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   Author  Topic: Motors  (Read 2922 times)
ClydeDET
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Re: Motors
 
« Reply #20 on: Apr 21st, 2006, 3:01pm »
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Well, the issue of transition between series, series /parallel, and parallel and reliability of relays to effectuate it would seem to be dealt with by the avriosu loco handbooks, and the discussions in such sources of historical descxription of loco operation as EARLY DIESEL DAYS ON THE SANTA FE (McCall)  or THE PA-4 LOCOMOTIVE.  THE little book on the "PA-4" (the M-K rebuilds of the ex-Santa Fe PAs for D&H with 251 prime movers, up-dated controls, etc) has quite a discussion of transition and how it was effectuated. Relays. Worked. Reliably. Same can be said for the controls on EMD locos, at least in teh early days.
 
Obviously - controls and mechanisms have changed 9and usually improved) over the years, with mechanical relays replaced by various solid-state devices and such.
 
COntrol of diesel-electric 9or for that matter - straight electric - locomotives isn't a matter of brute force and ignorance in action; really quite subtle and not all taht elegantly simple. Sometimes - would that it were...


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LV LOU
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Re: Motors
 
« Reply #21 on: Apr 22nd, 2006, 3:59pm »
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Actually,yes,they do transition on the fly,I recently found out.I was in an SD50,and you can both feel and hear the change.It's kind of awe inspiring to suddenly hear a huge " "thud" in something as big as an SD50,and get thrown back in the seat as it "shifts".

« Last Edit: Apr 22nd, 2006, 3:59pm by LV LOU » Logged

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jrz126
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Re: Motors
 
« Reply #22 on: May 23rd, 2006, 2:03pm »
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I have an internship at GE Transportation and I've been working on a simulator for about a year now. I've learned quite a bit as to how everything operates, both the locomotive and the controlling software that drives it.
 
First off, the controller can regulate the HP, Volts or current depending on the situation. Like when a train is just starting to move. it will require a large amount of current, so it will try to hold the current at a fixed level. Once it gets moving, the current comes down. So then it will try to hold the HP at a constant. It can also regulate the voltage. (I'd love to post some of the motor/alternator characteristic curves, but I dont think the managment would approve)
 
The traction motors are capable of transistions, I think they might even connect 2 tm's in series...but I havent had to include transistions on the simulator yet, and I dont have a schematic that involves transistions either. Certain Alternators are capable of transitions as well (Multiple windings inside).
 
Oh and the engines typically turn at 1050RPM max and 400 in idle.
 
It's amazing as to how much programming goes into controlling the Locomotives.


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towny72
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Re: Motors
 
« Reply #23 on: May 23rd, 2006, 7:03pm »
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JRZ i would guess this is on modern GE locos. And is how they get such high adhersion, limited wheel slip.......and why EMD needs to pick it up!

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silver_champion
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Re: Motors
  k149.jpg - 69197 Bytes
« Reply #24 on: Jan 25th, 2007, 12:22pm »
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Here is a picture of the engines inside of the E&F units

http://Forums.Railfan.net/Images/DieselTypes/k149.jpg
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silver_champion
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Re: Motors
  emdE8a.jpg - 70167 Bytes
« Reply #25 on: Jan 25th, 2007, 12:26pm »
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This is a picture of the motors of the E&F units

http://Forums.Railfan.net/Images/DieselTypes/emdE8a.jpg
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xpnctoc
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Re: Motors
 
« Reply #26 on: Dec 3rd, 2007, 6:19pm »
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on Mar 23rd, 2005, 11:30am, Cody wrote:       (Click here for original message)
I have never seen 4400 horses in one place and I have no idea what they could pull.    

 
  I had to laugh at that one. I don't know how much 4400 horses could pull either, but I do believe it would be considerably less than a 4400 "horsepower" locomotive could pull.  
 
Somewhere along the line I thought I read that when steam engines were invented the term "horsepower" was assigned a value considerably higher than the workload an actual horse could do. The idea was not to piss off those purists who thought such machines would never be as practical as the animals.
 
