the torque ratio between the two by fiddling with some phase angle, if I recall correctly.
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Richo
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Post by Richo » Tue, 30 Aug 2011, 05:17

Nah it was a bad idea - added complexity with little benefit.
2 motors + 2 controllers + a coupling.
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Post by aegidius » Sat, 08 Oct 2011, 16:02

Interesting point about eddy current losses in a large PM motor at speed; what do the Mars/Agni/Emrax users think? It must depend on the quality of the stator laminations and the symmetry of the windings (and circulating currents, if the motor is wound in delta)
Giles.

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