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what is transition?

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what is transition?
Posted by ndbprr on Friday, August 7, 2015 8:24 PM
Please give me a technical description please.
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Posted by oltmannd on Friday, August 7, 2015 9:03 PM

Reconnection of the traction motors from pairs in series, with each pair in parallel, to all in parallel. You do this when the main generator can't produce as much current as the motors can take. You run in series-parallel at slow speeds, say up to 20 mph or so, then make transition to full parallel.  

Generally, when four axles got traction alterntors, they did away with transition.  No more having to push huge amounts of current out through a commutator.  

On modern six axles, the traction alternator make transition instead - with two sets of windings being in series or parallel.

 

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

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Posted by Leo_Ames on Friday, August 7, 2015 9:10 PM

As speed increases, traction motors rotate faster. This creates a resistance to current flow due to backelectromotive flow, which causes the main generator voltage to rise. As this increases, the generator can be damaged by the increased voltage. So to protect generators from their limitations, traction motor transition happens to combat this.

Transition motor transition is generally composed of four steps: Series-Parallel; Series-Parallel-Shunt; Parallel; Parallel-Shunt. These changes happened with relays originally, then circuit boards, and now microprocessors for older locomotives that have been rebuilt but retain their original generator with its associated limitations.

In the old days, well into the 1950's in some cases, transition had to be done manually with the engineer monitoring his transition meter. But for many decades now, it's usually automatic. And I don't believe that Baldwin diesels had to do this, one reason perhaps why they were reknown for their low speed lugging capabilities. 

As far as I know, the AC generator that became standardized with the Dash 2 line started to end this practice. Traction motor transition only happened on the SD40-2 and SD45-2 and derivitives. The SD38-2 and 4 axle EMD's were setup for permanent parallel operation. 

Essentially, it's to protect the generator from overheating due to exceeding its rating for an extended period of time. 

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Posted by erikem on Saturday, August 8, 2015 12:10 AM

Both Oltmannd and Leo Ames gave accurate and mostly complete answers. I'll add some extra details.

Transition is a bit like a car/truck transmission. Mechanical power is the product of RPM times torque, where electrical power is voltage times current. Going up a steep grade, the transmission will be put in a low gear, which reduces speed in return for increased torque at the drive wheels. Conversely, the transmission would be put in a higher gear on a level road reducing available torque at the drive wheels but increases the maximum speed possible. Traction motors draw a lot of current when producing high tractive effort, however the fixed output power of the prime mover requires that the voltage to be reduced. Conversely, at high speeds, the motor voltages are high, but current draw is low.

The culprit responsible for transition in the bad old days was the commutator on the traction generator. The maximum voltage that the generator could reliably produce was limited by flashover, where the sparks from the brush interacting with the copper segments (AKA bars) of the commutator would initiate an arc between segments (limit is about 20V per segment). Once the flashover started, the only way to stop it was reducing generator voltage to near zero. The maximum current draw from the generaor was limited by both the wiring of the rotating armature and the current capacity of the commutator.

If space or weight were not an issue, it would be possible to make the generator large enough to handle the full range of voltage and current demanded by the traction motors over the whole locomotive speed range.

The alternator has a couple of advantages. The lack of a commutator allows for considerably higher voltages to be generated. Having the load carrying conductors on the stator makes it easier to have larger conductors and also to easier to cool thse conductors.

Getting back to transition/transmissions: The drooping voltage vs current characteristic of a traction generator or alternator is equivalent to a torque converter. With a big enough torque converter, a car transmision could work with a single gear (e.g. Buick Dynaflow or Packard Ultramatic), but most have three or more forward gears.

Finally DC series motors have shunting to work around their voltage/current limits. For a given output torque and motor speed, shunting reduces the required voltages and increases the required current. Commutator motors have flashover limits as well, so getting maximum power to a motor at high track speeds will often requiring field shunting.

 - Erik

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Posted by blue streak 1 on Saturday, August 8, 2015 5:26 AM

Wasn't there a SOU RR wreck of the Crescent in  Va due to engineer trying to get loco to transition and train overspeed happened ?

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Posted by timz on Saturday, August 8, 2015 4:43 PM

Leo_Ames
transition is generally composed of four steps: Series-Parallel; Series-Parallel-Shunt; Parallel; Parallel-Shunt.

In 1950, he means. No road engine built since 1972 has used shunting, has it?

In the old days, many locomotives never used full parallel. Did any Baldwin?

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Posted by Wizlish on Saturday, August 8, 2015 5:10 PM

blue streak 1

Wasn't there a SOU RR wreck of the Crescent in  Va due to engineer trying to get loco to transition and train overspeed happened?

