| 摘要 |
<p>The DC/DC power transformer is an arrangement for direct transformation of high electric powers from one DC voltage level to another DC voltage level without intermediate AC voltage network. The DC voltage is today basically used for transmission of high electric powers at long distances. The DC voltage levels for these transmissions are normally high. The DC/DC power transformer allows several DC voltage levels to be used in one and the same DC voltage network. The principle for this arrangement is that the valve windings (43, 45) from one or several converter transformers (47) are connected to two valve bridges, which generate opposing cyclically variating magnetic flows in the transformer cores (44). One of the valve bridges is operated as an inverter (49) and the other as a rectifier (46) and in this manner the power is transformed from one DC voltage level (Ud1) to another (Ud2). At the high voltage levels for which the invention is intended the leakage inductances in the transformers will be high as a consequence of the insulation levels and due to this special arrangements must be made in order to commutate the magnetic energy from one phase of the transformer to another without creating great losses. The arrangement is proposed in a line commutated alternative (figure 5) and in a selfcommutated alternative (figure 4). The first utilizes a third AC voltage reference winding (A3, B3, C3 in figure 5) for this commutation. In the second alternative an external over the bridge connected capacitor (48 in figure 4) is utilized for this commutation purpose. Both alternatives may be designed galvanically insulated or in autocoupling (figure 10).</p> |
