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Re: Kopp and SF continue to fight over downtown hsr station
Author: Dr Zarkoff
Date: 09-24-2009 - 22:01
Ever since they figured out the benefits of 3 phases and built transmission systems around this scheme, power companies have long been loath to shoulder single phase loads. OPB's explanation is more detailed than any I've seen before. To deal with the problem of large single phase loads on a 3 phase system, the electrical industry developed phase conversion.
The Reading's Wayne Jct substation was built to do this using the technology of the time: rotating machinery. It also changed the commercial power frequency of 60 cycles to the Reading's 25 cycle needs.
About 25 years ago, SEPTA replaced the rotating equipment with ABB (ASEA Brown-Boveri) solid state frequency/phase convertors, which took 3 phase, 60 cycle AC, rectified it to 1200v dc, and then chopped and smoothed it into single phase AC (there are step down transformers before and step up ones after, and the input 3 phase may have been transformed to 6 phase before being rectified, don't remember).
It seems to me that this sort of solid state conversion equipment would work to accomplish the same end even if the output frequency is 60 cycles.
The issue of inductive interference with BATRD's signal system is an open question. One of the reasons 100 cycles was used for the signal power on the PRR's NEC and the SFOBB (and probably the NH too) is that it isn't an even multiple of 60 cycles, thus reducing the effects of inductive interference to a minimum (see the NTSB's latest on the WAMTA wreck) .
The Reading's Wayne Jct substation was built to do this using the technology of the time: rotating machinery. It also changed the commercial power frequency of 60 cycles to the Reading's 25 cycle needs.
About 25 years ago, SEPTA replaced the rotating equipment with ABB (ASEA Brown-Boveri) solid state frequency/phase convertors, which took 3 phase, 60 cycle AC, rectified it to 1200v dc, and then chopped and smoothed it into single phase AC (there are step down transformers before and step up ones after, and the input 3 phase may have been transformed to 6 phase before being rectified, don't remember).
It seems to me that this sort of solid state conversion equipment would work to accomplish the same end even if the output frequency is 60 cycles.
The issue of inductive interference with BATRD's signal system is an open question. One of the reasons 100 cycles was used for the signal power on the PRR's NEC and the SFOBB (and probably the NH too) is that it isn't an even multiple of 60 cycles, thus reducing the effects of inductive interference to a minimum (see the NTSB's latest on the WAMTA wreck) .
