brushless motors efficiency/throttle position

[OshkoshMono]

I was just wondering if someone could explain this to me. I was told that these BL motors are very inefficient at partial throttle, which was news to me. Does this mean going back and forth full speed uses less battey than putting around? Thanks, -Nick

[Fluid]

The problem with running a lot at part throttle isn't motor efficiency and the packs, it's the ESC. The ESC will not tolerate part throttle without heating up - heating up a lot in some cases. That's the reason not to run at part throttle too much.

The motor's efficiency is tied more closely to voltage and amperage, not the position of the throttle. For example a Neu 1527/1D hits maximum efficiency at close to 250 amps - but you wouldn't want to run it there for very long.


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[OshkoshMono]

The problem with running a lot at part throttle isn't motor efficiency and the packs, it's the ESC. The ESC will not tolerate part throttle without heating up - heating up a lot in some cases. That's the reason not to run at part throttle too much.

The motor's efficiency is tied more closely to voltage and amperage, not the position of the throttle. For example a Neu 1527/1D hits maximum efficiency at close to 250 amps - but you wouldn't want to run it there for very long.


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Ok, kinda makes sense I guess. My ESC doesn't heat up much (maybe cuz it will handle 12s and i run 6s?) but the motor gets real hot. Do you know about how the PWM ( I think...) works on the ESC. The settings are 8, 12, or 15 khz..? Suppose to be matched up with the motor I guess...???

[Fluid]

You need to match the PWM and timing settings to the motor and its use. The motor maker should list the best frequency setting to use. The timing also needs to match the motor specs and the amp draw you use. Excessive timing can cause the motor to overheat, but it usually heats up the ESC too. Is the motor water cooled?

Let us know the exact motor, voltage hull and prop and we can help.


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[OshkoshMono]

You need to match the PWM and timing settings to the motor and its use. The motor maker should list the best frequency setting to use. The timing also needs to match the motor specs and the amp draw you use. Excessive timing can cause the motor to overheat, but it usually heats up the ESC too. Is the motor water cooled?

Let us know the exact motor, voltage hull and prop and we can help.


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Awesome! Thank you! I have an aeromarine titan 33 (can be seen in the build threads under"build pics of my aeromarine titan 33") I'm running 6s (2x3s 5000 thunderpower 30c & 2x3s 8000 SPC 20c) The ESC is a swordfish 240 running a fiegao 540 XL 12 labeled 1445 kv with a 45mm 2 blade graupner. Temps were pretty high on the motor so I went down to a 42mm graupner and temps seemed ok, so I ran it harder and.....cooked the motor. After waiting a couple mins for the boat to drift into shore, the motor was still at 270 deg and smelled none too good. The PWM is set to 8khz. I actually burnt my stomach on the water outlet, or the steam coming out of it...when I picked up my boat. Ooops. I just bought an ammo 36-88 1280kv motor from the swap shop, from forescott, I believe.
I should be able to run a 42 mm prop no problem right?? Or no? Any prop suggestions welcome! 2 blade 3 blade, mm... Thanks a TON for the help. I can't keep cooking parts.

[BakedMopar]

Ive recently ran into this same problem with a SV27 motor. No matter how small of a prop was on there the temps were never good. It was just a bad motor.

Is your driveline free? Is the boat running wet?

[Fluid]

The Feigao should run okay on 15 kHz with the timing advance on low (5-10).

You could have had a bum motor, or one which was mislabeled.



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[OshkoshMono]

Ok, thanks, hmmm. I'm thinking it was a bum motor. The driveline has a very slight angle to it. Almost straight. Is the teflon liner in the stuff tube supposed to be glued in place or allowed to free spin? Would that make a differance either way? As to running wet, maybe. I'll try to figure out how to mobile upload from my phone for a short vid.

[sailr]

Are you sure about that PWM? All the data I have says that inrunners use 8Khz for the PWM. 15-16Khz+ is for outrunners. I agree with the timing.

The Feigao should run okay on 15 kHz with the timing advance on low (5-10).

You could have had a bum motor, or one which was mislabeled.



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