What does the throttle operate?

[ricebrianrice]

In a diesel electric locomotive, what does the throttle operate?
Does it directly operate the engine, ala your car/truck, or does it control the voltage/amperage to the traction motors?

I read discussions about notch's on the throttle, but don't really understand what that does.

On the same note, does anyone have a one line or block diagram for diesel electric loco's?

I do know that the diesel engine turns the generator/alternator which then send power to the traction motors, but don't understand the details in between.

Thanks,
Brian

[CN Sparky]

Realistically, the throttle controls the amount of power you get.

Technically, the throttle operates the governor A,B,C and D solenoids for a certain engine RPM. Then the excitation system controls the amount of power output by gating SCR's, etc, to control the alternator or generator "field" to achieve the desired output. Most engines have a certain RPM associated with each throttle position, but some of the GE's have only a few different speeds (ie throttle 3-5 is all the same RPM) and control the alternator output strictly by increasing or decreasing the field current...

That's off the top of my head. I could look up the finer points for you, but I hope that gets the main idea across. I'm sure someone will correct me on some of those details anyhow

[Typewriters]

(Not correcting CNSparky's VERY good and most to-the-point ever description, but augmenting!)

In a general way, it's possible to say (covering all diesel-electric locomotives ever built here in the US) that the throttle itself either controls engine speed directly and then excitation is controlled automatically indirectly, or else that the throttle controls both engine speed AND excitation directly.

The first instance would be the common EMD locomotives of the 567 engine era (well, most of it, anyway) which have what was in places generally referred to as "LOAD REGULATOR CONTROL." This reference term comes from general Railway Fuel & Operating Officers' Association handbooks and implies that load (or load current, read as amperage) is controlled only by engine speed and any offsets built into the rotating equipment - for example, the common use of a shunt winding carrying a component of load current that acts to oppose the main field at low speed and high current.

What that means generally is that this type of control has very high load currents at low speeds with high throttle settings and overloads or slips without throttle reduction.

The other type of control is more complicated, and originally was developed and championed by ALCO-GE on their road locomotives powered by model 244 diesel engines; this type of load control is called "THROTTLE TRACTIVE EFFORT CONTROL" or else "THROTTLE RESPONSE CONTROL." In locomotives such as this, there are absolute upper limits placed on load current for every throttle notch. The limit is operative at any speed.

What this means generally is that this type of control will have to be near wide open at low speeds to obtain the highest load current, which is limited to safe values.

The first type of control requires no complicated circuitry or anything outside the generator and exciter. The other control needs to be more complex because it needs to be able to place limits on load current for each notch of the throttle. So, then, the first derives excitation strength (field strength) based on engine RPM and locomotive speed only while the second deliberately limits field strength to a maximum limit for every throttle notch.

In almost all cases the governor can prevent the engine itself from being overloaded by lowering (automatically) the setting of the (hydraulically connected) Load Regulator, which reduces excitation. Overload is detected by the governor having to inject more than a specified upper limit amount of fuel for a given engine speed. If that situation occurs, the governor will lower the load regulator setting until the balance of proper fuel rate to engine speed is reestablished.

This is why the first style of control is called "Load Regulator" control since that is usually the ultimate limiting factor. Throttle Response control has many more limits inserted in a more complicated system.

It's much more detailed than that, and complicated too, but what I've given here is a good short way to think of the two widely generalized 'types' of excitation control. You could look at our recent blog article about GE wheel slip control to read about some other artificial limits placed on excitation - in that case, I'm talking about Automatic Power Matching Control. (See the blog link in my signature below the post here.

We actually have some articles planned to cover this sort of topic upcoming on our locomotive blog. First in the works will be a redo of the first primer article that is still visible on the internet archive, on one of our now-down websites. You can see that archive here: http://web.archive.org/web/200910280543 ... imer1.html We intend to republish it on the new site with only minor changes.

-Will Davis

[WVU]

To start with, by no means am I disagreeing with CN Sparky and Typewriters. What they wrote is correct. Like was mentioned about energizing the Governor Valves, you also have a TH module also. Pin 4 is "A" valve, Pin 5 is "B" valve, Pin 6 is "C" valve and Pin 7 is "D" valve. Whatever combination of valves that is energizied for the governor, you will get a output from the TH module at Pin 3.

The excitation is controlled through the excitation system which consists of the TH module, which has a set voltage for each throttle notch that sends it’s output from TH-3 to the RC module at RC-3. This voltage will go through the RC module, which will apply a smooth application of voltage out of the RC module at RC-13 for a smooth start so the locomotive will not bog down or jump. The voltage coming out of the RC is not and instant voltage like you see coming out of the TH module. The RC module has capacitors built in it for timing and you can watch the output just build up. And by the way in notch 8 you want to see 50 VDC coming out of RC-13. The output from RC-13 will go to the SB module, which stands for Sensor Bypass, and the voltage goes to the base on the NPN transistor at pin 3 of the SB module. You then have a Main Generator Voltage feedback and a Main Generator current feedback from the Generator also that comes out of the PF module that goes to pins 4 & 5 of the SB module. The feedback out of the PF then goes to the emitter side of the NPN transistor. The turning on and the turning off of the NPN transistor on the SB module is what lets the current flow through the 13 & 14 windings of the SE module which stands for Sensor. When the voltage is greater at the base of the NPN transistor then the feedback voltage from the PF module that goes to the emitter of the NPN transistor, current will then flow through the 13 & 14 winding which will trigger the SCR for firing. When the feedback from the PF module at the emitter of the NPN transistor is greater then the voltage at the base of the NPN transistor the triggers are turned off, this happens so fast that you can not tell it’s happening. The voltage and current that flows through the NPN transistor is called the Reference Voltage and you can check it at pin 10 of the TH module and it should be a constant 68 VDC in idle to notch 8. This voltage will flow through the SB pin 1 and pin 7. It then flows through the GX module pins 8 & 4 and through the GV module pins 8 & 4 and through the SE module pins 13 and 14 and into the SB module at pin 2.

