不飽和リアクトルを用いた三相全波整流形直流アーク溶接機の電流波形および外部特性曲線の理論計算

Abstract

Voltage curent characteristics of three phase rectifier type d.c. welder with non-saturable series reactor (Fig. 1) are calculated for the cases when d.c. reactor Ln is zero and infinity, under the assumption that internal resistance is negligible compared to a.c. inductance L.. The results are shown in Fig. 2 and Fig. 3.It is worth to notice that in case of LD=0, the current wave form of d.c. side is similar to that of no load d.c. voltage for all part of the characteristics though the wave form of a.c. side varies according to the variation of the load resistance. See. Fig. 6. Point Q in Fig. 2 shows the critical point when the over lap angle u becomes less than 60°. Curve, QRS is given by equation (21).The curve in Fig. 3 can be divided into three parts PQ, QR, RS. Each of PQ and RS is linear and QR is circular. Equations for the parts are given in (36), (44), (48).The current wave forms of a.c. side are shown in Fig. 8. The range (a)-(b) of Fig. 8 is well known. In the range (b)-(d), the over lap angle u is constant and the phase angle φ increases from 30° to 60° as load resistance decreases. In the, range (d)-(f) which corresponds to RS of the characteristics shown in Fig 3, the phase angle rp increases from 60° to 90° and the angle β in which the phase current is equal to d.c. current ID which is maintained as constant due to infinite d.c. inductance decreases from 60° to zero as load resistance decreases to ideal short circuit.It is remarkable that for the interval 60-β, the load terminal is short circuited through the rectifiers of the sam polarity. The phase of the initiation of the short circuit is given in equation (38) for B phase. See Fig. 11.