| 摘要 |
1,088,801. Control of D.C. motors. I-T-E CIRCUIT BREAKER CO. Jan. 17, 1966 [Feb. 15, 1965], No. 2125/66. Heading H2J. A traction motor is energized from two D.C. sources 10, 11 through choppers 12, 13 and has two series field windings 16, 17 interconnected by inductors 19, 20 on a common core. The choppers are triggered alternately so that initially the sources are used sequentially and the fields are effectively in series, because the inductors 19, 20 have a high impedance (at the chopper frequency) due to their currents being in opposition. As the " on " time of the choppers is increased until they overlap, the sources operate in series and the inductor currents are no longer in opposition, thus reducing their impedance and so putting the field windings 16, 17 in parallel. The inductance of the circuit, increased if necessary by further inductors 50, 51, results in a sawtooth waveform enabling a current limit circuit (not shown) to be employed, which preferably switches on the inactive chopper when switching off the active one. |