[CN Sparky]

To start with, by no means am I disagreeing with CN Sparky and Typewriters. What they wrote is correct. Like was mentioned about energizing the Governor Valves, you also have a TH module also. Pin 4 is "A" valve, Pin 5 is "B" valve, Pin 6 is "C" valve and Pin 7 is "D" valve. Whatever combination of valves that is energizied for the governor, you will get a output from the TH module at Pin 3.

The excitation is controlled through the excitation system which consists of the TH module, which has a set voltage for each throttle notch that sends it’s output from TH-3 to the RC module at RC-3. This voltage will go through the RC module, which will apply a smooth application of voltage out of the RC module at RC-13 for a smooth start so the locomotive will not bog down or jump. The voltage coming out of the RC is not and instant voltage like you see coming out of the TH module. The RC module has capacitors built in it for timing and you can watch the output just build up. And by the way in notch 8 you want to see 50 VDC coming out of RC-13. The output from RC-13 will go to the SB module, which stands for Sensor Bypass, and the voltage goes to the base on the NPN transistor at pin 3 of the SB module. You then have a Main Generator Voltage feedback and a Main Generator current feedback from the Generator also that comes out of the PF module that goes to pins 4 & 5 of the SB module. The feedback out of the PF then goes to the emitter side of the NPN transistor. The turning on and the turning off of the NPN transistor on the SB module is what lets the current flow through the 13 & 14 windings of the SE module which stands for Sensor. When the voltage is greater at the base of the NPN transistor then the feedback voltage from the PF module that goes to the emitter of the NPN transistor, current will then flow through the 13 & 14 winding which will trigger the SCR for firing. When the feedback from the PF module at the emitter of the NPN transistor is greater then the voltage at the base of the NPN transistor the triggers are turned off, this happens so fast that you can not tell it’s happening. The voltage and current that flows through the NPN transistor is called the Reference Voltage and you can check it at pin 10 of the TH module and it should be a constant 68 VDC in idle to notch 8. This voltage will flow through the SB pin 1 and pin 7. It then flows through the GX module pins 8 & 4 and through the GV module pins 8 & 4 and through the SE module pins 13 and 14 and into the SB module at pin 2.

Very detailed Only thing not mentioned is that's pretty specific to the -2 series... ie, SD40-2, GP40-2, etc. You won't find a TH module on a GE, or anything SD50 or up.

[WVU]

On the SD50 it is the LC module and the GC module.

Now for a little GE Series 7 informotion (CHEC):Your Controller on the control stand sends out two signals for each throttle notch by sending a signal to the Governor for Engine Speeds and a signal to the RG card and RF card for Excitation of the Main Generator. The Signals are as follows
Throttle Notch Governor Valves Excitation
1 No Valves No Valves
2 A A
3 A,C C
4 B A,C
5 A,B,C,D B,C,D
6 A,B,C,D A,B,C,D
7 B,C B,C
8 A,B,C A,B,C
Excitation Valve Signals are sent to the Bottom of the CHEC Panel at the connections
"V" is for RGRLA (A valve)
"W" is for RGRLB (B valve)
"X" is for RGRLC (C valve)
"Y" is for RGRLD (D valve)
"N" is for Negative at the CHEC Panel
Governor Valves are at
2D-A for "A" Valve
2D-C for "C" Valve
2D-B for "B" Valve
2D-D for "D" Valve
2D-E for "ORS"
Control Stand Controller Outputs are as follows
THS-1 thru 8 for "Generator Field" is Cam "F" the 1GF1 wires
THS-2,4,6,8 Switch is for "A" valve and is Cam "G" which should have the 2AV wires
THS-3 thru 8 Switch is for "C" valve and is Cam "J" which should have the 1CV1 wires
THS-5 thru 8 Switch is for "B" valve and is Cam "H" which should have the 1BV1 wires

[WVU]

CN Sparky, the Valves did not show up the way I intended them to look in the last message I sent for the GE Series 7 units

Throttle Notch Governor Valves Excitation
1 No Valves No Valves
2 A A
3 A,C C
4 B A,C
5 A,B,C,D B,C,D
6 A,B,C,D A,B,C,D
7 B,C B,C
8 A,B,C A,B,C

[WVU]

CN Sparky, I tried to straighten out my mistake and I still did not fix it. The information that I have is stuff that I have dealt with for over 32 years that I have recorded and I go back to my files and do a lot of copy and paste when I answer things on RR.Net. Every thing looks good until I hit SUBMIT and then all the Valves I listed want to run together. Bottom line is at least I mentioned the cards.

[John_Perkowski]

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