SynRMs operate using the nonlinear region of a magnetic steel sheet, so the inductance expresses nonlinear behavior as well. This behavior distorts the excitation current waveform a great deal, making it impossible to run advanced projections that are accurate with calculation methods that follow linear formulas. Consequently, it becomes necessary to use the finite element method (FEM), which can handle nonlinear magnetic properties in material, detailed motor geometry, and transient currents.
This Application Note presents an evaluation of torque variations that occur when the phase of a sinusoidal wave current is changed.
Magnetic Flux Density Distribution and Average Torque per Current Phase
The magnetic flux density distribution at a rotation speed of 600 r/min and a current amplitude of 3.0 A is shown in fig. 1. The average torque at each current phase is shown in fig. 2. The magnetic flux density distribution changes with the current phase. When the current phase is 0 deg and 90 deg the average torque is 0, and when the current phase is 45 deg the torque reaches its peak.