| 摘要 |
<p>A tuned transformer element has its primary winding coupled, in series with a fuse of preselected rating, to the rails of the track circuit. A secondary winding supplies input energy to the track circuit receiver unit which detects occupancy conditions of the track section. A third winding is capacitor tuned to resonate with the primary winding at the track circuit frequency. Thus the transformer appears as a parallel resonant load of high impedance in multiple with the track receiver which then operates normally. At propulsion frequency, the impedance of the primary is small while the parallel capacitive reactance is large, so that the parallel network gives the transformer unit a low impedance at this frequency. If, due to unbalance in the rails, the propulsion current is large enough that its harmonics may energize the track circuit receiver to improperly register an unoccupied track section, the current in the primary winding exceeds the fuse rating and that primary circuit is opened to inhibit any track circuit receiver response.</p> |
