Q-119: I just bought my first brushless electric motor and
noticed that unlike all my previous ferrite motors, this new motor has three
wires coming out of it. My ferrite motors only required two wires.
I also read in the instructions that come with my brushless motor that if it
runs backward, swap any two of the three wires to get it to run in the correct
direction. What is that all about? Why can’t they just supply a wiring diagram
and employ color-coded wires?
A-119: The reader is obviously frustrated by this seeming lack of
instruction for his new brushless motors. In defense of the manufacturer(s), the
new brushless motors that operate from what is called a “sensorless” ESC have
become second nature to most electric enthusiasts. For that reason, I’m afraid
that the manufacturers are taking their instruction too casually.
The fact is that these new motors do have three wires exiting the case.
The companion brushless-motor ESC also has three input wires. Most manufacturers
suggest using individual, nonpolarized connector pins (such as MP Jet item
MJ21011 connector pins from Hobby Lobby) to make the connection of the three
wires between the motor and the ESC.
They suggest that you run up the motor initially to determine that it is
rotating in the correct direction. With a forward-facing motor, the rotation
should be counterclockwise and the airflow from the propwash should blow back
toward the rear, or tail, of the model.
If you find the propeller rotating opposite to that and the propwash blowing
forward of the aircraft nose, reverse any two of the three wires and the
rotation will be corrected. After you do that, you can easily place small tags
on each pair of wires for future identification.
I like to use multipin polarized connectors to join my brushless motor and ESC.
Once set up, I can easily move a particular motor to another model, which has
its own ESC inside the fuselage. I mount the motor in place, plug in the
connector, and I can go flying. I even do this at my flying field. It allows me
to share one motor with several aircraft.