Induction motor stray loss analysis method considering multi-parameter influence

Abstract

The invention discloses a rapid and accurate stray loss analysis method for an induction motor. A sine wave excitation space harmonic module, an inversion feed excitation space harmonic module and a stray loss module form a stray loss and space harmonic relation system; the stray loss system under the influence of the output power is composed of a surface eddy current loss system composed of a magnetization inductance module, a harmonic amplitude module and a surface eddy current loss module and a magnetic flux pulsation loss system composed of a harmonic amplitude module, a stator harmonic stray loss module, a rotor harmonic stray loss module and a magnetic flux pulsation loss module. The stray loss system under the influence of the output power, the stray loss system under the influence of the power supply frequency and the stray loss system under the influence of the total harmonic distortion of the current form a stray loss system under the influence of multiple factors; the loss analysis provided by the invention can distinguish stray loss values of motors with the same rated power but different efficiency levels.

Description

Technical Field

[0001] The invention belongs to the technical field of induction motors, and relates to the establishment and analysis of an induction motor stray loss model based on multi-parameter considerations. Background Art

[0002] The increasing focus on energy conservation has made motor efficiency a top priority for design engineers and motor drive systems. Operating existing motors in the high efficiency region and designing energy-efficient motors have always required accurate measurement of motor efficiency. Efficiency estimation uses two accurately calculated terms, the output power of the motor and the sum of all losses. The output power of the motor can be directly measured with high accuracy, while the losses in the motor, especially the magnetic losses, have always been challenging.

[0003] Core loss and stray loss are important factors affecting the efficiency of induction motors. Both losses depend on the temporal and spatial distribution of the motor flux density. The research on core loss is quite extensive. There are many core loss models, including but not limited to two-term or three-term core loss models based on the modified Steinmetz equation with variable loss coefficients and hybrid core loss models. However, stray loss still lacks a direct and accurate inverter motor model representation.

[0004] Stray losses in induction motors are additive core losses attributed to various temporal and spatial harmonics of the flux density. Spatial harmonics are caused by the placement of the coils in the slotted stator and variations in the flux path permeability. While previous studies have been extensively limited to spatial harmonics and sinusoidal excitations in dealing with stray losses, the evaluation of stray losses in the post-processing of finite element analysis results is another recent approach. However, unlike core losses, which consist of three components, stray losses consist of multiple sources, making post-processing estimation complex in terms of time, data storage, and computation. In addition, the development of logical assumptions supported by statistical analysis of a large amount of measured stray loss data is a novel approach. Such models accelerate the iterative motor design process and require less response time when incorporated into motor control compared to purely physics-based approaches. However, all available stray loss models have been developed specifically for sinusoidal power supplies. Stray loss models for PWM-excited induction motors have not been widely discussed, and there is still a lack of simple and generalized stray loss analysis formulas for inverter-fed induction motors that are applicable to a wide range of motor loads, frequencies, and switching. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a fast and accurate induction motor stray loss analysis model.

[0006] Step 1): The sinusoidal excitation space harmonic module, the inverter feed excitation space harmonic module and the stray loss module form a stray loss and space harmonic relationship block diagram. The input signal of the sinusoidal excitation space harmonic module is the number of turns per phase of the stator winding N ph , pole pair number p, vth spatial harmonic winding factor K w (v) and the spatial angle θ, the output signal is the Fourier decomposition of the magnetomotive force generated by the three-phase distributed winding F A (θ, t), F B (θ, t) and F C (θ, t); The input signal of the inverter-fed excitation space harmonic module is the Fourier decomposition of the magnetomotive force generated by the three-phase distributed winding F A (θ, t), F B (θ, t) and F C (θ, t), and the motor current amplitude I m The output signal is the net magnetomotive force (MMF) of balanced three-phase excitation; the input signal of the stray loss module is the magnetomotive force MMF of balanced three-phase excitation and the proportional coefficient K of the stray loss-magnetomotive force relationship of the i-th harmonic i The output signal is the stray loss SL under the cumulative effect of all the harmonics of the inverter motor's magnetomotive force.

