Current draw of a 3511KV 5407L with no load on 2s or 3s lipo? Need some help here.
 

Current draw of a 3511KV 5407L with no load on 2s or 3s lipo?

I suspect that my feigao has partiallly demagnetised. Right now i am having a current draw of 6A unloaded on 2S lipo. Is this normal?

That sounds pretty high. I will look later on and I think I have one of those laying around somewhere and a wattmeter. I will try to give a comparison, but usually its only 1 or 2 amps from what I have seen.

My 7XL will draw 6.5 amps no load on 6s lipo... so it could be right. Maybe check Fiegao website for idle currents?

Hi, thanks alot for the info. I've tried searching on feigao website but all I have found is the max current spec of the 540 motors.

No prod bob.
It's probably right... Fiegaos aren't exactly made with high quality control, so everyone's results may vary a bit.

I've tested the rest of my motors and found that motors with stator has a lower idle current. Motors without stator cores but have very strong magnets have higher idle current. Higher KV = higher idle current.

Well it all makes sense now. :D

All tested are 2 poles motors.

I don't understand your last post, a stator is the stationary portion of the magnetic field. Basically its the windings in the motor. So as I like to tell people who walk up to me and start speaking spanish: "No Nintendo."

Jeff

My mistake. I left out one word. Stator coil and stator core. Some brushless motors do not have stator cores (aka air cores) to concentrate the magnetic field. u aren't totally right either. :D Good day.

I was just trying to be funny. How am I not right? The stator is the stationary part of a brushless motor. It's also the stationary coils of an alternator or generator, or any motor type that uses a winding that is stationary position usually on the outside of the rotor or armature as the case may be. In an outrunner it's still the stationary portion of the motor.
I guess if you go by a wikipedia definition or something then I could be wrong. I guess you are referring to slotted vs slotless? (idk I’m asking)

Jeff

Oh my mistake again. That's the word I am looking for. Slotted!!! Thanks for bringing this up. Stators are usually made up of 2 parts the coil and the core. I have edited my post and meant to say stator core then. I didn't say that you were wrong just tat u only mentioned the coil and not the core. It was my mistake. Come on :lol: i made a mistake but it is not the end of the world. didn't u noticed that :D near the end of my post to you? :D:D:D:D

"No entiende" is spanish for "don't understand."

It's no big deal I was just missing what you were saying, I misunderstood what you were saying.

It would seem to me that a slotted motor would have a lower idle current than a non slotted motor (air core) due to having more inductance, thus more impedance (and lower Kv) than an aircore motor. Is this correct?

And how do you measure idle current? With the motor at a very low RPM without a load? What's the test procedure?

Jeff

That will be right. I am not sure about the part of the impedance though. :) The stator core concetrates the magnetic flux generated by the coil hence it takes less coil to produce the same power. But the savings in copper is offset by having a stator core.

All things being equal, having an iron core would do exactly as you say, but because of the iron core there would be a larger resistance to changes in current flow ie: inductance so that would lower the Kv and increase the impedance which changes with frequency (RPM).

"But the savings in copper is offset by having a stator coil."
And you meant to say core right?

I am not trying to nit pick , just understand.

Jeff

:lol:Yeah i meant to say core.

Sorry it took me so long. 3.4A on 2S, 5A on 3S.

Ok that's a 5407L right?

I guess my feigao is working fine. Max current draw on a 1/10 buggy was 33A on 3S sounds ok right? Race track will be different I understand.

So what is the test procedure for idle current?

Jeff

Hook the esc up to a wattmeter and apply full throttle. Check the amp reading.

The motor must be without any load (free load)

Well, it's a very complex and time consuming procedure, where you take any load off the motor and run the thing WOT and measure the currents using an eagletree or similar unit. Now, this is only for the non faint of heart and experienced RCist.

:whistle:

Woops, you know what, it an 8L purple feigao. Sorry about that. I can only read the 77A max sticker and the .0076 ohm on it which I think corresponds to an 8L motor. So a 7L would be higher than what I gave you. Ya I just hooked up my wattmeter and let it run full blast for a couple of seconds. I tried a couple times to be sure, but you dont want to run these things unloaded for too long.

33A peak on 3S sounds fine. In fact that might be a bit low. I'm assuming its a light buggy to get that number. But ya looks like it is ok.

Well I didn't know, I didn't think you were supposed to run them at full throttle without a load (though I have done it), and idle to me means low rpm. :neutral:

Jeff

free load actually. There is nothing wrong with testing motors without a load.

Hey thanks alot. 33A peak on 3S was tested on a low traction surface. Asphalt or grass will definitely result in a higher peak current.

j/k about that... well about it being complex and all. It's just the no load full rpm is what idle current would be. For instance, my 1512/3D on 6s lipo will consume only 1.5amps at 40,000rpm with no load.

Something I have learned about the feigao motors is they last forever as long as you cut the run short when they get to about 175 ish. Once they go over that and overheat, they become useless. So watch temps.

I forget you guys run all those low Kv motors, my lowest is 3.3Kv and they go up from there so my last 3 are well over 60K at 3S

Jeff