Of course, how they ended up with the formula Watts x 746 = HP is beyond me and seems rather arbitrary, but why break the Imperial measurement tradition and do anything with rounder numbers!?  


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CN Sparky
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Re: Motors
 
« Reply #27 on: Mar 22nd, 2008, 9:32pm »
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I know this thread goes back a while.. but I figured I could chime in with some specs and info that might satisfy the appetites of the curious. I apologize in advance if I go a little technical in my explanation.. some of it gets pretty complicated.... I find it helps to take notes on scrap paper... I like doing drawings with arrows
 
Ok, take a GP9 switcher for example. Our road/yard/switchers are rebuilt ones, 1800hp. They actually have three different power sources, which run the different electrical systems.  
 
1. The diesel engine drives the main generator (a "D14" model), which generates DC power for the traction motors.  
 
2. Physically connected to the main generator, but electrically separate, is an alternator which produces AC power for the cooling fans (radiator and traction motor blower fans; also fed to the traction motor blower fans in the slug on master/booster units), fridge (if it's an AC model) and any other AC electrical components.  
 
3. Lastly, there's a separate auxiliary generator mounted on top of the main generator, driven by gears thru a coupler at three times the engine rpm. Most units have a DC aux gen, but some have been converted to AC units. Unlike the main gen, the aux gen is self-excited. A voltage regulator keeps the aux gen at a constant 74 volts.
 
The auxiliary generator is very important... it feeds all the electrical systems on the locomotive - the controls, lights, contactors, computers, modules, etc. Most importantly, it provides field excitation for the D12 main generator and the D14 alternator. Without that field, the main gen doesn't produce any power for the traction motors...  
 
Now, you don't need to know this... but I find it pretty interesting, exactly how complex these old "main generators" actually are... skip ahead if you find this dull, most people do. I won't be offended
 
The main generator (D12 from here on in) has six different fields in it:  
 
1.Starting field, which is powered by the batteries to start the engine (using the D12 as a big starter motor)
 
2. Battery field, which is also fed from the batteries, produces the excitation field in the D12 which generates "main power" for the traction motors
 
3. Shunt field, which reduces the amount of excitation required, as D12 voltage increases. We achieve this by connecting external resistors in series with this winding.
 
4. Differential field, which acts in opposition to the battery field, helps to maintain a constant kilowatt output. In turns, this improves loading characteristics, by making it easier for the excitation control system to affect D12 output with only small changes in the battery field.
 
5. Compensating field, which effectively weakens the main field by distorting it at right angles. This cancels the effects of the magnetic field produced by load current in the armature.
 
6. Commutating field, last but not least.. to make my job easier, or so I like to think. This field minimizes the amount of arcing on the carbon brushes, so I have to change them less often (which I appreciate!!) I suppose it makes the D12 last longer too, so that's a good thing.
 
 
Ok, did I lose everyone yet? Ha ha, sorry about that... now, we've got all this DC power for tractive effort, AC power for blower motors, low voltage (74 volts DC, it still shocks people...) for all the electrical system... what to do with it!
 
The traction motors on the yard engines are a "D78" which is a rebuilt D77 motor. They are rated for 850 hp each, but they tend to overheat at high currents so you can't pull that much power for very long. Maximum continuous rating is something around 950 amps.. pretty good for such an old design.  
 
 
As far as transition and series/parallel/series-parallel goes.. well, that's a whole other thread in itself. I posted a bunch of info about the slug transition in the "slugs" message... but in general...
 
EMD GP38's, SD40's, etc, do transition from series to parallel with pairs of traction motors, just like the yard engines do... using a bunch of electromagnetic switchgear aka 'contactors'.  
 
Starting with the SD50's (54xx's), the main gen (actually it's an AR10 alternator... but the rectifier assemblies are part of the alternator assembly... so most people still call it a "main gen") was divided electrically into two halves... a giant contactor is used to connect the two halves of the alternator in series at higher speeds... that contactor is rated at 1000V and 5000A (no, that's not a typo! Five thousand amps...). Big stuff... most of the smaller contactors are puny in comparison, but they're still pretty beefy.. but I digress. Even the brand new 88xx's still do transition in the alternator.
 