Shipman, 1978.  NTSB RAR-79-04:

http://www.ntsb.gov/investigations/AccidentReports/Pages/RAR7904.aspx

http://specialcollection.dotlibrary.dot.gov/Document?db=DOT-RAILROAD&query=%28select+4028%29

(Note the PDF download icon at the bottom of the frame)

There is a brief description of transition on E8s on p.17. 

IIRC the lack of automatic reverse transition was observed to cause problems on PRR/PC when E units began to be used in freight service (e.g. on TrucTrains) - main generator flashover was what I remember seeing but I have no direct reference to post.  The 'solution' is to reduce the throttle all the way to zero when reducing speed, but freight crews (especially those familiar with more modern locomotives) might not have this 'learned' reflex...

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Posted by Leo_Ames on Monday, August 10, 2015 8:15 AM

timz

 

 
Leo_Ames
transition is generally composed of four steps: Series-Parallel; Series-Parallel-Shunt; Parallel; Parallel-Shunt.

 

In 1950, he means. No road engine built since 1972 has used shunting, has it?

 

In the old days, many locomotives never used full parallel. Did any Baldwin?

 

To the best of my knowledge, traction motor transition after 1950 still typically involved shunting (field weakening). 

Why do you think it didn't? I'm not expert, so if I'm wrong, I'd love to see you post any details you may have on this topic. But to the best of my knowledge, it certainly was still there such as with EMD's 35 series, like the GP35, and the high horsepower six axle Dash 2's where it's my understanding that variable field shuting is handled by a circuit board that handles traction motor transition. 

And while I don't know what "full parallel" is, many Baldwin diesels (Unsure about those intended for passenger service) are fairly well known for having their traction motors connected in parallel, with no traction motor transition happening as a result. It might not be full parallel, but they are permanently connected in some form, in this manner.

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Posted by daveklepper on Monday, August 10, 2015 8:39 AM

Field weakening thru field shunting was a requirment in the days of dc motors with the armeture and field normally in series (with one or the other reversed in polarity for reverse in direction) and all connections made and broken by operation of relays.  I do not understand any reason for field weakening with rotating bar non-commutator pure ac motors, having commuter control of the current and voltage in the field coils and the current in the rotating bars achieved only through induction from the field coils.  There is absolutely zero reason for shunts across the field coils for these motors.  However, switching from all-in-seiries, to series-parallel, to all-in-parallel may result in greater efficiency over a wide speed range.  Even this is less necessary than with dc motors, and I would not be suprised to hear of pure ac diesel-electrics that lack any transition.

Whether maximum speed operation is obtained with full parallel, that is all motors in parallel, or series parallel, depends on the rated and operating voltage of the motors and that of the electrical source, be it an alternator, generator, or third rail, or catenary, or batteries, or whatever (fuel cell, atomic pile?).  The Little Joes on the Milwaukee had full series operation at low speed and series parallel at high speed.  On the South Shore they had series-parallel at low speed and full parallel at high speed.  (The were wired as two separate four-motor locomotives in parallel for redundancy.)   They had three steps of transition, and used field shunting in both the low-speed and high-speed motor conntections at the upper speed range of each connection.

The Quill-connected ac-commutator motor GG-1s and New Haven EF-3's that were never required to run on dc, like the EP-3s and EP4s, also did not use field shunting.  This is because the multitap-transformer many-step throttle control gave enough flexibilty in input voltage to the motor that field shunting was unnecessary.   Or maybe it had been applied when new and removed?   This happened to the North Shore Electroliners (pure dc), or perhaps it was installed and never conntected.

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Posted by NorthWest on Monday, August 10, 2015 11:43 AM

Leo_Ames
But to the best of my knowledge, it certainly was still there such as with EMD's 35 series, like the GP35, and the high horsepower six axle Dash 2's where it's my understanding that variable field shuting is handled by a circuit board that handles traction motor transition.

The SD/GP35 were the last and largest locomotives to use the traditional bank of relays to achieve transition. Due to their power, this required a lot of relays which often failed. This was their primary cause of lack of reliability. After that, EMD went to solid state electronics, though not the modular types the Dash-2 series used until the DDA40X.

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Posted by timz on Monday, August 10, 2015 2:40 PM

Leo_Ames
high horsepower six axle Dash 2's where it's my understanding that variable field shuting is handled by a circuit board that handles traction motor transition.

Don't recall if Elwood's site has GP/SD40-2 service manuals-- if it does, you'll see no mention of shunting.

(Turns out he has GP38-2 and GP40-2-- no SD40-2.)

http://www.rr-fallenflags.org/manual/manual.html

Baldwin road B-Bs always? had two motors in series. The C-C's might have gone from three in series to two in series, but I suspect none of them went to full parallel.