[0007] Step 2): The surface eddy current loss system composed of the magnetizing inductance module, the harmonic amplitude module, and the surface eddy current loss module, and the flux pulsation loss system composed of the harmonic amplitude module, the stator harmonic stray loss module, the rotor harmonic stray loss module, and the flux pulsation loss module constitute the stray loss system under the influence of output power. The input signal of the magnetizing inductance module is, each slot conductor Z s , Winding factor K w , air gap length g, motor stack length L, average air gap diameter D, Carter coefficient K c And the vth harmonic saturation coefficient K Sv Indicates that the output signal is the magnetizing inductance L corresponding to the vth harmonic mv ; The input signal of the harmonic amplitude module is the base magnetizing inductance L m1 The magnetizing inductance L corresponding to the vth harmonic mv , the output signal is the base air gap flux density B m1 and the magnetic flux density amplitude B of the vth spatial harmonic mv ; The input signal of the surface eddy current loss module is the base air gap flux density B m1 , the magnetic flux density amplitude B of the vth spatial harmonic mv , speed N s , pole pair number p and base air gap flux density B m1 The fundamental eddy current loss P corresponding to the fundamental frequency ω1 Eddy1, the output signal is the surface eddy current loss SL surf , which is the output signal of the surface eddy current loss system. For the flux pulsation loss system, the input signal of the harmonic amplitude module is the slot leakage inductance L Slot , the magnetizing inductance L corresponding to the vth harmonic mv , base air gap flux density B m1 , slot distance t s and slot opening b s0 , the output signal is the harmonic amplitude B mtv ; The input signal of the stator harmonic stray loss module is the harmonic amplitude B mtv , speed N s and pole pair number p, the output signal is the stator harmonic stray loss SL pulsS ; The input signal of the rotor harmonic stray loss module is the harmonic amplitude B mtv , speed N R and pole pair number p, the output signal is the rotor harmonic stray loss SL pulsR The input signal of the flux pulsation loss module is the stator harmonic stray loss SL pulsS and rotor harmonic stray losses SL pulsR , the output signal is the total flux pulsation loss SL P .

[0008] Step 3): The stray loss system under the influence of multiple factors is composed of the stray loss system under the influence of output power, the stray loss system under the influence of power frequency, and the stray loss system under the influence of current total harmonic distortion (THD). The input signals of the stray loss system under the influence of power frequency are constants α, β, and the rated frequency f r The output signal is the stray loss SL under the influence of power frequency f The input signal of the stray loss system under the influence of total harmonic distortion of current is constant signals a, b, r, k and C, and the output signal is the stray loss SL under the influence of total harmonic distortion of current. T . Finally, the flux pulsation loss SL P , stray loss SL affected by power frequency f And the stray loss SL under the influence of total harmonic distortion of current T Together they constitute the stray losses SL of the induction motor.

[0009] The beneficial effects of the present invention are:

[0010] The purpose of this invention is to estimate the stray losses of induction motors during the design phase and normal operation. The proposed model is developed taking into account the changes in frequency, switching frequency and motor load to account for the influence of the inverter power supply. The phenomenological relationship between the stray losses and the motor equivalent circuit and power supply parameters is established, and the stray losses are described with these parameters as the main variables.

