by slcguy
I was reading on wikipedia about the PRR GG1's, and the article said that the PRR catenary system was 11,000 Volts at 25 hz. Is this true, this seems a bit unusual to me.
Railroad Forums
slcguy wrote:I was reading on wikipedia about the PRR GG1's, and the article said that the PRR catenary system was 11,000 Volts at 25 hz. Is this true, this seems a bit unusual to me.Yes it is true. So why is that unusual?
amtrakhogger wrote:Because the standard is 25,000 Volts 60 Hzslcguy wrote:I was reading on wikipedia about the PRR GG1's, and the article said that the PRR catenary system was 11,000 Volts at 25 hz. Is this true, this seems a bit unusual to me.Yes it is true. So why is that unusual?
Allen Hazen wrote:One further complication (I'm testing my memory here, so somebody please correct me if I'm wrong): you don't want the power current to swamp the signalling track circuit, so choices have to be made. With a DC electrification, it's easy: use AC for the track circuit. With an AC electrification, choose a different frequency. I.i.r.c., the 25 hz electrificattions in the Northeastern U.S. used 60 hz track circuits, and when some were converted to commercial frequency, the signalling had to be redone! I think it is now 100 hz in trackage with 60 hz power electrification.In the early days of PRR electrification it was found the 100 Hz used for cab signals was a fourth-order harmonic of the 25 Hz catenary AC frequency (25 Hz x 4 = 100 Hz) and they subsequently changed the cab signal frequency from 100 Hz to 91 2/3 HZ to avoid the problems caused by these harmonics.
GE-RULES wrote:In the early days of PRR electrification it was found the 100 Hz used for cab signals was a fourth-order harmonic of the 25 Hz catenary AC frequency (25 Hz x 4 = 100 Hz) and they subsequently changed the cab signal frequency from 100 Hz to 91 2/3 HZ to avoid the problems caused by these harmonics.That is correct. However, most of the off-the-shelf equipment designed for 100Hz operation works fine on 91 2/3 Hz.
limejuice wrote:Yeah I would think it would work without any issues. Probably the only modification made (if any) would be a change in the low pass filters to allow for a cleaner signal instead of operating on the edge of a 100 Hz LPF, but who knows the 100 Hz LPF may be broad enough to pass 91 2/3 Hz just fine without any degradation in signal.GE-RULES wrote:In the early days of PRR electrification it was found the 100 Hz used for cab signals was a fourth-order harmonic of the 25 Hz catenary AC frequency (25 Hz x 4 = 100 Hz) and they subsequently changed the cab signal frequency from 100 Hz to 91 2/3 HZ to avoid the problems caused by these harmonics.That is correct. However, most of the off-the-shelf equipment designed for 100Hz operation works fine on 91 2/3 Hz.