For this reason, spindle motors need electromagnetic field simulations that use the finite element method (FEM), which can account for detailed 3D geometry and magnetic saturation in materials, in order to carry out an accurate evaluation.
In this example, how the Speed-Torque curve, the Torque-Current curve and the magnetic flux density distribution of a spindle motor can be obtained.
Speed-Torque Curve / Torque-Current Curve
Fig. 1 shows the Speed-Torque curve, and Fig. 2 shows the Torque-Current curve.
The results show that the torque decreases as the speed increases, and increases as the current increases. From the Speed-Torque curve, it becomes apparent that the torque is almost directly inversely proportional to the rotation speed. From these results, it can be assumed that there is almost no influence from the inductance in the winding.
Magnetic Flux Density Distribution
It can be seen that, from the spindle motor’s structure, it has magnetic flux density distribution in the rotor core’s rotation axis direction. The magnetic flux density is high in the rotor core because the rotor core is thin in the magnet’s magnetic flux direction. High magnetic flux density causes magnetic saturation, which can lead to a decrease in torque.