Air-Gap Flux Density Waveform and Cross Magnetization

The air-gap flux density waveform refers to the variation of magnetic flux density in the air gap of a magnetic circuit. In a typical magnetic circuit, such as in an electric motor or generator, there are multiple poles with alternating magnetic fields. When the rotor (or armature) rotates, the air gap between the stator and rotor experiences varying magnetic fields.

Cross Magnetization

Cross magnetization occurs when the magnetic field in one pole tip affects the flux density measured under the adjacent pole tip. This phenomenon is commonly observed in magnetic circuits with multiple poles. The magnetic field from one pole tip has an impact on the flux density under the neighboring pole tip, leading to a decrease in the measured flux density.

Explanation

When the rotor rotates, the magnetic field generated by one pole induces a magnetic flux in the iron core. This flux travels through the iron core and reaches the air gap. However, due to the presence of neighboring poles, the magnetic field from one pole tip interferes with the magnetic field of the adjacent pole. This interference causes a redistribution of the magnetic flux, resulting in a decrease in the measured flux density under one pole tip.

Example

Let's consider a simple example of a two-pole motor. When the rotor rotates, the magnetic field from the north pole induces a magnetic flux in the iron core. This flux passes through the core and reaches the air gap. However, since there is a south pole adjacent to the north pole, the magnetic field from the south pole interferes with the magnetic field of the north pole.

Due to this interference, the flux density measured under the north pole will be lower than what would be expected if there was no neighboring pole. This decrease in flux density is attributed to cross magnetization.

Conclusion

In summary, the air-gap flux density waveform exhibits a decreased flux density under one pole tip due to cross magnetization. The presence of neighboring poles in a magnetic circuit causes the magnetic fields to interact and redistribute the flux, leading to a decrease in the measured flux density.