A stepper motor is DC motor that moves in discrete steps. It has multiple coils that are organized in groups called phases. By energizing each phase in sequence, the motor will rotate one step at a time. Stepper motors come in many different sizes and styles and electrical characteristics. How many characteristics do you know about a stepper motor? Most of you may know major features of it, such as small step angle, high positioning accuracy, high torque to inertia ratio, easy control with pulse signals, and stepping rate and accuracy. In fact, there are many important features of the stepper motor that you must know. Changzhou ACT Motor Co., Ltd., a leading stepper motor factory in China that has accumulated more than 10 years of experience in manufacturing stepper motors, introduces 12 important features of stepper motor drive system to help you know more about a stepper motor.
1. Even the same stepper motor will have the moment-frequency characteristics that vary greatly when different drive schemes are used.
2. When a stepper motor is in operation, pulse signals are added to each phase winding in turn in a certain order (the way the windings are powered on and off is controlled by the ring distributor inside the driver).
3. Unlike other motors, the stepper motor’s nominal rated voltage and rated current are only reference values, according to stepper motor manufacturers. The stepper motor is powered by pulse, so the power supply voltage is its highest voltage instead of the average voltage. Therefore, the stepper motor can operate beyond its rated range, but the value should not deviate too far from the rated value.
4. The stepper motor has no accumulative errors. The accuracy of most stepper motors is three to five percent of the actual step angle, and will not accumulate.
5. The maximum temperature allowed for the appearance of stepper motors. Too high stepper motor temperature will demagnetize the magnetic material of the motor, resulting in a drop in torque and even loss of step. So stepper motor factory suggests the maximum temperature allowed for the appearance of the motor should depend on the demagnetization point of the magnetic material of different motors. The demagnetization point of the magnetic material is usually above 130℃, and some even up to 200℃, so it’s completely normal that the temperature of the stepper motor appearance is at 80-90℃.
6. The torque of the stepper motor decreases with increasing speed. When a stepper motor rotates, the inductance of the motor’s phase windings will form a reverse electromotive force; the higher the frequency, the greater the reverse electromotive force. Under its action, the motor phase current decreases as the frequency (or speed) increases, which leads to decrease in torque.
7. The stepper motor can run normally at low speed, but cannot start and will be accompanied by whistling sound at frequency exceeding certain range. No-load start frequency is a technical parameter of the stepper motor, that is, the pulse frequency when the stepper motor can start normally in the case of no load. If the pulse frequency is higher than the no-load start frequency, the motor can not start normally, and may lose steps or block. In the case of a load, the start frequency should be lower. According to stepper motor manufacturers, the pulse frequency should have an acceleration process, i.e., the start frequency is lower, and then rise the frequency to the desired high frequency (motor speed from low speed to high speed) at a certain acceleration, so as to enable the motor to have high speed rotation.
8. The supply voltage of the hybrid stepper motor driver generally covers a wide range, and is usually selected according to the stepper motor’s operating speed and response requirements. Stepper motor factory finds that if the motor operating speed is higher or the response requirements are faster, the voltage should be large, but the ripple of the supply voltage should not exceed the maximum input voltage of the hybrid stepper motor driver, otherwise the driver may be damaged.
9. The supply current is generally determined according to the output phase current I of the driver. If a linear power supply is used, the supply current can generally be 1.1 to 1.3 times of I; if a switching power supply is used, the supply current can generally be 1.5 to 2.0 times of I.
10. When the offline signal FREE is at low power level, the current output from the driver to the motor is cut off and the motor rotor is in a free state (offline state). In some automation equipment, if direct rotation of the motor shaft is required without the driver being powered up, the FREE signal can be set low to keep the motor in offline state for manual operation or adjustment. After the manual operation is completed, the FREE signal is set high again to continue the automatic control.
11. Align the motor with the A+ and A- (or B+ and B-) of the driver wiring, then the rotation direction of a two-phase stepper motor after it is energized can be adjusted.
12. Four-phase hybrid stepper motor is generally driven by 2 phase stepping motor driver, so the four-phase motor can be connected into a two-phase motor through series connection or parallel connection method. Series connection method is generally used when the motor speed is low and the driver output current required is 0.7 times of the motor phase current, so less motor heat will be generated; parallel connection method, also known as high-speed connection method, is generally used when the motor speed is high and the driver output current required is 1.4 times of the motor phase current, so more stepper motor heat will be produced.
After reading the 12 features of the stepper motor above, you must learn more about the stepper motor, and will be able to make the best decision when choosing a stepper motor. If you have any questions or need any further information, please feel free to contact ACT Motor!
Post time: Jun-02-2022
