Features of CVK Series Stepper Motor and Driver Kits

Features of the CVK Series Stepper Motor and Driver Kits

Stepper motors are widely used in various applications due to their ease of use and accurate positioning. But in recent years, most users require high torque, low vibration and higher precision.

The CVK series is a stepper motor and DC input driver combination that offers higher torque, lower vibration, and higher precision than conventional stepper products. We have developed 1.8° products that emphasize torque and 0.72°/0.36° products that emphasize low vibration and high precision. The CVK series versions are also highly compatible with each other, facilitating standardization.

Here are the features and characteristics of the CVK series:

1. Introduction

Stepper motors are widely used in various applications due to their ease of use and highly accurate positioning capabilities. In recent years, there has been a continuous demand for high torque, low vibration, and high precision.

The CVK series is a DC input stepper motor and driver package that offers higher torque, lower vibration, and higher precision than conventional stepper products. The 1.8° stepper motor and driver package ("1.8° package") focuses on torque, and the 0.72°/0.36° stepper motor and driver package ("0.72°/0.36° package") offers low vibration and high precision. Drivers for the 1.8° and 0.72°/0.36° packages are highly compatible. Therefore, motors can be selected based on certain characteristics because the mounting characteristics of both packages are similar, facilitating standardization. Replacing motors can also be done easily.

Stepper motor drivers can operate with either AC or DC supply voltage. DC type drivers are generally cheaper, more compact and can be easily mounted in equipment. The CVK series was developed for DC supply voltage and is suitable for applications that require the driver to be mounted in the equipment (see Figure 1).

2. CVK Series Product Line

The CVK series offers a wide range of packages including 1.8° and 0.72°/0.36° stepper motors. High-resolution types with lowest vibration and highest accuracy offer excellent performance (see Table 1).

The difference between 1.8° and 0.72°/0.36° stepper motors lies in their structure. Figure 2 shows the stator of a 1.8° stepper motor, and Figure 3 shows the stator of a 0.72°/0.36° (specifically 0.72°) stepper motor.

Compared to 0.72° stepper motors, 1.8° stepper motors have fewer windings (phases), so the number of turns in the coil and the number of teeth on the stator are more, resulting in higher torque.

The difference in vibration between 1.8° and 0.72°/0.36° stepper motors is due to the different number of phases. In principle, the motor vibration should be the same for 1.8° and 0.72°/0.36° stepper motors, as long as the step angle is the same. But in practice the torque variation produced by each phase is very small, causing the motor to jitter. Since the 0.72°/0.36° stepper motor has more phases, the torque variation produced is dispersed, resulting in lower vibration than the 1.8° stepper motor. For the same reason, it is very accurate in positioning. Figure 4 shows the stator of a 0.36° high-resolution stepper motor.

The high-resolution type has finer and smaller teeth than the standard type (0.72°). Due to these features, the variance of the generated torque is dispersed, making it not only low in vibration but also high in positioning accuracy.

3. Features of the CVK series

CVK series has the following features:

Higher torque than conventional stepper motors

Low vibration, micro-stepping drive over the entire speed range

Universal driver design for 1.8° and 0.72°/0.36° stepper motors

The driver has the following features:

Small and slim form factor

Compatible with pulse input line driver or open collector type pulse signal

Simple current setting

Equipped with protection function (alarm output)

Extended operating ambient temperature range

4. Features of the CVK series

4.1. Torque characteristics

Torque characteristics are improved over conventional DC input products. The 1.8° package adopts a bipolar drive system(1), which is not available in our conventional stepper products. As a result, low-speed torque is improved. The 0.72°/0.36° package adopts winding specifications that focus on high-speed torque.

High-speed operation quickly switches the motor winding current before the current rises, which causes a drop in torque. To avoid this, the number of turns in the coil can be reduced, which reduces the impedance and speeds up the current rise. However, the torque is reduced by reducing the number of turns in the coil. To solve this problem, the driver is built to be compatible with high current output.

Figure 5 shows the speed-torque characteristics of the CVK 1.8° package (CVK244AK) and the conventional stepper product (CMK244-PAP). In addition, Figure 6 shows the speed-torque characteristics of the CVK 0.72° package (CVK544AK) and the conventional product (CRK544PAP).

