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  #1  
Old 06-12-2021, 03:09 PM
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flytoday flytoday is offline
 
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Default Reverse Flap DC Motor Reverse

PROBLEM: You have a DC motor, like a flap motor, that is operating/rotating unexpectedly in the opposite direction.

Such as command flaps down, but they move up. This could apply to any DC motor where the polarity get swapped to make the motor operate in two directions, such as an RV flap or trim motor.

Helping a friend with his factory plane, and all wires tested, verifed connected properly, limit switches working, but flaps go up when commanded down, and vise versa. In earlier day's troubleshooting he had disassembled and reassembled the motor.

In 1st picture the permanent magnets are installed, not removable, in a "can". No markings or key to insure assembly orientation is the same as disassembly.

Well, these magnets are different from each other. The magnetic North and South poles have opposite orientations in this "can", one magnet North, other side South. And after 2 days of head-scratching, we took it apart, rotated the "can" 180 degrees in reference to the bottom plate where the wires connect to the brushes, and armature rests into. The 180 degree rotation fixed the "spin wrong way" problem.

Lesson Learned - When you disassemble a DC motor, make reference marks so relationship of permanent magnets are reassembled as original.

Carl
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  #2  
Old 06-12-2021, 03:56 PM
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I hate to tell you this after all that work, but all you have to do to make it operate the reverse direction is to swap the two wires wherever they are connected - no motor disassembly required.
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  #3  
Old 06-12-2021, 06:33 PM
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Quote:
Originally Posted by Ironflight View Post
I hate to tell you this after all that work, but all you have to do to make it operate the reverse direction is to swap the two wires wherever they are connected - no motor disassembly required.


Concur Paul, and we knew that, but would a good engineer be satisfied without fully understanding why the motor reversed? Unexplained anomaly???

See you at Osh 21....

Carl
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