mariners-academy.com

MAGNETIC CENTERING

In Electric Machines such as Motors and Generators, the shaft tends to maintain a distinct axial position when running. This position may be different from the position of the shaft at rest and, in the case of motors, when the machine is running with a coupled load.
The Magnetic center is caused due to the magnetic forces between the rotor and stator attract each other. These magnetic forces tend to ensure that the gap between the stator and the rotor is as small as possible. Hence, if the axial position of the machine at rest(mechanical center) is different from the magnetic center, the rotor of the machine may slightly move axially to the magnetic center when running without load.

Consequences of wrong Magnetic centering :-

If the magnetic center is not set properly when the machine is reassembled after any maintenance work, the rotor may tend to shift beyond the axial limits permitted by the bearings. This is particularly true for sleeve bearings. This may cause the rotor to rub against the thrust collars of the bearing.

GENERATOR THRUST BEARING :-

Generator thrust bearing is placed at the nearest main bearing to the alternator and consist of nothing but the provision of some bearing surface on both side of main bearing such that one bearing surface bears to the crankweb side while the other may contact the collar on the shaft.