## 3 Results and Discussion
As a result of THD analysis, the THD value of the magnet that was magnetized with the yoke in case 3 (6.2%) is much higher than those magnetized with the yoke in cases 1 and 2 (3.5%). If the flux distortion of  
Figure 6: Schematic illustration of magnetization yoke and Nd\({}_{2}\)Fe\({}_{14}\)B permanent magnet used for the preparation of specimens. Figure 7: Surface flux analysis results of magnetized bonded permanent Nd\({}_{2}\)Fe\({}_{14}\)B magnet in (**a**) case 1; (**b**) case 2; and (**c**) case 3.  
the magnetization of the magnet is increased, the efficiency of driving the motor for a long time is lowered, which can generate noise. The shift in the yoke coil creates a pole with a non-uniform magnetic flux of the Nd\({}_{2}\)Fe\({}_{14}\)B magnet, so that the deviation of flux peak and density becomes very high. As a result of the magnetic field simulation for the design conditions in case 3 (Figure 9), it was confirmed that the low flux was emitted at poles 2 to 6. The simulation results are consistent with the surface magnetic flux density analysis results. Figure 10 shows the results of the measurement of the back EMF of the motors manufactured using the Nd\({}_{2}\)Fe\({}_{14}\)B bonded magnets in cases 1 through 3 [13]. Generally, the power (\(P\)) of the motor can be expressed by the torque and angular velocity (\(\omega\)) of the motor, as well as by the BEMF (e) and the stator core current (I) [14; 15]. \[P=T\times\omega=(2\times\mathrm{r}\times\mathrm{F})\times\omega=(2\times \mathrm{r}\times\mathrm{B}\times\mathrm{I}\times\ell)=\mathrm{e}\times\mathrm{I}, \tag{1}\]  
From Equation (1), the BEMF (e) can be expressed as follows:  
Figure 2:0  
If the current applied to the stator core is constant, the back electromotive force is correlated with B, the flux value of the rotor, which is the Nd\({}_{2}\)Fe\({}_{14}\)B permanent magnet magnetized in Equation (2). Therefore, in cases 1 and 2, where uniform flux is generated at each yoke pole, a uniform flux is formed in the entire rotor, and the equivalent BEMF value of 710 and 708.6 mV can be confirmed when the motor is mounted. However, when the magnets were magnetized with the yoke in case 3, which had low magnetic flux values at poles 2 to 7, and the forces were applied to the rotor, a low BEMF value of 688.4 mV was confirmed. Figure 2:1 Magnetic property and total harmonic distortion analysis results obtained with Nd\({}_{2}\)Fe\({}_{14}\)B magnets using a magnetized yoke in cases 1–3 ((**a**) flux density; (**b**) maximum flux; and (**c**) THD). Figure 2:2 Magnetic simulation of magnetized Nd\({}_{2}\)Fe\({}_{14}\)B rotor with a magnetizing yoke in case 3. In addition, Figure 11 shows the measurement results for back EMF (3\(\times\)) that were generated during the motor operation [16; 17]. In general, the value of BEMF (3\(\times\)) indicates the discrepancy between the physical rotation of the rotor and the electrical rotation. As a result of the analysis of the BEMF (3\(\times\)) value of the motor using each rotor with a black rotor, it was confirmed that the motor using yokes in cases 1 and 2 measured 1.25 and 1.28 BEMF (3\(\times\)). However, in case 3, where a non-uniform magnetic flux emission was confirmed, a high BEMF (3\(\times\)) value of 7.87 was obtained.