CN103986397B - Brshless DC motor permanent magnet fault detection method - Google Patents

Abstract

The invention discloses a kind of brshless DC motor permanent magnet fault detection method, comprise the steps: fixed rotor, motor is carried out stall experiment, can obtain following relational expression: e=K_sIsin (γ ')=K_si_β；The COEFFICIENT K of corresponding stator current I and coil flux linkage can be obtained by this relational expression_s；In motor operation course, detection motor coil on counter electromotive force e, and according to counter electromotive force e calculate permanent magnet space electrical angle be at γ 90 produce space magnetic field density amplitude B_fsin(γ)；Space magnetic field density amplitude B of permanent magnet that will obtain_fWhether sin (γ) contrasts with reference amplitude set in advance, it may be determined that have demagnetization or loss of excitation to occur.The brshless DC motor permanent magnet fault detection method of the present invention, has the fault state that i.e. would know that permanent magnet without dismantling permanent magnet, detects the advantages such as the most effective.

Description

Brshless DC motor permanent magnet fault detection method

Technical field

The present invention relates to a kind of brshless DC motor permanent magnet fault detection method.

Background technology

Brshless DC motor is made up of motor body and driver, is a kind of typical electromechanical integrated product.Brushless electric machine is Refer to brushless and the motor of commutator (or collector ring), also known as commutatorless machine.It is stained with on the rotor of motor and to have magnetized Permanent magnet, in order to detect the polarity of motor rotor, at motor built with position sensor.

In the application of brshless DC motor, permanent magnet fault location is typically a difficult point.Winding method due to stator coil Impact, the fault such as loss of excitation that can be detected motor permanent magnet by specific algorithm, but it cannot be accurately positioned, this Sample just maintenance to motor causes the biggest difficulty because the dismounting of permanent magnet, install, detect the most cumbersome.

Summary of the invention

The present invention is for avoiding weak point present in above-mentioned prior art, it is provided that a kind of brshless DC motor permanent magnet fault inspection Survey method, fast and effeciently to detect the fault state of permanent magnet.

The present invention solves that technical problem is by the following technical solutions.

Brshless DC motor permanent magnet fault detection method, is characterized in, comprises the steps:

Step 1: fixed rotor, carries out stall experiment to motor, can obtain following relational expression:

E=-K_sIsin (γ ')=-K_si_β(1)；

In formula (1), e: counter electromotive force；I: stator current；K_s: the coefficient of coil flux linkage, γ ' for stator current at static α β Electrical angle in coordinate system.

Step 2: the COEFFICIENT K of corresponding stator current I and coil flux linkage can be obtained by the relational expression (1) in step 1_s；

Step 3: in motor operation course, the counter electromotive force e on detection motor coil, and calculate permanent magnet according to counter electromotive force e It is space magnetic field density amplitude B that γ-90 place produces in space electrical angle_fsin(γ)；

Step 4: space magnetic field density amplitude B of permanent magnet that will obtain in step 3_fSin (γ) and reference amplitude set in advance Contrast, it may be determined that whether have demagnetization or loss of excitation to occur.First, when permanent magnet does not occur loss of excitation, real by zero load Test measures K_fBB_fThe value of sin (γ), by K_f=K_sBB can be calculated_fSin (γ) also saves as reference value；Then detection is run During B_fSin (γ), if detected value is less than the original reference value measured and preserve, illustrates that permanent magnet there occurs demagnetization or loss of excitation.

In described step 3, space magnetic field density amplitude B_fThe calculating process of sin (γ) is:

Motor makes detection coil open circuit when running, now in detection coil, no current flows through, and it does not produce shadow to motor space magnetic field Ringing, the coil-end voltage of detection is equal to its counter electromotive force:

$e=-\frac{{\mathrm{d\ψ}}_s+{\mathrm{d\ψ}}_f}{\mathrm{dt}}={-K}_{s}I\frac{d\cos \left({\mathrm{\γ}}^{\′}\right)}{\mathrm{dt}}{-K}_f{B}_f\frac{d\cos \left(\mathrm{\γ}\right)}{\mathrm{dt}}={-\mathrm{\ωK}}_{s}I\sin \left({\mathrm{\γ}}^{\′}\right){-\mathrm{\ωK}}_f{B}_f\sin \left(\mathrm{\γ}\right)---\left(2\right);$

Now above formula (2) can be become:

