The capabilities of a hysteresis motor can be judged based upon an evaluation of its behavior under two specific operating conditions: 1) starting conditions, and 2) steady state synchronous operating conditions at maximum torque. It is easier to conduct an experimental study on the behavior of a hysteresis motor under starting conditions than the second operating conditions. Furthermore, the starting behavior of hysteresis motors is of great importance from two perspectives: 1) usually the maximum torque of hysteresis motors is produced under the starting conditions. It consists of two components of hysteresis torque and induction torque. However, the induction torque is not produced at synchronous speed. In addition, it can be argued that
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Note that all of these motors are entirely circumferential flux type. Motor M1 has a 3mm disk, while the thickness of the only disk of motor M7 is 6mm. Similarly, the thickness of both disks of motor M4 is 3mm, but motor M9 has two 3mm and 6mm disks. The results indicated that the input power, starting torque and power factor of motors with thin disk, i.e., M1 and M7, are greater than those of motors with thick disk, i.e., M4 and M9. In other words, increasing volume of hysteresis material by too much enlarging the thickness of disk in a circumferential flux motor aggravates the performance of the motor. This happens because the increase in thickness of disk(s) leads to lower flux density magnitude in the disk(s) and ultimately lowers the area of operating hysteresis loop. Furthermore, for a thick disk, the radial component of flux cannot be disregarded in comparison with its circumferential component. In fact, such a two-dimensional field distribution will affect the overall performance of the motor. Also, It is clear from Fig. 6 8 that motors with thick disk require higher terminal voltage to produce a given …show more content…
9 11 is that the input power factor of all single-sided motors is unexpectedly larger than that of corresponding double-sided motors. As mentioned above, the length of end windings and subsequently the leakage flux are higher in single-sided motors. This leaves an adverse effect on the power factor of these motors. However, there are two large air gaps in a double-sided motor, mitigating its magnetizing reactance and as a result, the contribution of magnetizing current to the total current of the motor increases, which in turn curtails the power factor. In other words, since there is a relatively large effective air gap in double-sided motors with slotless core, the reduction of power factor due to the increased magnetizing current overruns the increase of power factor due to lower leakage flux of end windings. Consequently, the power factors of these motors are smaller than those of the corresponding single-sided motors. The smaller power factor implies that despite larger volume of hysteresis material in double-sided motors, the input power and generated torque are not so larger in comparison to the single-sided types, not to mention that they might be even smaller in certain cases. For instance, Fig. 7 9 and Fig. 8 10 indicate that for low to middle currents, the input power and torque generated by double-sided motor M5 are larger than those by single-sided motor M2. For higher currents, however, the input power and torque of M5 are
Note that all of these motors are entirely circumferential flux type. Motor M1 has a 3mm disk, while the thickness of the only disk of motor M7 is 6mm. Similarly, the thickness of both disks of motor M4 is 3mm, but motor M9 has two 3mm and 6mm disks. The results indicated that the input power, starting torque and power factor of motors with thin disk, i.e., M1 and M7, are greater than those of motors with thick disk, i.e., M4 and M9. In other words, increasing volume of hysteresis material by too much enlarging the thickness of disk in a circumferential flux motor aggravates the performance of the motor. This happens because the increase in thickness of disk(s) leads to lower flux density magnitude in the disk(s) and ultimately lowers the area of operating hysteresis loop. Furthermore, for a thick disk, the radial component of flux cannot be disregarded in comparison with its circumferential component. In fact, such a two-dimensional field distribution will affect the overall performance of the motor. Also, It is clear from Fig. 6 8 that motors with thick disk require higher terminal voltage to produce a given …show more content…
9 11 is that the input power factor of all single-sided motors is unexpectedly larger than that of corresponding double-sided motors. As mentioned above, the length of end windings and subsequently the leakage flux are higher in single-sided motors. This leaves an adverse effect on the power factor of these motors. However, there are two large air gaps in a double-sided motor, mitigating its magnetizing reactance and as a result, the contribution of magnetizing current to the total current of the motor increases, which in turn curtails the power factor. In other words, since there is a relatively large effective air gap in double-sided motors with slotless core, the reduction of power factor due to the increased magnetizing current overruns the increase of power factor due to lower leakage flux of end windings. Consequently, the power factors of these motors are smaller than those of the corresponding single-sided motors. The smaller power factor implies that despite larger volume of hysteresis material in double-sided motors, the input power and generated torque are not so larger in comparison to the single-sided types, not to mention that they might be even smaller in certain cases. For instance, Fig. 7 9 and Fig. 8 10 indicate that for low to middle currents, the input power and torque generated by double-sided motor M5 are larger than those by single-sided motor M2. For higher currents, however, the input power and torque of M5 are