stepper motor drive system characteristics

(1) Even if it is the same stepping motor, when using different drive schemes, its torque-frequency characteristics are quite different.

(2) When the stepper motor is working, the pulse signal is added to the windings of each phase in turn in a certain order (the ring distributor in the drive controls the way the windings are turned on and off).

(3) The stepping motor is different from other motors. Its nominal rated voltage and rated current are only reference values; and because the stepping motor is powered by pulse, the power supply voltage is its highest voltage, not the average voltage, so stepping The motor can work beyond its rated value range. But the selection should not deviate too far from the rated value.

(4) The stepper motor does not accumulate errors: the accuracy of the general stepper motor is three to five percent of the actual step angle, and it does not accumulate.

(5) The maximum temperature allowed by the appearance of the stepper motor: If the temperature of the stepper motor is too high, the magnetic material of the motor will be demagnetized first, resulting in a decrease in torque and even loss of step. Therefore, the maximum temperature allowed by the appearance of the motor should depend on the different magnetic materials of the motor. Generally speaking, the demagnetization point of magnetic materials is above 130 degrees Celsius, and some are even as high as 200 degrees Celsius. Therefore, the surface temperature of the stepper motor is completely normal at 80-90 degrees Celsius.

(6) The torque of the stepper motor will decrease with the increase of the speed: when the stepper motor rotates, the inductance of each phase winding of the motor will form a back electromotive force; the higher the frequency, the greater the back electromotive force. Under its action, the phase current of the motor decreases with the increase of frequency (or speed), resulting in a decrease in torque.

(7) The stepper motor can run normally at low speed, but if it is higher than a certain frequency, it will not start, accompanied by howling sound. The stepper motor has a technical parameter: no-load start frequency, that is, the pulse frequency at which the stepper motor can start normally under no-load conditions. If the pulse frequency is higher than this value, the motor cannot start normally and may lose steps or stall. In the case of load, the starting frequency should be lower. If you want the motor to rotate at a high speed, the pulse frequency should have an acceleration process, that is, the start frequency is low, and then increase to the desired high frequency according to a certain acceleration (the motor speed increases from low speed to high speed).

(8) The power supply voltage of the hybrid stepping motor driver is generally a wide range (for example, the power supply voltage of IM483 is 1248VDC), and the power supply voltage is usually selected according to the working speed and response requirements of the motor. If the motor has a high working speed or a fast response requirement, then the voltage value is also high, but note that the ripple of the power supply voltage cannot exceed the maximum input voltage of the drive, otherwise the drive may be damaged.

(9) The power supply current is generally determined according to the output phase current I of the driver. If a linear power supply is used, the power supply current can generally be 1.1 to 1.3 times I; if a switching power supply is used, the power supply current can generally be 1.5 to 2.0 times I.

(10) When the offline signal FREE is low, 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 the motor shaft is required to be directly rotated (manual mode) when the drive is not powered on, the FREE signal can be set low to take the motor offline for manual operation or adjustment. After manual completion, set the FREE signal high again to continue automatic control.

(11) The four-phase hybrid stepping motor is generally driven by a two-phase stepping driver. Therefore, the four-phase motor can be connected into two-phase using the series connection method or the parallel connection method when connecting. The series connection method is generally used in the occasions where the motor speed is low. At this time, the driver output current required is 0.7 times of the motor phase current, so the motor heat is small; the parallel connection method is generally used in the occasions where the motor speed is high (also known as high-speed connection). Method), the required driver output current is 1.4 times the motor phase current, so the stepper motor generates more heat.

 

By Jessica


Post time: Nov-16-2021