POWER PLANT OPERATION

Mr. G. I. Rhodes, electrical engineer of the Interborough Rapid Transit Company of New York City, delivered the second of his lectures on "The Economics of Power Plant Operation" yesterday afternoon.

Mr. Rhodes first discussed the alternating current feeder system and gave an account of the troubles that had been experienced in making the first underground cables for an 11,000 volt system. He classified the causes for the burnouts into two groups: the first containing inherent faults in the cables, and the second accidental injuries to the cables. Under the latter head he mentioned the process of electrolysis.

Mr. Rhodes then took up the subject of the difficulties which had been met with in regard to surges started by feeder burn-outs. He went on to point out the value of induction generators which operate in parallel with turbo-units in limiting the excessive rush of short-circuit burn-outs. The direct current end of the system was then discussed. On the Interborough Rapid Transit Company about 88 per cent, of the alternating current power which is generated is delivered to the third rail. The losses which are sustained take place as follows: transmission, 2 per cent.; transformers, 3 per cent.; converters, 5 per cent.; and auxiliaries, 2 per cent.

Interborough System in New York.

The lecturer then began an explana- tion of the Interborough system feeder layout. He showed that it was designed especially to give the minimum variation of voltage on the third rail.

In closing, Mr. Rhodes mentioned the merits of installing the Tungsten lamps in all subway trains in New York, instead of increasing the size of the copper feeder which would be a very expensive step. A number of these Tungsten lamps have already been tried out, but until they are used throughout, the present trouble will remain. The carbon filaments of the lamps grow dim and almost go out when the train starts, due to the excessive voltage drop in the third rail. The superiority of the Tungsten lamp lies in the fact that its candlepower varies considerably less in proportion to the change in the third rail voltage