[0011] 1. The present invention can be used in the motor design stage to minimize stray losses;

[0012] 2. The loss model proposed in this invention is applicable to motors that have been put into operation. Except for the nameplate data and preliminary routine test data, there is no detailed design and material data;

[0013] 3. The loss analysis proposed in the present invention can distinguish the stray loss values ​​of motors with the same rated power but different efficiency levels, and can determine the stray loss of the motor under different loads. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will be further described in detail below in conjunction with the accompanying drawings;

[0015] Figure 1 It is a block diagram of the relationship between stray loss and space harmonics;

[0016] Figure 2 It is the block diagram of the stray loss system under the influence of output power;

[0017] Figure 3 It is the equivalent circuit diagram of a sinusoidally excited three-phase induction motor;

[0018] Figure 4 It is a block diagram of the stray loss system under the influence of multiple factors; DETAILED DESCRIPTION

[0019] like Figure 1 As shown in the figure, the system block diagram of the relationship between stray loss and spatial harmonics of the induction motor is composed of a sine wave excitation spatial harmonic module, an inverter feed excitation spatial harmonic module and a stray loss module. The input signal of the sine wave excitation spatial harmonic module is the number of turns per phase of the induction motor stator winding N. ph , pole pair number p, space angle θ and the vth spatial harmonic winding factor K w (v), the output signal is the Fourier decomposition of the magnetomotive force generated by the three-phase distributed winding F A (θ, t), F B (θ, t) and F C (θ, t);

[0020] The input signal of the space harmonic module with inverter-fed excitation is the peak value I of the stator current i(t) m And the output signal F of the sine wave excitation space harmonic module A (θ, t), F B (θ, t) and F C (θ, t), the output signal is the net magnetomotive force F S(θ, t), the Fourier decomposition of the magnetomotive force generated by the single-phase distributed winding of the three-phase induction motor is as follows (the rest of the terms are similar and belong to common knowledge):

[0021]

[0022] where i(t)=I m sin(ωt), ω is the angular frequency of sinusoidal alternating current, K w (v) is the winding factor of the vth spatial harmonic. N ph , p and θ are the number of turns per phase, number of pole pairs and spatial angle of the stator winding respectively. For a three-phase motor with a balanced current, the net magnetomotive force is the sum of the magnetomotive forces of all three phases, which are shifted 120° in space and are given by formula (2):

[0023] F S (θ,t)=F A (θ,t)+F B (θ,t)+F C (θ,t) (2)

[0024] The input signal of the inverter-fed excitation space harmonic module is the Fourier decomposition of the magnetomotive force generated by the three-phase distributed winding. A (θ, t), F B (θ, t) and F C (θ, t), and the motor current amplitude I m , the output signal is the net magnetomotive force MMF of balanced three-phase excitation.

[0025] For balanced three-phase excitation, the net magnetomotive force can be expressed as follows:

[0026]

[0027] In the formula, A v is the amplitude of the vth spatial harmonic, expressed as:

[0028]

[0029] Formula (3) represents multiple traveling waves rotating in different directions. The propagation speed of all these harmonics of the magnetomotive force wave is less than the synchronous speed, that is, the speed of the fundamental wave of the magnetomotive force wave. The magnetomotive force wave corresponding to the spatial harmonic number v = 6k-1 (for a positive integer k) is opposite to the fundamental wave, while the magnetomotive force wave with a harmonic number of 6k+1 is opposite to the fundamental wave. The spatial harmonics higher than the 7th order can be ignored.

[0030] The input signal of the stray loss module is the net magnetomotive force F of the balanced three-phase excitation S (θ, t) and the proportionality coefficient K of the relationship between the stray loss of the i-th harmonic and the magnetomotive force iThe output signal is the stray loss SL under the cumulative effect of all the harmonics of the inverter motor's magnetomotive force.

[0031] For an inverter power induction motor, the motor current of the x-phase of the motor is composed of the nth harmonic current magnitude I m (n) and phase angle The Fourier sum of gives:

[0032]

[0033] For a three-phase motor, x∈[a,b,c], Evaluation of equations (1) and (2) for the magnetomotive force relative to the current expression (5) gives:

[0034]

[0035] In formula (6), is the sum of the positive rotating magnetomotive force waves, is the sum of the reverse rotating magnetomotive force waves; from formula (6), it can be seen that the harmonics in the current superimpose various high-frequency waves on the magnetomotive force waves corresponding to the fundamental frequency, and all these rotating magnetomotive force waves will produce additional stray losses.

