No Control Over DC Motor Speed After Bearing Change - Help Needed

In summary, the dc motor has failed because of damaged coils, and the tacho-generator or encoder is not working because the connection is not correctly fastened.
  • #1
Arifur
8
0
After bearing failure of 24V, 15A dc motor. We change the bearing of the dc motor. But after changing it the motor is running forward/ reverse but there is no control over the speed.

Where is the problem? Is that in the techo or drive card?
Any body please help.

Helping in highly appreciated...
 
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  • #2
Suggestions:

1) The stator and rotor have scratched each other, and some of the windings have been damaged.

2) The tacho-generator or encoder has been damaged, due to a skew shaft.
 
  • #3
Thnx Hesch for your suggestion, but there is no screech between rotor and stator.
In case of winding failure it won't run, isn't it?
 
  • #4
Arifur said:
In case of winding failure it won't run, isn't it?
I don't know how your motor is made up, but I think that electronic commutation of the motor is used. In this case I'm sure that the drive will report an error in a coil.

In case of a mechanical commutation, there is a lot of coils in the motor, and if one of these are damaged, the motor will be unstable. The drive, which then is a simple dc-drive, will not detect/report an error.

But what about the tacho-generator/encoder? Connect an oscilloscop and see if they are running stable.

( I've seen so many times in case of an error, that the mechanical connection from motor shaft to e.g. encoder shaft is not correctly fastened. )
 
  • #5
Here is a good troubleshooting guide that may be of some help.

To expand on what Hesch is saying about multiple commutator coils: when you check the brushes, if there are more than one pair, you can remove some of them so there is only one pair left, (that is two brushes on directly opposite sides). Now when you rotate the armature and read the ohmmeter you can check each of the commutator windings separately, as you slowly turn the rotor by hand (with all power disconnected!) Be sure to replace all the other brushes when done. Don’t forget to check the tachometer (if equipped) for output signal.
 
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Likes Hesch

1. Why has the DC motor speed changed after the bearing replacement?

The DC motor speed may have changed after the bearing replacement due to changes in the motor's mechanical and electrical properties. The new bearing may have different friction characteristics, which can affect the motor's speed. Additionally, the replacement process may have caused damage to other components of the motor, leading to changes in its performance.

2. Is it normal for the DC motor speed to decrease after a bearing change?

It is not necessarily normal for the DC motor speed to decrease after a bearing change, as it depends on various factors such as the type and quality of the replacement bearing, the condition of other motor components, and the accuracy of the replacement process. However, a slight change in speed is expected as the motor adjusts to the new bearing.

3. Can the motor speed be adjusted after a bearing replacement?

Yes, the motor speed can be adjusted after a bearing replacement. However, the method for adjusting the speed may vary depending on the type of DC motor and its control system. It is recommended to consult the motor's manual or seek professional help for the appropriate speed adjustment procedure.

4. How can I troubleshoot the issue of no control over the DC motor speed after a bearing change?

To troubleshoot the issue of no control over the DC motor speed, you can start by checking the connections and wiring of the motor and its control system. Make sure all components are properly connected and functioning. If the issue persists, it is recommended to consult a professional for further inspection and troubleshooting.

5. Can a faulty bearing replacement cause damage to the DC motor?

Yes, a faulty bearing replacement can cause damage to the DC motor. If the new bearing is not compatible with the motor or is installed incorrectly, it can cause excessive strain on the motor and other components, leading to potential damage. It is important to carefully select and install the correct bearing to avoid any potential damage to the motor.

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