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Posted by Randy Stahl on Monday, August 10, 2015 4:56 PM

I've never seen a dash 2 with field shunting.

On the interurbans field taps were installed inside of the traction motors. No external reistors were used. Field tapped equipment have 5-6 traction motor leads.

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Posted by Phelps on Monday, August 10, 2015 7:02 PM
The reason for the different motor connections on the Milwaukee versus South Shore Little Joes was, of course, that the Milwaukee was 3300 V DC nominal and the South Shore was 1500 V DC. So, the final connection of each gave ~1500+ volts across the individual motors.
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Posted by Leo_Ames on Monday, August 10, 2015 7:59 PM

timz

 

 
Leo_Ames
high horsepower six axle Dash 2's where it's my understanding that variable field shuting is handled by a circuit board that handles traction motor transition.

 

Don't recall if Elwood's site has GP/SD40-2 service manuals-- if it does, you'll see no mention of shunting.

 

(Turns out he has GP38-2 and GP40-2-- no SD40-2.)

http://www.rr-fallenflags.org/manual/manual.html

Baldwin road B-Bs always? had two motors in series. The C-C's might have gone from three in series to two in series, but I suspect none of them went to full parallel.

 

I don't know if Baldwin BB's always did. I'm hesitating in stating that this is a case for every Baldwin diesel locomotive, since I'm in no position to lodge such a claim.

I would think that transition would be especially useful for higher speed power, aiding the locomotive in quickly accelerating to the upper ranges of its capabilities, for instances where perhaps this standard wasn't exactly standard. But that many Baldwin diesels did have their traction motors permanently connected in parallel, is to the best of my knowledge, a well established fact. 

As for the Dash 2 series, what's variable field shunting then? I've seen that mentioned several times as a duty handled by its electronics, presumably by the same circuit card (s?) tasked with handling traction motor transition. 

I thought it was essentially the same principle, just allowing many more stages of traction motor transition for the greatest efficency and performance possible with the technology, compared to the old relays and such that were creating servicing and reliability issues as horsepower rose and they became more complicated. 

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Posted by daveklepper on Tuesday, August 11, 2015 9:32 AM

But do not forget that field shunting does mean loss of some power in the shunting resistors themselves.

On the North Shore Electroliners, the decision was made not to use the field shunting that the motors had because top speed and acceleration were both sufficient without use of field shunting.  But one step of transition, from series to parallel (each two-motored truck), was used.   As I remember, and as exemplified by 709 at Branford, the standard equipment was typical with three transitions and field shunting.

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Posted by timz on Tuesday, August 11, 2015 12:29 PM

Leo_Ames
that many Baldwin diesels did have their traction motors permanently connected in parallel, is to the best of my knowledge, a well established fact.

In series-parallel, you mean.
Leo_Ames
I've seen that mentioned several times as a duty handled by its electronics
Try to find it in the GP38-2 or GP40-2 service manual.

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Posted by Leo_Ames on Tuesday, August 11, 2015 2:46 PM

timz
Try to find it in the GP38-2 or GP40-2 service manual.

I'm just passing along what I've read. I don't vouch for its level of accuracy.

That said, if it's a function integrated into one of the circuit boards, I'm not sure I would find it, even if it is happening like I've read?

Beyond basic diagnostics, I don't think it goes into great detail and only provides the basic functionality of each card. Or at least that's how it essentially looks to me.

There's no need for the person servicing the locomotive to know much more than basic troubleshooting where the cards inserted into the Dash 2's electrical cabinet are concerned. Check the manual and proceed to pull the offending card that's associated with a particular problem, and replace it. 

They're not actually doing any repairs to the circuit board itself. That's sent off to a 3rd party vendor if it's to be refurbished. 

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Posted by Wizlish on Tuesday, August 11, 2015 5:59 PM

daveklepper
On the North Shore Electroliners, the decision was made not to use the field shunting that the motors had because top speed and acceleration were both sufficient without use of field shunting.

I read something about this - Dave Klepper probably remembers where.  In the reference they called it 'field weakening' and it was done with coils.  The apparatus was in place for one test run, during which apparently speeds of 108 mph were reached (on the comparatively small-diameter Electroliner wheels).  Promptly at the conclusion of the test the coils were physically torched off...

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Posted by Randy Stahl on Tuesday, August 11, 2015 6:29 PM

The Electroliner didn't have field shunts , it had field taps on the field coils.

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Posted by Leo_Ames on Tuesday, August 11, 2015 7:05 PM

There's a story in Trains about that. They were beating the grade crossings, which as I recall, is the reason why.

