Stepper motor parameters - Solutions - Huaqiang Electronic Network

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Stepper motor inherent step angle: It indicates the angle at which the motor rotates every time the control system sends a step pulse signal.

The number of phases of the stepper motor: refers to the number of coil groups inside the motor. Currently, two-phase, three-phase, four-phase, five-phase stepping motors are commonly used. The number of phases of the motor is different, and the step angle is also different. Generally, the step angle of the two-phase motor is 0.9°/1.8°, the three-phase is 0.75°/1.5°, and the five-phase is 0.36°/0.72°.

Holding torque: refers to the moment that the stator locks the rotor when the stepper motor is energized but does not rotate. It is one of the most important parameters of a stepper motor. Usually, the torque of the stepper motor at low speed is close to the holding torque.

Phase number: The number of pairs of excitation coils that generate different pairs of N and S magnetic fields refers to the number of coil groups inside the motor. Currently, two-phase, three-phase, four-phase, and five-phase stepping motors are commonly used. The number of phases of the motor is different, and the step angle is also different. Generally, the step angle of the two-phase motor is 0.9°/1.8°, the three-phase is 0.75°/1.5°, and the five-phase is 0.36°/0.72°. When there is no subdivision driver, the user mainly chooses the stepping motor with different phase numbers to meet the requirements of the step angle. If you use a subdivision drive, the 'phase number' will become meaningless, and the user can change the step angle by simply changing the number of subdivisions on the drive. Currently the most widely used are two-phase and four-phase, four-phase motors are generally used as two-phase, and the cost of five-phase is higher.

Number of beats: The number of pulses required to complete a periodic change of the magnetic field or the conductive state is represented by n, or the number of pulses required for the motor to rotate through a pitch angle. Taking a four-phase motor as an example, there is a four-phase four-shot operation mode, that is, AB. -BC-CD-DA-AB, four-phase eight-shot operation mode is A-AB-B-BC-C-CD-D-DA-A.

Inherent step angle: Corresponding to a pulse signal, the angular displacement of the rotor of the motor is indicated by θ. θ = 360 degrees (number of rotor teeth J * running beats), taking the conventional two-phase, four-phase, rotor teeth as a 50-tooth motor as an example. The four-shot running step angle is θ=360°/(50*4)=1.8 degrees (commonly known as the whole step), and the eight-shot running step angle is θ=360 degrees/(50*8)=0.9 degrees (commonly known as Half step). This step angle can be called 'the inherent step angle of the motor', it is not necessarily the true step angle of the actual working of the motor, and the true step angle is related to the driver.

Positioning torque (DETENT TORQUE): The locking torque of the motor rotor itself (caused by the harmonics of the magnetic field tooth shape and mechanical errors) when the motor is not energized. DETENT TORQUE has no unified translation method in China, which is easy for everyone to produce. Misunderstanding; since the rotor of a reactive stepper motor is not a permanent magnet material, it does not have a DETENT TORQUE.

Maximum static torque: also called holding torque (HOLDING TORQUE), the motor is under the action of rated static electricity (energized), when the motor is not rotating, the locking torque of the motor shaft, that is, the torque of the stator locking the rotor. This torque is a measure of the motor's volume (geometry) and is independent of the drive voltage and drive power. Usually the torque of the stepper motor at low speed approaches the holding torque. Since the output torque of the stepping motor is continuously attenuated as the speed increases, the output power also changes with the increase of the speed, so the holding torque becomes one of the most important parameters for measuring the stepping motor. For example, when people say that a 2N.m stepper motor, unless otherwise specified, is a stepper motor that maintains a torque of 2N.m.
Although the static torque is proportional to the number of electromagnetic ampere-turns and the air gap between the fixed-tooth rotors, it is not advisable to reduce the air gap excessively and increase the static ampere to increase the static torque, which will cause the motor to Heat and mechanical noise.
Maximum static torque selection:
The dynamic torque of the stepper motor is difficult to determine at once. We often determine the static torque of the motor first. The static torque selection is based on the load on which the motor operates, and the load can be divided into two types: inertial load and friction load. A single inertia load and a single friction load are not present. When starting directly (generally by low speed), both loads should be considered. When starting acceleration, the inertia load is mainly considered. For constant speed operation, only the friction load should be considered. Under normal circumstances, the static torque should be 2-3 times of the friction load. Once the static torque is selected, the base and length of the motor can be determined (geometry).

The application of stepper motors is mainly attributed to three aspects:
Good overload, used in places where speed and position are strictly required;
The control is convenient, the stepping motor is rotated in units of “steps”, and the digital features are relatively obvious, which brings great convenience to computer control.
The structure of the whole machine is simple and the structure is simple and compact.