FE motor question

Help Support intlwaters.com:

Wasted wages

Well-Known Member
Joined
Jan 2, 2006
Messages
1,048
Can anyone give a quick explanation on why the newer brushless motors have three wires going into them ?

Is it wound like an alternator on a car is?
In a 3 phase delta configuration?

Any technical links to how the speed controllers convert the DC battery voltage to the input voltage for the motor windings would be appreciated!
 

RaceMechaniX

Well-Known Member
Supporting Member
Joined
Apr 27, 2007
Messages
2,765
Brushless motors are three phase AC motors. In the simplest configuration you have three stator phases and 2-pole rotors. Stators can be wound as Delta or Wye. Most car motors are sensored and have a hall effect array to measure rotor angle. This is used for smooth starting at low RPM. For boats it makes no difference and 99% of motors and controllers can be run in "sensorless" mode. For boats, most of the motors are "inrunner" style where the rotor is on the inside of the stator. Rotor poles are typically 2/4/6. The more poles typically the more torque per amp of output from the motor.

Wikipedia BLDC
 

Wasted wages

Well-Known Member
Joined
Jan 2, 2006
Messages
1,048
Another question....

Are these FE motors that are used on outboards waterproof ?? or water resistant ??

What's the procedure after a flip and sitting upside down till the retrieve boat picks it up ?
are the bearings and windings sealed ?
 

RaceMechaniX

Well-Known Member
Supporting Member
Joined
Apr 27, 2007
Messages
2,765
You should treat an outboard FE motor just like a nitro motor. If it gets dunked you should blow out the water and use something like Corrosion X to displace the water and prevent corrosion of the shaft and stator laminations. After the day, ideally you take the motor off the lower and add oil to both bearings.
 

Wasted wages

Well-Known Member
Joined
Jan 2, 2006
Messages
1,048
When you say blow out the water, aren't the motors completely closed up and sealed ?
Sorry for all the stupid questions, but I have never seen a FE boat up close and in person...
 

donaldhuff

Member
Joined
Feb 13, 2017
Messages
15
I agree with the "blow it out" part, but I have taken apart a couple of hundred motors by now. And some of them have come into my shop dripping with corrosion X, easy to tell because they STINK!

That oily stinky stuff does attack some of the rubber heat shrink that some motors use for insulation. I have rewound a few motors that burned up because the oils turned the insulation to mush. And that allowed the leads to short between each other.

If you do use corrosion X or wd40, I suggest blowing as much of it out as you can.

I just blow mine out with air and run it again to get it warm. I do understand that outboards are a different matter though and may need special attention.

To answer your question Wasted wages, NO neither the windings nor the bearings are sealed. If you can run it after dunking it and blowing out, that will get it warm enough to dry most of the water out.
 

donaldhuff

Member
Joined
Feb 13, 2017
Messages
15
Tyler, off subject a bit but, are they really AC current? Or is the esc just pulsing the DC and controlling the "ON time" of the pulse, and then switching the polarity of the next pulse. which in a way is like changing the hertz.
 

RaceMechaniX

Well-Known Member
Supporting Member
Joined
Apr 27, 2007
Messages
2,765
Hi Don, when we speak about ESC's the input current to the ESC is DC and the output is AC. AC current and waveforms can be quite different depending on the type of commutation used. Most of the inexpensive ESC's use "block" commutation where the current is pulsed and the average voltage seen by the motor looks like a trapezoid. You can think of it more like a digital on/off for each phase. Better ESC's use a "sinus" or FOC (Field Oriented control). The ESC pulses the current at a variable turn on/off time and the average phase voltage is closer to a sine waveform that a trapezoid. It is a more complex control algorithm and to run this more efficiently the ESC needs to monitor the AC current supplied to each phase. The ESC measures the AC currents and uses this in a closed loop current control loop. It results in a more efficient motor.

There is an in between control style called "six step" which is half way between a trapezoid style and sinus style. Most hobby ESC's use a 6-step and only a few use sinus control. Some ESC's will switch between a six step and block commutation depending on the load. For example partial throttle versus full throttle. The image below shows a good comparison between the three styles of commutation.
 

RaceMechaniX

Well-Known Member
Supporting Member
Joined
Apr 27, 2007
Messages
2,765
SLS definitely does: SLS ESC's

Kontronik has all the hardware in the Kosmik line of ESC's, but not sure they are implementing it.

YGE might be on the newer ESC's.
 

darryl whitman

Well-Known Member
Joined
Aug 26, 2012
Messages
399
Go to flite test .com , it's a simple build airplane site, they show a test , using corrosion X on motor- esc- receiver and battery, drop it in a 5 gal, of water an run it , that should help you understand the benefits of corrsionX I have ran servos on the out side with no problems using corrsionX an mild grease.
 

Zach Davis

Well-Known Member
Joined
Jan 29, 2008
Messages
632
Have you run a Sinusoidal controller? Is there any noticeable difference?
 

RaceMechaniX

Well-Known Member
Supporting Member
Joined
Apr 27, 2007
Messages
2,765
Yes I have, the rotor runs cooler, but the stator tends to run a little hotter. Most of the FOC controllers I have run switch at higher frequencies than standard controllers which also makes a difference.
 

Latest posts

Top