Characteristics of Stepper Motors

01

Even for the same stepper motor, the moment-frequency characteristics vary greatly when using different drive schemes.

2

When the stepping motor is in operation, the pulse signals are added to the windings of each phase in turn in a certain order (in a way that the windings are energised and de-energised by the ring distributor inside the driver).

3

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 pulses, the power supply voltage is its highest voltage, not the average voltage, so the stepping motor can work beyond its rated range. But the selection should not deviate too far from the rated value.

4

Stepping motor has no accumulated error: generally the precision of stepping motor is three to five per cent of the actual step angle, and it is not accumulated.

5

Maximum permissible temperature of stepping motor appearance: high temperature of stepping motor will firstly demagnetise the magnetic material of the motor, which will lead to torque drop or even out of step, so the maximum permissible temperature of motor appearance should depend on the demagnetisation point of the magnetic material of different motors; in general, the demagnetisation point of the magnetic material is more than 130 degrees Celsius, and some of them even reach up to more than 200 degrees Celsius, therefore, it is completely normal for the stepping motor to have a temperature of 80-90 degrees Celsius in the appearance. Therefore, the temperature of the stepping motor exterior is 80-90 degrees Celsius is completely normal.

The torque of the motor will decrease with the increase of the rotational speed: when the stepping motor rotates, the inductance of the winding of each phase of the motor will form a reverse electromotive force; the higher the frequency, the larger the reverse electromotive force. Under its action, the motor's phase current decreases with increasing frequency (or speed), resulting in a decrease in torque.

7

Stepping motor can run normally at low speed, but if higher than a certain frequency can not start, and accompanied by whistling sound. Stepping motor has a technical parameter: no-load start frequency, that is, the stepping motor in the no-load situation can start the pulse frequency, if the pulse frequency is higher than the value, the motor can not start normally, may occur step loss or blocking. In the case of a load, the starting frequency should be lower. If the motor is to reach high speeds, the pulse frequency should be accelerated, i.e. the start frequency should be low, and then accelerated to the desired high frequency (motor speed from low to high).

8

The supply voltage for hybrid stepper motor drivers is generally a wide range, and the supply voltage is usually selected according to the motor's operating speed and response requirements. If the working speed of the motor is high or the response requirement is fast, then the voltage value is also high, but be careful that the ripple of the supply voltage should not exceed the maximum input voltage of the driver, otherwise the driver 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 be taken as 1.1 to 1.3 times of I. If a switching power supply is used, the power supply current can be taken as 1.5 to 2.0 times of 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 direct rotation of the motor shaft (manual mode) is required without the drive being energised, the FREE signal can be set low to take the motor offline for manual operation or adjustment. After manual operation is complete, the FREE signal is set high again to continue automatic control.

11

A simple way to adjust the direction of rotation of a two-phase stepper motor after it has been energised is to swap the A+ and A- (or B+ and B-) of the motor and driver wiring.