The story said that it was disabled but left in place, and could been easily enabled again with just a few minutes of work but never was.

If I'm not dreaming it, the other set also was modified in this way, but never ran a test. 

Edit: The Trains story I remembered was from November 1982.

It says that they were built with field taps, but that the Electroliners were designed for the installation of field shunts but weren't originally built with them. The 801-802 was modified in this way in December 1950, successfully raising the top speed well past the century mark. 

It was disabled after the test because they were almost overrunning grade crossing protection, and out of concern of sustained 100mph+ operation on 31 1/4" wheels. 803-804 got this modification in May 1951 and ran a test before it too was disabled. 

The ballast coils were eventually torched off several years later since they interfered with routine inspections, according to this story in Trains that includes a 1st hand account from the man that cut the ballast coils off. But while automatic field shunting couldn't be done without them, they'd of only needed about an hour of work in the shop to enable manual control. 

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Posted by M636C on Tuesday, August 11, 2015 11:52 PM

Nobody seems to have mentioned the EMD "Super Series" wheelslip control system, which (ironically, given the name) required all motors to be permanently connected in parallel.

This was used in the 50 and 60 series, and after using the AR16 alternator in earlier SD50s (twice the size of an AR10), they adopted transition inside the alternator in the AR11 and following designs, where effectively two separate alternators on the same shaft switched between parallel at starting for high current to series at higher speed for high voltage.

The older units with the AR16 were liked by crews because there was no transition at all, and in Australia 84 JT26C-2SS units fitted with AR16s have found a niche for more than thirty years dragging heavy grain trains up steep grades. They have had two complete rebuilds in that time maintaining the same basic specification.

I believe GE had transition within the alternator on later DC six motor models.

M636C

NDG
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Posted by NDG on Wednesday, August 12, 2015 2:50 AM

Odds and Ends.

Here is a Enginemen's Manual illustrating the C-Line Locomotive w/ Westinghouse Equipments, which contains Electrical Schematics.

http://www.rr-fallenflags.org/manual/clc-opsman.pdf

When ' Making Upward Transition' around 20 MPH, there were two soft clicks from within the Electrical Cabinet.

When Throttle first opened, there were two separate Clicks from within Electrical Cabinet.

When Throttle closed, two Pneumatic-like Clicks.

Good locomotives, held rail very well and pull for hours and not complain.

Expensive to operate as beaten in all their lives on 1% or more for hours, at 100 F or 30 Below near or in the Red continously.

Here are some photos from 1971 illustrating lift rings and fans, etc.  Both had S/G at one time.

CP 4065.

CP 4104.

I have never seen lift rings, front nor rear used in a Rwy. Shop.  Not enough height clearance??

CP 4105.

http://www.railpictures.net/viewphoto.php?id=392814&nseq=3


Thank You.

 

 

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Posted by Wizlish on Wednesday, August 12, 2015 5:52 AM

NDG
I have never seen lift rings, front nor rear used in a Rwy. Shop. Not enough height clearance??

I think of these rings the same way I think of 'hardpoints' on an airframe.  There are very limited places you can tie onto a covered-wagon structure to lift or move it, and the rings are connected to the 'right' internal structure in the 'right' ways to allow lifting without distortion or damage.

As noted in the 'other' thread (now identified just by a period in its title, ".") a predominant use of the rings was in wrecks, to allow the locomotive to be lifted or moved with cranes.  In a shop it's probably easier to use jacks, or spreaders under the underframe if lifting with an overhead crane, but I defer to people with direct knowledge.

NDG
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Posted by NDG on Wednesday, August 12, 2015 10:28 AM

More Data. re Lifting Locomotives from CLC Manual in previous.

SECTION 238. WRECKER LIFTING DATA 'C' LINE UNITS
LIFTING PRECAUTIONS
Maximum Permissible Span
Diesel-electric locomotive frames are designed to be supported at the bolsters. Frames can be damaged when too long a span is allowed between points of sling support. This applies whether the lift is made from couplers or from front or rear jacking pads, or rear collision post special lifting lugs.
All "C" Line locomotives can be lifted at the extreme end PROVIDED the other end is supported AT THE BOLSTER.
Lifting with Trucks Attached
Where it is necessary to lift units at the extreme ends, trucks should be dropped. This lowers the weight lifted 43 to 50 tons depending upon the type unit involved.
However, frames used on "C" Line locomotives are amply strong to permit lifting operations with the trucks attached as long as one end is supported at the bolster. If trucks are to be lifted with the car-body, springs should be blocked; and blocking placed between journal boxes and pedestal tie bars. This will reduce the required lift to a minimum.
Lifting at Couplers
As an emergency lift in case of a wreck, a unit may be lifted by the coupler shank provided proper blocking is used between the top and sides of coupler shank and coupler pocket. Although this operation has been done without damage, it should only be used in extreme emergencies. A new coupler should be available as breaking or bending of the coupler is likely to occur.
Truck Center Plate Protection
Where one end only of a unit is lifted, care must be taken to avoid breaking the center plates between truck and bolster at the other end. Although one end can drop considerably BELOW rail height without damage to the liners on the truck remaining on the rail, the same does not apply when the derailed end if lifted ex-cessively high.