[0036] The stray loss under the cumulative effect of all magnetomotive force harmonics of the inverter-fed induction motor can be expressed as:

[0037]

[0038] Where SL(i) is the net spurious loss of the i-th time harmonic and all spatial harmonics. i K is the amplitude of the magnetomotive force corresponding to the i-th current harmonic. i k is the proportionality coefficient of the stray loss-magnetomotive force relationship of the i-th harmonic, i =K i / K2. Since the magnetomotive force is linearly related to the current, the series sum used in equation (7) is proportional to the total harmonic distortion (THD) of the motor current (a directly measurable quantity), so the stray losses of the inverter-fed induction motor can be expressed as:

[0039]

[0040] Where f(THD) is a single-valued monotonic function of the total harmonic distortion of the motor current.

[0041] like Figure 2As shown in the figure, the stray loss system under the influence of output power consists of two parts: a surface eddy current loss system composed of a magnetizing inductance module, a harmonic amplitude module, and a surface eddy current loss module, and a flux pulsation loss system composed of a harmonic amplitude module, a stator harmonic stray loss module, a rotor harmonic stray loss module, and a flux pulsation loss module. The input signal of the magnetizing inductance module is: s , Winding factor K w , air gap length g, motor stack length L, average air gap diameter D, Carter coefficient K c And the vth harmonic saturation coefficient K Sv Indicates that the output signal is the magnetizing inductance L corresponding to the vth harmonic mv , given by formula (9):

[0042]

[0043] Where μ0 is the magnetic permeability, which represents the relationship between the magnetic flux density and the magnetic field strength in a vacuum. s is the motor speed, a l is the air gap length at the slot, and p is the number of pole pairs of the motor.

[0044] The input signal of the harmonic amplitude module is the base magnetizing inductance L m1 The magnetizing inductance L corresponding to the vth harmonic mv , the output signal is the base air gap flux density B m1 and the magnetic flux density amplitude B of the vth spatial harmonic mv .

[0045]

[0046] In the formula, F mv is the fifth harmonic, and F1 is the fundamental frequency magnetomotive force. v and λ1 are the relative permeabilities of the vth harmonic path and the fundamental wave path, respectively. sv and λ 1s They are the fundamental frequency harmonic passthrough and the fundamental frequency specific permeability respectively.

[0047] The input signal of the surface eddy current loss module is the base air gap flux density B m1 , the magnetic flux density amplitude B of the vth spatial harmonic mv , speed N s , pole pair number p and base air gap flux density B m1 The fundamental eddy current loss P corresponding to the fundamental frequency ω1 Eddy1 , the output signal is the surface eddy current loss SL surf , which is the output signal of the surface eddy current loss system.

[0048] The various components of stray losses in induction motors are actually additional eddy current losses (P Eddy ). These harmonics are generated by the change of air gap flux caused by gap, magnetic saturation and leakage flux, P Eddy Given by formula (11):

[0049]

[0050] Among them, B mv and ω v are the flux density amplitude and angular frequency of the vth spatial harmonic, k e is the eddy current loss coefficient. That corresponds to the basic air gap flux density B m1 and eddy current loss at fundamental frequency ω1

[0051]

[0052] The SL caused by the vth harmonic is as follows:

[0053]

[0054] The surface eddy current losses SL corresponding to these harmonics surf for:

[0055]

[0056] From (9) and (10), we can get:

[0057]

[0058] Using the expression for sawtooth leakage inductance, the sawtooth leakage inductance is the sum of all harmonic magnetizing inductances except the fundamental:

[0059]

[0060] According to formulas (15) and (16), we can get

[0061]

[0062] For the flux pulsation loss system, the input signal of the harmonic amplitude module is the slot leakage inductance L Slot , sawtooth leakage inductance L lsz , the magnetizing inductance L corresponding to the vth harmonic mv , base air gap flux density B m1 , slot distance t s and slot opening b s0 , the output signal is the harmonic amplitude B mtv ;

