Cogging torque causes speed to fluctuate when motors rotate, and vibration and noise in machinery. With the latest models, cogging torque has been significantly reduced to help improve the performance of users’ equipment.
Figure 1 shows a comparison of cogging torque waveforms. The SANMOTION K motors, for every size, have more than a half lower cogging torque compared with our current motors.
Figure 1 Comparison of cogging torque waveforms
The magnet and armature core shapes were designed to minimize cogging torque while maintaining torque characteristics. In addition to devising a method for laminating electromagnetic steel plates, we also introduced a technique for automating magnet attachment, achieving consistent product quality.
In this way, we devised not only product performance but also manufacturing technology, with the product design and production line design advanced simultaneously from the initial development phase.
Generally, increasing the winding fill factor within a slot can reduce copper loss. Moreover, in DC motors there is mechanical loss that occurs with the mechanical sliding of the brushes and commutators. For the SANMOTION K, we have increased the winding fill factor to reduce copper loss, and optimized the material and number of brushes, consequently reducing mechanical loss.
Figure 2 shows a comparison of loss and frame temperature rise between the new and current 42 × 42 mm 60 W models. In line with a 31% reduction in loss compared with our current model, frame temperature rise has been reduced by 25% while the motor efficiency has been improved by about 10%.
This high efficiency limits temperature rise, so it has little impact on the temperature of users’ equipment and contributes to energy-saving in equipment.
The SANMOTION K motors feature high efficiency, low torque fluctuation, and low motor temperature rise, and can help improve the performance of the user's equipment and create new value. We will continue to pursue the ease-of-use unique to DC servo motors, and meet the needs of current and new applications and markets by combining product design and manufacturing technologies.
Figure 2 Comparison of loss and temperature rise values
(42 × 42 mm 60 W motors, at rated output)