Application Note

ELECTROMAGNETIC SIMULATION OF BRUSHLESS DC MOTOR INSIDE SOLIDWORKS

In this article, a BLDC motor has been created and simulated using, respectively, SOLIDWORKS and EMWorks2D (see Figure 1). The proposed model has been studied in [1]. The BLDC model is automatically generated using MotorWizard. It is a motor software provided by EMWorks allowing both automatic design and simulation of electric motors. In addition to MotorWizard, EMWorks provides a 2D electromagnetic software (EMWorks2D) utilizing finite element method (FEM) and integrated inside SOLIDWORKS. In this application, EMWorks2D is used to compute magnetic results (magnetic flux density, field intensity, torque, inductances, flux linkage, etc.) of the simulated example. Torque results versus both rotor position and ampere-turns will be compared to reference results.

Figure 1 contains the 2D geometry of the simulated BLDC motor [1]. It consists of a 3-phase machine with 12 slots and 6 poles. stator and rotor cores are made of steel (1000 as relative permeability). The rotor poles, having surface mounted structure, are made of ferrite permanent magnets (Br=0.4T). The shaft has non-magnetic material. The double layers windings are arranged on 3 phases with a coil pitch equal to 1. Each phase has 1456 turns. The excitation currents versus rotor position are shown in Figure 2.

Figures 3a) and 3b) give respectively fringe and vector plot of the magnetic flux distribution inside the motor.

Figure 4 superimposes fringe plot of the magnetic flux density and the magnetic vector potential contour lines.

Figure 4 - Flux lines

The figure below shows the load torque results computed by EMWorks2D for an angle range from 0 deg to 40 deg and compares them with the presented results in [1]. The torque curve is characterized by small ripples amplitude but considerably a high number of ripples (totally 18 ripples in one full revolution). The maximum and the minimum values of the computed torque are respectively 2.05 N.m and 1.53 Nm. The average developed torque is around 1.89 Nm. Figure 6 shows the torque evolution versus the ampere-turns. It is proportional to the excitation. This linear dependency of the static torque generated by the BLDC is considerate as an advantage of brushed DC motor. Hence, it is an inherited advantage to the BLDC without using commutators and brushes.