Featured Model 3 has 310 mile range

The guy you quoted was the only one in that thread who claimed they use synchronous motors. And what he said about the reason was entirely wrong and devoid of any reality. Every other source I find everywhere says they use induction motors, including Musk himself:


"Answer is complex for electric motors. We use an AC induction motor fed by a DC pack thru an IGBT inverter, which kinda "digitizes" DC power"

That's the end of that one.

You should also watch this:

"It's hard to get high efficiency over a complicated drive cycle" -- Elon Musk.

 

that's called a conclusary statement. You need to say WHY you have a conclusion - not just a conclusion.

Great .... The convincing authority is a tweet by musk? Don't get me wrong - musk is a bright guy, he has a bachelor's degree in Business from The Wharton School & a bachelor's in physics. I'm sure his awkward way of describing a motor is based on his understanding, but he's not an electrical engineer. Don't feel threatened about a more authoritative source, & anyone is free to believe any source.
In a light most favorable however, I understand how if one believed Tesla's had purely inductive motors that they might be less efficient at low speeds, but the record-setting 500+ mile >5miles per/kWh feat, flies in the face of the notion teslas are less efficient in a low speed scenario (imo)
As Bob so eloquently said, we'll just have to agree to disagree (agreeably ... my addendum)
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"If the motor used just AC it would be a asynchronous induction motor, which is a unpredictable motor to use in vehicles due the slipping in the electromagnetic field when a voltage is induced in the rotor (The output-speed is slower than the rotation of the electromagnetic field."

That statement has no basis in reality whatsoever. First of all, there's no need whatsoever for precise position or speed control in a vehicle. ICE's don't have that and lots of those are on the road. It's not necessary because the vehicle has a not of inertia and because you're precise location is not important. Secondly, there's a concept called "flux vector control" or "field oriented control" (same thing, two different names) that allows you to have precise control over the rotor of an induction machine despite slip and without a rotor encoder. If that guy knew anything at all, he would have never made such a dumb claim. Third, it's actually much harder to control a synchronous motor because of the lack of rotor damping and the stiffness of the torque angle.

I'm sure his awkward way of describing a motor is based on his understanding, but he's not an electrical engineer.[/quote]

Nor does he need to be, since the differences are easy to spot. For example, a synchronous machine has to have either a set of slip rings and brushes or a brushless exciter and a set of rotor diodes. In the videos of the machine being made, I see neither one. You think Musk has been building slip rings or brushless exciters by the tens of thousands without his knowledge?

I sited the extremely-involved owner of the company and the chief power engineer of the company. You sited a random guy on a forum who is contradicted by every other source as well as his own ignorance.

 

Huh?

Synchronous permanent magnet motors as used in the majority of EVs do not need slip-rings or a brushless exciter.

However they do need a method of sensing rotor position which are not required for induction motors.

kevin

 

We aren't talking about PM machines, we're talking about wound-field machines.

No they don't. Some have them, but it's not required. All the PM machines I use on model airplanes are sensorless.

 

(sigh)
certainly this will be branded another ignorant electrical engineer because it disagrees with personal belief.

Does a synchronous motor have slip rings or not? - Quora

yep, from over a decade ago, when motor controllers, processors, & electronics were much less complex & slower. Times are changing. Like I said before we wasted more threads' calling people ignorant, etc - feel free to believe whatever you want.
....... only it would still be interesting to hear some kind of reconciliation about how Tesla's could be so inefficient at low power, per the "record range" example a few threads above - yet still be able to set high mileage distance records .
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You cannot easily use sensorless motors where you need to easily reverse or start from zero speed with a significant inertial load.

To get any EMF generated in the coils to use them to sense position requires that the motor be run open-loop to start.

All PM motors in EVs use a position sensor.

kevin

 

That guy is wrong.

Look, I have a Masters degree in Power Electrical engineering, specializing in power electronics and electric machines. My Masters Thesis was on the dyno testing of a custom-built 3-phase PM machine. I've bought three-phase induction machines from 10HP to 2.5MW and installed and commissioned them with and without variable frequency motor drives. One of them was a very special, state-of-the-art application Rockwell Automation had never done before, probably because it was my idea (it used a 40Hz machine with special properties designed specifically for my application). I've worked on synchronous PM machines as large as 4 meters in diameter. The current controls research machines I specified, developed, helped assemble, wrote the control software for, and have worked on for 15 years have one each - an induction machine (480V three-phase) and a synchronous machine (4,160V three-phase with a brushless exciter). I've had both machines apart and have been inside both of them. They're both 650kW. I've been an invited speaker to teach this stuff to undergraduate and graduate college classes.

