What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

My next electrical question

Dugaru

Well Known Member
Okay so my old Kubota alternator turned “backwards” when installed on my O-320. From what I can tell this is typical, and my (limited) grasp of ancient high school physics tells me that the rotation direction should make no difference in terms of generating electricity.

Does it make a difference in some other way? I figure it must or manufacturers wouldn’t bother to spec it. I’m told that on twins with engines that rotate in different directions, there are different alternators to make sure each rotates in the “right” direction. That would suggest there is a “right” direction. What am I missing?
 
Others more knowledgeable than me hopefully will speak up but the internal fan sets the direction….
 
Most alternators have a fan, internal or externa). These fans are directional, so will move air much more effectively when spun in the designed direction. Many here run auto alternators in the wrong direction and report good results, so can't state how big of an issue this is.

Lary
 
Alternator

An alternator produces alternating current (AC).
It is rectified in to direct current DC that is used in the aircraft.
The direction of rotation does not matter from an electric point.
But without proper cooling from the fan things may get to hot.
If you have an alternator rated for 50 A operating at 15 A, in the
wrong direction would probably not produce to much heat.
Increasing the load running it in the wrong direction will kill the
alternator.
 
Just My Opinion

I have an old WW2 electric motor / generator training manual. It shows how the rotating armature drags the field lines around in the direction of rotation. I think that there might be some tweaking of the brushes to phase the armature with the field due to this. The worst case is that it wont be very efficient, but there is no such thing as "reverse" AC voltages.
 
If you have been running it for a long time in one direction the brushes will more than likely make some noise and wear a bit as the rebed to the other direction. The other thing to consider is bearings that have been going in one direction will start to wear the races. Going the other direction may cause premature bearing failure.
 
Back
Top