Features
• Precise position control
A stepper motor rotates at a fixed step angle, much like the second hand of a clock. This angle is called the basic step angle. Mingzhi offers two basic step angles as standard motors: a two-phase stepper motor with a basic step angle of 1.8° and a three-phase stepper motor with a basic step angle of 1.2°.
• Simple pulse signal control
The system requiring high-precision positioning is shown below. The pulse signals emitted by the controller can accurately control the rotation angle and speed of the stepper motor.
What is a pulse signal?
A pulse signal is an electrical signal whose voltage repeatedly changes between ON and OFF.
Each ON/OFF cycle is recorded as one pulse. A single pulse signal command causes the motor output shaft to rotate one step.
The signal levels corresponding to the ON and OFF voltage conditions are referred to as "H" and "L" respectively.
Main features of stepper motors:
1. The accuracy of a stepper motor is 3-5% of the step angle, and it does not accumulate. (Stepper motors only have periodic errors and no cumulative errors.)
II. The maximum permissible temperature of the stepper motor's exterior. It features no accumulated error (100% accuracy).
Third, the torque of a stepper motor decreases as the rotational speed increases.
4. The stepper motor can run normally at low speed, but it cannot start if the speed is higher than a certain speed, and it is accompanied by a whistling sound.
Some characteristics of stepper motors:
(1) Stepper motors have no accumulated error: The accuracy of a typical stepper motor is three to five percent of the actual step angle, and it does not accumulate.
(2) When the stepper motor is working, the pulse signal is applied to each phase winding in a certain order (the winding is powered on and off by the ring distributor in the driver).
(3) Even for the same stepper motor, the torque-frequency characteristics can vary greatly when using different drive schemes.
(4) Unlike other motors, the nominal rated voltage and rated current of a stepper motor are only reference values. Also, because a stepper motor is powered by pulses, the power supply voltage is its highest voltage, not the average voltage. Therefore, a stepper motor can operate beyond its rated range. However, it should not deviate too far from the rated value when selecting a stepper motor.
(5) Maximum allowable temperature of stepper motor surface: If the temperature of the stepper motor is too high, the magnetic material of the motor will demagnetize, which will lead to a decrease in torque or even loss of steps. Therefore, the maximum allowable temperature of the motor surface should depend on the demagnetization point of the magnetic material of different motors. Generally speaking, the demagnetization point of magnetic materials is above 130 degrees Celsius, and some are even above 200 degrees Celsius. Therefore, the surface temperature of the stepper motor is completely normal at 80-90 degrees Celsius.
(6) The torque of a stepper motor decreases as the speed increases: When a stepper motor rotates, the inductance of each phase winding of the motor will generate a back electromotive force; the higher the frequency, the greater the back electromotive force. Under its action, the phase current of the motor decreases as the frequency (or speed) increases, thus causing the torque to decrease.
(7) Stepper motors can operate normally at low speeds, but they cannot start above a certain frequency and are accompanied by a whistling sound. A stepper motor has a technical parameter: the no-load starting frequency, which 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. Under load, the starting frequency should be even lower. To make the motor reach high speed, the pulse frequency should have an acceleration process, i.e., a lower starting frequency, and then gradually increasing to the desired high frequency (motor speed increasing from low to high).
(8) Four-phase hybrid stepper motors are generally driven by two-phase drivers. Therefore, they can be connected in series or in parallel to make them usable as two-phase motors. Series connection is generally used in applications with lower motor speeds. In this case, the required driver output current is 0.7 times the motor phase current, resulting in less motor heat generation. Parallel connection is generally used in applications with higher motor speeds (also known as high-speed connection). In this case, the required driver output current is 1.4 times the motor phase current, resulting in greater motor heat generation.
(9) The power supply voltage of a hybrid stepper motor driver is generally a wide range (e.g., the power supply voltage of IM483 is 12-48VDC). The power supply voltage is usually selected according to the motor's operating speed and response requirements. If the motor's operating speed is high or the response requirement is fast, then the voltage value should also be high. However, it should be noted that the ripple of the power supply voltage should not exceed the driver's maximum input voltage, otherwise the driver may be damaged.
(10) The power supply current is generally determined based on 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. (11) 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 automated equipment, if it is required to directly rotate the motor shaft (manual mode) without disconnecting the driver from the power supply, the FREE signal can be set low to take the motor offline for manual operation or adjustment. After manual operation is completed, the FREE signal is set high to continue automatic control.
(12) To adjust the rotation direction of a two-phase stepper motor after it is powered on, simply swap the A+ and A- (or B+ and B-) wires of the motor and driver connection.
