| 摘要 |
<p>A b s t r a c t Static power converter Static power converters are devices for converting electrical power, and comprise one or more sets of diodes, or sees of thyristors, and, as appropriate, a power-converter transformer, reactors, switching units, and further auxiliary devices. They are designed, inter alia, as rectifiers, inverters, and converters, and are used for operating electrical machines. During operation, static power converters are subject to current harmonics, which lead to undesirable feedback perturbations affecting the current-supply system. If no protective measures are adopted, dangerous overvoltages can occur in the process of switching off inductive loads, and both these loads and the semiconductor components of the power converters are particularly endangered by such overvoltages. In order to reduce these undesirable effects, a power-converter bridge (20) of a converter (21) possessing a direct-current intermediate circuit, intended for connection to a machine representing an inductive load, on the machine side, via machine phase-conductors (U,V,W), e.g. for connection to an asynchronous machine possessing a slipring-rotor (23), is designed with thyristors in the bridge arms, with facilities for turning these thyristors off. The thyristors are operated at a comparatively high switching frequency, so that the power-converter bridge (20) supplies an alternating current which is comparatively near-sinusoidal, and which exhibits a low harmonics con-tent. Following the turning off of the thyristors, the energy stored in the rotor windings of the a synchronous machine (23) is temporarily stored in the capacitors (5) of an overvoltage protection unit (22), these capacitors (5) being connected to the alternating-voltage terminals of the bridge circuit (20), so that no impermissible over-voltages occur.</p> |
