Therefore, how the permagnetic synchronous motor of position-sensor-free is started rapidly and accurately is the technical barrier in this field always.

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If installation site transducer on permagnetic synchronous motor not; Then need estimate the turned position of rotor through detecting the signal of telecommunication (like electric current, voltage etc.); But in practical operation, this method often can not realize higher accuracy, and for zero-speed and low speed situation; Because the signal of telecommunication is very little, can't estimate the turned position of rotor especially accurately.

Magnetic or photoelectrical position sensor are installed on rotor and support in the existing permagnetic synchronous motor usually, thereby the residing turned position of rotor is confirmed.But thereby the adding of transducer can increase the cost that moment of inertia on the machine shaft influences efficiency of motor and increases motor undoubtedly; In addition; The adding of transducer has also proposed more complicated requirement to the manufacture craft of motor, in case and faulty sensor, motor then can't normal starting.

Starting process is the significant process that motor uses, and especially for permagnetic synchronous motor, owing to laid permanent magnet on the rotor, its starting process is more more complicated than common induction machine.Simply; Since the magnetic field that permanent magnet produces be fix and do not have a symmetry in the magnetic field that the induction machine rotor produced; Thereby compare with common induction machine,, need at first to confirm the turned position of rotor if will correctly start to motor; So that on stator, apply correct three-phase alternating current starting voltage, make the permagnetic synchronous motor starting.

Pass through technique scheme; At first the rotor rotation with permagnetic synchronous motor arrives the locking turned position; Lock starting and permanent magnet synchronous machine on turned position at this then; Well solved the rotor-position problem identificatioin of position-sensor-free permagnetic synchronous motor, made the rotor starting process more steadily reliable.

Preferably, steps A wherein) when the time that applies second voltage signal reached for second time, stops to apply second voltage signal in.

Preferably, the angle between wherein said centre position and the said locking turned position is 90 degree.

Preferably, the scope of the angle between wherein said centre position and the said locking turned position is 60 degree-120 degree.

Preferably, wherein this method is at step B) also comprise before: A) said stator is applied second voltage signal, this second voltage signal makes said rotor rotation to a centre position.

Preferably, wherein, the scope of the said very first time is 1s-2s.

Preferably, step B wherein) when the time that applies first voltage signal reaches the very first time, stops to apply first voltage signal in.

Preferably, wherein said locking turned position is the position that fixed position or starting are set before, and said first voltage signal generates according to this locking turned position.

To achieve these goals; The present invention provides a kind of permagnetic synchronous motor starting method; Wherein this permagnetic synchronous motor comprises stator and the rotor with permanent magnet; This method comprises: B) said stator is applied first voltage signal, this first voltage signal makes said rotor rotation to a locking turned position; C) said stator is applied the ac voltage signal that can produce rotating magnetic field, make said electric motor starting.

To the problems referred to above that exist in the prior art, the purpose of this invention is to provide a kind of permagnetic synchronous motor starting method, so that the permagnetic synchronous motor of position-sensor-free can be started more accurately.

Accompanying drawing is to be used to provide further understanding of the present invention, and constitutes the part of specification, is used to explain the present invention with following embodiment, but is not construed as limiting the invention.In the accompanying drawings:

Embodiment

Be elaborated below in conjunction with the accompanying drawing specific embodiments of the invention.Should be understood that embodiment described herein only is used for explanation and explains the present invention, is not limited to the present invention.

In general permagnetic synchronous motor, stator is supplied power by three-phase electricity, and rotor has permanent magnet, and magnetic field that stator current produces and permanent magnet interact, thereby rotor can be rotated.The starting process of permagnetic synchronous motor is a kind ofly to begin through rotating the process that boost phase finally moves with desired rate from inactive state.

A kind of execution mode of permagnetic synchronous motor starting method provided by the present invention has been shown among Fig. 1.

As shown in Figure 1, in step 110, said stator is applied first voltage signal, this first voltage signal makes said rotor rotation to a locking turned position.

Said locking turned position is that motor is beginning to start the required position that is positioned at of rotor before.This locking turned position can be predefined fixed position, also can be in the preassigned position of prestart.

The size of first voltage that is applied is to be determined by the locking turned position.For three-phase permanent magnet synchronous motor, this first voltage is three-phase voltage, and this three-phase voltage locks onto p-m rotor on the determined locking turned position through electromagnetic interaction.Because the locking turned position is certain, and locked rotor is also confirmed the position of rotor with regard to being equivalent to behind this position, thereby can lock the turned position from this motor is started.

