Tesla Secret

But it is still power in equals power out, so more torque is required to push that 300 Amps. The device is just more capable of doing it, and should/could/would get there at presumably a lower rpm.
But yeah, that is for generators and motors, not alternators.
One supposes that slight additional gains could be wrested from making a more precise surface quality and gap match between the rotor core 'faces', and the stator (magnet core) 'faces'.
They are probably pretty close already though. Something like 0.015" with a 5 thou plus or minus tolerance, allowing the mass production mills to spin 'em off in bigger lots between inspections, and requiring less matching at assembly time. ------------------------------ No objection to power in =power out but to the idea that the device will, by going to permanent magnets, can have a higher current capacity.
1) Note that the current rating of an alternator or motor IS NOT determined by the field strength. It is a thermal limitation. For a given speed and winding, the voltage available IS determined by field strength. Certainly, IF you could triple the field strength then you could triple the voltage and power (not the current) or get the rated voltage and power at a lower speed. If you want to triple the current capability - a rewind is needed. My complaint is with "The more magnetic flux = more amps" which is nonsense. 2)Since the best Neodymium magnets have a flux density of about 1.4T and electrical steel can go higher than that (about 1.6T) there is little to be gained - On top of this, the electrical steel in machines is kept below the knee of the saturation curve (say 1.1- 1.2 T) in order to limit core losses (as well as magnetizing current which is not an issue with permanent magnets). You won't get the much higher fields and if you had them, the losses would be higher than those involved with the conventional field winding.
Conclusion: If you want a permanent magnet generator or motor- start from scratch with a proper design which takes advantage of the permanent magnet's characteristics .
Small permanent magnet alternators have been around a long time -remember the old bicycle "generators", the faster you go, the brighter the light. Newer magnets do allow more output per unit weight and volume and better efficiencies.
There is no inherent difference between a motor and a generator except for the direction of the energy flow. (electronics such as switching in brushless DC motors excluded as this is not actually part of the energy conversion between electrical and mechanical ).
Don Kelly cross out to reply
Reply to
Don Kelly
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In article , Nunya wrote:
It's a great pity you didn't learn something about alternators then, while you were at it. - Why, for any given engine speed, they are typically spun at about three times the speed of a dynamo. The reason they can produce useful output at engine idle speed is because they are spinning at around 3000rpm - which is what this particular thread is all about - not whether or not you are a competent machinist or engine re-builder.
Reply to
Stuart
We're talking about the same thing. I thought you were saying that on those motors/generators/alternators ALL they did was replace the mags. But it appears you know that is not true, Jim "the OP", never said ALL they did was replace the mags... and I think that's where the confusion set in.
I stated to Jim that the new type of motors were like the older type "on steroids", in response to his statement:
"The same was said about getting more power out of an alternator than thought possible. You don't need a coil to energize a magnetic field, you just need much stronger magnets. The more magnetic flux = more amps...so that $99 100Amp stock alternator can easily be converted into a $300 200-300A with a few minor modifications."
Which is ambiguous now that you've pointed that out. We don't know what other "minor modifications" he is talking about. I assumed a total re-build to convert the alternator from a brush & coil to a brushless permanent mag. type using rare-Earth mags. instead of a magnetized hunk of iron.
Is that how new alternators and electric motors are constructed on newer vehicles?
I don't know what the PF increase would be, but I'd easily accept a 300% increase if that's what Jim said. He's pretty sharp with electronics (I've known him on Usenet for nearly 10 years).
Reply to
G. Morgan
He's not even a competent troll.
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Reply to
Michael A. Terrell
We're talking about the same thing. I thought you were saying that on those motors/generators/alternators ALL they did was replace the mags. But it appears you know that is not true, Jim "the OP", never said ALL they did was replace the mags... and I think that's where the confusion set in.
I stated to Jim that the new type of motors were like the older type "on steroids", in response to his statement:
"The same was said about getting more power out of an alternator than thought possible. You don't need a coil to energize a magnetic field, you just need much stronger magnets. The more magnetic flux = more amps...so that $99 100Amp stock alternator can easily be converted into a $300 200-300A with a few minor modifications."
Which is ambiguous now that you've pointed that out. We don't know what other "minor modifications" he is talking about. I assumed a total re-build to convert the alternator from a brush & coil to a brushless permanent mag. type using rare-Earth mags. instead of a magnetized hunk of iron.
Is that how new alternators and electric motors are constructed on newer vehicles?
I don't know what the PF increase would be, but I'd easily accept a 300% increase if that's what Jim said. He's pretty sharp with electronics (I've known him on Usenet for nearly 10 years). ------------------------------------------ The problem is not the electronics but the basic motor/generator operation per se. There are two problems with Jim's statement a) the best rare earth magnets don't give anything near a 3-fold increase in flux- possibly a difference of 10 % - if the stator core can handle it without saturating. A 3-fold increase would drive the stator into heavy saturation and core losses would be horrendous. b) assuming a 3- fold increase, without a rewind which is, not generally a trivial job, then the current rating will not change- still 100A . His statement "more magnetic flux=more amps" is wrong unless the stator is rewound for 1/3 the turns and 3 times the effective conductor area of each turn- not really a minor modification. c) An alternator with a permanent magnet field will have no voltage regulation- so it might be necessary to replace the diodes with SCR's which can be controlled. A PM automotive alternator using SCR's and a suitable electronic controller (digital or analogue) designed from scratch might offer some efficiency advantage (likely less than 10%) but lower weight and volume, while eliminating the brush (there are other ways to eliminate brushes but for such a small machine, they aren't worth while). Considering the PM motors available that could be quite an advantage, but the economics might not be there yet.
As for PF- I assume that you mean power factor which has nothing to do with this.
Don Kelly cross out to reply
Reply to
Don Kelly
Wow, alright. Big discrepancy between 10% and 300%. I'm in way over my head here, technically. I took AC/DC circuits, relay logic, semiconductors, and digital electronics classes... none of which qualify me to design an alternator!
Jim?
:-))
Reply to
G. Morgan

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