Features of Practical Implementation of Three Phase Transformer-Rectifier Device with Pulse of Rectified Voltage P=12

Abstract

When developing three-phase multi-channel transformer-rectifier devices (TRD) with the summation of channel currents by means of a trans filter (TF), for example, for the number of channel L = 2 (P=12), depending on the conditions of the TRD application, particularly on the secondary windings and on the value of the frequency of the supply voltage. There can be a problem of an extremely inequality distribution of the current between the channels. The reason for this problem is the practical impossibility of fulfilling the requirement of equality to the value of $\sqrt 3 $ of the transformation coefficient (KTV) of voltage transformer (TV) between its two 3-phase windings with the topology "star" and "delta". The paper demonstrates that the approximation of the KTV parameter to the ideal value of $\sqrt 3 $ by increasing the number of turns above the calculated value allows us to find a combination of them, which makes it possible to reduce the inequality of the current division between the channels. However, in the end, this leads to the redistribution of TV and to the deterioration of its weight and size indicators. In order to eliminate this drawback, another method for the synthesis of the TRD-12 structure is considered, in which, instead of TF in each phase of two secondary windings, one single-phase two-winding current transformer (CT) is installed. They provide for the equalization of currents in the channels. Since the condition ${{\text{K}}_{{\text{TV}}}} = \sqrt 3 $ must also be satisfied between the two CT windings, the effect of the deviation of the real value of the KTV from the ideal value was also carried out here. It is shown that the influence of this factor, as well as the factor of the deviation of the analogue coefficient in TV, on the inequality of the current distribution between the channels is insignificant. The recommendations are given on the use of two versions of TRD-12 (with TF and with CT).