ORIGINAL: websterphreaky
I've seen a few discussions on this topic, the maximum length that the wire between a brushless motor and ESC can be. I'm looking for a concrete answer, based on REAL electronics engineering fundamentals, not old wives tales (don't tell my wife I said that).
Some model planes, especially Glow to Electric conversions just don't allow for putting the ESC within a standard wire length (as delivered with the motors and ESC), so can distances like 9", 12" 15", 20" be acceptable? Can changing the wire guage size conpensate for longer distances?
Would love answers from the Forums Electronics Engineers, state your MS of EE origin or IEEE Certificate :^) Seriously.
From Model Aviation - Battery Clinic column July 08:
LONG BATTERY TO ESC WIRES OR LONG MOTOR WIRES FROM ESC?
There has been a fair amount of controversy on this subject as e-flighters move into multi-engine models. Logic would tell us that just lengthening the battery leads so the ESCs could be located in the engine nacelles for cooling would be the way to go. Well that isn’t the way it goes according to those that design the ESCs.
Patrick del Castillo of Castle Controllers has this to say, “On the HV controllers especially, the battery-ESC length is the critical length. You should not extend the wires more than a total length of greater than 12" without additional capacitors. On the motor side, length is less critical 18" is fine.
While Bob Boucher (Astrobob)
http://www.astroflight.com has this to say on the subject with a bit more detail,
“I will repeat the message previously given. I hope you heed some sound advice
based on theory and practice.
1. Wire resistance my rob you of a bit of power but will not destroy
your speed control or motor.
2. Wire inductance will not damage your motor nor will you be able to
detect any effect even with 100 feet of wire.
3. Wire inductance will kill the mosfets in your control and may even blow the caps.
You must keep battery wires as short as practical. Short means 1 foot or less.
Brushed or brushless, it makes no difference.
Here are some example of problems some customer have had;
1. Blimp with 30 feet of wire to ESC near the steering motor in the tail.
ESC rating 60 volts 50amps, motor load at 12v was 20 amps. Result instant smoke first run of motor. I replaced control at no cost. Same result instant smoke. Then I was told about long wires and ran a test with 3 ft cord result 30 volt switching spikes on 100 uf input capacitor. I had the customer put the ESC near battery in gondola. 30 ft wire to motor-end of problems.
We have customers running very long wires to motors for industrial applications
with no problems, hundreds of feet or more.
With ESC keep battery wires short. PERIOD!
But if you must run long battery leads Shultze shows us how to add extra capacitors (English and German):
http://www.schulze-elektronik-gmbh.d...e/gfutc-de.pdf