ESC to Motors wiring.

Hi, this question is not specific to APMcopter, but still in the same field of multicopters :)

I currently have an rce- tricopter http://rcexplorer.se/projects/2012/07/the-tricopter-v2-6hv/ (running on 3s)

with DT750 motors swinging 1147 gemfans at about 18-19 amp max. I am using turnigy plush 25amp ESCs. I like my current setup it is not acrobatic but still very responsive and gives me easy 15min flights on 3s 2700mah 35c batteries. (install 9x5 props and you could do all the rolls and loops)

I am using turnigy awg16 wires for apm power module to ESCs and from ESCs to motors. PM to esc wire length is about 10cm and ESC to motor about 25cm. The thickness of the wires does not allow me to put PM and power distribution in-between the plates (what i would like to do), so my power module just hangs really ugly on the bottom. I have some spare 18awg wires which should hold max 25amps is it advisable to switch all of my wiring to 18awg? Also, since there are 3 wires from esc to motor is the amp loading per wire lower than from PM to ESC, if so is it lower by a third or by a half?

Thank you!

Good questions Artem because the answer isn't simple. It's not a question of if 18 AWG wire is adequate because even 24 AWG is adequate (it won't melt).

Here is the rub (trade):

- any size wire will generate heat so the smaller wire you go, the more heat loss, so the ship doesn't fly as long.

- but as you go larger, you add more weight, so the ship doesn't fly as long.

So you end up with a trade. What I do for duration ships is to calculate the watts per gram for adding weight and the heat loss by going to smaller wires. With those calculations, you can then determine the optimal wire size and know the penalty for going smaller or larger. If you want to look at that worksheet and enter your numbers, I'll post it for you. But when you keep reading you probably won't see the need.

On the wires to/from the ESC: Both wire sizes should be the same from a current perspective (but you may have other considerations). At any one instant, only two of the ESC to Motor wires is carrying current, so the load is still carried by only two wires.

My guess is that your ship will see if converting from 16 AWG to 18 AWG between the battery and ESC:

- a 0.1% loss in efficiency from heat loss

- a 0.4% gain in efficiency from weight loss

- for a net efficiency gain of 0.3% or a whopping 3 second gain in flight duration.

Replies

MR60

Hugues January 27, 2014 at 1:55pm

Hi Artem,

For you issue I would recommend you do a huge investment in this 33$ all in one 25 amps Quadro ESC. Not only will you gain compacity but you will reduce your weight and reduce EMI interferences,eliminate the need of a PDB and reduce your cabling.

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=...
MR60

Forrest Frantz January 23, 2014 at 1:35pm

Good questions Artem because the answer isn't simple. It's not a question of if 18 AWG wire is adequate because even 24 AWG is adequate (it won't melt).

Here is the rub (trade):

- any size wire will generate heat so the smaller wire you go, the more heat loss, so the ship doesn't fly as long.

- but as you go larger, you add more weight, so the ship doesn't fly as long.

So you end up with a trade. What I do for duration ships is to calculate the watts per gram for adding weight and the heat loss by going to smaller wires. With those calculations, you can then determine the optimal wire size and know the penalty for going smaller or larger. If you want to look at that worksheet and enter your numbers, I'll post it for you. But when you keep reading you probably won't see the need.

On the wires to/from the ESC: Both wire sizes should be the same from a current perspective (but you may have other considerations). At any one instant, only two of the ESC to Motor wires is carrying current, so the load is still carried by only two wires.

My guess is that your ship will see if converting from 16 AWG to 18 AWG between the battery and ESC:

- a 0.1% loss in efficiency from heat loss

- a 0.4% gain in efficiency from weight loss

- for a net efficiency gain of 0.3% or a whopping 3 second gain in flight duration.

This reply was deleted.

ArduCopter User Group

Replies