Abstract
A vibration-based diagnostics method of large-power 1JAH5 (Siemens) DC motors over 660 kW used in paper machines is proposed in the article. When studying vibration spectrograms it was found that 8 Hz frequency shock loads considerably prevail over vibration, which corresponds to this motor rotor speed. The cause of vibration initiation generated by the motor rotor spinning was determined by theoretical methods. Vibration on the one hand appears as a result of bearings wear accompanied by bearing cage deformation and their shaft spinning axes reciprocal displacement, and on the other hand, by shaft eccentricity radii enhancement which causes dynamic loads increase affecting bearing units. The authors of the paper have come to the conclusion that in order to lower vibration of the motor it is necessary to replace the bearings with the new ones, the former due to a long-term service (over 30 years), vibration and shock load effects having exhausted their life span.
Highlights
The main reason for motor base vibration is violent vibrations of rotor with worn-out bearings [1,2,3,4,5]
In this paper the reason for electromechanical complex (EMC) increased vibration is theorized by the authors aiming at its further improvement and service life increase
When carrying out vibration tests of large-power DC motor comprised in EMC, the following spots were selected: 4 on each support (Fig. 1)
Summary
The main reason for motor base vibration is violent vibrations of rotor with worn-out bearings [1,2,3,4,5]. Bearings vibration with rotation frequency can appear for one of three reasons: bearing ring slipping on the mounting seat, outer ring rolling off or inner ring wearing [1,2,3,4,5,6]. The last two reasons are accompanied by the bearing geometry change and by shaft eccentricity initiation. It becomes evident that dynamic shaft eccentricity is the most dangerous one, because as it rotates, inertia force appears having additional force impact on constructional elements as well as swinging the construction itself. The force which appears when unbalanced shaft with dynamic eccentricity rotates changes directionally with the period corresponding to the shaft full turn and is proportional to its squared rpm [7]. Static eccentricity does not have any significant impact on the machine operation
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