Some clearance is provided to absorb normal deflections, but in rerailing this i s mostly absorbed by deflection of the truck springs. Lift of one end only should never exceed 8" above the rail unless the other end is lifted sufficiently to separate the center plates on its truck and bolster. This precaution must be taken both under wreck conditions and in maintenance removal o f a truck.
Use of Special Lifting Lugs on Square End Collision Posts
Special lifting lugs can be applied as an extra at the top of square-end collision posts on "C" Line units. (Nose ends have lifting pads accessible through removable covers on each side of the pilot. All pads are designed for use with the standard railroad wrecker hooks without the use of special lifting levers.
These special collision post lifting lugs are designed for VERTICAL lifting only. Any attempt to slide the locomotive by attaching to these lugs will most likely result inconsiderable additional damage.
LIFTING DATA
Lifting Pads
At bolsters, square end corners, and at nose end. Pilot side openings with bolted covers for wrecker hook access to nose end pads. All pads designed for use with standard R-1044 railroad wrecker hook without use of lifting levers.
Bolster lifting pads designed to be lifted using 8055964 lifting device in common use in railroad diesel shops.
Standard Lifts
1. At bolsters.
2. At end lifting pads if opposite bolster is supported.
3. Vertical lift only on square end collision post lugs.
Emergency Lift
By coupler shank if opposite bolster is supported.

 

Thank You.

NDG
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Posted by NDG on Friday, August 14, 2015 12:54 AM

Addendum.

In this case D/B means, in addition, Dog's Breakfast in regards to Transition as several Diciplines in use here with different characteristics, gearing and full time ratings.

On a mixed-builder consist the headlights were NOT Trainlined thru and to operate the Headlight on the trailing unit for a reverse move, the Trainman or Fireman would have turn it On/Off from the trailing cab. B Units had a switch inside rear door.

Rear headlights on cab units were moveable between cab units and plugged in to a receptical near mounting bracket, and often there was not a light there when required.

Some Engineers would put one up themselves. Others would whine and go without, blaming it all on the Shops.

On a long back up move with a B-Unit leading, the Trainman stood in a side engineroom door. Ditto an A backing Up.

Saved arm wear or getting brushed off at speed by bushes and deep snow above stirrups

Thank You.

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Posted by oltmannd on Friday, August 14, 2015 7:48 AM

Leo_Ames

 

 
timz

 

 
Leo_Ames
high horsepower six axle Dash 2's where it's my understanding that variable field shuting is handled by a circuit board that handles traction motor transition.

 

Don't recall if Elwood's site has GP/SD40-2 service manuals-- if it does, you'll see no mention of shunting.

 

(Turns out he has GP38-2 and GP40-2-- no SD40-2.)

http://www.rr-fallenflags.org/manual/manual.html

Baldwin road B-Bs always? had two motors in series. The C-C's might have gone from three in series to two in series, but I suspect none of them went to full parallel.

 

 

 

I don't know if Baldwin BB's always did. I'm hesitating in stating that this is a case for every Baldwin diesel locomotive, since I'm in no position to lodge such a claim.

I would think that transition would be especially useful for higher speed power, aiding the locomotive in quickly accelerating to the upper ranges of its capabilities, for instances where perhaps this standard wasn't exactly standard. But that many Baldwin diesels did have their traction motors permanently connected in parallel, is to the best of my knowledge, a well established fact. 

As for the Dash 2 series, what's variable field shunting then? I've seen that mentioned several times as a duty handled by its electronics, presumably by the same circuit card (s?) tasked with handling traction motor transition. 

I thought it was essentially the same principle, just allowing many more stages of traction motor transition for the greatest efficency and performance possible with the technology, compared to the old relays and such that were creating servicing and reliability issues as horsepower rose and they became more complicated. 

 

I don't think any Dash 2 had field shunting.  The last EMD locomotives with field shunting were SD45s.

The increasing voltage rating of rectifying diodes eliminated the need for field shunting.

The "poster child" for field shunting was the GP35.  What a dog!

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

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