A method for obtaining parameters of a stationary linear induction motor based on the finite element method

Abstract

This invention discloses a method for obtaining parameters of a stationary linear induction motor based on the finite element method. The motor's rotor is stationary, and the method can account for the magnetic saturation of the primary core and secondary yoke. It is applicable to both short-primary and long-primary linear induction motors. First, the induction plate of the secondary winding is removed from the calculation model. Under current source excitation mode, an AC current with a preset current and frequency is applied to the input terminal of the primary winding. The current magnitude is varied, and the total equivalent resistance, reactance, and maximum air gap normal magnetic flux density of the motor are obtained under different current inputs. Then, the induction plate of the secondary winding is restored to the calculation model. Under current source excitation mode, an AC current with a preset current and frequency is applied to the input terminal of the primary winding, and the total equivalent resistance, reactance, and maximum air gap normal magnetic flux density of the motor are obtained. Finally, based on the above calculated values, the parameters in the T-type equivalent circuit of the induction motor are calculated.

Description

Technical Field

[0001] This invention relates to the field of motor analysis and testing, and in particular to a method for obtaining parameters of a stationary linear induction motor based on the finite element method. Background Technology

[0002] Because there is no wheel-rail contact, vibration is low and comfort is good. Maglev trains do not rub against the track during operation, resulting in low noise. Due to their advantages of speed, low energy consumption, environmental friendliness, and safety, maglev trains have a very promising future. The linear induction motor is the core power source for medium- and low-speed maglev trains; therefore, obtaining accurate parameters of the linear induction motor directly affects the smoothness of the train's operation. Current methods for obtaining motor parameters commonly use experimental or model-based theoretical calculations to determine the excitation resistance R in the T-type equivalent circuit of the induction motor. m Magnetizing Reactance X m Parameters such as secondary leakage inductance X2 and secondary resistance R2, etc. Figure 1 As shown, it is relatively easy to conduct short-circuit simulation experiments in model-based theoretical calculation methods; however, it becomes difficult to conduct no-load simulations on models of finite size, and it is impossible to obtain comprehensive parameters. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention discloses a method for obtaining parameters of a stationary linear induction motor based on the finite element method. The motor's mover is stationary, and the method can account for the magnetic saturation of the primary core and secondary yoke. This method is applicable to both short-primary and long-primary linear induction motors. First, the induction plate of the secondary winding is removed from the calculation model. Under current source excitation mode, an AC current with a preset current and frequency is applied to the input terminal of the primary winding. The current magnitude is varied, and the total equivalent resistance, reactance, and maximum air gap normal magnetic flux density of the motor are obtained under different current inputs. Then, the induction plate of the secondary winding is restored in the calculation model. Under current source excitation mode, an AC current with a preset current and frequency is applied to the input terminal of the primary winding, and the total equivalent resistance, reactance, and maximum air gap normal magnetic flux density of the motor are obtained. Finally, based on the above calculated values, the parameters in the T-type equivalent circuit of the induction motor are calculated.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A method for obtaining parameters of a stationary linear induction motor based on the finite element method includes the following steps:

[0006] The first step is to perform a 1:1 modeling of the linear induction motor in finite element software based on the physical model of the linear induction motor, and set it to three-dimensional eddy current field analysis; the primary resistance R1 and the primary leakage reactance X1 are known parameters;

[0007] The second step involves removing the induction plate, which serves as the conductive layer of the motor's secondary winding, from the computational model, while retaining the secondary yoke, which serves as the magnetic layer. In current source excitation mode, an AC current with a preset current I1 and frequency f is applied to the input terminal of the motor's primary winding. The magnitude of the current is varied, and the total equivalent resistance R of the motor under different current inputs is obtained. en Total equivalent reactance of the motor X en The maximum value of the normal magnetic flux density in the air gap, B mzn The corresponding relationship is:

[0008]

[0009]

[0010] in, The phasor of the phase-induced electromotive force. R is the phase current phasor. m and X m These are the resistance and reactance in the excitation branch, respectively. The subscript n indicates the corresponding value under the nth excitation current value; Re() is the function to take real numbers, and Im() is the function to take imaginary numbers;

[0011] The third step is to restore the induction plate of the motor's secondary winding in the calculation model. Under the current source excitation mode, an AC current with a preset current I1 and frequency f is applied to the input terminal of the motor's primary winding, and the total equivalent resistance R of the motor is obtained. t Total equivalent reactance of the motor X t The maximum value of the normal magnetic flux density in the air gap, B mzt The maximum value of the air gap normal magnetic flux density B obtained in the second step mzn In the middle, find the maximum value B of the normal magnetic flux density in the air gap. mzt The closest value, defined as B. mzi Then search for B mzi The corresponding total equivalent resistance R ei Reactance X ei Finally, calculate the parameters in the excitation branch and the secondary branch, and the corresponding relationship is as follows:

[0012] R t1 =R t -R1 (3)

[0013] R m =R mi =R ei -R1 (4)

[0014] X m =X mi =X ei -X1 (5)

[0015] X t1 =X t-X1 (6)

[0016]

[0017]

[0018] Among them, R mi and X mi B respectively mzi R corresponds to the resistance and reactance in the excitation branch. t1 and X t1 R1 and R2 are the total resistance and reactance of the excitation branch and the secondary branch, respectively, while R2 and X2 are the resistance and reactance of the secondary branch, respectively.

