| 摘要 |
The invention relates to an arrangement for forming the actual current values of currents with harmonics of a three-phase voltage system, the frequency and amplitude of the fundamental oscillation of which can be adjusted by means of a pulse width modulator. The actual current values (iR, iS, iT) are continuously supplied to a sample and hold circuit (6). The sample and hold circuit (6) is connected at the output to an evaluating circuit (7) for forming the current amount (i) and the current phase angle ( phi i). The current amount and the current phase angle are input as control signals to the pulse width modulator (8). The input of the sample and hold circuit (6) is supplied with trigger signals (TR) for sampling the instantaneous actual current values ((iR, iS, iT). The trigger signals (TR) only occur at the times within the period at which the amount of the actual current value is equal to or essentially equal to the amount of the fundamental current oscillation. This largely eliminates the interfering influence of the harmonics in the detection of the actual current value. The trigger signals (TR) can be either precalculated or they are derived from the signals generating the timing of the pulse-width modulator (8). <IMAGE>
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