When you operate or run electric machines including generators and motors, the shaft always comes with a specific axial position. Moreover, this position is not the same as when the shaft is at rest. As for an electric motor, the position is also different when while operating these, there is a coupled load involved. Because of this, it is important to understand the value and reasons for any shift of the motor’s magnetic center to ensure its proper operation.[Tweet “The magnetic center results from the magnetic forces that exist between the stator and rotor as these attract one another”]
Mainly, the magnetic center results from the magnetic forces that exist between the stator and rotor as these attract one another. When there is a magnetic force, it helps maintain the smallest possible gap between these two components in an electric motor. With this in mind, once the mechanical center of the machine that is not used varies from the magnetic center, it may lead to the machine’s rotor to move axially towards the magnetic center in a slight manner. This arises once the machine is running without any load.
Magnetic Center’s Shift from Mechanical Center
When it comes to machines, there is a way to determine magnetic centering to maintain excellent operation. An external indicator is positioned securely on the stator, and this detects and points to a particular groove found on the rotor. This is a way to indicate the machine’s magnetic center. However, the rotor’s axial shift may occur even when it is running. For instance, there is the impact of the cooling fan as it runs.
When there is a difference in the motor’s core stack length, this results in inequality in the magnetic forces found in both the non-drive and drive-end. Furthermore, magnetic forces help balance both ends as the rotor shifts axially. The best thing to do is to maintain accurate magnetic centering, which can be done as the external indicator is placed precisely on the stator.
Issues with Incorrect Magnetic Centering
There are some problems that may result from poor magnetic centering. There is a possibility for the rotor to shift beyond its axial limitations, which is often caused by the bearings. This occurs with an incorrect setting of the magnetic center once the electrical machine is repaired and reassembled, as well as any maintenance works performed to it. The rotor may rub against the bearing’s thrust collar, and this can result in future concerns as the overall performance of the motor parts is impacted negatively.
Therefore, it is important to adjust and correct the magnetic center to avoid these problems. The right position of the magnetic center can be improved while the machine is not being used. It is best to check with the manufacturer’s recommendations when you place the magnetic center to the proper position since there are usually two ways to do this such as by moving the stator or the bearings.
As you perform these intricate, yet crucial tasks in correcting the motor’s magnetic center, make it a point to consider what the manufacturer requires to ensure the best results that will ensure the performance and lifespan of your machinery.