$K_f{B}_f\sin \left(\mathrm{\γ}\right)=-\frac{e+\mathrm{\ω}{K}_{s}I\sin \left({\mathrm{\γ}}^{\′}\right)}{\mathrm{\ω}}=-\frac{e+\mathrm{\ω}{K}_s{i}_{\mathrm{\β}}}{\mathrm{\ω}}---\left(3\right);$

Acquisition space magnetic field density amplitude B can be calculated according to above formula (3)_fsin(γ)。

Compared with the prior art, the present invention has the beneficial effect that:

The brshless DC motor permanent magnet fault detection method of the present invention, by calculating the space magnetic field density width that can try to achieve permanent magnet Value B_fSin (γ), by space magnetic field density amplitude B of permanent magnet_fSin (γ) contrasts with reference amplitude set in advance, permissible Determining whether that demagnetization or loss of excitation occur, it is not necessary to dismounting permanent magnet i.e. would know that the fault state of permanent magnet, detection is the most effectively.

The brshless DC motor permanent magnet fault detection method of the present invention, has the event that i.e. would know that permanent magnet without dismantling permanent magnet Barrier situation, detects the advantages such as the most effective.

Below by way of detailed description of the invention, the invention will be further described.

Detailed description of the invention

The brshless DC motor permanent magnet fault detection method of the present invention, comprises the steps:

Step 1: fixed rotor, carries out stall experiment to motor, can obtain following relational expression:

E=-K_sIsin (γ ')=-K_si_β(1)；

In formula (1), e: counter electromotive force；I: stator current；K_s: the coefficient of coil flux linkage, γ ' for stator current at static α β Electrical angle in coordinate system.

Step 2: the COEFFICIENT K of corresponding stator current I and coil flux linkage can be obtained by the relational expression (1) in step 1_s；

Step 3: in motor operation course, the counter electromotive force e on detection motor coil, and calculate permanent magnet according to counter electromotive force e It is space magnetic field density amplitude B that γ-90 place produces in space electrical angle_fsin(γ)；

Step 4: space magnetic field density amplitude B of permanent magnet that will obtain in step 3_fSin (γ) and reference amplitude set in advance Contrast, it may be determined that whether have demagnetization or loss of excitation to occur.(first, when permanent magnet does not occur loss of excitation, real by zero load Test measures K_fBB_fsin(_γ) value, by K_f=K_sBB can be calculated_fSin (γ) also saves as reference value；Then detection is run During B_fSin (γ), if detected value is less than the original reference value measured and preserve, illustrates that permanent magnet there occurs demagnetization or loss of excitation.)

In described step 3, space magnetic field density amplitude B_fThe calculating process of sin (γ) is:

Motor makes detection coil open circuit when running, now in detection coil, no current flows through, and it does not produce shadow to motor space magnetic field Ringing, the coil-end voltage of detection is equal to its counter electromotive force:

$e=-\frac{{\mathrm{d\ψ}}_s+{\mathrm{d\ψ}}_f}{\mathrm{dt}}={-K}_{s}I\frac{d\cos \left({\mathrm{\γ}}^{\′}\right)}{\mathrm{dt}}{-K}_f{B}_f\frac{d\cos \left(\mathrm{\γ}\right)}{\mathrm{dt}}={-\mathrm{\ωK}}_{s}I\sin \left({\mathrm{\γ}}^{\′}\right){-\mathrm{\ωK}}_f{B}_f\sin \left(\mathrm{\γ}\right)---\left(2\right);$

Now above formula (2) can be become:

$K_f{B}_f\sin \left(\mathrm{\γ}\right)=-\frac{e+\mathrm{\ω}{K}_{s}I\sin \left({\mathrm{\γ}}^{\′}\right)}{\mathrm{\ω}}=-\frac{e+\mathrm{\ω}{K}_s{i}_{\mathrm{\β}}}{\mathrm{\ω}}---\left(3\right);$

Acquisition space magnetic field density amplitude B can be calculated according to above formula (3)_fsin(γ)。

At this point it is possible to waveform and stator current β component by counter electromotive force carry out fault diagnosis to permanent magnet, wherein B_fSin (γ) is permanent magnet at the magnetic density that space electrical angle is γ-90 place, by detecting the change of corresponding magnetic density amplitude Change, it may be determined that whether permanent magnet there occurs demagnetization.