Rotor rotation is depended on multiple factor to locking the required time of turned position; Comprise initial position of rotor and the gap that locks the turned position, voltage swing etc.,, can guarantee that rotor has forwarded the locking turned position to through setting a time threshold value for the ease of control; Such as when the duration that applies first voltage signal reaches the very first time; Can think that rotor has forwarded the locking turned position at this moment certainly to, at this moment can stop to apply first voltage signal, directly get into next step.The scope of the wherein said very first time is 1s-2s.

When locking turned position when being the fixed position, also can be on this position sensor installation whether rotor reached the locking turned position judge.

In step 120, said stator is applied the ac voltage signal that can produce rotating magnetic field, make said electric motor starting.Stator is applied three-phase alternating voltage, produce rotating magnetic field, rotate thereupon thereby drive p-m rotor with fixed magnetic field, synchronous up to realizing, thus the starting process of realization permagnetic synchronous motor.

Fig. 2 shows in another embodiment of the invention, the step 210 among Fig. 2 with 220 with Fig. 1 in step 110 with 120 corresponding, different is that before step 210, the method among Fig. 2 is further comprising the steps of:

Step 203 applies second voltage signal to said stator, and this second voltage signal makes said rotor rotation to a centre position.

The centre position is the position that differs certain angle with the locking turned position, can elect the difference between centre position and the locking turned position as 60 degree&#;120 degree usually, preferably, differs 90 degree between centre position and locking turned position.

In step 203, at first with rotor rotation to the centre position, when rotor rotation behind the centre position, more further in step subsequently with the locking turned position of rotor from middle rotated position.

The centre position is similar to the terminal of locking process.Before rotor rotation is arrived the locking turned position; If differ about 180 degree between rotor present located position and locking turned position; First voltage that is applied to p-m rotor act on rotor shaft circumferentially (promptly with the perpendicular cross section of rotor shaft in the direction tangent with rotating shaft) component very little; The time that rotor is moved to determined locking turned position needs is longer; And because the restriction (such as rotating shaft lubricity, permanent magnet distribution etc.) of electric machine structure; Even possibly cause rotor can't turn to locking turned position (just in time be 180 when spending, rotor can't rotate in theory) in this case, thereby can't realize the starting of rotor.

Set a centre position; Can avoid taking place the situation that rotor does not rotate on the one hand; Can when rotor-position is spent near 180 with the locking turned position, be the process that rotor provides twice acceleration on the other hand, avoid rotor just can turn to the locking turned position through the long time.Certainly; For initial position of rotor and the more approaching situation in locking turned position; The time that meeting increase locking process is set in centre position, but at this moment average corresponding to the locking time of various initial position of rotor, help the setting of the said very first time more.

In one embodiment of the invention, can set another time threshold, confirm whether rotor reaches said centre position, stop to apply second voltage when second voltage reached for second time, directly enter into step subsequently such as setting when applying.

The selection mode and the very first time that it is pointed out that for second time are distinguished to some extent.The reason in setting centre position by mentioned earlier can be known; Needn't, rotor begin to carry out twist-lock step subsequently after arriving the centre position again; In fact, as long as rotor just can directly carry out step subsequently from initial position certain angle that squinted.Therefore, can be less value with second time set, such as said second time can be 0.5s-2s.

In above method, the step 220 among the step 120 among Fig. 1 and Fig. 2 is about the process that rotor is quickened gradually and rotating magnetic field final and that stator produces is rotated synchronously.The permagnetic synchronous motor acceleration control procedure that this rotation is quickened and final synchronous accelerator can adopt those skilled in the art to know and extensively adopt.In one embodiment of the invention; Can also realize permagnetic synchronous motor is quickened control by PMSM vector control model; In the PMSM vector control theory, thereby the three phase static coordinate system transformation can be convenient to motor is quickened control to two cordic phase rotators system more.

Pass through technique scheme; At first the rotor rotation with permagnetic synchronous motor arrives the locking turned position; Lock starting and permanent magnet synchronous machine on turned position at this then; Well solved the rotor-position problem identificatioin of position-sensor-free permagnetic synchronous motor, made the rotor starting process more steadily reliable.

More than combine accompanying drawing to describe preferred implementation of the present invention in detail; But; The present invention is not limited to the detail in the above-mentioned execution mode; In technical conceive scope of the present invention, can carry out multiple simple variant to technical scheme of the present invention, these simple variant all belong to protection scope of the present invention.

