| 摘要 |
1368202 Inverting systems; standby systems ALLMANNA SVENSKA ELEKTRISKA AB 24 Jan 1972 [25 Jan 1971] 3214/72 Headings H2F and H2H A standby system for use in the event of mains failure comprises two poly- or single phase thyristor converter bridges A, B each having A.C. terminals connected to output leads R, S, T, in the 3-phase circuit shown, connected to a load L, and each having D.C. terminals connected to an accumulator battery BA via respective inductances R1-R4, a capacitor bank K being connected between the A.C. leads of the two bridges as shown, the bridges being in antiparallel connection with respect to the D.C. source. In operation with the mains inputs R<1>, S<1>, T<1> functioning, both switches S1, S2 are closed and bridge B which acts as a rectifier supplies a charging current through the cell BA. Gating of the thyristors is effected by a control device SDB which is itself controlled by an oscillator which is dependent on the mains input. In the event of mains failure, the contact S1 opens, oscillator O becomes free-running and bridge A inverts the power from the D.C. source BA and supplies this to the load L. A voltage sensor SO applies a signal to comparison circuits JR-JT for comparison with a reference and error signals #UR-#UT are passed to phase shifting devices DR-DT which lie in series between the oscillator O and the control device SDA for the bridge and cause the oscillator output to be phase shifted in accordance with the error signal with respect to the input at SDB. The thyristors in each bridge are gated in the conventional manner to render bridge B a rectifier and bridge A an inverter and gating signals are applied to respective pairs of devices at intervals of 180 degrees of the inputs at SDA, SDB. According to the phase shift introduced, the available power will be shared between that passed out via R, S, T, to the load L and that retained as a circulating component between the bridges, and thus that applied to the load L controlled via this phase shift. In a modification, Fig. 4 (not shown), two units as in Fig. 1 shown are employed in parallel and connected to a common D.C. source. The phase shift between signals applied to respective control devices SDA, SDB in each unit is now maintained constant and a variable phase angle is introduced between the two units and the A.C. output is taken either as the vector sum or difference of the separate outputs. By varying the said phase angle, the magnitude of the output A.C. may be changed.
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