Hybrid stepping refers to the combination of the advantages of permanent magnet and reactive, divided into two phases and five phases, the two-phase step angle is generally 1.8 degrees and the five-phase step angle is generally 0.72 degrees, this stepper motor The most widely used.
In "The structure and working principle of HB type hybrid stepper motor", we have already understood its structure and working principle in detail. The next Xiaobian will lead you to learn more about HB type hybrid stepping motor and phase number. The relationship between the number of rotor teeth and the number of main poles. This article first introduces the expressions of the number of phases of the stepper motor, the number of teeth of the rotor, and the number of main poles. Secondly, the general form of the magnetic circuits within and between phases is introduced.
Stepper motor phase number, rotor tooth number and main pole number expressionIf the HB type stepping motor is P-phase, the number of teeth of the rotor can be known as θs=180°/PNr according to the equation θs=180°/PNr. At this time, the number of main poles of the stator 1 phase (the sum of the A "bar A" phases) is m, and it is evenly arranged, and the number of fine teeth of the inner diameter is the same. The magnetic path where the permanent magnets of the rotor generate the magnetic flux is shown by the dashed line in the figure below, and a closed magnetic circuit is formed between A "bar A". Unlike the odd-numbered phases such as three-phase HB and five-phase HB type that will be described later, a closed magnetic circuit cannot be formed between A and A, and a closed magnetic circuit needs to be formed across other phases such as B-phase and C-phase. The former is called phase magnetic circuit type, and the latter is called phase magnetic circuit type.
Two-phase HB type stepper motors are all in-phase magnetic circuits, while three-phase HB type stepper motors have two forms of magnetic circuits in phase and magnetic circuits in phases. The following figure shows a three-phase HB type stepper motor with six poles. There are no small teeth on the poles and the number of teeth on the rotor is small. This figure describes the stator and rotor flux path, in which (a) is an in-phase magnetic circuit, (b) is an interphase magnetic circuit.
For example, in the magnetic circuit in phase (a), the stator main pole A1 and the adjacent B phase B1 or C2 phase C2, when excited in the next phase, will attract the rotor teeth with the same polarity as A1. The five rotor teeth on the rear side of the permanent magnet are shown with hatching, which is opposite in polarity to the rotor teeth on the front side. Similarly, figure (b) is the interphase magnetic circuit. The stator main pole A1 and the adjacent B phase B1 or C phase C2, when excited to the next phase, will attract the rotor teeth with the A1 heterogeneity. The four rotor teeth on the rear side of the permanent magnets are shown with hatching, which is opposite in polarity to the front rotor teeth and is the same as (a) the magnetic circuit.
In-phase magnetic circuit general formAs shown in the following figure (a) is an in-phase magnetic circuit, the main magnetic poles have mP. Because the pitch is equal, the pitch 1 between the A-phase and the B-phase of the adjacent phase is 360°/mP. When A is connected to the exciting current, its pole corresponds to the tooth with the opposite polarity of the rotor. When the B phase is further energized, and the same polarity as the A phase is produced on the B pole, the rotor teeth rotate to the B phase. For the sake of simplicity, the stator teeth of the A and B phases in the figure are simplified from single teeth to multiple teeth.
At this time, the pitch 2 of the rotor tooth, which is opposite to the phase A of the rotor tooth and the phase B of the next, is 360° n/Nr (n is an integer), and the step angle is the difference between 1 and 2:
Substitute θs=180°/PNr into the above equation:
Nr=m(nP±1/2)
This is an expression of the rotor teeth Nr, the number of phases P, and the number of main poles m in the in-phase magnetic circuit. In the above formula, Nr must be an integer, otherwise it has no meaning. At this point it is important to note that m must be even.
Two-phase HB hybrid stepping motor, when P = 2, the main pole is 8 (m = 4) into the above formula, get: Nr = 8n ± 2
This is a relational expression of a two-phase HB type hybrid stepper motor. The step angle of the two-phase HB type stepping motor is usually 1.8°, and n=6 is substituted into the above equation to obtain Nr=50.
The main pole of the stator of the two-phase HB hybrid stepper motor is 8, and the structure of the rotor teeth is as shown in the figure below.
The step angle of the two-phase HB stepping motor is 0.9°, the main pole of the stator is 16, m=8, n=6, and the structure of the rotor teeth is 100 as shown in the figure below.
The main pole of the two-phase 3.6° stepper motor stator is 4 (unbalanced electromagnetic force will be generated between stator and rotor, so this structure is discouraged), according to Nr=m(nP±1/2), when P = 2, When m=2 and n=6, Nr=25 is obtained. The small picture shows two phases, the main pole of the stator 4 and the 3.6° stepper motor structure. The shape of the stepper motor is 42mm stepper motor and it is used for 5 inch 48TPI FDD (floppy disk drive). When it is three phases, the formula is Nr=m(nP±1/2), m=4, n=4, P=3 to obtain Nr=50. The number of stator main poles is mP=12, and the step angle θs is 1.2°.
Above: Relationship between different magnetic circuits and step lengths. Picture (b) is the phase-to-phase magnetic circuit, the stator pitch is equal, the total number of main poles is mP, and the pitch between adjacent phases A and B is 1 and In-phase magnetic circuit pitch is the same as 360°/mP. The A-phase is excited, and its rotor teeth with opposite polarity are relatively attracted. Secondly, the phase B excitation produces the same polarity as phase A, attracting the corresponding rotor teeth. For ease of understanding, the multi-tooth structure is simplified to a single-tooth structure.
At this time, the pitch 2 between the rotor teeth opposed to the A-phase pair of rotor teeth and the B-phase is 360° (n±1/2)/Nr (n integer) as shown. So the step angle is the difference between 1 and 2:
If the phase-to-phase magnetic circuit is three-phase, let P=3:
Nr=m(3n±1)
In the three phases, the main magnetic pole is a multiple of 3, and in the simplest three-phase three main pole, m=1 becomes the following formula:
Nr=3n±1
The following figure shows the structure of n = 3, Nr = 8, using the above formula Nr = 3n ± 1 and θs = 180 ° / PNr, can be calculated to obtain Nr and θs, as shown in the following table.
The design must pay attention to the three main pole HB stepper motor will produce unbalanced electromagnetic force. Since only three coils are used, it is attractive for applications with low-cost motors.
When three phases, the main pole of the stator 6, m=2, the following formula: Nr=2(3n±1). The motor structure with n=3, Nr=16, step angle of 3.75° is shown in the figure below.
For three phases, the main pole of the stator 9, m=3, then Nr=3(3n±1). n=7, Nr=60, step angle 1° motor, axial section as shown below.
For three phases, the main pole of the stator 12, m=4, then Nr=4(3n±1). The axial sectional view of stepper motor with n=8, Nr=100 and step angle of 0.6° is shown in the figure below:
The above is a brief introduction of the relationship between the number of phases, the number of main poles and the number of teeth of the HB-type hybrid stepping motor in the phase-symmetric symmetry of the magnetic circuit in the phase and the phase-to-phase magnetic circuit and the main pole of the stator. Not only do these basic principles need to be understood when designing a motor, but when using a motor, the structure, performance, and dimensions of the motor must also be systematically understood, and the internal structure of the motor and methods for solving the problem can be derived based on the number of phases and the step angle.
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