Would anybody have any information on Brushed DC electric motors, 24V,
1500W, and typically how much magnetism (and power output) is going to be lost over 3-6 years? Solutions, if any?- posted
17 years ago
Would anybody have any information on Brushed DC electric motors, 24V,
1500W, and typically how much magnetism (and power output) is going to be lost over 3-6 years? Solutions, if any?
About 0%. What makes you think they'll lose magnetism? It isn't 1940 any more.
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I think most modern magnets, especially the powerful rare earth variety, will hold their magnetism almost indefinitely, and even older magnets do not deteriorate very much when they have a complete magnetic path (like the "keepers" on old horseshoe magnets. The iron in the rotor of a DC motor serves the same function. However, I have heard that magnets can lose their field when overheated, as may happen in electric vehicles when you subject the motor to overload conditions. I believe this happens at the "Curie Point", and I don't know if it is a permanent loss or if magnetism returns when cooled.
I am convinced that three phase AC induction motors are the best choice for vehicles, and they are increasingly being used in locomotives. They are very rugged and inexpensive, requiring very little maintenance, and have very impressive power to size and weight ratios if you use PWM VF drives and push the frequency to 150 Hz, or even beyond 400 Hz with special laminations. The drive electronics are more complex, but the technology is well understood and controllers are often quite inexpensive.
Paul
It depends on how you control the armature current as well as the armature design. Provided you allways keep the current withing the motors rating you should not suffer any demagnetisation.
Does such large motor contain a permanent magnet at all? Just wondering.
Piotr
When we talk about Brushed DC motors, I guess the answer is no. Please correct me if I'm wrong.
I think however that we in the future will see electronically commutated high speed PM motors in this power range.
I have been experimenting on light, high speed, iron less motors for model airplanes, and if this technique is extrapolated to electric cars I think it would be feasible to make a 20kW motor with 95% efficiency weighing 10 Kg or even less.
But the auto industry is known to be conservative, so I don't expect to see this technique in cars in my lifetime :-(
-- Sven Wilhelmsson http://home.swipnet.se/swi
2 HP? I don't see why not.
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In the normal case it is better to use copper to magnetize a motor of this size. An exception may be when efficiency is very important.
-- Sven Wilhelmsson http://home.swipnet.se/swi
In motors of less than 1/2 horsepower or thereabouts, the amount of power required for the field coils becomes a prohibitively large fraction of the total power, which makes permanent-magnet motors attractive. Above that, the field coils are not a big problem.
Cheers,
Phil Hobbs
Funny you should say that, Ive just been looking at a hybrid mini. fantastic performance and 80 miles to the gallon.
I'm got three 36V 2hp motors, all of which are PM DC motors.....
Michael
Bring back the Fiat 500 I say!
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Toyota's current production hybrid vehicles already use electronically commutated permanent magnet motors with powers of up to 110KW.
keviin
I've been servicing a CNC lathe for 29 years now, that uses two PM brushed DC motors on their servos (3 horsepower). Under normal conditions, the motor doesn't lose it's magnetism. On the other hand, if the motors bell housing builds up with too much carbon dust inside it (from the brushes) and it flashes over, sometimes it will weaken the magnets. This causes the servo's to become unstable. We then either have to have the motor's permanent magnets re-magnetized (preferred) or change the servo's response circuits. Brian
The BMW Isetta.
-- Paul Hovnanian mailto:Paul@Hovnanian.com ------------------------------------------------------------------
Are you a robot?
-- Paul Hovnanian mailto:Paul@Hovnanian.com ------------------------------------------------------------------
Can you get 5 people and one suitcase in one of those?
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Here's a link to it, who wouldn't want one of these?
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