[0063] The change in the main magnetic flux rate due to the change in the rotor position leads to the pulsation loss of the stator and rotor flux. In the case of closed or narrow rotor slots, the impact of the rotor slots is small. The eddy current frequency generated by the stator slot flux pulsation is The eddy current frequency generated by the rotor slot flux pulsation is Where f1 is the fundamental frequency. The amplitudes of the stator and rotor harmonics are as follows:

[0064]

[0065] Among them, K tv is the stator and rotor harmonic amplitude coefficient. When the deviation is ignored

[0066]

[0067] Among them, L Slot is the slot leakage inductance, and the magnetizing inductance L corresponding to the vth harmonic mv Meet L mv >>L Slot +L lsz .

[0068]

[0069] where t s and b s0 They represent the slot distance and slot opening respectively.

[0070] The input signal of the stator harmonic stray loss module is the harmonic amplitude B mtv , speed N s and pole pair number p, the output signal is the stator harmonic stray loss SL pulsS The SL corresponding to each stator harmonic is calculated as follows:

[0071]

[0072] Combining formula (18) and (21), we can get

[0073]

[0074] The input signal of the rotor harmonic stray loss module is the harmonic amplitude B mtv , speed N R and the pole pair number p,

[0075] The output signal is the rotor harmonic stray loss SL pulsR ;

[0076]

[0077] The input signal of the flux pulsation loss module is the stator harmonic stray loss SL pulsSand rotor harmonic stray losses SL pulsR , the output signal is the total flux pulsation loss SL P .

[0078] SL P =SL surf +SL pulsS +SL pulsR (twenty four)

[0079]

[0080] in, The equivalent circuit of a three-phase induction motor with sinusoidal excitation is as follows: Figure 3 As shown, L lS , L lR and L m They are the stator leakage inductance, rotor leakage inductance and magnetizing inductance of the motor corresponding to the equivalent circuit of the classic T model.

[0081] like Figure 4 As shown in the figure, the stray loss system under the influence of multiple factors is composed of the stray loss system under the influence of output power, the stray loss system under the influence of power frequency, and the stray loss system under the influence of current total harmonic distortion. The input signals of the stray loss system under the influence of power frequency are constants α, β, and the rated frequency f r The output signal is the stray loss SL under the influence of power frequency f ;

[0082] At a constant switching frequency f sw and load torque T L In this case, SL increases with the base frequency, and the rate of increase of SL with the power supply frequency f is greater than 1. When the power supply frequency is 0, SL is also 0. f The relationship with the power supply frequency f is as follows:

[0083]

[0084] The input signal of the stray loss system under the influence of total harmonic distortion of current is constant signals a, b, τ, k and C, and the output signal is the stray loss SL under the influence of total harmonic distortion of current. T ; As the network stray loss approaches, the stray loss increases with f sw / f decreases monotonically. In addition, the stray loss decreases with f sw The rate of change of / f depends on f sw / f. This rate increases with f sw / f increases. Therefore, the change of stray loss shows a downward trend with the change of τ:

[0085]

[0086] The general solution given by formula (27) is:

[0087]

[0088] Where a, b, τ, k, and C are equation constants. Formula (28) converts the change in stray loss to constant T L f sw / f to connect.

[0089] Because when T L When T increases, only the fundamental current increases, so the total harmonic distortion of the current increases with T L The change of rotor resistance slip ratio of high-order harmonic current can be ignored because their synchronous speed value is large, so the harmonic current decreases with T L The change in (or slip) is very small.

