This evaluation deals with the investigations carried on the different AC horizontal motors to monitor their performance, and also to assess the axial force on the motor bearings. Under 'load' conditions, the axial force on the bearings is a net resultant of the forces generated by both driven assemblies, and it is affected by operating parameters, design and alignment of the system. However, under 'no-load' operation of a motor, the axial force experienced by the motor bearings reveals the design, manufacturing accuracy, constructional tolerances, asymmetry due to imperfect centring of the rotor in the stator box, non-linear stator bore, non-circular bore, bend shaft, shaft deflection and overhanging weight of motor. Thus, the axial force on the bearings under 'no-load' conditions reflects the 'quality' of a motor.
The investigations reveal that under 'no-load' the axial force experienced by various motor bearings of good quality motors is very low and subsequently will have no effect on the behaviour and operating life of the bearings. Also, it confirms that motors with low axial force on bearings have been manufactured to a reasonable accuracy. However, the axial force under load, exerted by the driven equipment, may affect the performance and life of the motor bearings.
The axial force on the bearings of a rotor of a horizontal AC motor appears to be due to an unbalanced magnetic pull as soon as the motor is started. The unbalanced magnetic pull (UMP) in a motor is generated because of a...
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