[0019] Beneficial effects:

[0020] With this invention, all parameters of the motor can be obtained by setting it to be relatively stationary relative to the primary and secondary windings of the motor within a limited computational model size, taking into account the effect of the saturation effect of the magnetic material inside the motor. Attached Figure Description

[0021] Figure 1 This is the equivalent circuit diagram of a T-type induction motor. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0023] This invention discloses a method for obtaining parameters of a stationary linear induction motor based on the finite element method. This method calculates the parameters of a linear induction motor under stationary conditions, considering the magnetic saturation of the primary core and secondary yoke. To accelerate the finite element calculation, the solver can be set to an eddy current field. To improve calculation accuracy, the calculation model can be set to a three-dimensional electromagnetic field model.

[0024] exist Figure 1 In the circuit, the primary resistor R1 and the primary leakage reactance X1 are connected in series to form two parallel branches: the excitation branch and the secondary branch. The excitation branch is connected to the excitation resistor R. m and excitation reactance X m The primary circuit is constructed in series, with the secondary branch consisting of the secondary resistance R2 / s and the secondary reactance X2 connected in series. The primary resistance R1 and primary leakage reactance X1 are assumed to be known. The method for calculating the parameters of a linear induction motor considering magnetic saturation under static conditions based on the finite element method, according to this invention, includes the following steps:

[0025] The first step is to perform a 1:1 modeling of the linear induction motor in finite element software based on its physical model, and set it to three-dimensional eddy current field analysis.

[0026] The second step involves deleting the induction plate (i.e., the conductive layer) of the motor's secondary winding in the calculation model, while retaining the secondary yoke (i.e., the magnetic layer). Using a current source excitation mode, an AC current with a preset current I1 and frequency f is applied to the input terminal of the motor's primary winding. The magnitude of the current is varied, and the total equivalent resistance R of the motor under different current inputs is obtained. en Total equivalent reactance of the motor X en The maximum value of the normal magnetic flux density in the air gap, B mzn The correspondence is as follows:

[0027]

[0028]

[0029] in, The phasor of the phase-induced electromotive force. R is the phase current phasor. m and X m These are the resistance and reactance in the excitation branch, respectively. The subscript n indicates the corresponding value under the nth excitation current value; Re() is the function to take real numbers, and Im() is the function to take imaginary numbers.

[0030] The third step is to restore the induction plate of the motor's secondary winding in the calculation model. Under the current source excitation mode, an AC current with a preset current I1 and frequency f is applied to the input terminal of the motor's primary winding, and the total equivalent resistance R of the motor is obtained. t Total equivalent reactance of the motor X t The maximum value of the normal magnetic flux density in the air gap, B mzt The maximum value of the air gap normal magnetic flux density B obtained in the second step. mzn In the middle, find the maximum value B of the normal magnetic flux density in the air gap. mzt The closest value, defined as B. mzi Then search for B mzi The corresponding total equivalent resistance R ei Reactance X ei Finally, in Figure 1 The parameters in the excitation branch and secondary branch can be calculated, and their corresponding relationships are as follows:

[0031] R t1 =R t -R1 (3)

[0032] R m =R mi =R ei -R1 (4)

[0033] X m =Xmi =X ei -X1 (5)

[0034] X t1 =X t -X1 (6)

[0035]

[0036]

[0037] Among them, R mi and X mi B respectively mzi R corresponds to the resistance and reactance in the excitation branch. t1 and X t1 R1 and R2 are the total resistance and reactance of the excitation branch and the secondary branch, respectively, while R2 and X2 are the resistance and reactance of the secondary branch, respectively.

[0038] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for obtaining parameters of a linear induction motor at rest based on a finite element method, characterized in that, Comprising the following steps: First, according to the physical model of linear induction motor, 1:1 modeling is carried out in finite element software, and it is set to three-dimensional eddy current field analysis; the primary resistance R1 and the primary leakage reactance X1 are known parameters; Second step, delete the induction plate of motor secondary as the conductive layer in the calculation model, keep the secondary yoke as the magnetic layer, apply the preset current I1 and the alternating current of frequency f at the input end of motor primary winding in the current source excitation mode, change the current size and obtain the total equivalent resistance R of motor under different current input en , the total equivalent reactance X of motor en , the maximum value of air gap normal magnetic density B mzn The corresponding relationship is: wherein is a phase induced electromotive force phasor, is a phase current phasor, R m and X m are resistance and reactance in the field branch, respectively, subscript n denotes the corresponding value at the n-th excitation current value; Re() is a real number function, and Im() is an imaginary number function. Third step, restore the motor secondary induction plate in the calculation model, in the current source excitation mode, the motor primary winding input end to apply a preset current I1 and frequency f AC power, and obtain the total equivalent resistance R t , the total equivalent reactance X t , the maximum air gap normal magnetic density B mzt ; the maximum air gap normal magnetic density B mzn obtained in the second step, find the value closest to the maximum air gap normal magnetic density B mzt , and define it as B mzi , and find the total equivalent resistance R ei , reactance X ei corresponding to B mzi ; finally, calculate the various parameters in the excitation branch and the secondary branch, the corresponding relationship is: R t1 = R t - R1 (3) R m = R mi = R ei - R1 (4) X m = X mi = X ei - X1 (5) X t1 = X t - X1 (6) Among them, R mi and X mi B respectively mzi R corresponds to the resistance and reactance in the excitation branch. t1 and X t1 R1 and R2 are the total resistance and reactance of the excitation branch and the secondary branch, respectively, while R2 and X2 are the resistance and reactance of the secondary branch, respectively.

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