JPH09168271A - Synchronous motor and control method thereof - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: 1000 rpm without using a speed reducer as a noise source.
An object of the present invention is to provide a small-sized and inexpensive motor system that can achieve the following stable low-speed rotation. A stator (11) having M teeth (12) provided on an inner peripheral portion thereof and a rotor (15) having N salient poles (16) provided on an outer peripheral portion, and a total of (M) slots (13) are provided. It is divided into 2m slot groups 131 to 136, and each phase from the first phase to the m-th phase is assigned to each slot group one by one in a fixed order along the circumferential direction. A total of m windings 14U, V, W are provided, and each winding passes through each slot belonging to the two slot groups to which one phase is assigned, and in each of the two slot groups. A motor in which each slot has the same passing direction and is wound between the two slot groups so that the passing directions are opposite to each other, and a total of m windings are connected to each other in a star connection method is manufactured. .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synchronous motor and its control method. The rated speed of a single-phase or three-phase induction motor widely used as an industrial motor is 1
000-3000 rpm. Therefore, a speed reducer is required for low speed applications. When using a speed reducer, the operating noise becomes loud. Due to such a situation, there is a demand for a small-sized and inexpensive motor that can obtain high torque and stable low-speed rotation.

[0002]

2. Description of the Related Art A variable reluctance motor (hereinafter referred to as "VR")
Type motor) is known as a type of stepping motor with a small torque that allows open loop control, and it is mainly used for closed loop control in applications such as machine tools that require a large torque at a relatively low speed. Is used as a direct drive motor (DD motor).

FIG. 5 is a diagram showing a schematic structure of a conventional VR type motor 80. The VR type motor 80 shown in FIG.
A stator 81 in which a three-phase winding 84 is provided on an iron core (core including a yoke) having individual teeth 82, and 14 salient poles 8
7 and a rotor 86 made of a high magnetic permeability material (soft magnetic material). Two small teeth 83 facing the salient pole 87 are provided at the tip of each tooth 82.

In the VR motor 80, the winding 84 of each phase of U, V and W is formed in a concentrated winding form so that each tooth 82 is circulated by utilizing the slots 85 on both sides thereof.
Is wound. Then, two coils that surround the facing teeth 82 with the rotor 86 sandwiched therebetween are connected in series to form a winding 84 of one phase.

When such a VR type motor 80 is used as a DD motor and low speed rotation is realized, a high resolution position sensor is attached to a stator 81 and a rotor 86 is installed.
The rotation control was performed by detecting the rotation angle position of the coil and adjusting the excitation timing of each winding.

[0006]

A conventional VR type motor 8
In 0, each slot 85 corresponds to the two pole teeth 82 on both sides.
Since one winding 84 passes through, it is necessary to increase the cross-sectional area of the slot 85. Therefore, the stator 81 having an extremely large outer diameter as compared with the outer diameter of the rotor 86 is required, and the VR motor 80 cannot be downsized.

Further, in the related art, since the rotation control is performed by using the position sensor, there is a problem that the control system becomes expensive. An object of the present invention is to provide a small and inexpensive motor system that can realize stable low-speed rotation of 1000 rpm or less without using a speed reducer as a noise source.

[0008]

According to another aspect of the present invention, there is provided a synchronous motor having a stator having M teeth at a first angular pitch on an inner peripheral portion and a second angular pitch on an outer peripheral portion. A rotor provided with N salient poles, and a total of M slots between the teeth are divided into a total of 2 m slot groups including a plurality of adjacent slots as a group. Each phase from the first phase to the m-th phase is assigned to the group one by one in a fixed order along the circumferential direction, and a total of m windings are provided to the stator, one for each phase. The respective windings pass through the respective slots belonging to the two slot groups to which one phase is assigned, and the passing directions of the respective slots are equal in each of the two slot groups. The passing direction is opposite between the two slot groups. It is wound so that a motor sum of m of said winding is connected by star connection form one another.

According to another aspect of the motor of the present invention, the number of slots belonging to each slot group is equal to each other. The motor of the invention of claim 3 is a variable reluctance type synchronous motor in which the number N of the salient poles and the number M of the teeth satisfy the expression (1).

N = M ± 2 (1) The motor of the invention of claim 4 is a hybrid type synchronous motor in which the number N of the salient poles and the number M of the teeth satisfy the equation (2).

N = 2M ± 2 (2) According to the control method of the invention of claim 5, each of the windings is connected to the positive electrode of the DC power supply through a switching element for each of the phases, and each of the phases is connected. To the negative electrode of the DC power supply through another switching element, and by rotating the ON / OFF state of each of the switching elements on the positive electrode side and the negative electrode side of the DC power supply in a fixed order, the rotor is rotated. To detect the total current flowing through each of the windings,
Each switching element is controlled so that the detected value becomes constant.

