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  #1  
Old 03-20-2005, 01:47 PM
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which motor pulls more amp? 540 or 550?

I have asked this in different forum, but there are Experts here.

Here the question, all things being equal like the voltage and the number of turns and timing, Which motor would pull more amps? a 540 or a 550?

and why?
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  #2  
Old 03-20-2005, 03:43 PM
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ElectricThunder ElectricThunder is offline
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I believe the 550 would be able to pull more amperage because it has that much more wire on its armature (the arm in a 550 is longer, thus allowing more wire to be wrapped around it). However, seeing as how a 550 generally has more torque, it probably won't need to pull as many amps under an equal load as a 540 motor, because the 540 motor has less torque. At least I THINK that's how it works. I'm more into brushless now...so I kinda forgot a bit about brushed...lol!
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Old 03-20-2005, 08:59 PM
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Pretty close, but all other things being equal, I'd actually expect the 550 motor to pull more amps, since more overall power requires more current.....
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Old 03-20-2005, 09:40 PM
TimisTim TimisTim is offline
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I dont think the amount of wire will draw more current, since all the brushless long cans pull less amps that there short can counterparts.

feigao 8L = 77amps
feigao 8s = 81amps

I think it really has to do with the internal resistance of the wires, the more wire the more resistance the less rpm's and amp draw.
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Old 03-20-2005, 11:26 PM
TrickSpeed TrickSpeed is offline
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if the number of winds are the same, then the 550 will draw more current.
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Old 03-21-2005, 02:02 PM
kschauwe kschauwe is offline
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Quote:
Originally Posted by TrickSpeed
if the number of winds are the same, then the 550 will draw more current.
The 550 will draw less amps, because the wire in the windings are longer = more resistance = less current draw.
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Old 03-21-2005, 02:04 PM
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Quote:
Originally Posted by kschauwe
The 550 will draw less amps, because the wire in the windings are longer = more resistance = less current draw.
If that is true then will a 380 draw even more amps?
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Old 03-21-2005, 02:12 PM
kschauwe kschauwe is offline
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If the wire diameter of a 380 was the same as a 540, the yes it would. Their arm's are smaller in diameter, and shorter in length than a 540. And ever one I've seen, has thinner wires.
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Old 03-21-2005, 02:22 PM
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Very interesting, here's why I was wondering.

I'm wanting to convert the limit of an esc to the other size motor. Without knowing the amps of the motor or the amps of the esc. For example a EVX may give a limit of 2 19 turn motors (550) I would like to know what the limit is for 540 motors?

Another example would be a DTX intellispeed esc that had a 16 turn limit (540 size) what would be the limit for 550 size?

What do you'all think? and thanks for the info so far.
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Old 03-21-2005, 02:30 PM
kschauwe kschauwe is offline
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The EVX isn't designed for 540 motors. There's no 540's that can handle 14.4 volts.
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Old 03-21-2005, 03:27 PM
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Yes there is plenty of 27 turn motors (540) that will, but that really wasn't the point to the question as I may sometimes use 10 or 12 volts on the evx anyways.
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Old 03-22-2005, 08:24 PM
xrayracer xrayracer is offline
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kschauwe was not wrong. the 540 were originally a 6v motor and we can over run them to use 14.4v the com and brushes were not designed for handling the higher voltages (originally). The fact that the 540 has been well built to handle more voltage means nothing. See an electric motor is an electric motor. you put the winds in to have the thing run in a certain rpm band that will allow it to survive at the speed the engineers felt would make the motor perform and last. run a 6v motor at 12v and the thing will spin way faster. The drawbacks are increased brush wear, bushings will prematurely fail for higher friction levels and the windings or armeture may not be rated for that speed. We, rc electric racers, are pushing the design limits of these motors beyond to support are performance envelope.
10 years ago we raced Johnson 540 motors in a spec class to try something different in oval racing. those "standard 540 cans" did not have the power that are normal stock cans had because they could not pull the amps. and the only reason we used a 540 can was because the 1/10 scale was originally designed around them. The 550 is a bigger armature and magnets and will allow for more amps and torque of a comparatively similar 540 can. why? Flywheel effect as well as the magnets. Where are the 550 cans used? in rc trucks and monsters, where torque is more important then rpm.
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Old 03-23-2005, 04:07 AM
TimisTim TimisTim is offline
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I still dont see what torque has to do with amps, I though torque had to do with the size and weight of the armature. I really think it boils down to less wire = less resistance = more amps. If this was true then it would only matter how much wire and the size of it was stuffed in the 550 can. On average it seems that the 550 has more wire than the 540 thus would pull less amps. This would explain the lower rpm/Kv values and the need to use more cells to make up for the slower (but more torquey [sp? wrd?]) 550 motor.

I may have it all wrong though and will be watching this thread to learn more.
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