交流アーク熔接機の温度上昇試験法について

Abstract

In testing temperature rise of A. C. arc welder, it has been conventionally accepted to load the welder with fall load current, with secondary terminals being directly short circuited.Under this condition, the position of moving core or moving coil, as the case may be, is different from their normal full load working position, in which case secondary terminal voltage is not zero, but is the sum of arc voltage and voltage drop along the welding cable.Difference of position of moving core or coil causes diffence in distribution of leakage flux, which in turn results difference in stray load loss, and also it may cause difference in ventilating effect of the winding.These effects, individually or combined, will ultimately affect the temperature rise of the winding.In this respect it is desirable to load welders with secondary resistance, that gives the secondary terminal voltage of same r. m. s. value as actual arc voltage, but this is rather infeasible from the practical point of view.In this paper we propose to replace the secondary load resistance with reactor, and the effect is fully discussed. In this case moving core or coil is pre-adjusted to the position at which rated full load current can be delivered at rated primary voltage and at rated secondary output voltage of narmally loaded condition, and the secondary current is adjusted to rated full load value by changing the reactance or impedance connected to the secondary terminals.By doing so, we can reproduce the same ventilating condition, together with same copper loss and stray load as normal full load condition.But, secondary terminal voltage becomes somewhat lower, and flux interlinking with the secondary winding becomes correspondingly lower, than resistance loaded condition. (Fig. 5)Iron loss of arc welder is, however, usually small as compared to the sum of copper loss and stray load loss, therfore small difference of the core loss due to the above mentioned slight. change of flux density of the core just below the secondary winding, can be neglected, and we can get almost same result of temperature rise.Necessary secondary load reactance can be obtained easily by making loop or coil of several turns with secondary lead wire, and its reactance value can be adjusted by changing the shape of coil or its number of turns.