The windings of each phase are wound around the stator in a distributed winding form and do not go around the teeth of the stator. Only one coil side of the winding of one phase is accommodated in one slot, and a sufficient amount of winding can be accommodated even if the sectional area of the slot is reduced. For each phase winding connected in star connection
Power is supplied so that a rotating magnetic field is generated across these windings. The rotation speed of the rotor is proportional to the rotation speed of the magnetic field. That is, the rotor rotates in synchronization with the rotation of the magnetic field.

[0013]

1 is a diagram showing a winding structure of a motor 1 of the present invention, and FIG. 2 is a U-phase winding 14U in the motor 1.
FIG.

The motor 1 includes a U-, V-, and W-phase winding 14
Stator 1 in which U, 14V and 14W are wound in distributed winding form
1 and a rotor 15 made of a high magnetic permeability material
Type motor. Forty-eight teeth 12 are provided on the inner peripheral portion of the stator 11 at a constant angular pitch p1. Fifty salient poles 16 are provided on the outer peripheral portion of the rotor 15 at a constant angular pitch p2. Each salient pole 16 sequentially faces each tooth 12 when the rotor 15 rotates. In the circumferential direction, the width of the tip of the tooth 12 is the same as the width of the tip of the salient pole 16.

The stator 11 has a total of 48 slots 13 sandwiched by adjacent teeth 12. FIG. 1 (A)
In the figure, the number in parentheses indicates the number conveniently attached to each slot 13. In the illustrated example, each slot 13
In contrast, numbers 1 to 48 are given clockwise. Each slot 13 is 8 in total, 6 (= 2 × 3)
The slots are divided into individual slot groups 131 to 136, and the U, V, and W phases are assigned to these slot groups 131 to 136 one by one in a fixed order along the circumferential direction. In the motor 1, clockwise, U, W, and V are assigned in this order. That is, slots 1 to 8
Slot group 131 to which the slot belongs and slot group 134 to which the slots 13 to 25-32 belong correspond to the U phase, and
The slot group 132 to which the 16th slot 13 belongs and 3
The slot group 135 to which the 3rd to 40th slots 13 belong corresponds to the W phase, and the slot group 133 to which the 17th to 24th slots 13 belong and the slot group 136 to which the 41st to 48th slots 13 belong to the V phase. Corresponding to.

Each winding 14U, 14V, 14W passes through a total of 16 slots 13 belonging to the two slot groups to which the corresponding phases are assigned, and the passing direction of each slot 13 in each of the two slot groups. Are equal to each other and the passage directions are reversed between the two slot groups. For example, in the U-phase winding 14U, the passage direction of each slot 13 of the slot group 131 is from the back side of the paper surface of FIG.
The passing direction of each slot 13 of No. 4 is from the front side to the back side of the drawing.

The windings 14U, 14V and 14W can be wound in a drum shape or an annular shape. Depending on the diameter of the stator 11 and the length in the axial direction, one that can use the conductor more effectively may be selected. FIG. 2 shows an example of drum-shaped winding. In practice, dozens or more conductors pass through each slot 13.

As shown in FIG. 1B, each winding 14U, 14
The V and 14W have one end that is in the same relationship in the winding direction and are commonly connected, and the other end that is individually connected to the terminals U, V, and W of each phase. That is, the winding 14
U, 14V and 14W are connected in a star connection form.
Here, for example, when a current Iu in the direction shown by the arrow in FIG.
In (A), current flows from the back side to the front side of the paper, and in the slot group 134, current flows from the front side to the back side.

In the motor 1 having the above-described structure, only the windings 14U to W of one phase pass through each slot 13, and the winding amount is half that of the conventional concentrated winding. Since the slot 13 has a small cross-sectional area, it is possible to pass a sufficient number of the windings 14U to W even if the slot 13 has a small cross-sectional area. Therefore, even if the slot 13 is small, a sufficient magnetomotive force can be obtained. The size of the motor 11, that is, the size of the motor 1 can be reduced. Further, since the excitation is performed by simultaneously passing currents through the windings of a plurality of phases, the utilization factor of the windings 14U to 14W becomes high, and a large torque can be generated. Salient pole 16 facing tooth 12
A large ratio of the number of the salient poles 16 facing the teeth 12 to the total number of teeth also contributes to an increase in torque.

