traction motors

[Anonymous]

I find this thread very interesting. For quite a while we have been hearing how the AC was such an improvement but still a lot of DC power is being sold. I know that there is a large cost difference but you have to wonder when CN and NS shy away from the stuff.

[wabash1]

thanks for the info . i can tell you i was not impressed i was in notch 3 before it started vibrating and moving the engine was a up c44-ac anyways the 70 mac was better but not impressive.

[Saxman]

J,

On the CN, we regularly tear coal trains apart at Valparaiso, IN coming east with a loaded train of 120-25 hoppers, 17,000 tons and two BNSF 70MAC's. This is not a steep grade by western standards but it does have several curves in it. The common thread seems to be if the speed drops below 5 MPH,teh HPT is less than 0.5 and there is wheel slip. I have not seen the TE meter go above 170,000 either.

[Anonymous]

I've never seen a 70MAC above 170,000lbs..and that was serious uphill at 8mph with coal. Soooo..in my simple brain I figure I'm doing about 1200 amps with a 40, and I usually luck out. I use the tractive effort bar like a load meter (which it is) and, wait for just a slight reduction in TE, then give it another notch, like a 40. I'm BNSF, but I've run the SP GEACs, and the best I got out of them was 175,000. I remember the guys I fired for in the 60's talk about big steamers (4-8-4s) that would only exert like 90,000lbs, so these engines are pretty amazing...like a 40!!

[wabash1]

yes it was a sick one. not impressed. also you can have 3 dash 9 or 3 sd70 on line drawing 1300-1400 amps and not pull one apart if the slack is kept strecthed.at 7mph we are pulling 101 coal cars out of the mine with 3 dash 9 on line as long as you dont let it get slack you wont break anything so the 250,000 isnt a problem if moving and strecthed. but one last question what is the max te will these ac motors go.

[Saxman]

Sounds like you had a "sick" lcomotive if you were only drawing a tractive effort 50(00) in notch 8. The tractive effort bar or meter reads in thousands. I know of no conversion factor to change tractive effort to amps. Tractive effort is just another way of showing how hard the engine is pulling. If you had an amperage of say 1100 amps at 5 MPH up a grade what are some things you would start worring about? Short Time rating? Wheel slip and a kuckle or drawbar? The same scenario with AC might be a TE of 200,000, 5 MPH, no short Time rating with AC still the worry of wheel slip and a knuckle or drawbar. What happens when there is about 250,000 pounds of force on the knuckle?

Answer your question?

[wabash1]

on the ac traction motors it goes by traction effort on dc it list amps. what is the conversion to amps on these motors. if im pulling 600 amps i know whats going on. if im pulling te 25 i dont have the slights idea whats going on other then im not moving. in 8th notch best it ever did was te50. i was not impressed with the ac traction motors. dynamic was just as sad. is there a conversion or do we suffer with this new technology