Abstract
In the Japanese a. c. electric railway system, the AT feeding system is regarded as the standard feeding system because it is found suitable for feeding power to the electric car.
In the a. c. electric car, a. c. electric power is converted to d. c. electric power in order to drive d. c. motors, thereby generating higher harmonics in the a. c. side current. On the other hand, as the feeding circuit is a distributed constant circuit composed of RLC, the capacitor of the feeding circuit and the inductance on the side of the power supply cause a parallel resonance at a specific frequency and magnify higher harmonics current. For this reason, in the system of conventional lines which have long feeding distances, a higher harmonics resonance suppressor (i.e., CR equipment) composed of a resistance and a capacitor has hitherto been connected to the end of a feeding circuit. However, connection of a CR circuit to a high voltage circuit of 44kV resulted in increasing the power loss caused by the resistance, which posed a problem to be solved.
We have sought an appropriate place of installation and structure of the CR equipment with a view to reducing the power loss without negatively affecting the higher harmonics resonance suppressing function. The result shows that by merely installing the CR suppressor at the sectioning post we can successfully reduce the number of the CR suppressors; and by parallel-connecting the reactor to the resistance of the CR suppressor we can make two currents flow separately, i.e., the commercial frequency current to the reactor side and the higher harmonics current to the resistance side. This improvement contributes to the reduction of power loss and has already been implemented on the conventional lines.