GE's, on the other hand... their excitation control system is totally different and much better than the EMD method (in my humble opinion!). The excitation system regulates the output voltage and amps, which eliminates the need for traction motor or alternator transition. There are still contactors, which are used to connect the traction motors in parallel, but they are used to disconnect the TM's from the main power when reversing direction, going into Dynamic Braking, etc... not for transition. There are far fewer power contactors in a GE compared to an EMD. The main alternator produces AC power, which is rectified externally using nine rectifier modules... but now I'm getting into nitty-gritty details.. maybe more than I need to...!?
 
 
FYI, the 8 notches each correspond to an amount of horsepower. Voltage, amps, etc, vary depending on load. Things like wheel slip can derate the power temporarily. Systems such as the load regulator (on EMD's), and excitation control system (GE's) maintain constant horsepower operation, as train speed varies... those systems get pretty complicated, and I don't even know all the details there
 
Here's an example... GE Dash 8 locomotive... Notch 1 puts out 175 hp, Notch 2 = 400 hp, etc... notch 7 is 3350, and notch 8 is 3990. But here's the odd bit.. Notches 3 through 6 are all 888 engine rpm, it's through changes in the excitation control system that produce the extra power while maintaining constant engine rpm.
 
I was doing a load test earlier this week... GE Dash 9, it was putting out close to 4500 hp at times... around 1260 volts and 2500 amps. Makes for a very warm hairdryer....!!


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Robbman
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Re: Motors
 
« Reply #28 on: Apr 22nd, 2008, 4:32am »
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on Mar 22nd, 2008, 9:32pm, CN Sparky wrote:       (Click here for original message)

 
The traction motors on the yard engines are a "D78" which is a rebuilt D77 motor. They are rated for 850 hp each, but they tend to overheat at high currents so you can't pull that much power for very long. Maximum continuous rating is something around 950 amps.. pretty good for such an old design.  
 

 
 
Not exactly an old design (well... not as old as a GP9 came with), a D78 is basically a D87 (introduced with the 50 series) armature in a D77 (introduced with the 40 series) case... interchangeable with the orignal D47 motor.


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Pilot.Dean
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Re: Motors
 
« Reply #29 on: Jul 29th, 2008, 10:23pm »
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CN Sparky,
 
Thank you for an informative and well written post.  
 
This appears to indeed be a very complex subject, and I wonder how much training in such details the train drivers are given?
 
For the design engineers at GE/EMD, etc, they surely understand all this and more, but I imagine the train drivers understand the fundementals and how to apply them, but not much more. In other words, you don't have to know how to build it to drive it, but you do have to know enough to understand its limitations.  
 
It is that way being an airline pilot; you are taught basic theory, practical application, structure, and limitations, and with experience and training learn to apply what you know smoothly and efficiently, while still never REALLY TRULY understanding the physics that makes the thing fly!


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twalsh29
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Re: Motors
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« Reply #30 on: Aug 1st, 2011, 8:17pm »
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Here is how an SD70Ace works.  The inertial blower brings air inside the inertial room where the turbo end of the engine is housed.  The turbo pressurizes air into the aftercoolers which condense it further, at which point it enters the 2 stroke diesel engine.  The engine runs in 1 of 8 different throttle positions, all computer controlled (no governer).  The generator is self exciting and its field in computer controlled.  So regardless of the engine speed, its power output is a function of excitation which is controlled by the computer system.  The throttle effectively servs only as a horsepower limiter at this point.  In fact there is a HP rating for each throttle position.  The central computer system monitors engine, wheel slip, generator, etc.. etc... etc...  The software causes everything to happen in its time and correct ratio.  The AC power produced by the generator is fed to 2 rectifiers which feed 2 inverters.  The inverters outputs are also very precisely controlled by the computer.  If you study the curve of any AC electric motor (AC traction motor), you will see that when it starts under load, the current is maximum, and as the load gets moving, the current reduces while the counter EMF (back electromotove force) increases.  In order to compensate for the increasing back emf the voltage is increased.  So an SD70Ace at full speed is running on maximum voltage and whatever current is required for the mathematics to make around 4400 HP.  As for what that voltage is... it may be proprietary.  I will have to find out.
 
