Stepper motors have 12 characteristics, how many do you know

Update:14 Dec 2020

The hybrid stepping motor is roughly composed of a stator, a rotor and an end cover.

The rotor is composed of a rotor core and a permanent magnet. The magnet is magnetized along the rotor axis, with one end having an N pole and the other end having an S pole. The outer ring of the rotor core is small teeth.

There are large magnetic poles on the stator and small teeth on each magnetic pole. A coil is wound on each magnetic pole. After the coil is energized, the magnetic poles will be excited to form corresponding N and S poles.

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Even the same stepping motor, when using different drive schemes, its torque-frequency characteristics are very different.

When the stepping motor is working, pulse signals are applied to each phase winding in turn in a certain order.

Stepping motors are different from other motors in that their nominal rated voltage and rated current are only reference values; and because stepping motors are powered by pulses, the power supply voltage is the highest voltage, not the average voltage, so stepping motors can exceed Its rated value range works. But the selection should not deviate too far from the rated value.

The stepping motor does not accumulate errors: the accuracy of the general stepping motor is 3 to 5 percent of the actual step angle, and it does not accumulate.

The maximum temperature allowed by the appearance of the stepping motor: Too high temperature of the stepping motor will first demagnetize the magnetic material of the motor, resulting in a decrease in torque and even loss of step. Therefore, the maximum temperature allowed on the appearance of the motor should depend on the demagnetization point of 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, so the external temperature of the stepping motor is completely normal at 80-90 degrees Celsius.

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, which leads to the decrease of torque.

The stepping motor can run normally at low speed, but if it is higher than a certain frequency, it will not start, accompanied by howling. The stepping motor has a technical parameter: no-load starting frequency, that is, the pulse frequency that the stepping 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 step or stall. Under 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 power supply voltage of the hybrid stepping motor driver is generally a wide range, 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.

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.

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. In some automation equipment, if the motor shaft is required to be directly rotated when the drive is not powered, the FREE signal can be set low to make the motor offline for manual operation or adjustment. After manual completion, set the FREE signal high again to continue automatic control.

Use a simple method to adjust the direction of rotation of the two-phase stepping motor after it is energized, just swap the A+ and A- of the motor and driver wiring.

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 phases by using a series connection method or a 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 required driver output current is 0.7 times 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. The output current is 1.4 times the motor phase current, so the stepping motor generates more heat.

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