Reversing the direction of a shaded pole motor

[homebrewed]

Yesterday I ran into an "interesting" problem. The fan motor in our old food dehydrator seized up so I went looking for a replacement. It turns out that the motor is physically identical to the one used in a very common bathroom exhaust fan (that probably was no accident). Since we have a load of stuff in the dehydrator I immediately ran over to my local big-box hardware store and picked up a replacement motor. A little while later, congratulating myself on a quck & easy job, I turned the dehydrator back on -- and discovered that the motor turns the opposite direction compared to the old one, so the air flow was reversed! Flipping the fan blade over didn't work (I should have known that before I tried it).

I looked online for fan blades with a reverse twist on them but nothing that was an easy drop-in. Thought about making a fan blade but before going down that rat hole I did a search for reversing the direction of a shaded-pole induction motor and found exactly what I was looking for -- here. Now that's a solution I can get behind! And since I used wire nuts to install the replacement motor (rather than soldering) it will be a quick and easy R & R.

This will be the third motor in the food dehydrator. It was difficult to find a replacement after the original motor died, and that was 15 to 20 years ago. The little appliance-parts shop we got it at is long-gone so finding this little trick will greatly increase the availability of fan motors.

 

[silence dogood]

Not sure if it will work physically on this motor. But all you have to do is take it apart and turn the armature 180 degrees. Put it back together. It will then run on the opposite direction. The other thing that you could do on the old motor is take it apart and clean and relubricate the bearings. I've repair many of these motors just by doing that.

 

[Eddyde]

Decades ago, I did exactly that to a shaded pole motor in a turntable. It would play backwards and I could listen to the hidden lyrics in rock albums!

 

[Ulma Doctor]

if you were so inclined, you could add the correct fan and use a counter rotating fan stack arrangement and get some more performance!

 

[ChazzC]

Not sure if it will work physically on this motor. But all you have to do is take it apart and turn the armature 180 degrees. Put it back together. It will then run on the opposite direction. The other thing that you could do on the old motor is take it apart and clean and relubricate the bearings. I've repair many of these motors just by doing that.

Only helps if the shaft lengths are the same on each end.

However, disassembling and clean & lube is worth a try: I’ve kept a bath exhaust fan going for 30+ years by vacuuming out the dust, cleaning & lubricating the bearings every couple of years; I have a spare motor, almost impossible to replace without taking it out of the ceiling.

 

[homebrewed]

Not sure if it will work physically on this motor. But all you have to do is take it apart and turn the armature 180 degrees. Put it back together. It will then run on the opposite direction. The other thing that you could do on the old motor is take it apart and clean and relubricate the bearings. I've repair many of these motors just by doing that.

I did lube the bearings and verified that the motor spun freely but it just buzzed loudly when I plugged it in. There's something else going on, maybe an internal short in the windings.

 

[homebrewed]

I did lube the bearings and verified that the motor spun freely but it just buzzed loudly when I plugged it in. There's something else going on, maybe an internal short in the windings.

Oh, and the shaft on the other end of the armature is just long enough to go into the bushing so no joy there.

The stator is completely symmetrical except for the shade windings so flipping it over worked. It's running happily in the food dryer as I type, blowing air the correct direction.

 

[silence dogood]

Oh, and the shaft on the other end of the armature is just long enough to go into the bushing so no joy there.

The stator is completely symmetrical except for the shade windings so flipping it over worked. It's running happily in the food dryer as I type, blowing air the correct direction.

Well, I tried. You did everything right. Yeah, there is probably a short in the winding. This may take some doing and may not be worth it. Instead of mounting the motor the usual way, turn the whole thing 180 degrees and mount it backwards. Good luck.

 

[Bi11Hudson]

Reversing a shaded pole motor is not as easy as a wound pole motor. If possible, "flipping" the motor in the mounting brackets will answer. But that is limited by the physical dimensions of the motor. And the availibility of a double ended shaft. Of course. if the windings are reversed, the rotor is reinstalled in the correct position so the output shaft is where it's needed. Complicated. . .

Not sure if it will work physically on this motor. But all you have to do is take it apart and turn the armature 180 degrees. Put it back together. It will then run on the opposite direction. The other thing that you could do on the old motor is take it apart and clean and relubricate the bearings. I've repair many of these motors just by doing that.

Then there is the reversing the "armature" as mentioned above. In an AC motor, the armature is the stationary part, the windings. The rotor is the rotor, the armature is not the rotor. Then a simpler solution is to find a fan with the opposite pitch. If it is oversized, it can be trimmed a little, but balance is the big issue there. It can be done, but. . .

Ultimately, I concur with Silence Dogood, cleaning and lubing the motor will usually suffice. So long as the bearings are not worn to the point that the rotor is rubbing and the windings are not burned up, it should run. Shaded pole motors do not have much torque but run at synchronous speed. That's why they are used in clocks. . .

The "shading" is accomplished with a copper (usually) band around part of the pole piece. That creates a second phase magneticaly, in essence making a 2 phase motor. Reversing the motor means physically reversing the reletionship of that "shaded" portion, not practical on small motors.

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