The present invention proposes to detect by the way of adding motor and additionally arranging induction coil, and stator coil can be avoided to be carried when being connected The impact come, effectively detects the fault state of permanent magnet, and coil axis is consistent with A phase axis, and coil is that whole pole span is long, Its Cleaning Principle is as follows:

1, the magnetomotive force of space air gap is stator current and the generation of permanent magnet linear superposition；

The magnetomotive peak swing of first-harmonic that single-phase concentrated and full-pitch windings produces on air gap is:

$F_{\mathrm{\φ}1}=\frac{4}{\mathrm{\π}}\frac{\sqrt{2}}{2}{\mathrm{qN}}_k{I}_k=\frac{4}{\mathrm{\π}}\frac{\sqrt{2}}{2}\frac{{\mathrm{pqN}}_k}{p}\frac{I_k}{a}=0.9\frac{N_{1}I}{p}=\mathrm{kI}---\left(4\right);$

When motor is three-phase symmetric winding, the axis+A taking A phase winding is initial point, then when flowing through any size of current, Synthesis magnetomotive force spatial distribution in α β coordinate system is:

In above formula (4) and (5), N₁: be often in series the number of turn；The full-pitched coil number of the q: every pair pole；A: parallel branch number； I: phase current；I_k: coil current；

Now air gap synthesis magnetomotive force is

${\stackrel{\→}{f}}_{\mathrm{air}}={\stackrel{\→}{f}}_f+{\stackrel{\→}{f}}_I=(\frac{3}{2}k(i_{\mathrm{\α}}+{\mathrm{ji}}_{\mathrm{\β}})+F_f{e}^{\mathrm{j\γ}})e^{\mathrm{j\θ}}---\left(6\right);$

In above formula (6), γ: permanent magnet axis and the space electrical angle angle of A phase axis；θ: be initial point for A axle axis Space electrical angle.

2, synthesis air-gap field is produced by stator current and permanent magnet linear superposition；

When motor operates in linear zone, does not arrives saturation region, magnetic field intensity is linear with magnetic density, and its resultant magnetic field is full Foot linear superposition theorem, its magnetic density is the magnetic density linear superposition with stator current generation magnetic density of permanent magnet generation:

${\stackrel{\→}{B}}_{\mathrm{air}}={\stackrel{\→}{B}}_f+{\stackrel{\→}{B}}_I=\frac{\mathrm{\μ}}{l_{\mathrm{air}}}{\stackrel{\→}{f}}_{\mathrm{air}}---\left(7\right);$

In above formula (7), μ: air-gap permeance；l_air: gas length.

3, the magnetic linkage in coil；

The magnetic linkage produced by stator current in coil is:

$\begin{array}{c}{\mathrm{\ψ}}_s=\frac{1}{p}{\∫}_{-\frac{\mathrm{\π}}{2}}^{\frac{\mathrm{\π}}{2}}{N}_2\mathrm{lR}{B}_I\cos ({\mathrm{\γ}}^{\′}+\mathrm{\θ})\mathrm{d\θ}=\frac{N_2\mathrm{lR\μ}}{{\mathrm{pl}}_{\mathrm{air}}}{\∫}_{-\frac{\mathrm{\π}}{2}}^{\frac{\mathrm{\π}}{2}}{f}_I\cos ({\mathrm{\γ}}^{\′}+\mathrm{\θ})\mathrm{d\θ}\\ =\frac{N_2\mathrm{lR\μ}}{{\mathrm{pl}}_{\mathrm{air}}}3\mathrm{kI}\cos \left({\mathrm{\γ}}^{\′}\right)=K_{s}I\cos \left({\mathrm{\γ}}^{\′}\right)=K_s{i}_{\mathrm{\α}}\end{array}---\left(8\right);$

In above formula (8), γ ': stator magnet kinetic potential and the angle of A axle axis.

The magnetic linkage that permanent magnet produces in coil is:

$\begin{array}{c}{\mathrm{\ψ}}_f=\frac{1}{p}{\∫}_{-\frac{\mathrm{\π}}{2}}^{\frac{\mathrm{\π}}{2}}{N}_2\mathrm{lR}{B}_f\cos (\mathrm{\γ}+\mathrm{\θ})\mathrm{d\θ}=\frac{N_2\mathrm{lR}}{p}{\∫}_{-\frac{\mathrm{\π}}{2}}^{\frac{\mathrm{\π}}{2}}{B}_f\cos (\mathrm{\γ}+\mathrm{\θ})\mathrm{d\θ}\\ =\frac{{2N}_2\mathrm{lR}}{p}{B}_f\cos \left(\mathrm{\γ}\right)=K_f{B}_f\cos \left(\mathrm{\γ}\right)\end{array}---\left(9\right);$

