When EMD (for example) rates a locomotive at 4,000HP. Is that hp rating at the prime mover’s flywheel (bhp), or is that 4,000 hp what the traction motors are putting to the rails. To me that seems like alot of power to turn a generator/alternator, I would want that power put to the rails.
Just something I have been thinking about for along time.
Locomotives are rated at generator output.
We know DRN is no dope, but conventional wisdom is that (in the US) the locomotive rating is the input into the alternator/generator for traction purposes. Doesn’t include power for blowers etc-- in the US.
In years past, median output for an SD40-2 was probably not more than 2400 at the rail. Some people claim transmissions in newer units are more efficient, but I’ve never clocked them.
The Horse power comes from the Prime mover itself. A 4400 HP diesel engine (has 12 cylinders) each cylinder, If calculated right, puts out about 366.6 HP.
Now you have to imagine that a 4400 HP Diesel engine in run 8 is putting out an unbelievable mount of torque. Now that locomotive is working hard with a coal train. That torque is used to spin that generator to the amount of electricity/ amperage that the traction motors need. That generator can put out 1000+ amps if need be. Generators range with the type of prime mover the locomotive has. So when HP comes into play its how much the Disesl engine can put out able to spin the generator. The new SD70ACe puts out 4300 HP but the torque coming off that shaft is higher than that of an AC4400CW. Making these locomotives the most powerful of locomotives.
So maybe this has cleared you up a bit on what is what here.
James
The SD70 ACe, rated at 4300 HP, is less powerful than an ES44AC, which should be rated at about 4390 HP if it is the same as the old AC4400 for which more data is available.
As regards torque, the GE engine runs at 1050 rpm (again if it is the same as the AC4400) while the EMD engine runs at 950 rpm. If the power is the same, the torque from a lower speed engine will be higher to generate the same power output. So it may be true that the EMD engine has a higher torque (I haven’t calculated it out) but by the time the AC hits the traction motor, it makes no difference.
The EMD engine “loads up” faster and this can translate into faster acceleration, but that is not related to maximum torque.
M636C
Tim has it exactly right. The common rating is shaft HP into the main generator that’s used to generate electric power for the traction motors. It’s commonly referred to as Traction HP. Traction HP plus the external auxiliary HP equals the Brake HP. Typical aux HP on a Dash 2 would include the air compressor, cooling fans, traction motor blower, dust bin blower (inertial air filter) and aux gen output. Engine mounted auxiliaries are not counted toward BHP (water and oil pumps, for example)
Net Traction HP is the electical power out of the main generator.
Rail HP is the physical HP applied to the rails.
BHP - auxiliary HP = THP
THP * main gen eff. = NTHP
NTHP - traction motor, wiring, contactor electrical losses plus mechanical losses = rail HP.
What???Your post was totally confusing and about as clear as mud.
As far as torque the 6250 HP HDL in an CW60AC is the most powerful ever put in a locomotive.
I think we have beat this topic to death. There is a feature on this forum called “search” that will answer all of the orginal posters questions.
Great info, thanks
It really takes that kind of power to turn a generator or alternator? In my mind I’m picturing a 350 Chevy SB that is putting out 350 hp doing the same thing. At work we have a protable generator/welder that used to have a 15 hp engine on it, that engine blew up and we threw a 7 hp engine on. The 7 hp engine spins the generator/welder just as good as the more powerful engine. The generator has a max output of 220 vAC and 70 amp max load before the breaker “pops”. I’m guessing in the railroad enviroment the more volts/amps a traction motor needs, the harder it is to keep the generator spinning??
Somebody else will have to calculate the AC power, but as everyone knows 220 DC volts at 70 amps would be 15.4 kilowatts, or 20+ horsepower-- so probably that 7 hp engine can’t produce anywhere near 70 amps when the voltage is maximum. I suppose your generator doesn’t ever need to produce maximum current and maximum voltage at the same time?
We just use it to charge batteries and run the chop saw.
Pimp Z26,
How big is the generator you use in the shop? The generator itself, not the engine? Maybe 12" to 15" in diameter and 18" long?Maybe less than that?
OK ignore my guess! The biggest locomotive alternator I know of is the EMD AR16 which is about 5 feet in diameter and about ten feet long. The AR10, which is much more common, is again about five feet in diameter and about 6-7 feet long. The AR16 was good for 3800 HP and the AR10 worked up to 3600 HP. GE alternators are generally bigger in diameter, say 6 feet, but shorter, say 5 feet, because they are rigidly bolted to the diesel engine.
The alternator works by using magnetic fields to generate the electric current. The higher the current generated, the bigger the magnetic field and the greater the resistance the alternator rotor the internal part connected to the diesel crankshaft) experiences from the current in the stator (the fixed outer circular part) which is supplying the motors.
So the diesel is connected to the wheels electrically, not through a torque converter and drive shafts, but the force on the diesel is exactly the same either way.
Your 350 cubic inch engine would not turn the locomotive alternator at all once it was running at power setting beyond th
Small correction Peter, The RMS is what a voltmeter will read, it doesn’t mean the voltage is lower. Household voltage, known as 120vac, is actually 170 VAC peek but just because the meter reads 120 doesn’t mean there is any less voltage there.
Thanks for the info M636C, you cleared up what was confusing me. Thanks again.
Chad
Yes - I knew what I was trying to say, but your explanation is what I should have written.
The RMS is useful in considering the power and the heating or resistive load, though.
M636C
True, Just thought I should point that out.