Portescap has recently introduced the P532 Series Disc Magnet Step Motor with encoder to deliver best-in-class motor acceleration and power rate and thus outperform the standard Brushless DC motor in a wide range of applications.
Stepper motors typically run at 2,000 RPM or less in an open loop, while brushless motors that can run at much higher speeds are typically used in closed loop applications. In the last few years, trend is to use a stepper motor in closed loop with a torque higher than a brushless motor system, because of its higher pole count. What we are typically looking at is the middle range of revolutions per minute [RPM] as a sweet spot for disc magnet motors. The sweet spot opens up in applications in the few thousand RPM range, where a closed loop disc magnet motor system can be more cost-effective than a brushless solution.
There are several different types of stepper motor technologies. Can stack steppers use sheet metal parts and a very simple construction, but offer very low torque output. The next step up is to use hybrid motors, which use machined parts, higher resolution, and pole counts, resulting in higher torque capabilities. But because of a higher pole count and the complex construction, the big challenge has always been top end speed. The higher pole count creates a higher number of commutations per revolution of the motor. Losses at higher speeds become much more significant and there is more heat generated, versus a brushless motor, which typically uses a lower pole count that enables it to run faster.
Comparing the disc magnet technology to a hybrid stepper, main differentiator is the disc magnet which doesn’t use a cylindrical magnet that you would find in a typical hybrid stepper. Portescap’s new design uses a high-energy magnet but the motor inertia is significantly minimized by spinning a disc rather than a cylinder. The output torque is thus less due to lesser usage of magnetic material, making our disc motor an ideal fit for applications that need low inertia, lower torque and higher speed. While the hybrid stepper typically can’t operate beyond 1,000 RPM to 2,000 RPM, disc magnet motors can operate effectively up to 5,000 RPM, and with smaller motors even reaching up to 10,000 RPM.
P532 Disc Magnet Motor
Since stepper motors were typically run in open loop, standard design practice has always been to add a safety factor. If the application needs one milli Newton meter of torque at 500 RPM, the motor may be sized to two milli Newton meters of torque to ensure the motor will move reliably to the commanded position. Closing the loop adds feedback to confirm the position, and the application is able to run at higher speeds without adding the safety factor.
Another advantage of steppers is that they can be driven above their rated current because they are normally not run at a 100 percent duty cycle. Most applications are run at 25 percent or less, which enables the application to utilize 1.5 to 2 times the stepper motor’s rated current, while keeping the size of the motor smaller and achieving a higher torque output. By closing the loop, an application can maximize that advantage by boosting the current, especially with the safety factor no longer a consideration.
Portescap’s P532 series motor has a diameter of 52mm, length up to 55 mm, and rated torque of 0.2 Nm (boosted up to 0.5 Nm). This allows the P532 to deliver fantastic dynamic performance such as acceleration up to 400K rad/sec2. Such performances are perfectly suited for applications where rapid changes in rotation are required ( +/- 3,000 RPM a few ms). Application examples include miniature motors for electronic yarn guide, medical XY tables and miniature motors for robotics.
Portescap’s P532 series motor has a unique multipolar design requiring no additional iron to the rotor and therefore giving this motor a very low inertia (12E-7 kgm2). Closing the position loop with the encoder, it is capable of exceptional accelerations which, together with a high speed of up to 6,000 RPM, make this motor technology suitable for fast incremental motion.
Manufacturing industry is constantly looking to innovate and enhance machine design efficiency that raises output, while reducing operating costs and losses. With its unique design and encoder as a standard feature, the P532 series disc magnet motor enables machine builders to improve the overall design efficiency of their machine. As a result, these RoHS-compliant step motors are an ideal solution in textile, life science, medical, fluid handling and industrial automation equipments.