Dan Jones Â Incremotion Associates, Inc.
Stepping motors are used in hundreds of position based applications.Â The new CVK 5 phase hybrid step motor above all other motor typesÂ produce the most accurate position motor performance for a wide range of applications including industrial, medical, scientific, semiconductor and robotics not using feedback devices.Â Both the CVK 0.72 degree/step motor and theÂ 0.36Â°/step motor have significantly improved the step accuracy over previous step motor models.Â The combination of the new 5 phase step motor and drive package furnishes the user with the most accurate step motor with the lowest vibrations and audible noise.
The 5 phase CVK step motor family is composed of 2 step angles, 0.72Â° per step and the more accurate 0.36Â°/step models.Â The 0.72Â°/step models are available in three sizes with the 60 mm Â size (2.36 inches square) the largest.Â The high resolution 0.36Â°/step are available in the 2 larger sizes (42 mm and 60 mm).Â Torque values reach 1.7 Nm or 240 oz-in in the larger 0.72Â°/step motor models.Â More torque is developed in all models within the same frame sizes than earlier step motor models.
Figure 1 displays the new Size 24 (60 mm) 0.72Â°/step motor torqueÂ reaches 40.0 oz-in (0.28 Nm) that is 27 percent higher than the previous CRK 5 phase step motor.Â The 5 phase CVK step motor can develop higher speed performance than its 2 phase step motor counterpart.Â The 5 phase CVK step motor has a higher number of phases than the 2 phase step motor.Â The higher phase count of the 5 phase step motor leads to a greater dispersion of vibrations or resonances.Â This results in a lower vibration signature than the 2 phase step motor can achieve.
For the same reason the CVK 5 phase step motor has a much higher position accuracy.Â The 0.36Â°/step CRK 5 phase step motor out performs the 0.72 degree/step motor because of its finer stator and rotor teeth enabling it to perform not only with lower vibrations or resonances but also higher positioning accuracy.
The 5 phase CRK torque performance utilizes a winding design that focuses on high speed torque while the 2 phase CVK step motor delivers low speed high torque.Â High speed operation requires that the phase winding must switch at ever faster rates to achieve higher torque performance. Figure 2 provides a plot that compares the two size 24 hybrid step motors (2 phase and 5 phase).Â This figure verifies the higher torque, low speed performance for the 2 phase CVK model as well as the higher torque, higher speed operation of the 5 phase CVK models.
A speed sensor, a DC tachogenerator is used to transform speed to voltage that can be measured and displayed along with the motors’ speed fluctuations or ripple in volts peak-to-peak (Vp-p).Â Figure 3 details the superior 5 phase CVK vibration performance versus the earlier equivalent sized CRK motors.Â Â Figure 4 shows the performance comparison between the new 2 phase CVK 1.8Â°/stepÂ and the new CVK 5 phase 0.72Â°/step motors with the exception of a single resonance (vibration) point below 200 rpm.Â The new Oriental Motor smooth drive functions as a major supporter to better vibration performance along with the new CVK winding updates.Â It provides a pure sinusoidal current waveform with a higher current capability to achieve the best possible vibration performance.
Step Position Accuracy
The CVK 5 phase step by step position accuracy is within 0.05 percent at full step.Â If the microstep driver does not supply a sinusoidal waveform, the step position will deteriorate compared to a normal full step.Â The new CVK driver output currentÂ waveformÂ during microstepping provides a more accurate signal that minimizes any negative impact on all CVK step motor types including the 2 phase 1.8Â°/step motor.Â A more conventional microstep driver does not possess the correction circuitry of the new CVK driver.Â Figure 4 displays the step accuracy of the CVK 0.72Â°/step motor against the earlier CRK 0.72Â°/step motor.Â The CVK 0.72Â°/step motor is 3 time more accurate than its earlier CRK counterpart.Â The high resolution 0.36Â°/step motor achieves a step accuracy of less than Â± 0.015 arc minutes as show in Figure 5.
The CVK driver package is slimmer than the previous drive package.Â The pulse drive system inside the CVK driver utilizes the line driver method that is capable of entering higher frequency pulses more efficiently than the more conventional open collector method.Â The line driver method has better electrical noise resistance.Â It has been designed to completely replace earlier driver models.
The new 5 phase CVK combined CVK step motor family from Oriental Motor provides the next level in enhanced position accuracy against all 0.72Â°/step and the 0.36Â°/step motor.Â It has better torque than its 5 phase CRK predecessor as well as better step position accuracy.