| Interconnection cables,as the carrier of signal and energy transmission in electromechanical equipment,are an indispensable part of realizing system functions.Because of the cables' antenna effect,they provide a main gateway for electromagnetic interference and play a major role in electromagnetic compatibility.Therefore,the modeling and calculating for electromagnetic interference of them are studied systematically in this dissertation,which provide theoretical basis and modeling method for analyzing electromagnetic compatibility of interconnection cables.Specifically,the main research contents are as follows:(1)Study on the calculation method for radiated electromagnetic interference and shielding effectiveness of shielded single core cable.An analytical technique is developed to evaluate radiated electric field and shielding effectiveness of shielded cable.Firstly,the function relating the current on the screen to that on the inner conductor is modeled by the transfer impedance with Kley's method,and the total electromagnetic radiation is obtained by the hertzian dipole technique.Then,the shielding effectiveness expression of shielded cable is created according to its definition which is defined by its transfer impedance.On this basis,the effect of cross-section parameters on the shielding effectiveness is analyzed.Finally,numerical simulations by commercial software CST and an experiment are carried out to validate the proposed method.(2)Study on the multiconductor reduced technique to model the electromagnetic interference on cable bundles within a braided shielding structure.To handle the modeling of the electromagnetic interference prediction of complex cable bundles,the multiconductor reduced technique is proposed to simplify the modeling process by reducing the complete model into four groups.Firstly,the conductors are grouped together on the basis of the knowledge of Z-smith chart.Then,the distribution parameter of the reduced model is obtained according to the relationship between the whole and reduced model.By means of the distribution parameter calculation formula of an ideal conducting cylindrical shield,the geometrical characteristics of the reduced cable bundles are determined.Finally,numerical simulations such as electromagnetic coupling or radiation and its application inside an enclosure,are carried out to validate the efficiency and advantage of the proposed approach.(3)Study on the calculation method for determining the critical cable spacing for acceptable crosstalk.An analytic method for determining the critical cable spacing is proposed to guide wiring of adjacent cables.Firstly,a calculation formula for crosstalk is derived and a validation by numerical simulation is given.Then,the function of crosstalk with cable spacing is created by redefining the formula,through which the crosstalk curve with cable spacing is draw out.On this basis,the critical cable spacing is defined via a critical point on the crosstalk curve and physical meaning of the critical point is explained by using of the fringe field around the victim cable.Finally,an experiment is conducted to validate the proposed calculation method of the critical cable spacing.(4)Study on the calculation method of the field-line coupling interference inside a shielding enclosure.A hybrid method based on the electromagnetic topology is developed for the analysis of electromagnetic coupling effect in complicated electric systems.Firstly,a coupling mechanism of cable inside a shielding enclosure is established and the electromagnetic interactions from exterior fields to interior cable are determined by the way of conductive and radiation coupling interference.Then,the total load disturbance voltage of cable is calculated by determining BLT equation of the two interference paths.On this basis,numerical simulation and numerical integration method are applied to solve the BLT equation with Agrawal model.Finally,numerical simulations by commercial software CST are carried out to validate the proposed method.(5)Study on the application of modeling and calculation method of electromagnetic interference on cables.An efficient approach is proposed for predicting electromagnetic interference of motor and its drive system under field-circuit and transmission line coupling.As the common mode interference circuit is the main source of electromagnetic emission,its propagation path is analyzed.On this basis,the key components' models in conduction path of common mode interference are established.Then,the system's electromagnetic interference prediction model is obtained by the use of multiconductor reduced method.The field-circuit and transmission line coupling joint simulation method is used to analyze the proposed prediction model and the results are in good agreement with experiment measurement.Finally,the influence of cross-section geometrical and wiring parameters on the electromagnetic interference of cable is discussed by means of the presented methods of calculating radiated electromagnetic interference and shielding effectiveness of braided shielding cable,and determining the critical cable spacing for acceptable crosstalk.The main innovations of this dissertation are as follows:(1)Proposed an analytical method for shielding effectiveness of braided cableThe transfer impedance between the screen and inner conductor is an important indicator,which describes the characteristic of radiated electromagnetic fields and shielding effectiveness.The obtainment of currents on the shield is the basis of calculating the total radiation field.The proposed method gives an analytical formula for shielding effectiveness with the transfer impedance,which provides theoretical basis for the evaluation of shielding effectiveness and design of geometrical configuration of shielded cable.(2)Proposed an multiconductor reduced method for cable bundlesFor modeling electromagnetic radiation and coupling of multiconductor cable bundles,this dissertation simplifies the multiconductor into no more than four groups with the multiconductor transmission line theory.Compared with the numerical simulation of the complete cable model,the required computation time is markedly reduced and the complexity of modeling the completely shielding cable bundles is significantly simplified.The proposed method provides an effective modeling technique for shielding effectiveness simulation of the complex cable bundles.(3)Proposed a hybrid method for calculating the coupling to cable inside a shielding enclosure.The proposed method utilizes electromagnetic topology to simplify the solution of a complex system into that of many subsystem problems,which significantly reduces the difficulty for analyzing the coupling to cable in electronic equipment.Compared with conventional analytical and numerical approaches,the presented hybrid method simplifies the modeling process and possesses better efficiency based on the combination of analytical calculation and numerical simulation. |
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