Question about power capacity of electrical motors.

We have such a material and it is called silver.

Current density and power are two different things.

The actual issue is temperature rise because of winding resistance.

The problem with electric airplanes is the lack of a power source that is comparable to gasoline or jet fuel not the weight of electric motors.

No, you need to reduce resistive losses and/or get rid of heat.

On Sat, 15 Jul 2017 13:43:55 -0400, Robert Clark

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Got a super-battery to go with your super-motor, though?

Solar cells work so long as you stay above the cloud and keep to the lit hemisphere!

piglet

Only for powered sailplanes otherwise the area available to collect energy is too small to meet power requirements.

Teslas accelerate in short manic bursts. The motor would fry if it ran steady-state at full power.

And the power/weight ratio drops a lot if you include the batteries.

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Very true - the Tesla Model S could not complete the Nurburgring course at one time because the motor overheated. The motor is liquid cooled - even the rotor has oil passing through the center.

I don't know about the Tesla but the motors in other EVs are designed with a peak to average load factor of 3 or 4 to 1.

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Not only that but increasing the copper usage efficiency doesn't reduce the weight of the magnetic material which is at least 50% of the weight.

kevin

That would make the chop shops happy.

Props are rather old-school, too.

And.

The albatross is a proof-of-concept that covers fish-powered flight. There's enough energy storage for overnights, too. So one needs SOMETHING for energy, but it doesn't have to replace hydrocarbons, it only has to replace fish.

You can build one with superconductors, but you have to be careful of three things:

1. Type 2 superconductors have AC losses. Preferably, this would be done with type 1, at LHe temperatures.
2. You can't use magnetic materials very well. Well, you could -- but you'd only be gaining a paltry ~tesla before saturation, when you have several tesla available with the superconductor. They'd also be lossy, putting out heat that you don't need.
3. The cryocooler is going to set you back more, in space and power, than doing it with copper in the first place, not to mention the expense (and making slip rings, and low resistance connections, and..).

Although one neat thing is, you can avoid slip rings by using a superconducting loop for the rotor (thus you get a superconducting BLDC machine). Much stronger than NdFeB, and as long as the cryocooler never shuts down, it never demagnetizes.

Tim

-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website:

Of course the clutch disc in my Mustang, taken alone, has an even more remarkable ratio for the same reason--the actual power is being generated elsewhere.

Cheers

Phil Hobbs

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Tesla EVs are unusual among EVs in that they use induction motors so there are no permanent magnets in the rotor - all the others do use rare earth magnets.

kevin

Barbers, salad stores or those stripping stolen cars?

But quit efficient.

And what in regards to electric motors?

Guess.

Depends on your definition of "efficient". 777s are quite efficient,

No OR, dumbshit. *AND*

Decline.

So are roller skates.

So what?

Or what in regards to electric motors?

motor design is very mature, there are other things in the chain that you can optomize

Actually early Tesla motors (and most electrical equipment of the time) were rather poorly designed and inefficient because the materials not being very good and the designs of magnetic circuits were very open and lossy.

Tesla invented a gas turbine with no blades of up to 95% efficiency which is the real winner over a typical gasoline engine.

Right. Which may give them some advantage in heat tolerance, because NdFeB has a relatively low Tc compared to other motor materials (iron, copper and polyimide).

A superconducting magnet would still preferably be "PM" (as I described), because of losses. I mean, the reason a squirrel-cage rotor moves in the first place, is entirely because of loss -- field gets trapped ("dragged") through it, and hence a change of angle generates torque. :)

(Hmm, you could still do it without magnetizing the (superconducting) rotor, it would just have to be constructed differently so that repulsion works instead. You'd have a "pushing" rather than a "pulling" motor. :) The slip frequency would of course still be zero.)

Tim

But ice skates are even better! So we just need this cryocooler (already present as described in the previous posts) to be able to cool down a sufficient part of the environment and do it fast enough before the car, I mean sleigh, arrives!

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Exactly.

So then why is their Tesla car electric?! O wait, you mean