Need to prove that in addition each the concrete technical characterictic described in above-mentioned embodiment under reconcilable situation, can make up through any suitable manner.For fear of unnecessary repetition, the present invention is to the explanation no longer separately of various possible compound modes.

In addition, also can carry out combination in any between the various execution mode of the present invention, as long as it is without prejudice to thought of the present invention, it should be regarded as the disclosed content of the present invention equally.

Permanent magnet synchronous motor

permanent magnet synchronous motor (PMSM) - is a synchronous electric motor whose

(PMSM) - is a synchronous electric motor whose inductor consists of permanent magnets.

The main difference between a permanent magnet synchronous motor (PMSM) and an induction motor is in the rotor. Studies1 show that the PMSM has an efficiency of approximately 2% more than a highly efficient (IE3) induction electric motor, provided that the stator has the same design, and the same variable frequency drive is used for control. In this case, permanent magnet synchronous electric motors in comparison with other electric motors have the best performance: power/volume, torque/inertia, etc.

A permanent magnet synchronous motor, like any rotating electric motor, consists of a rotor and a stator. The stator is the fixed part. The rotor is the rotating part.

Interior permanent magnet synchronous motor

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Typically, the rotor is located inside the stator of the electric motor, there are also structures with an external rotor - inside out electric motors.

Constructions of a permanent magnet synchronous motor: on the left - standard, on the right - inside out.

The rotor consists of permanent magnets. Materials with high coercive force are used as permanent magnets.

An electric motor with non-salient pole rotor has an equal direct and quadrature inductances L d = Lq, whereas for an electric motor with salient pole rotor the quadrature inductance is not equal to the direct Lq &#; Ld.

The cross sections of the rotors with a different ratio of Ld/Lq. Magnets marked black. Figure e, f shows axially layered rotors, figure c, and h shows the rotors with barriers.

Also, according to the design of the rotor, the PMSM are divided into:
• surface permanent magnet synchronous motor;
• interior permanent magnet synchronous motor.

Rotor of a surface permanent magnet synchronous motor

Rotor of an interior permanent magnet synchronous motor

The stator consists of an outer frame and a core with windings. The most common design with two- and three-phase winding.

Depending on the stator design, a permanent magnet synchronous motor can be:
• with distributed winding;
• with concentrated winding.

Electric motor stator with distributed winding

Electric motor stator with concentrated winding

Distributed call such a winding, in which the number of slots per pole and phase Q = 2, 3, ...., k.

Concentrated called such a winding, in which the number of slots per pole and phase Q = 1. In this case, the slots are evenly spaced around the circumference of the stator. The two coils forming the winding can be connected both in series and in parallel. The main disadvantage of such windings is the impossibility of influencing on the form of the EMF curve [2].

Three-phase distributed winding circuit

Three-phase concentrated winding circuit

The form of the back EMF of the electric motor can be:
• trapezoidal;
• sinusoidal.

The form of the EMF curve in the conductor is determined by the distribution curve of the magnetic induction in the gap around the stator circumference.

It is known that the magnetic induction in the gap under the salient pole of the rotor has a trapezoidal shape. The EMF induced in the conductor has the same form. If it is necessary to create a sinusoidal EMF, then the pole tips are given such a shape that the induction distribution curve would be close to sinusoidal. This is facilitated by the bevels of the pole tips of the rotor [2].

The principle of operation of a synchronous motor is based on the interaction of the rotating magnetic field of the stator and the constant magnetic field of the rotor. The concept of the rotating magnetic field of the stator of a synchronous motor is the same as that of a three-phase induction motor.

The principle of operation of a synchronous motor is based on the interaction of the rotating magnetic field of the stator and the constant magnetic field of the rotor.

Start

Stop

Rotating magnetic field of a synchronous motor

The magnetic field of the rotor, interacting with the synchronous alternating current of the stator windings, according to the Ampere's Law, creates torque, forcing the rotor to rotate (more).

Permanent magnets located on the rotor of the PMSM create a constant magnetic field. At a synchronous speed of rotation of the rotor with the stator field, the rotor poles interlock with the rotating magnetic field of the stator. In this regard, the PMSM cannot start itself when it is connected directly to the three-phase current network (current frequency in the power grid 50Hz).

