Stepper motor structure and working principle:
1. A stepper motor is an open-loop control element that converts electrical pulse signals into angular or linear displacement. Under non-overload conditions, the motor's speed and stopping position depend only on the frequency and number of control pulse signals.
2. The more pulses, the greater the angle of motor rotation.
3. The higher the frequency of the pulse, the faster the motor speed, but it cannot exceed the maximum frequency, otherwise the motor torque will decrease rapidly and the motor will not turn.
According to the principle of torque generation, torque can be divided into:
(1) Reactive type: The rotor has no windings, and the stepping operation is achieved by the reactive torque generated by the excited stator windings.
(2) Excitation type: Both the stator and rotor have excitation windings (or the rotor uses permanent magnets), and stepping operation is achieved by electromagnetic torque.
Based on the magnitude of the output torque, they can be divided into:
(1) Servo type: The output torque is in the range of a few percent to a few tenths (Nm), which can only drive small loads. It needs to be used with a hydraulic torque amplifier to drive larger loads such as machine tool tables.
(2) Power type: The output torque is above 5~50 N.m, which can directly drive large loads such as machine tool worktables.
Based on the number of stators, they can be divided into:
(1) Single stator type (2) Double stator type (3) Triple stator type (4) Multi-stator type
Based on the distribution of windings in each phase, they can be divided into:
(1) Radial distributed: The phases of the motor are arranged in a circular pattern.
(2) Axial distributed: The phases of the motor are arranged sequentially along the axial direction.
Motor radial distribution
Stepper motor working principle:
When a DC current flows through phase A winding, according to the principles of electromagnetism, a magnetic field is generated in the AA direction. Under the influence of the electromagnetic force of this magnetic field, the rotor is attracted, causing the rotor teeth to align with the teeth on the stator's AA magnetic pole. If phase A is de-energized and phase B is energized, the new magnetic field's electromagnetic force attracts the rotor's two poles to align with the teeth on the BB magnetic pole, causing the rotor to rotate 60° counterclockwise. Typically, the angle the rotor rotates each time the energization state of the stepper motor windings changes is called the step angle. If the control circuit continuously controls the stepper motor windings in the sequence A→C→B→…, the stepper motor rotor will continuously rotate clockwise. If the energization sequence is changed to A→B→C→A…, the stepper motor will rotate in reverse.
1. The above describes the working process of a three-phase single three-step circuit. Besides this, there are also three-phase double three-step and three-phase six-step circuits. The energizing method of a three-phase double three-step circuit is to simultaneously energize two phase windings: e.g., AB-BC-CA-AB-... The control method of a three-phase six-step circuit is: A→AB→B→BC→C→CA→A→...
2. The motor's speed is related to the frequency of phase sequence switching; the faster the switching, the faster the motor rotates. The direction of motor rotation is also related to the phase sequence.
3. The angle of rotation of the motor per cycle is called the step angle θ. The step angle is related to the structure of the motor. θ = 360° / mzk, where m is the number of phases of the stator winding, Z is the number of teeth of the rotor, and K is the energizing mode. For m phases and m cycles, k = 1; for m phases and 2 m cycles, k = 2.
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