Devices, systems, and methods for relieving stress

1. A method comprising:

via a device that originates sub-harmonic vibrations, said device directly attached to a first end of a rotor of an electric motor, applying a first vibration treatment, at a first predetermined sub-harmonic frequency, to said first end of said rotor of said electric motor for a first predetermined time period, said rotor thermally sensitive, said first predetermined sub-harmonic frequency determined based upon a measured first harmonic or resonance frequency, laminations of said rotor strapped to prevent flaring, a shaft and a core of said rotor not coupled via a key, said first vibration treatment adapted to reduce internal stresses in said rotor, thereby reducing a vibration level of said rotor.

2. The method of claim 1 , further comprising:

applying a second vibration treatment applied to a second end of said rotor, said second vibration treatment at a second determined sub-harmonic frequency.

3. The method of claim 1 , further comprising:

measuring a roundness of said rotor, said roundness indicative of a shape of said rotor.

4. The method of claim 1 , further comprising:

prior to said first vibration treatment, removing said key.

5. The method of claim 1 , further comprising:

prior to said first vibration treatment, mounting said rotor on two V-blocks, each V-block positioned on an inboard side of a shaft bearing mounting location of said rotor.

6. The method of claim 1 , further comprising:

placing said device that originates sub-harmonic vibrations on said first end of said rotor.

7. The method of claim 1 , further comprising:

determining that said first harmonic vibration frequency of said rotor is between approximately 35 Hertz and approximately 95 Hertz as a precondition to said first vibration treatment.

8. The method of claim 1 , further comprising:

determining said first sub-harmonic vibration frequency.

9. The method of claim 1 , further comprising:

determining a harmonic vibration frequency of said first end of said rotor, and

determining said first sub-harmonic vibration frequency based upon said harmonic vibration frequency.

10. The method of claim 1 , further comprising:

determining a first harmonic vibration frequency of said first end of said rotor

determining a second harmonic vibration frequency of said first end of said rotor;

determining a second sub-harmonic vibration frequency based upon said second harmonic frequency; and

applying a second vibration treatment at said second determined sub-harmonic vibration frequency for a second predetermined time period.

11. The method of claim 1 , further comprising:

determining a first harmonic vibration frequency of said first end of said rotor

determining a second harmonic vibration frequency of said first end of said rotor; and

applying a second vibration treatment at a second determined sub-harmonic vibration frequency for a second predetermined time period if a difference between said first harmonic vibration frequency and said second harmonic vibration frequency is greater than approximately 2 Hertz.

12. The method of claim 1 , further comprising:

placing said device that originates sub-harmonic vibrations on a second end of said rotor.

13. The method of claim 1 , further comprising:

placing said device that originates sub-harmonic vibrations on a second end of said rotor; and

determining a harmonic vibration frequency of said second end of said rotor;

determining a second sub-harmonic vibration frequency based upon said harmonic vibration frequency of said second end of said rotor, and

applying a second vibration treatment, at a second determined sub-harmonic frequency, to said second end of said rotor of said electric motor for a second predetermined time period.

14. The method of claim 1 , further comprising:

determining a first harmonic vibration frequency of a second end of said rotor

determining a second harmonic vibration frequency of said second end of said rotor;

determining a second sub-harmonic vibration frequency based upon said second harmonic vibration frequency; and

applying a second vibration treatment, at a second determined sub-harmonic frequency, to said second end of said rotor of said electric motor for a second predetermined time period.

15. The method of claim 1 , further comprising:

determining a first harmonic vibration frequency of a second end of said rotor;

determining a second harmonic vibration frequency of said second end of said rotor;

determining a second sub-harmonic vibration frequency based upon said second harmonic vibration frequency; and

applying a second vibration treatment at said second determined sub-harmonic vibration frequency if a difference between said first harmonic vibration frequency and said second harmonic vibration frequency is greater than approximately 2 Hertz.

16. The method of claim 1 , further comprising:

installing said key between said shaft and said core.

17. The method of claim 1 , further comprising:

axially attaching said core to said shaft at one end.

18. The method of claim 1 , further comprising:

axially attaching said core to said shaft at one end; and

machining said rotor such that a measure of roundness of said rotor is within a predetermined range.

19. A method comprising:

reducing a measured vibration level of an electric motor rotor via a vibration treatment applied at a determined sub-harmonic frequency to a first end of said rotor for a predetermined time period by a device that originates sub-harmonic vibrations, said device directly attached to an end of said rotor of said electric motor, laminations of said rotor strapped, during said treatment, to prevent flaring, a shaft and a core of said rotor not coupled via a key during said treatment.