A permanent magnet synchronous motor requires a control system, for example, a variable frequency drive or a servo drive. There are a large number of control techniques implemented control systems. The choice of the optimal control method mainly depends on the task that is put in front of the electric drive. The main methods for controlling a permanent magnet synchronous motor are shown in the table below.

Control Advantages Disadvantages

Sinusoidal

Scalar Simple control scheme Control is not optimal, not suitable for tasks where the variable load, loss of control is possible Vector Field oriented control With position sensor Smooth and precise setting of the rotor position and motor rotation speed, large control range Requires rotor position sensor and powerful microcontroller inside the control system Without position sensor No rotor position sensor required. Smooth and precise setting of the rotor position and motor rotation speed, large control range, but less than with position sensor Sensorless field oriented control over full speed range is possible only for PMSM with salient pole rotor, a powerful control system is required Direct torque control Simple control circuit, good dynamic performance, wide control range, no rotor position sensor required High torque and current ripple

Trapezoidal

Open loop

Simple control scheme Control is not optimal, not suitable for tasks where the variable load, loss of control is possible

Closed loop

With position sensor (Hall sensors) Simple control scheme Hall sensors required. There are torque ripples. It is intended for control of PMSM with trapezoidal back EMF, when controlling PMSM with sinusoidal back EMF, the average torque is lower by 5%. Without sensor More powerful control system required Not suitable for low speed operation. There are torque ripples. It is intended for control of PMSM with trapezoidal back EMF, when controlling PMSM with sinusoidal back EMF, the average torque is lower by 5%.

Popular methods to control permanent magnet synchronous motors

To solve simple tasks is usually used trapezoidal control with Hall sensors (for example, computer fans). To solve problems that require maximum performance from the electric drive, field-oriented control is usually selected.

One of the simplest methods of control of a permanent magnet synchronous motor is - trapezoidal control. Trapezoidal control is used to control the PMSM with trapezoidal back EMF. At the same time, this method also allows you to control the PMSM with a sinusoidal back EMF, but then the average torque of the electric drive will be lower by 5%, and the torque ripples will be 14% of the maximum value. There is a trapezoidal control without feedback and with feedback by the rotor position.

The open loop control (without feedback) is not optimal and may lead to the release of the PMSM out of synchronism, i.e. to loss of controllability.

The closed loop control can be divided into:
• trapezoidal control by position sensor (usually by Hall sensors);
• trapezoidal control without sensor (sensorless trapezoidal control).

As a rotor position sensor for three-phase trapezoidal control, three Hall sensors built into an electric motor are commonly used, which allow determining the angle with an accuracy of ± 30 degrees. With this control, the stator current vector takes only six positions for one electric period, as a result of which there is ripple torque at the output.

Trapezoidal control by Hall sensors

Field-oriented control (FOC) allows you to smoothly, accurately and independently control the speed and torque of a brushless motor. For the operation of the field oriented control algorithm, it is necessary to know the position of the rotor of the brushless motor.

There are two ways to determine the rotor position:
• by the position sensor;
• sensorless - by calculating the angle by the real-time control system based on the information available.

PMSM field oriented control by position sensor

The following types of sensors are used as angle sensors:
• inductive: resolver, inductosyn, etc .;
• optical;
• magnetic: magnetoresistive sensors.

Field Oriented Control of Permanent Magnet Synchronous Motor using a rotor position sensor

Field-oriented control of PMSM without a position sensor

Since the s sensorless vector control methods for brushless AC motors began to be developed, thanks to the rapid development of microprocessors. The first sensorless methods for estimating the angle were based on the property of the electric motor to generate back EMF during rotation. The motor back EMF contains information about the position of the rotor, therefore, by calculating the value of the back EMF in the stationary coordinate system, you can calculate the position of the rotor. But when the rotor is not rotating, the back EMF is absent, and at low speed the back EMF has a small amplitude, which is difficult to distinguish from noise, therefore this method is not suitable for determining the position of the motor rotor at low speed.

There are two common techniques for sensorless start PMSM:
• start by the scalar method - start on a predetermined characteristic of voltage dependence to frequency. But scalar control severely limits the capabilities of the control system and the parameters of the electric drive as a whole;
• high frequency signal injection method &#; works only with the salient pole PMSM.

Field Oriented Control of Permanent Magnet Synchronous Motor without rotor position sensor with scalar start

At present, sensorless field-oriented control of PMSM in the full speed range is possible only for motors with salient pole rotor.