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The impact of the accuracy class of bearings, rotational speed, load, clearances, and fits on the vibration levels of electric motor bearing units is investigated. The ways to reduce the vibrations of mechanical origin are offered. The boundary vibration levels of asynchronous motors limited by vibration levels of 40 dB at a frequency of 5 Hz and 80 dB at a frequency of 10,000 Hz are determined. The effect of increasing the rotational speed and load on the vibration levels of bearing units has been determined, and reserves for reducing vibration while ensuring the optimum bearing preload on the shaft journal have been identified. It is established that the clearance between the cap and the bearing when it is fixed in the housing (primer) does not ensure the unambiguity of the bearing unit assembly, which results in a large variation in vibration levels compared with rigid and elastic fixation. The results of this research can be applied to all types of traction electric motors.

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Experimental studies of vibrations of asynchronous electric motors (EMs) of the electric bus traction electric drive are carried out in the paper. The presented studies are based on generalization of the diagnostic features of vibration characteristics and statistics concerning the limiting values of vibration parameters of EMs and their dependence on the technical condition. The analysis of the obtained results allowed us to determine the permissible vibration levels of EMs in the frequency range from 5 Hz to 10 kHz. The method of diagnosing EMs traction electric drive according to the indicators of vibration levels is developed, which allows to evaluate their technical condition. The values of the permissible vibrational accelerations of the electric bus EMs are determined, which enable to estimate their technical level. This method allowed to develop classes of evaluation of the EMs technical condition by the level of their vibration, which makes possible to predict their resource.

The electric motor (EM) is one of the main components of any system. The EM quality is set at the design and manufacturing stages, and its technical condition is maintained during operation. Therefore, the development of methods for the EM quality determining at its all life cycle stages is urgent. In the paper, for the first time, we proposed the system approach to traction EM quality estimation on the vibration parameter basis. This approach differs in that the study of EM vibration is carried out in 1/3 octave spectrum of frequencies from 50 Hz to 10 kHz (dB), which allows revealing all existing faults or "weak places" of EM. This method is universal for all types of EM. It is based on the results of the largescale experiments using the system analysis and the objectives tree method and allows combining individual problem solutions to improve the quality of design, manufacture, and operation of EM into a single integrated system of quality assessment.