Model of Contactless Power Transfer in Software ANSYS

Transcription

1 POSTE 06, PAGUE MAY 4 Model of Contactless Power Transfer in Software ANSYS adek Fajtl Dept of Electric Drives and Traction, Czech Technical University, Technická, 66 7 Praha, Czech epublic fajtlrad@felcvutcz Abstract This paper describe a model of contactless power transfer CPT analyzed in multiphysics software ANSYS This paper also mentions equations for determining basic parameters of CPT The last part describe the analysis of the CPT model and its useage for developing new electric vehicles charger based on contactless energy transfer This article also shows electromagnetic field created by CPT operations and its possibly effects on its surroundings Keywords CPT, Contactless energy transfer, Contactless power transfer, Maxwell Ansys, Simplorer Ansys Introduction of CPT The contactless power transfer CPT transfers electric energy between physically unconnected electric devices CPT consists of two large air-gap coils where is induced electric current CPT has many useful advantages which make possible its use in environments where other electric transmission ways of would be impractical or even dangerous Many electric devices are based on CPT such as electric toothbrush charger, mobile phone charging or transportation applications Basic CPT components are shown in figure Fig Contactless power transfer principal scheme Basic CPT parameters As shown in Fig, CPT consists of many components which are high frequency compensated power supply, two air coils CPT transformer for contactless power transfer and compensation and rectifier for storage energy in batteries Transformer operates at high frequency due to achieve high efficiency High operation frequency increases CPT transformer impedance and transferred reactive power To reduce reactive power the capacitance compensation is used on the primary and secondary CPT transformer side Basic CPT transmission parameters The basic parts of contactless power transfer of electric energy is a CPT transformer created by two copper coils with large air gap and its shielding Figure shows the CPT transformer equivalent circuit

2 ADEK FAJT, MODE OF CONTACTESS POWE TANFE IN SOFTWAE ANSYS Four basic capacity compensation are used They differ in capacitors connection They are series-series (used for charging batteries, shown in figure 5), series-parallel (fig 6), parallel-series (fig 7), parallel-parallel (fig 8) Fig The CPT transformer equivalent circuit Basic electrical CPT transformer parameters are primary and secondary inductances, primary and secondary resistance and mutual inductance M Mutual inductance is given by equation : M k V () Value of transferred power P is given by equation : P M Q 0 S I () Impedance of contactless power transfer Z CPT is given by equation 3: Z CPT M j * j j Efficiency of contactless energy transfer η is given by equation 4: is: (3) * M M (4) If equation 5 is fulfilled: M 0 (5) maximal efficiency η max of contactless powert transfer max (6) M Capacity compensation parameters It is obvious from equation 5 that transferred power depends on the CPT transformer parameters but also on operational frequency and the transformer quality To maximize the transferred active power value it is necessary to compensate reactive power Fig 5 Series-series capacity compensation Fig 6 Series-parallel capacity compensation Fig 7 Parallel-series capacity compensation Fig 8 Parallel-parallel capacity compensation To compensate reactive power in the secondary side, capacitor value has to be: C 0 Table shows equations for capacitors values used in primary compensations: SS SP C C C C M (7)

3 POSTE 06, PAGUE MAY 4 3 PS C C 4 M PP C M C 4 M M C Tab Equations for primary capacity compensation values 3 Analytically calculated CPT parameters Basic CPT parameters and its efficiency depends on CPT transformer electric parameters which are self and mutual inductances, resistivity or transferred power In my study I use two circular spiral plates as two coils with large air gap To determine the self and mutual inductances of the CPT transformer it's necessary to choose basic physical parameters of the transformer coils such as coil dimensions, coil shape, space between coils or material from which they are formed These parameters significantly affect properties of the transmitted power so they have to be properly determined Basic scheme of spiral coil shows fig 9 These equations count on fact that coils are formed from litz wires and losses caused by high operational frequency such as eddy-current losses don't impact 3 CPT Model in s Ansys Foregoing text described basic equations for computing parameters of electric device for contactless power transfer used for charging batteries These equations are very simplistic and don't conclude many other factors that has impact on CPT operation These factors are for example transformer coils mutual misalignment, stray magnetic flux which flows through other automobile parts created from magnetic materials Figure 9 shows created model of the CPT transformer created in software Maxwell and calculated its parameters Spiral coils parameters are mean diameter a 0 cm, thickness height b 0, cm and number of turns N 0 Model of whole electric device for contactless power transfer is shown in figure 0 This model is created in software Simplorer and include model of CPT transformer Due to co-simulation of softwares, whole contactless power transfer and charging batteries with power supply from 3phase network can be modelled and simulated From analysis of this simulation can be obtain important CPT charger operational parameters such as transferred active power, load current, reactive power, efficiency, optimal operational frequency, electromagnetic field of CPT transformer and many others Model of contactless power transfer was created in ANSYS software This model consists of two parts First part is the CPT transformer model shown in figure 0 Second part is whole CPT system created in Simplorer This CPT system also include CPT transformer model and is shown in figure Fig 9 Spiral coil parameters The spiral coil self inductance is given by equation 8: an 6 (8) *0 8a b where a [cm] is coil mean diameter, b [cm] is thickness of the coil layers and N is number of turns Mutual inductance M of two coils is given by equation 9: Fig 0 CPT transformer model in Maxwell M k V (9) where k V is mutual bond factor

