d L i A simple soft-switched reluctance motor drive circuit was d t Abstract proposed, involving only four switching devices with three motor and the output torque was increasctl by means of shorter currentdevice during powering period, higher efficiency can be performed. 1. birroditcrioii = d L i +~d i windings. The sysleiii yields less EMI, because of soft switching, d t d t = w, -i + L -IFF tail-length. As this system utilizes only one series switching d e d t d L d iEnormous amount of power electronic drives are used for industrid facilities and offices, lately.The switched reluctance motors are also rigorously inivestigated in these days. and various kinds of reluctance motor drive circuits have been presentcd. Electric vehicle is one of the most promised field of reluctance motor applications because of their simple and rigid structure, and tlie future possibility of lower cost than that of induction motors' is also strongly focused point.This motor has relatively high reactance and the stored excited energy has to be retrieved after each powering period. Therefore the energy retrieval period usually 'becomes longer and the shorter retrieval period is desired to obtain higher output power and higher efficiency. For this purpose, some kinds of driving circuits are already proposed. Many of them are utilizing hard switching i:ypes[l]-[3], and they may cause high electro-magnetic intei-ference: (EMI) and lead to rather liigli switching losses. A soft-switched type drivecircuits with resolinill circuit was also reported[4], and it seeins to Iiave less EM1 and less switcliing losses. However, they utilize continuous resonant-switcliings, and may result in high resonant circuit losses. This paper deals with soft-switched type drive-circu.it, including only four switching devices, and has the merits of l o i~ switching losses, low EMJ, and higher efficiency. Fig. 1 shows the structure of the reluctance motor dealt in this paper, and each winding inductance varies according to the rotational angle 0 as sclicinatically depicted iii the figure.
It. Relitcfaiice Torqrte GerierafioiiInductance L, of phase-a winding assumed to vary 1ine.arly up and down, during 0 = -30 to +30 degrees. The 0the.r windinginductances and L, also vary as the same way, with thlt 30 degree (mechanical) angle-differences. When the voltage v is applied across the motor winding, tlie fluxlinkage k and v are written iii dh dt v = -where the winding resistance is neglected. As h is rep,resented by the product of inductance L and tlie current i , then the voltage v be comes as follows.
Novel uniform nano/micron-sized ZnO spheres assembled from the aggregation of nano-particles have been synthesized by hydrothermal method. It was observed that ZnO spheres with controllable diameter were obtained when various volume ratios of triethanolamine (TEA) to H2O were used. Increasing the volume ratio of TEA to H2O could result in the formation of loosely packed ZnO spheres. The UV-visible absorption spectra show that the absorption peak red-shifts with the increasing average diameter of the spheres.
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