What is the problem for the motor which have a 2XLF with 1X sideband

1) If your DF(dominant frequency) is 2xLF at 1xTS with sidebands and your DP (dominant plane) is radial than suspect BROKEN ROTOR BARS.

2) If your DF(dominant frequency) is 2xLF at 1xTS with slip sidebands and your DP (dominant plane) is radial than suspect ECCENTRIC ROTOR.

3)If your DF(dominant frequency) is 2xLF, slot frequency + sidebands and your DP (dominant plane) is radial than suspect LOOSE SLOT.


Cheers,

Zeeshan

Pls refer to the attachment

2XLF.doc (26 Kb, 56 downloads)

I notice it is a pump, how many impeller blades are there? maybe 4
firstly increase the lines of resolution recollect, potential for blade pass frequency invert dB then show spectra

I had a similar symptom on a slow speed vertical motor (324 rpm 13.2kv 3500 hp, tilting pad radia/thrust bearings on top, deep groove bearing on bottom).

A post about that motor is attached.

The pattern disappeared after the motor was refurbished/rewound. One thing noted during the repair was a loose fit at the lower bearing housing (had to be sleeved).

So it seems like maybe the pattern could possibly be dynamic eccentricity, in our case due to bearing housing looseness. Although I'm not sure how much effect comes from a few mils clearance in bearing housing, and I don't want to jump to conclusions from one case. Also, I think slow speed motors can produce different electrical-related symptoms than higher speed motors, because the poles of slow speed motors cover such a small arc. We have also seen dynamic eccentricity (later confirmed by examination of upper bearing clearances) show as simple 1x on one of the sister motors....and that 1X dropped immediately upon powerdown.

This message has been edited. Last edited by: electricpete,

OneXSidebands2LF.mht (73 Kb, 32 downloads)