When the train goes into Dynamic Braking, some contactors are switched, the traction motors become 6 generators all feeding the inverter which operates as a rectifier in the other direction, feeding all the power being produced by the traction motors to the resistor grid on top of the cooling hood in the rear.  The blower blows all this power off in the form of heat energy (World's largest hair dryer).  Since the traction motors are loaded via the resistor grid, they experience back emf, and that is what helps slow the loco down along with the air brakes.  The same type of thing happens in your Toyota hybrid car when you brake, only it charges its own battery that way.
 
So, if that doesnt give you specific numbers for electrical characteristiks, at least you have an overall understanding of the behaviors.  All the software is proprietary, and the SD70Ace does NOT change from series to parallel and back like some others.


http://Forums.Railfan.net/Images/DieselTypes/28280.jpg
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twalsh29
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Re: Motors
 
« Reply #31 on: Aug 1st, 2011, 8:21pm »
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PS.  I build SD70Aces, test them, drive them, repair them, inspect them etc etc etc...

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Eggroll
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Re: Motors
 
« Reply #32 on: Mar 14th, 2012, 2:08am »
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on Mar 26th, 2005, 9:47pm, Cody wrote:       (Click here for original message)

 
We need a locomotive electrician out there to answer in more detail.  My question is how do they accelerate?....what is the throttle lever connected to?.... does it adjust the field of the motor with the genset being a governed, "constant speed" variety?   or does it just increase the frequency of the genset by giving it more fuel?

 
The throttle lever is connected to a camshaft that operates 6 switches.  one that lets it know it's out of idle, one that closes on notches 2,4,6,8, one that close on notch 3-8, one that close on 5-8 and one that close on 5 and 6, and a stop switch for MU shutdown.  
 
the 4 switches that are for the different notches are connected to governor valves a,b,c and d.  a,b, and c all increase fuel, while d takes fuel away.  A valve is energized at 2,4,6, and 8, B valve is 3-8, C valve is 5-8, and d valve is energized at 5 and 6 and at idle if the engine is equipped with a low idle feature which is usually enabled when the reverser is in the center position.  Due to AAR standards, these are all standardized in the trainline through MU cables so an engine with EFI works the same way except the "valves" are controlled by whatever system is controlling the engine.  8th notch has A, B, and C valves energized putting maximum fuel into the engine.  6th notch has all 4 valves energized which is putting max fuel from A, B, and C, but has some fuel restricted because D is energized.  Normal idle has no valves energized, and low idle has A and D energized which adds and restricts fuel at the same time resulting in a low idle rpm.  
 
depending on the engine, say a 70 for instance, each notch makes the computer put the engine at a certain HP output.  volts are higher at high speeds while amps are higher at low speeds.  Amps =torque while voltage = speed.  Also, someone mentioned 746 watts per HP which isn't accurate on the railroad.  locomotives use 700 watts/hp for their ratings.  I've never gotten an answer why, but working as an electrician in the real world before getting on at the railroad has always left me perplexed about this different standard for HP.    
 
As I mentioned in a different post, the computer (or TH card in a dash 2 control system) will recognize inputs off those throttle switches to determine how much excitation to apply to the rotating field of the main generator.  the SCR assembly will gate the 3 sine waves of the 3 phase alternator (technically a generator in EMDs since the rectifier is part of the generator housing) later in the cycle to only let small amounts of electricity pass.  The higher the notch/demand the earlier it gates the electricity through in the wave to apply more power to the field.  Obviously this is all solid state and happens very very quickly.  
 
hope this helps, I could ramble on about this stuff all day.


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CHESSIEMIKE
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Re: Motors
 
« Reply #33 on: Mar 14th, 2012, 8:43pm »
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Welcome to The Forums Eggroll. I have read several of your posts and found them very informative.
Thanks,
CHESSIEMIKE


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