FIG. 3 is a diagram showing an excitation sequence of the motor 1. When the motor 1 is used, the windings 14U to W are excited by a three-phase sinusoidal current to generate a rotating magnetic field. In FIGS. 3A to 3F, the arrow in the rotor 15 indicates the magnetic field direction. Angular pitch p1 and angular pitch p
2, the teeth 12 and the salient poles 16 are slightly displaced from each other, so that the magnetic resistance (reluctance) between the rotor 15 and the stator 11 is minimum in synchronization with the rotation of the magnetic field. The rotor 15 rotationally moves to a stable position without deviation. Each rotation of the magnetic field causes the rotor 15 to rotate by two salient poles 16, that is, 14.4 (2 × 360/50) °. In the motor 1, since the salient poles 16 are larger than the teeth 12, the rotation direction of the rotor 15 is the same as the rotation direction of the magnetic field. If the salient poles 16 are less than the teeth 12, the rotor 15
The direction of rotation of is opposite to the direction of rotation of the magnetic field.

The rotation speed V of the rotor 15 is expressed by equation (3). V = 120 f / P (3) V: Rotational speed [rpm] f: Frequency [Hz] P: Number of rotor poles (number of salient poles) In the motor 1, when the motor 1 is rotating at a constant speed, the rotor 15 The self-inductance is almost constant regardless of the rotation angle position of, and the mutual inductance changes periodically.

The control method of the motor 1 will be described below. The motor 1 is similar to a known stepping motor in terms of iron core structure, and is similar to an AC motor in terms of winding structure. From these things, a variable frequency inverter is suitable as a drive power source for the motor 1. However, normal V
The VVF inverter cannot excite the entire frequency range without excess or deficiency, and cannot operate normally. Motor 1
In order to drive normally, the AC servo control or the control to make the exciting current constant may be performed. The former requires various sensors including high resolution position sensors. Therefore, driving by an inverter that supplies a constant current is optimal.

FIG. 4 is a block diagram of the control system 100 of the motor 1. The control system 100 includes an inverter 110 that supplies three-phase electric power to the motor 1, and a controller 120 that controls switching of the inverter 110.

The inverter 110 is a DC power supply VE having a rectifier circuit DB that receives a three-phase commercial AC and a smoothing capacitor C1, and a three-phase drive inverter circuit INV,
And a current detection circuit CS. The inverter circuit INV has six transistors (switching elements) Q1 to Q6. Freewheeling diodes are connected in parallel to the respective transistors Q1 to Q6.

The U-phase winding 14U of the motor 1 is connected to the positive electrode of the DC power supply VE via the transistor Q1 and to the negative electrode of the DC power supply VE via the transistor Q4. Similarly, the V-phase winding 14V is connected to the transistor Q
2 and Q5 are connected to the DC power supply VE, and the W-phase winding 14W is connected to the DC power supply V through the transistors Q3 and Q6.
E is connected.

For example, when the transistors Q3, Q4 and Q5 are on and the others are off, the current Iw (= -Iu) from the terminal W to the terminals U and V as shown in FIG.
-Iv) flows.

The controller 120 has a step-out prevention calculation unit 121 composed of a microprocessor and is configured to perform PWM control on the inverter circuit INV so that the exciting current of the motor 1 becomes constant.

The detection value ia of the current detection circuit CS is sampled by the sample hold circuit 123 in synchronization with the PWM carrier signal (triangular wave signal). If the sampling timing is set to the zero-cross point of the carrier signal, one of the transistors Q1 to Q3 and one of the transistors Q4 to 6 are always on, so the detected value i
It can be avoided that a becomes zero.

The sampled detection value ia is input to the current amplifier 124. The current amplifier 124 adds the detection value ia to the signal ib from the out-of-step prevention calculation unit 121, amplifies it, and outputs a command value e0. The multiplier 125 multiplies the correction coefficients a, b, and c of each phase provided from the current shunt circuit 126 by the command value e0, and outputs the sine wave signal e of each phase.
1 to 3 are generated. These sine wave signals e1 to 3 are P
The WM circuit 127 compares the carrier signal with the carrier signal, thereby generating a switching control pulse for each phase.
Then, on / off control of the transistors Q1 to 6 is performed by the drivers 128 to 130 provided for each phase based on the switching control pulse.

The current detection circuit CS is specifically 0.1 Ω.
It can be configured by inserting a shunt resistor of a certain degree on the negative electrode side of the DC power supply VE. Hall detector, current transformer,
Alternatively, it is not necessary to provide an insulation type circuit such as a photocoupler, and a sufficient function can be obtained by a configuration in which the voltage across the terminals of the shunt resistor is sampled without insulation.

