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Old 02-17-2017, 01:01 AM   #1 (permalink)
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Default AC or DC

I couldn't find the answer to a question that came up today from someone who oggled my Karma. Are our electric motors DC or AC like Teslas?
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Old 02-17-2017, 11:01 AM   #2 (permalink)
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I couldn't find the answer to a question that came up today from someone who oggled my Karma. Are our electric motors DC or AC like Teslas?
I don't think any EV manufacturer uses DC motors. Our cars use AC Permanent Magnet motors. Tesla uses AC Induction Motors.
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Old 02-17-2017, 12:07 PM   #3 (permalink)
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Thank you - so I assume that would mean over time the permanent magnets could weaken, whereas the Tesla battery would not. I wonder what the life of our magnets are?
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Old 02-17-2017, 12:57 PM   #4 (permalink)
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Thank you - so I assume that would mean over time the permanent magnets could weaken, whereas the Tesla battery would not. I wonder what the life of our magnets are?
Magnets are your least of the problems when it comes to the traction motors
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Old 02-17-2017, 01:04 PM   #5 (permalink)
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Thank you - so I assume that would mean over time the permanent magnets could weaken, whereas the Tesla battery would not. I wonder what the life of our magnets are?
AFAIK, absent abuse or extreme heat, the magnets used in electric motors retain their power, well, permanently. I don't think this is an issue you need to be concerned about.

"Tesla battery?" I assume you meant the Tesla Motor. Again, the choice between Induction and Permanent magnet motors is driven by a number of factors and they each have their positive and negative points. I don't think magnet longevity really factored into the decision.

Here is an article that compares the various electric motor designs. It may be bit too detailed for casual interest, but I thought you may find it interesting. Specifically, this quote is very relevant to this thread (Note, the Tesla mentioned in the quote is a unit of measure of magnetic density, not the car):

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The magnets in permanent-magnet motors

Rare-earth elements are those 30 metals found in the periodic table’s oft-omitted long center two rows; they’re used in many modern applications. Magnets made of rare-earth metals are particularly powerful alloys with crystalline structures that have high magnetic anistropy — which means that they readily align in one direction, and resist it in others.

Discovered in the 1940s and identified in 1966, rare-earth magnets are one-third to two times more powerful than traditional ferrite magnets — generating fields up to 1.4 Teslas in some cases.

Permanent magnets are used in MRI machines, portable electronic devices, hysteresis clutches, accelerometers, and — last but not least —permanent-magnet rotary and linear motors.
Hope this helps.
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Old 02-17-2017, 01:19 PM   #6 (permalink)
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Great that does help - very interesting!

Yes, I didn't mean "battery" - apologies.
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Old 02-17-2017, 01:41 PM   #7 (permalink)
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Something that may be worthwhile mentioning is that the Fisker Karma motors are synchronous and thus require DC excitation so they are not really a pure AC motor in that they require a DC source to initialize rotation. These aren't pure AC PM motors from that perspective.
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Old 02-18-2017, 11:35 AM   #8 (permalink)
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Something that may be worthwhile mentioning is that the Fisker Karma motors are synchronous and thus require DC excitation so they are not really a pure AC motor in that they require a DC source to initialize rotation. These aren't pure AC PM motors from that perspective.
OK; so it's an AC motor but it needs a bit of DC fluffing to get going, and honestly, who doesn't?
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