Eastern Railroad Discussion > Max # of Electric Engines in a Block?

Not sure where this question might go, but I’ll start here.  Considering that each electric (non-diesel) engine will pull X number of amps, there must be a limit as to how many engines can be in a consist.  I am thinking of mostly freight here.  I would guess it would depend on how many separate circuits in the block.

This could be a major limiting factor in the length of freight pulled by electrics.

Any  thoughts?
 

It depends on the capacity of the entire system from the overhead catenary system to the substations and on to the supply from the power company. 

Too many variables, I guess.
 
Thanks.
 

> there must be a limit as to how many engines can
> be in a consist.

You mean , there must be a limit assuming they're
all on line.

Probably none of us knows what limits it--
for all we know you could hook 20 units together
in one string, all on line, and run them, with
no train anyway. But SP used to limit it to 10.

On the hills, UP limits the tonnage pulled
by head-end units with no helper. Don't recall
whether they limit the head-end axles too.
Probably you're not allowed to have six AC
units on line on the head end eastward from
Roseville or Bakersfield, even if the tonnage is low?

Under catenary, there must be some substation
limit on the amps a train can pull at one spot,
but none of us knows what it is. Think we've seen
pics of four PRR E44s on a train, but we don't
know if they were all on line, and we don't know
how far out the engineer pulled the throttle.
 



Edited 1 time(s). Last edit at 01/28/19 15:39 by timz.

When NJ Transit provides service to the Hunt in Far Hills every year, about half the special trains are pulled by diesels.  The Gladstone Line is single track, overhead electric.


(That's the Far Hills Race Meeting, but I don't know anyone who actually calls it by that name...)

 

When I was at SEPTA in 1983 after taking over from Conrail, there were some restrictions on how many cars could be in a consist, and I think the limit was three or four on the Doylestown Branch.  The night of the strike, I took a train of seven MU cars from Doylestown to Reading Terminal, and the guidance I got was to not take a lot of power to avoid dumping the catenary.  We got to Reading Terminal just fine.  Since we were taking over from Conrail, who had taken over from Reading (was Penn Central involved, I think not), the long time restrictions were buried.  

I think that I once read somewhere that the Pennsy had to be very careful double-heading their GG1's in freight service...so much so that the throttle had to be set up to not it go past the 18 or so notch on the throttle.  Can anyone confirm my story?
 

Marty Harrison
Knob Noster, MO

Depends on the construction and infrastructure of the system and the capabilities of the power supply system. What the PRR constructed was much more capable than either the Reading, Lackawanna or other electric system which only operated electric commuter cars.

RWJ

livesteamer Wrote:
-------------------------------------------------------
> I think that I once read somewhere that the Pennsy
> had to be very careful double-heading their GG1's
> in freight service...so much so that the throttle
> had to be set up to not it go past the 18 or so
> notch on the throttle. 

We've recently seen several photos posted here of four GG1's on freight, all with pans up, which means all were running. I don't know of any restrictions, but it seems that if several heavy trains were all drawing lots of amps at the same time in a given electrical block, something could go boom in a substation.

The GN electrification between Skykomish and Wentachee (WA) had no specific limit on locomotives, but the train dispatchers were responsible for distributing the power among the trains, issuing train orders specifying maximum amps to draw.

https://www.trainorders.com/discussion/read.php?11,2301132,2301132#2301132

TAW

CPR_4000 Wrote:
-------------------------------------------------------
> ... it seems that if several heavy trains were all drawing lots of amps at the same
> time in a given electrical block, something could go boom in a substation.

And then nobody is moving. :)


The South Shore passenger service is careful about how many powered cars are moving on the same circuit at the same time. Generally there is on circuit per track in each direction from each substation. Under normal schedules trains are not close enough to be on the same circuit. When the South Shore runs extra trains (such as the Notre Dame specials) they try to space out the trains so only one is moving in a circuit at a time. Other trains can be present, just not moving.  The higher current draw of the new cars required upgrades on both the South Shore and the Metra Electric line.

One of the big questions is what is the voltage of the system, as the voltage goes up the Amps go down for a given amount of power(Watts).

See Wikipedia at Railway electrification system - Wikipedia https://en.wikipedia.org/wiki/Railway_electrification_system

Standard voltages are 600 V DC, 750 V DC, 1.5 KV DC, 3 KV DC, 11 KV AC 16.7 Hz, and 25 KV AC 50 or 60 Hz single phase (to train at specific points on the track.   Entire AC system is probably three phase, but with substantial phase break gaps when changing the phase.) 

There are variations.

Electrified rails are usually under 1 KV, or 1.5 KV if well protected.

Overhead conductors or catenary are used at any voltage.  For example, trolleys and subways are typically 500 to 800 volts.

Bill