The motor 1 of this embodiment can be operated at a low speed like a stepping motor. It is also the same as the stepping motor that stepping out occurs when a torque larger than the rated torque is applied. Therefore, the out-of-step prevention calculation unit 121 is provided. The current detection circuit CS can simultaneously detect the average value of the direct current in addition to the substitute value of the alternating current. This means that the effective input power can be detected because the DC voltage is constant. The average value of the DC current is input to the step-out prevention calculation unit 121 via the average value sampling circuit 122. On the other hand, since the rotation speed V is known from the input frequency f, the motor torque T can be calculated. Therefore, the motor torque T is obtained from the average value of the current and the input frequency f, and when the overload occurs, the exciting current may be temporarily increased, or the motor 1 may be overheated due to a long overload. For example, it is useful to stop the power supply. Such processing can be easily performed by the microphone processor. The input power Wi, the motor torque T, and the rotation speed V are expressed by the following equations.

Wi = Vdc × Idc T = 60 × Wi / (2π · V) V = 120 × f / P Wi: Input power [W] Vdc: DC voltage [V] Idc: DC average current [A] T: Motor torque [NM] P: Number of poles f: Frequency [Hz] V: Rotation speed [rpm] According to the above-described embodiment, the windings 14U, 14V, 14W.
Since the winding method is distributed winding, it is possible to reduce the diameter of the stator 11 and downsize the entire motor. Winding 1
Since 4U, 14V, and 14W are connected in a star shape, connection with the drive system is possible only by providing three lead wires. Further, the inverter circuit 110 can be configured by using general-purpose power electronic parts,
It is possible to reduce the cost of the drive system.

Although the VR type motor 1 is exemplified in the above embodiment, the present invention is also applicable to a hybrid type motor using a permanent magnet. In the case of the hybrid type, the number of teeth 12 and the number of salient poles 16 may be selected so as to satisfy the above formula (2). Stator 11
The number of teeth 12 of the rotor, how to wind the windings 14U, 14V, 14W or how to process the windings between the slots, the number of salient poles 16 of the rotor 15, the number of phases, other, the structure and shape of the motor 1,
The material, the configuration of the control system 100, and the like can be variously changed in accordance with the gist of the present invention.

[0034]

According to the first to fourth aspects of the present invention,
The size of the rotor can be reduced while ensuring a predetermined torque.

According to the fifth aspect of the present invention, stable low speed rotation of 1000 rpm or less can be realized without using a speed reducer as a noise source and a sensor for detecting the rotational angle position of the rotor.

[Brief description of the drawings]

FIG. 1 is a diagram showing a winding structure of a motor of the present invention.

FIG. 2 is a development view of U-phase windings in a motor.

FIG. 3 is a diagram showing an excitation sequence of a motor.

FIG. 4 is a block diagram of a motor control system.

FIG. 5 is a diagram showing a schematic structure of a conventional VR type motor.

[Explanation of symbols]

 1 Motor (Synchronous Motor) 11 Stator 12 Tooth 13 Slot 14U, 14V, 14W Winding 15 Rotor 16 Salient Pole 131-136 Slot Group p1 Angular Pitch (First Angular Pitch) p2 Angular Pitch (Second Angular Pitch) Q1 ~ 6 transistors (switching elements) VE DC power supply

Claims (5)

[Claims] 1. A stator having M teeth at a first angular pitch on an inner peripheral portion and N at a second angular pitch on an outer peripheral portion.
And a rotor provided with (N ≠ M) salient poles, and a total of M slots between the teeth are divided into a total of 2 m slot groups including a plurality of adjacent slots as a group. , For each slot group, each phase from the first phase to the m-th phase is assigned one by one in a fixed order along the circumferential direction, and the stator has one m for each phase in total. Windings are provided, and each of the windings passes through each of the slots belonging to the two slot groups to which one of the phases is assigned.
Each of the slot groups is wound such that the passing directions of the slots are the same and the passing directions are opposite between the two slot groups, and the total of m windings are star-shaped. A synchronous motor characterized by being connected in a die connection form. 2. The synchronous motor according to claim 1, wherein the number of the slots belonging to each slot group is equal to each other. 3. The synchronous motor according to claim 2, wherein the number N of the salient poles and the number M of the teeth satisfy the following equation. N = M ± 2 4. The synchronous motor according to claim 2, wherein the number N of the salient poles and the number M of the teeth satisfy the following equation. N = 2M ± 2 5. The method for controlling a synchronous motor according to claim 1, wherein each winding is connected to a positive electrode of a DC power source for each phase via a switching element, Further, the rotor is connected to the negative electrode of the DC power source through another switching element for each of the phases, and the ON / OFF state of each of the switching elements on the positive electrode side and the negative electrode side of the DC power source is switched in a fixed order, thereby making the rotor A method for controlling a synchronous motor, characterized in that the synchronous motor is rotated, and at that time, a total sum of currents flowing through the respective windings is detected and each switching element is controlled so that a detected value becomes constant.