As mentioned earlier, 1.8° stepper motors have higher torque in the low speed range compared to 0.72° stepper motors, whose design focuses on high-speed torque. Figure 7 shows the speed-torque characteristics of CVK 1.8° and 0.72° stepper motors.

4.2. Vibration characteristics

Since stepper motors rotate in angular increments, sometimes vibration caused by the stepping can be a problem. By utilizing a speed sensor called a DC tachometer generator, the speed is converted into a voltage, which can indicate the relationship between speed and speed fluctuation (Vp-p). Figure 8 shows a comparison between a CVK 1.8° stepper motor and a conventional stepper product. Figure 9 shows a CVK 0.72° stepper motor and a conventional stepper product.

The CVK series operates with microstepping drivers throughout the entire speed range, resulting in low vibration regardless of speed. With Oriental Motor's unique smooth drive function, vibration is reduced when operating in the speed range of 0 to 50r/min. With Oriental Motor's phase correction of the current, vibration is also reduced when operating in the speed range of 50 to 200r/min. In addition, with the vibration suppression control built into the CVK driver, vibration is reduced when operating in the speed range of 500r/min and above. Compared to conventional stepper motor products, both the 1.8° and 0.72° stepper motors have successfully reduced vibration, and the vibration characteristics do not change even if the step angle changes. This is a result of Oriental Motor's unique microstepping control function.

A comparison of the vibration characteristics of the CVK 1.8° and 0.72° stepper motors is shown in Figure 10. As shown, the 0.72° stepper motor has lower vibration than the 1.8° stepper motor.

Figure 11 shows a comparison of the vibration characteristics of the CVK 1.8° package with the same motor and a commercially available stepper motor driver IC. The CVK 1.8° package has lower vibration than the commercially available driver.

4.3. Stop position accuracy

The stop position accuracy of the stepper motor is within ±0.05° of the full step. During microstepping, if the output current of the driver is not a sine wave with less distortion, the stop position accuracy will be reduced compared to full stepping. Compared with conventional stepper products, the driver output current waveform of the CVK series during microstepping is more accurate. This leads to improved stop position accuracy. Figure 12 shows the stop position accuracy of the CVK 1.8° stepper motor and the conventional product (CMK 1.8° stepper motor).

Figure 13 shows the stop position accuracy of the CVK 0.72° stepper motor and the conventional stepper product (CRK 0.72° stepper motor). Similarly, the driver output current waveform and stop position accuracy of the 0.72° stepper motor are also improved. Compared with the 1.8° stepper motor, the 0.72° stepper motor has more windings, so the stop position accuracy is higher. In addition to the standard 0.72° stepper motor, the stop position accuracy of the 0.36° high-resolution type is also greatly improved. Figure 14 shows the stop position accuracy of the 0.36° high-resolution type stepper motor.

5. Features of CVK series drivers

5.1. Universal Driver Design for 1.8° and 0.72°/0.36° Stepper Motors

The 1.8° and 0.72°/0.36° packages share the same hardware design. Since both share the same driver functionality, footprint, connectors, and I/O signal layout, they are easily interchangeable. Table 2 shows the driver's motor connector pinout. The connectors for the 1.8° and 0.72°/0.36° stepper motors are universal, as shown in Table 2, with each color of motor lead corresponding to a different color.

When using both 1.8° and 0.72°/0.36° stepper motors or changing from 1.8° to 0.72°/0.36° stepper motors to reduce vibration, no changes to wiring or pulse input are required. Regarding step angle, 1.8° and 0.72°/0.36° stepper motors share the same setting switches, as shown in Table 3.

5.2. Small and slim appearance

Although the CVK series of drivers have improved characteristics compared to conventional DC input package products, their driver frame size remains the same. It is thinner than conventional stepper motor products (0.72°/0.36° CRK series), which allows for a reduction in overall device size. Figure 15 shows the dimensions of the CVK series drivers, and Figures 16 and 17 show the dimensions of conventional stepper motor product drivers.

5.3. Compatible with pulse input line drivers

The pulse drive system of the CVK series driver is compatible with the line drive method in addition to the open collector method, which is the same as the conventional DC input package. Compared with the open collector method, the line drive method can more easily input higher frequency pulses, so it can operate at high speed even if a high resolution is set. In addition, the line drive method has good resistance to electrical noise and has the advantage of being able to use pulse lines over long distances. Figure 18 shows the connection diagram of the pulse drive system.