Contact Less Energy Transfer

1 Contactless Energy Transfer to a Moving Actuator Jeroen de Boeij, Student Member, IEEE , Elena Lomonova, Jorge Duarte Member, IEEE and Andr ´ e Vandenput, Senior Member, IEEE Abstract— In this pape r a new topolog y for contactless ener gy transf er is pr oposed and tes ted that can trans fer ener gy to a moving actuator using inductive coupling. The proposed topology prov ides long- stro ke conta ctle ss ener gy trans fer capab ilit y in a pl ane and a short- st ro ke movement of a fe w mi ll imet er s perp endi cula r to the plane. In addit ion, it is tolerant to smal l rotations. The experimental setup consi sts of a platf orm with one seconda ry coil, which is attach ed to a linear actuator and a 3-pha se brushless electromotor. Unde rneath the platf orm is an array of pri mar y coi ls, that are each connected to a hal f- brid ge squar e wave power supply . The energy transfe r to the electromotor is measured while the platform is moved over the array of primary coils by the linear actuator. The secondary coil moves with a stroke of 18 cm at speeds over 1 m/s, while up to 33 W power is transferred with 90% efficiency. Index Terms— Contactless energy transfer , inductive coupling, moving load. I. I NTRODUCTION Most high- prec ision machines are positioning stages with mul ti ple de gre es of fre edo m (DOF), whi ch oft en con sis t of cascad ed lon g- and sho rt- str oke linear act uat ors that are sup por ted by mec han ica l or air bea rin gs. Usu all y , the lon g str oke act uat or has a mi cro meter acc ura cy , whi le the submicro n accuracy is achi ev ed by the shor t-st roke actuator . To build a hig h-p rec isi on machine, as much distur ban ces as poss ible should be el iminat ed. Common sources of disturbances are vibrations, Coulomb and viscous friction in beari ngs, crosstalk of mult iple cascaded actuators and cabl e slabs. A pos sibil ity to inc rea se thr oug hpu t, while ma int ain ing acc ura cy is to use par all el proces sin g, i.e . move men t and positioning in parallel with inspection, calibration, assembling, scanning, etc. To meet the design requirements of high accuracy while impr ovi ng perf orma nce, a new design appro ach is nece ssar y , espec iall y if vac uum operation is consi dere d, which will be required for the next generation of lithography machines. A lot of disturbance sources can be eliminated by inte grat ing the casc aded long - and shor t-st roke actuator into one actu ator system. Since most long-st roke movements are in a plane, this can be done by a contactless planar actuator. A contactless planar actuator or planar motor is supported by magnetic bear ings that levitat e the actu ator plat form, while contr olli ng all six DOF of the platform. Long- stro ke line ar movement in 2D is also provided by the mag net ic bea rin g This research is sponsored by SenterNovem. SenterNovem is an agency of the Dutch Ministry of Economical Affairs. J. de Boe ij is wit h the Dep artment of Ele ctr ica l Eng ine eri ng of the Eind hov en Uni vers ity of Techno logy , Eind hov en, The Neth erlan ds; (e- mail:[email protected]) while small translations in height and small rotations remain possible. Magnetic bearings can also operate in vacuum. Pa ral lel pro ces sin g req uir es po wer on the pla tf orm to dri ve the actua tor s on the platf orm. In ord er to remove as much distur banc es as poss ible , the power transfer needs to be con tac tless, i.e. wit hou t wires fro m the gro und to the pla tfo rm. A coi l top olo gy and geo met ry for a contac tle ss ene rgy tr ans fer sys tem is pro pos ed for ene rg y tra nsf er to a pla nar mo vin g pla tfo rm. The pla tfo rm is equ ipp ed wit h permanent magnets and is levitated and propelled by a matrix of coils, which are fixed to the ground. Such a planar actuator is cur ren tly und er in ve sti ga tio n at Ein dho ven Uni ve rsi ty of Tech nol ogy [13]. The aim of thi s res ear ch pro jec t is to trans fer ene rgy to the movin g pla tfo rm con ti nuousl y and at ev ery pos ition in ord er to enhance the fun cti onalit y of the plat form, whil e main tain ing the adv anta ges of opera ting without contact and cables slabs. When ener gy is transf er re d to a mo vi ng load (i.e. an electromotor) by means of inductive coupling, one has to deal with a changing coupling between a primary and secondary coil. The change in coupling results in a different characteristic of the ener gy tr ans fer capab ili ty of the syste m as is sho wn in [1], [2], [3], [4] and [5]. Most of these systems can only tran sfer energ y at cert ain position s ([1] , [2]) or the y suf fer from large changes in power tran sfer capabili ty throu ghout the range due to the changing coupling ([4], [5]). Another solution for transferring energy to a moving load is using elongated primary coils in combination with elongated cor es [7]. Thi s results in a sta ble ener gy tr ansfer but the st roke is li mi te d by the si ze of the pr imar y coil . If long stro kes are requ ired, the syst em beco mes hea vy and bulk y . The topology proposed and tested in this paper provides long- stroke contactless energy transfer (CET) in a plane with only small changes in power transfer capability. II. CET TOPOLOGY The design of the primary and secondary coil is optimized to get a co upli ng th at is as cons ta nt as po ss ib le for a suf ficien tly large area. This area should be larg e enoug h to all ow the secondary coi l to move fro m one prima ry coi l to the next one without a large reduction in coupling. If this can be achieved, the power can be transferred by one primary coil that is closest to the secondary coil. When the secondary coil moves out of ran ge the first primary coil is tur ned off and the next one wil l be energize d. T o ens ure a smo oth ener gy transfer to the moving load, the position dependence of the coupling should be minimized, while keeping the coup ling high enough to get a high-efficiency energy transfer.

Contact Less Energy Transfer

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