 

Yeah, I agree. I'm just saying it's not required for the machine type. It's better for accurate timing especially with high-inertia loads. The encoders in the Prius are resolvers, if I recall correctly.

 

The Prius and others that have seen all use resolvers - usually a planar design.

kevin

 

Makes sense. They're darned near bullet proof.

 

those are certainly weighty credentials. I say this with no disrespect or ill intent, but that's anecdotal & I'll explain what I mean. My (retired 15yrs now) EE father-in-law designed a lot of the electronic controllers for early computers & even top secret junk that he still can't talk about to this day, for hydrogen bombs. His credentials are weightier than my wife's Uncle Kenny, who himself is an EE. Over the decades, Uncle Kenny has regularly tormented my father-in-law for not being able to understand some of the lofty junk that he has designed, consulted on, & troubleshooted. What's the takeaway? At worst, lofty credentials don't make someone right, nor does the lack of weighty credentials make the credential holder wrong. And somewhere between the black & white (of the notion, "i'm right & others are wrong") - there is the gray area. At best... hey, people disagree, & hopefully they can do so without necessarily being branded ignorant.
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Trust me - induction motors don't have slip rings. That's one of the main reason they are industrial mainstay machines. And wound-field synchronous machines have to have either slip rings or some sort of brushless exciter to get the field currents to the rotor.

Induction machine, no slip rings: Induction motor - Wikipedia

Synchronous machine, slip rings in the foreground (gold colored with wires running to brushes that ride on them): Synchronous motor - Wikipedia

If you want to read about field-oriented-control (usually for induction machines, but not always), Wiki has an article: Vector control (motor) - Wikipedia

I strongly suspect Tesla uses at least some variation of that to control their cars' induction machines, which they are unquestionably are:

 

What a remarkable achievement tesla has made. They will have my money in 3 years.

 

Whew! After reading all that .... I still do not understand.

But don't explain. I wouldn't understand the explanation either.

I'm just grateful we have EE's, ME's, CE's and all the other "E's."

 

And a lot of new competition in that time frame. Way too early to be making a decision IMNSHO.

Imagine you are sitting in the Florida Keys yesterday and want to evacuate 500 miles North in some unknown direction following the news and going where safety seems available as well as lodging. You have an EV...or a ICE...or a hybrid. All fully fueled as you make your decision. Which do you take?

(An aside, my cruise from San Diego with a last stop in the Keys was rerouted to a trip around Cuba when a storm came up. OTOH, we got to witness a night time evacuation of a sick passenger in 10 foot swells by lowered basket by the Coasties helo. Right impressive flying . I'd been dropped onto a deck vertically but seeing them extract having to hover alongside and run the extract diagonally! Friends from Poland/Germany just had to detour this week as their cruise out of Ft Lauderdale planned to go to every island hit by Irma. They were detoured to South America.)

 

The keys? Get on a airplane thursday. You don't want to be driving in that traffic jam or wait. My brother flew down to get mom on a plane out of sarasota. F'. All those stations are closed in miami. Down there you want an phev or a bev. 200 mile range? That could get you to a better airport, and will turn to 300 in a traffic jam.

Houston - 200 mile range - much better than a gasser. You could have fueled up and gotten out later.

Strange comparison though. Austin had gas lines for 3 days after the huricane and we weren't even close. People were joking about how much better a plug-in would be.

Why the f' would you try to drive 500 miles from the keys? 500 miles from key west is still in the huricane zone, with long gas lines and traffic jams. Sure if you waited until today - but that was a dumb decission.

 

I don't live in a hurricane state and don't plan on anytime in the future.

 

well ... since we're hallucinating the highest of all improbabilities - where one would have to be somewhat deficient for waiting around so long - I'm going to be taking SpaceX.

On a more sobering note, our son in law & daughter left the Nashville area early this morning with our 3 grandkids, rather than wait to see what happens. You see, sometimes nature is horribly unkind, & has its own way of thinning out the chromosomes if those with the least likely probability of survival. So, we can make up all of the nonsensical suppositions that come to mind. But people based in reality know what to do, and then do it.
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