[0090] For inverter-fed induction motors, the change in stray losses is related to the change in three power supply parameters: output power (P out ), power frequency (f), and f / f sw (τ). The SL increment changes corresponding to the changes in the above three parameters are as follows:

[0091]

[0092] The stray losses SL and SL of the induction motor proposed by the present invention are f and SL T The final expression of is:

[0093] SL=SL P SL f SL T =K Grid K Inv P out (30)

[0094] in,

[0095]

[0096] Among them, L lS , L lR and L m They are the stator leakage inductance, rotor leakage inductance and magnetizing inductance of the motor corresponding to the equivalent circuit of the three-phase induction motor.

[0097] like Figure 3 As shown, the stray loss SL of the induction motor proposed by the present invention is ultimately composed of the total magnetic flux pulsation loss SL output by the stray loss system under the influence of the output power P , the stray loss SL obtained by the stray loss system under the influence of power frequency f, stray loss under the influence of total harmonic distortion of current, stray loss SL of system output T , obtained by fitting formula (30).

[0098] The accompanying drawings and detailed description of the present invention referred to above as examples of the present invention are used to explain the present invention, but do not limit the meaning or scope of the present invention described in the claims. Therefore, those skilled in the art can easily realize modifications from the above description. In addition, those skilled in the art can change the order of the steps of the method described herein according to the environment of the process or equipment. Therefore, the scope of the present invention should not be determined by the embodiments described above, but by the claims and their equivalents.

[0099] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A fast and accurate method for analyzing stray losses of an induction motor, characterized in that: The following steps are involved: Step 1): The stray loss and spatial harmonic relationship system is composed of a sinusoidal wave excitation spatial harmonic module, an inverter feed excitation spatial harmonic module and a stray loss module; the input signal of the sinusoidal wave excitation spatial harmonic module is the number of turns per phase of the stator winding N ph , pole pair number p, vth spatial harmonic winding factor K w (v) and the spatial angle θ, the output signal is the Fourier decomposition of the magnetomotive force generated by the three-phase distributed winding F A (θ, t), F B (θ, t) and F C (θ, t); The input signal of the inverter-fed excitation space harmonic module is the Fourier decomposition of the magnetomotive force generated by the three-phase distributed winding F A (θ, t), F B (θ, t) and F C (θ, t), and the motor current amplitude I m The output signal is the net magnetomotive force MMF of balanced three-phase excitation; the input signal of the stray loss module is the magnetomotive force MMF of balanced three-phase excitation and the proportional coefficient K of the stray loss-magnetomotive force relationship of the i-th harmonic i , the output signal is the stray loss SL under the cumulative effect of all harmonics of the inverter motor's magnetomotive force; Step 2): The surface eddy current loss system composed of the magnetizing inductance module, the harmonic amplitude module, and the surface eddy current loss module and the flux pulsation loss system composed of the harmonic amplitude module, the stator harmonic stray loss module, the rotor harmonic stray loss module and the flux pulsation loss module constitute the stray loss system under the influence of the output power; the input signal of the magnetizing inductance module is the conductor Z of each slot s , Winding factor K w , air gap length g, motor stack length L, average air gap diameter D, Carter coefficient K c And the vth harmonic saturation coefficient K Sv Indicates that the output signal is the magnetizing inductance L corresponding to the vth harmonic mv ; The input signal of the harmonic amplitude module is the base magnetizing inductance L m1 The magnetizing inductance L corresponding to the vth harmonic mv , the output signal is the base air gap flux density B m1 and the magnetic flux density amplitude B of the vth spatial harmonic mv ; The input signal of the surface eddy current loss module is the base air gap flux density B m1 , the magnetic flux density amplitude B of the vth spatial harmonic mv , speed N s , pole pair number p and base air gap flux density B m1 The fundamental eddy current loss P corresponding to the fundamental frequency ω1 Eddy1 , the output signal is the surface eddy current loss SL surf , which is the output signal of the surface eddy current loss system; for the flux pulsation loss system, the input signal of the harmonic amplitude module is the slot leakage inductance L Slot , the magnetizing inductance L corresponding to the vth harmonic mv , base air gap flux density B m1 , slot distance t s and slot opening b s0 , the output signal is the harmonic amplitude B mtv ; The input signal of the stator harmonic stray loss module is the harmonic amplitude B mtv , speed N s and pole pair number p, the output signal is the stator harmonic stray loss SL pulsS ; The input signal of the rotor harmonic stray loss module is the harmonic amplitude B mtv , speed N R and pole pair number p, the output signal is the rotor harmonic stray loss SL pulsR ; Magnetic flux pulsation loss module The input signal is the stator harmonic stray loss SL pulsS and rotor harmonic stray losses SL pulsR , the output signal is the total flux pulsation loss SL P ; Step 3): The stray loss system under the influence of multiple factors is composed of the stray loss system under the influence of output power, the stray loss system under the influence of power frequency and the stray loss system under the influence of current total harmonic distortion (THD); Stray losses under the influence of power frequency The input signal of the system is constant α, β, and the rated frequency f r The output signal is the stray loss SL under the influence of power frequency f ; The input signal of the stray loss system under the influence of total harmonic distortion of current is constant signals a, b, r, k and C, and the output signal is the stray loss SL under the influence of total harmonic distortion of current. T ; Finally, the flux pulsation loss SL P , stray loss SL affected by power frequency f And the stray loss SL under the influence of total harmonic distortion of current T Together they constitute the stray losses SL of the induction motor.