The magnetic linkage linear superposition that synthesis magnetic linkage in coil is produced respectively by permanent magnet and stator coil is:

$\mathrm{\ψ}=\frac{1}{p}{\∫}_{-\frac{\mathrm{\π}}{2}}^{\frac{\mathrm{\π}}{2}}{N}_2\mathrm{lR}{B}_{\mathrm{air}}\mathrm{d\θ}=\frac{N_2\mathrm{lR\μ}}{{\mathrm{pl}}_{\mathrm{air}}}{\∫}_{-\frac{\mathrm{\π}}{2}}^{\frac{\mathrm{\π}}{2}}{f}_{\mathrm{air}}\mathrm{d\θ}={\mathrm{\ψ}}_s+{\mathrm{\ψ}}_f---\left(10\right);$

4, counter electromotive force detection permanent magnet method

Motor makes detection coil open circuit when running, now in detection coil, no current flows through, and it does not produce shadow to motor space magnetic field Ringing, the coil-end voltage of detection is equal to its counter electromotive force:

$e=-\frac{{\mathrm{d\ψ}}_s+{\mathrm{d\ψ}}_f}{\mathrm{dt}}={-K}_{s}I\frac{d\cos \left({\mathrm{\γ}}^{\′}\right)}{\mathrm{dt}}{-K}_f{B}_f\frac{d\cos \left(\mathrm{\γ}\right)}{\mathrm{dt}}={-\mathrm{\ωK}}_{s}I\sin \left({\mathrm{\γ}}^{\′}\right){-\mathrm{\ωK}}_f{B}_f\sin \left(\mathrm{\γ}\right)---\left(2\right);$

Now above formula (2) can be become:

$K_f{B}_f\sin \left(\mathrm{\γ}\right)=-\frac{e+\mathrm{\ω}{K}_{s}I\sin \left({\mathrm{\γ}}^{\′}\right)}{\mathrm{\ω}}=-\frac{e+\mathrm{\ω}{K}_s{i}_{\mathrm{\β}}}{\mathrm{\ω}}---\left(3\right);$

At this point it is possible to waveform and stator current β component by counter electromotive force carry out fault diagnosis, wherein B to permanent magnet_fsin(γ) For permanent magnet at the magnetic density that space electrical angle is γ-90 place, by detecting the change of corresponding magnetic density amplitude, permissible Determine whether permanent magnet there occurs demagnetization.

The brshless DC motor permanent magnet fault detection method of the present invention, by calculating the space magnetic field density width that can try to achieve permanent magnet Value B_fSin (γ), by space magnetic field density amplitude B of permanent magnet_fSin (γ) contrasts with reference amplitude set in advance, permissible Determining whether that demagnetization or loss of excitation occur, it is not necessary to dismounting permanent magnet i.e. would know that the fault state of permanent magnet, detection is the most effectively.

In above formula (1), e: counter electromotive force；I: stator current；K_s: the coefficient of coil flux linkage.

In above formula (2), e is back-emf, and ψ s is the magnetic linkage that stator current produces, ψ_fThe magnetic linkage produced for permanent magnet, γ is permanent magnetism Body and the angle of A axle axis, γ ' is the angle of stator magnet kinetic potential Yu A axle axis, K_sFor the coefficient of stator coil magnetic linkage, K_fFor Permanent magnet flux linkage coefficient, ω is angular rate.

In above formula (3), e is back-emf, and γ is the angle of permanent magnet and A axle axis, and γ ' is stator magnet kinetic potential and A axle axis Angle, K_sFor the coefficient of stator coil magnetic linkage, K_fFor permanent magnet flux linkage coefficient, ω is angular rate.

In above formula (4) and (5), N₁: be often in series the number of turn；The full-pitched coil number of the q: every pair pole；A: parallel branch number； I: phase current；I_k: coil current；P is number of pole-pairs, and k is that input current produces the magnetomotive winding coefficient in space, N_kFor often The series line number of turns of circle.I_A1Refer to the amplitude of A phase input current, I_B1Refer to the amplitude of B phase input current, I_C1Refer to C phase input current Amplitude,Specify the first-harmonic magnetomotive force vector that sub-A phase current produces in space,Specify the first-harmonic that sub-B phase current produces in space Magnetomotive force vector,Specify the first-harmonic magnetomotive force vector that sub-C phase current produces in space,Electron current is specified to produce in space Magnetomotive force vector, i_αAnd i_βSpecify electron current component in α β coordinate system, θ be A axle axis be the space electrical angle of initial point.

