shaft misalignment on electric motor 2

[progesteron]

shaft misalignment on transmiting power cause energy loss beside of premature demage on machine parts.
shaft misalignment cause bad friction in transmiting system such as flexible coupling.
this phenomena cause relative motion between driving shaft and driven shaft and reduce the rotational speed (rpm).
Power(P) = T.n......
in this case is just speed reduction only,..? how about torque,..?
can u give me explanation or reference to solve this problem,..?
thanks,....

 

[electricpete]

It is hard to understand what you are saying. For large industrial machinery, slight misalignment of the coupling will generate vibration and forces which can decrease the life of the equipment. However, the friction losses associated with that misalignment are insignificant compared to the machine power. There is virtually no detectable change in power or efficiency of the machine. Therefore even less detectable change in speed.

One detailed review of effects of coupling misalignment are at:

http://www.ulb.ac.be/polytech/laborulb/

 

[kassad]

Well i guess that the torque would not be fully transmitted from the driving machine to the driven machine due to shaft misalignment. Furthermore the motor will draw a higher current and will eventually burn out. The burn out time will depend on the degree of misalignment.

 

[electricpete]

If misalignment affects the life of the motor it will be through vibration effects. To me it seens ridiculous to think that misalignment would overload an otherwise-properly-loaded motor to the point of thermal failure.

The increase in power is very small if detectable at all.

Some more discussion at:

http://www.reliability-magazine.com/ubb2000/ubb/Forum2/HTML/000422.html

 

[jbartos]

Suggestion: It depends on the state of misalignment. The significant misalignment can cause:
1. Noticeable vibrations as posted above
2. Motor - Load set structural damages. Consequently, this may affect the motor speed way down to the motor stalling and ultimately the motor protective devices trip.
3. Noticeably increased friction, and temperature.
The above depends on a type of coupling being used. There are types of couplings specifically built to allow the motor - load angular misalignments.

 

[electricpete]

You are welcome and encouraged to discuss the destructive effect of increased motor electrical loading due to misalignment.

Here is my point:

Vibration and reaction forces are the primary mechanicsm by which misalignment impacts on motor reliability. Only in very extreme circumstances would electrical loading changes from misalignment cause any significantly impact on motor reliability.

That major effect of vibration and forces should be understood/acknowledged before proceeding to a discussion of the minor effects of loading.

 

[jbartos]

Suggestion: Visit

http://www.maintenanceresources.com/ReferenceLibrary/Alignment/WhyShaft.htm

for a shaft distortion, etc.

http://www.maintenanceresources.com/ReferenceLibrary/Alignment/Importance.htm

for the shaft misalignment examples.

http://www.textronpt.com/institute/courses/mmodule4.htm

for a failure to start.

http://www.yachtsurvey.com/alignment.htm

for an entire drive system being damaged.

http://web.utk.edu/~hines/publications.html

for several papers on the motor shaft misalignment.
etc. for more info