2. A fast and accurate induction motor stray loss analysis method according to claim 1, characterized in that: The sinusoidal excitation space harmonic module is the Fourier decomposition of the magnetomotive force generated by the single-phase distributed winding of the three-phase induction motor, as follows: where i(t)=I m sin(ωt),I m is the stator current peak value, ω is the angular frequency of the sinusoidal alternating current, K w (v) is the winding factor of the vth spatial harmonic, N ph , p and θ are the number of turns per phase, number of pole pairs and space angle of the stator winding respectively, F B (θ, t), F C The acquisition of (θ, t) is obtained by spatially shifting 120° based on the above formula.

3. A fast and accurate induction motor stray loss analysis method according to claim 1, characterized in that: The inverter-fed excitation space harmonic module is obtained by the following formula: F S (θ,t)=F A (θ,t)+F B (θ,t)+F C (θ,t) Among them, F S (θ, t) is the net magnetomotive force.

4. A fast and accurate induction motor stray loss analysis method according to claim 1, characterized in that: The input signal of the magnetizing inductance module is, each slot conductor Z s , Winding factor K w , air gap length g, motor stack length L, average air gap diameter D, Carter coefficient K c And the vth harmonic saturation coefficient K Sv Indicates that the output signal is the magnetizing inductance L corresponding to the vth harmonic mv , given by formula (9): Where μ0 is the magnetic permeability, which represents the relationship between the magnetic flux density and magnetic field strength in a vacuum, N s is the motor speed, a l is the air gap length at the slot, and p is the number of pole pairs of the motor.

5. A fast and accurate induction motor stray loss analysis method according to claim 1, characterized in that: The input signal of the harmonic amplitude module is the base magnetizing inductance L m1 The magnetizing inductance L corresponding to the vth harmonic mv , the output signal is the base air gap flux density B m1 and the magnetic flux density amplitude B of the vth spatial harmonic mv , specifically: In the formula, F mv is the fifth harmonic, F1 is the fundamental frequency magnetomotive force, λ v and λ1 are the relative permeabilities of the vth harmonic path and the fundamental wave path, respectively. sv and λ 1s They are the fundamental frequency harmonic passthrough and the fundamental frequency specific permeability respectively.

6. A fast and accurate induction motor stray loss analysis method according to claim 1, characterized in that: The stator harmonic stray loss module is obtained by the following formula: Among them, the harmonic amplitude B mtv , speed N s And the number of pole pairs p, the base air gap flux density B m1 , basic eddy current loss P Eddy1 .

Images