Transitioning

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Transitioning
Posted by CW45 on Friday, July 06, 2018 8:41 AM

I have read that in the first days of diesel locos, and pretty far into more modern ones, the engineer would have to make the transition from the traction motors being all in series at start up, to truck motors in parallel, but trucks in series, to all traction motors in parrallel at speed.  He also had a resistor bank to handle back EMF he had to deal with and he did this all himself.  Of course mistakes could be catastrophic.  It became more automatic as the technology changed,  to now I am sure total computer control where the engineer just advaces the throttle.  But, would love to have an older engineer describe what he did to get the trian moving and up to speed and all the circuits he handled to do so.

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Posted by timz on Friday, July 06, 2018 1:16 PM

CW45
He also had a resistor bank to handle back EMF he had to deal with

Don't think you'll find any mention of such a thing in any operating manual. Early diesels had resistors for field shunting, but the engineer didn't worry about them.

You'd think manual transition would be a simple enough thing for the engineer to handle-- watch the amp gauge and when it reaches 700 amps (or whatever) you switch to series-parallel. Apparently RRs found you couldn't trust the engineer that much, so automatic transition has been the usual since... middle 1950s?

Road engines never connected all their motors in one series string. Some early C-Cs never got into full parallel either -- they went from three motors in series to two in series, and that was it.

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Posted by oltmannd on Friday, July 06, 2018 2:55 PM

timz

 

 
CW45
He also had a resistor bank to handle back EMF he had to deal with

 

Don't think you'll find any mention of such a thing in any operating manual. Early diesels had resistors for field shunting, but the engineer didn't worry about them.

You'd think manual transition would be a simple enough thing for the engineer to handle-- watch the amp gauge and when it reaches 700 amps (or whatever) you switch to series-parallel. Apparently RRs found you couldn't trust the engineer that much, so automatic transition has been the usual since... middle 1950s?

Road engines never connected all their motors in one series string. Some early C-Cs never got into full parallel either -- they went from three motors in series to two in series, and that was it.

 

Last locomotives I knew of that didn't have completely automatic transition were the RDG SW1000s.  The had automatic transition from series-parallel to parrallel, but not in the other direction.  Don't know why, but Conrail modified them to fully automatic.

-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/

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Posted by blue streak 1 on Friday, July 06, 2018 8:30 PM

SOU RR had a passenger train overturn due to high speed because engineer could not get loco to transistion.  Details lost to time.  Anyone ?

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Posted by Randy Stahl on Saturday, July 07, 2018 5:36 AM

oltmannd

 

 
timz

 

 
CW45
He also had a resistor bank to handle back EMF he had to deal with

 

Don't think you'll find any mention of such a thing in any operating manual. Early diesels had resistors for field shunting, but the engineer didn't worry about them.

You'd think manual transition would be a simple enough thing for the engineer to handle-- watch the amp gauge and when it reaches 700 amps (or whatever) you switch to series-parallel. Apparently RRs found you couldn't trust the engineer that much, so automatic transition has been the usual since... middle 1950s?

Road engines never connected all their motors in one series string. Some early C-Cs never got into full parallel either -- they went from three motors in series to two in series, and that was it.

 

 

 

Last locomotives I knew of that didn't have completely automatic transition were the RDG SW1000s.  The had automatic transition from series-parallel to parrallel, but not in the other direction.  Don't know why, but Conrail modified them to fully automatic.

 

Generator flashovers. There never seemed to be a problem with the engineers making forward transition. The problem was the train slowing down and the engineers not making backward transition. 

I worked with some FP7s or F7s that had all manual transition. I think we had some GE U series on the milwaukee that had a motoring lever also. 

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Posted by CSSHEGEWISCH on Saturday, July 07, 2018 6:44 AM

Even after automatic transition became the standard, a manual transition lever could still be found on many throttle stands.

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Posted by SD70Dude on Sunday, July 08, 2018 1:41 AM

Our F3A has a manual transition lever on the control stand, but the last position is automatic.  In that position would it automatically transition one-way, but require manual intervention in the other direction?

Due to our slow operating speeds we never get out of first (can't remember the position names).

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Posted by zardoz on Sunday, July 08, 2018 10:10 AM

With multiple locomotives in the consist, the Engineer had to pay attention to the feel of the power as the train neared transition speed. One did not want all locomotives to transition at the same speed--if they did it could result in unwanted slack action due to surges in pulling power. If the Engineer determined that transition was happening at the same time, he might briefly reduce the throttle position during transition.

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Posted by M636C on Sunday, July 08, 2018 7:12 PM

The early SD50s had no transition, and all the motors were in parallel all the time. The motors permanently in parallel was a requirement for the super series wheelslip system.

This required a huge alternator, the AR 16 which was the same diameter as an AR10 but twice as long.

In Australia, we bought 99 locomotives with this electrical gear but with 3000HP 645E3B engines. Most of these are still in service. Many have spent their entire lives hauling grain on steep grades, and they have had a number of major overhauls to keep them in top condition indefinitely. Others have been sold off to shortline operators but keep working even though they look pretty sad.

Later locomotives had the AR11 alternator (similar in size to the AR10) that had two windings that could be connected in series for high speed (and high voltage) and in parallel for low speed (and high current). The GE "GRG" alternators were similar. So the only transtion was in the alternator itself. The AR11 was limited to 3830 HP, so the SD60 was limited to this power although the engine was good for 4000HP.

Since AC motors run at a speed determined by the frequency and not the voltage they don't need transition.

Peter

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Posted by erikem on Sunday, July 08, 2018 10:30 PM

M636C

Since AC motors run at a speed determined by the frequency and not the voltage they don't need transition.

There may be some advantage to have a "dual voltage" winding to be connected in parallel at high speeds and in series at low speeds. This would be more important with a permanent magnet synchronous motor as the terminal voltage will vary directly with speed.

 - Erik

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Posted by M636C on Monday, July 09, 2018 6:15 AM

erikem
 
M636C

Since AC motors run at a speed determined by the frequency and not the voltage they don't need transition.

 

 

There may be some advantage to have a "dual voltage" winding to be connected in parallel at high speeds and in series at low speeds. This would be more important with a permanent magnet synchronous motor as the terminal voltage will vary directly with speed.

 - Erik

 
I was thinking of asynchronous "squirrel cage" motors which are, as far as I know, used in the great majority of rail traction applications.
 
I know the French have used synchronous motors in their electric locomotives and in some TGV trains but I think they are now using asynchronous motors as elsewhere.
 
I have heard that permanent magnet motors have been proposed for use in submarines, where the atmospheric conditions around the motor can cause very rapid deterioration of insulation.
 
Peter
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Posted by erikem on Monday, July 09, 2018 11:23 PM

I remember sitting through a presentation of GE's research into synchronous traction motors. One reason is that efficiency would be improved at very low speeds  where the slip with an induction motor isn't much less than the rotational speed. Another is that the permanent magnets would produce a higher rotor flux density resulting in more torque for a given motor current.

I am guessing that one reason for the French using synchronous motors was that they would assist with the commutation of the thyristors in the inverter. We should be seeing locomotive sized SiC FET modules in the near future.

 - Erik

 

NDG
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Posted by NDG on Tuesday, July 10, 2018 11:04 AM
 
FWIW.
 
Example.
 
Transition.
 
DL&W EMD  F3 Manual. 1946.
 
 
From this site.
 
 

Thank You.

 

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