In above formula (6), γ: permanent magnet axis and the space electrical angle angle of A phase axis；θ: be initial point for A axle axis Space electrical angle.F_fRefer to the magnetomotive force amplitude that permanent magnet produces in the air gap of space.

In above formula (7), μ: air-gap permeance；l_air: gas length；For the magnetic density vector of synthesis in the air gap of space；The magnetic density vector produced for permanent magnet in the air gap of space；The magnetic density produced for stator current in the air gap of space is vowed Amount.

In above formula (8) and (9), γ ': stator magnet kinetic potential and the angle of A axle axis, I is stator current amplitude, K_sFor stator The coefficient of coil flux linkage, p is number of pole-pairs, N₂For detection coils connected in series around the number of turn, R is stator inner circle radius, and l is circular shaft in stator Long, BB_IThe close size of first-harmonic magnetic produced in space for stator current；BB_fThe close size of first-harmonic magnetic produced in space for permanent magnet；θ is Detection hub of a spool axis is the space electrical angle that initial point launches.K_s: the coefficient of stator current coil flux linkage, K_f: permanent magnet flux linkage Coefficient.

In above formula (10), ψ is that stator current and permanent magnet act on the magnetic linkage size produced in detection coil, ψ jointly_sFor stator The magnetic linkage that electric current produces in detection coil, ψ_fThe magnetic linkage produced in detection coil for permanent magnet.

Claims (1)

1. brshless DC motor permanent magnet fault detection method, is characterized in that, comprises the steps:

Step 1: fixed rotor, carries out stall experiment to motor, can obtain following relational expression:

E=-K_sIsin (γ ')=-K_si_β(1)；

In formula (1), e: counter electromotive force；I: stator current；K_s: the coefficient of coil flux linkage；γ ' is stator magnet kinetic potential and A The angle of axle axis；

Step 2: the COEFFICIENT K of corresponding stator current I and coil flux linkage can be obtained by the relational expression (1) in step 1_s；

Step 3: in motor operation course, the counter electromotive force e on detection motor coil, and calculate permanent magnet according to counter electromotive force e It is space magnetic field density amplitude B that γ-90 place produces in space electrical angle_fsin(γ)；

Step 4: space magnetic field density amplitude B of permanent magnet that will obtain in step 3_fSin (γ) and reference amplitude set in advance Contrast, it may be determined that whether have demagnetization or loss of excitation to occur；

In described step 3, space magnetic field density amplitude B_fThe calculating process of sin (γ) is:

Motor makes detection coil open circuit when running, now in detection coil, no current flows through, and it does not produce shadow to motor space magnetic field Ringing, the coil-end voltage of detection is equal to its counter electromotive force:

$e=-\frac{{\mathrm{d\ψ}}_s+{\mathrm{d\ψ}}_f}{dt}=-K_{s}I\frac{d\cos \left({\mathrm{\γ}}^{\′}\right)}{dt}-K_f{B}_f\frac{d\cos \left(\mathrm{\γ}\right)}{dt}=-{\mathrm{\ωK}}_{s}I\sin \left({\mathrm{\γ}}^{\′}\right)-{\mathrm{\ωK}}_f{B}_f\sin \left(\mathrm{\γ}\right)---\left(2\right);$

In above formula (2), e is back-emf, and ψ s is the magnetic linkage that stator current produces, ψ_fThe magnetic linkage produced for permanent magnet, γ is forever Magnet and the angle of A axle axis, γ ' is the angle of stator magnet kinetic potential Yu A axle axis, K_sFor the coefficient of stator coil magnetic linkage, K_fFor permanent magnet flux linkage coefficient, ω is angular rate；

Now above formula (2) can be become:

$K_f{B}_{f}sin\left(\mathrm{\γ}\right)=-\frac{e+{\mathrm{\ωK}}_{s}Isin\left({\mathrm{\γ}}^{\′}\right)}{\mathrm{\ω}}=-\frac{e+{\mathrm{\ωK}}_s{i}_{\mathrm{\β}}}{\mathrm{\ω}}---\left(3\right);$

Acquisition space magnetic field density amplitude B can be calculated according to above formula (3)_fsin(γ)；

In above formula (3), e is back-emf, and γ is the angle of permanent magnet and A axle axis, and γ ' is stator magnet kinetic potential and A axle axis Angle, K_sFor the coefficient of stator coil magnetic linkage, K_fFor permanent magnet flux linkage coefficient, ω is angular rate；

i_αAnd i_βSpecify electron current component in α β coordinate system.