4 4 ADEK FAJT, MODE OF CONTACTESS POWE TANFE IN SOFTWAE ANSYS Fig Whole contactless power transfer system 4 CPT Model Analysis By analyzing this CPT model in software ANSYS was gain graphs and data for whole contactless power transfer and its operational parameters Computed data by software Maxwell and Simplorer are mentioned in table with data computed from analytical equations for contactless power transfer This solution is computed for CPT transformer air gap 0, m and operational frequency ω 0 00 khz CPT parameter Analytical CPT analysis [μh] 9,84,0 [μh] 9,84,0 M [μh] 0,905 0,0986 C [μf] 0,73,504 C [μf] 0,73,504 Tab Computed CPT parameters From analysis of CPT model in ANSYS software was gained graphs of basic operational parameters and functions such as power supply voltage, current, power and parameters of transferred power Figure shows graph of self inductance dependence on air gap and slide Figure 3 shows graph of coupling coefficient k V dependence on air gap and slide Figure 4 shows graph of mutual inductance M dependence on air gap and slide Figure 5 shows dependence of transferred current on operational frequency with static compensation parameters Figure 6 shows dependence of induced voltage in secondary winding on operational frequency with static compensation parameters Fig CPT self inductance dependence on air gap and slide

5 POSTE 06, PAGUE MAY 4 5 Fig 3 CPT coupling coefficient dependence on air gap and slide Fig 4 CPT mutual inductance M dependence on air gap and slide

6 6 ADEK FAJT, MODE OF CONTACTESS POWE TANFE IN SOFTWAE ANSYS Fig 5 Transferred current dependence on operational frequency Fig 6 Induced voltage dependence on operational frequency 5 Conclusion This article describes basic analysis of contactless power transferred modelled and co-simulated in softwares Maxwell and Simplorer Basic principles of contactless battery charging are mentioned Basic CPT operational parameters are computed from analytical equations and they are also gained from CPT model analysis From graphs obtained from CPT analysis it's obvious that CPT operational parameters are strongly dependent on layout of CPT coils, air gap between them and their slide Due to CPT has to operate at resonance frequency, CPT power supply has to be able to operate flexible with high range of operatinal frequency Acknowledgements esearch described in this article was supervised by Ing Karel Buhr, CSc, FEE CTU in Prague and supported by the Czech Grant Agency under SGS research program No SGS6/080/OHK3/T/3

7 POSTE 06, PAGUE MAY 4 7 eferences [] Sallan, J; Villa, J ; lombart, A; Sanz, J F; Optimal Design of CPT Systems Applied to Electric Vehicle Battery Charge IEEE Transaction on Industrial Electronics, vol 56, no 6, pp 40-49, June 009 [] Chwei-Sen Wang; Stielau, O H; Covic, G A; oad models and their application in the design of loosely coupled inductive power transfer systems Power System Technology, 000 Proceedings PowerCon 000 International Conference on, vol, pp [3] Chwei-Sen Wang; Stielau, O H; Covic, G A; Design considerations for a contactless electric vehicle battery charger, IEEE Transactions on Industrial Electronic, vol 5, no 5, pp , Oct005 [4] Van der Pijl, F F A; Ferreira, J A; Bauer, P; Polinder, H; Design of an Inductive Contactless Power System for Multiple Users Industry Applications Conference, 006 4st IAS Annual Meeting Conference ecord of the 006 IEEE, vol 4, pp , 8- Oct 006 [5] ICHIKAWA, Schinji TOYOTA JIDOSHA KABUSHIKI KAISHA NONCONTACT EECTIC POWE ECEIVING DEVICE, NONCONTACT EECTIC POWE TANSMITTING DEVICE, NONCONTACT EECTIC POWE FEEDING SYSTEM, AND EECTICAY POWEED VEHICE [patent] Japan AH0F384FI, Date [6] Sample, A P; Meyer, D A; Smith, J ; Analysis, Experimental esults and ange Adaptation of Magnetically Coupled esonators for Wireless Power Transfer IEEE Transactions on Industrial Electronics, vol 58, no, pp , Feb 00 [7] ee ; Wilson ; Carter Ch; "Electronic transformers and circuits", A Wiley-Interscience Publication, New York, 988 [8] Fajtl, - Buhr, K: Electromagnetic Compatibility of Contactless Power Transfer Modeled in FEM Analysis Software In PIES 05 - Progress in Electromagnetics esearch Symposium Prague, 05, ISBN [9] Košík, M - Fajtl,, Buhr, K - ettl, J: Model of Power Electronics Used for Electic Vehicles Contactless Charging In PIES 05 - Progress in Electromagnetics esearch Symposium Prague, 05, ISBN About Author adek FAJT was born in the Czech epublic He graduated the Faculty of Electrical Engineering of the Czech Technical University in Prague, where he obtained a title Ing (0) He currently studies doctoral studies at the Department of Electric Drives and Traction in the Faculty of Electrical Engineering of the Czech Technical University in Prague