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Horsepower in electrics

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Horsepower in electrics
Posted by Enzoamps on Thursday, July 27, 2017 10:57 PM

I could be mistaken, but I thought diesel electric locomotives were rated by the prime mover.  A 4000 horsepower engine meant a 4000hp locomotive.  As far as I know, the traction motors or alternator/generator might be a limiting factor, but not what the specification refers to.

I was reading about some electric locomotives, like the E44 or GG1 on the PRR.  And one was referred to as a 4000hp or 6000hp locomotive.  Without a prime mover diesel engine, I am left with only traction motors.  SO how exactly is power rated in electric locomotives?  I understand concepts like drawbar pull or maximum tonnage, but the ratings I saw were horsepower.

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Posted by beaulieu on Thursday, July 27, 2017 11:42 PM

To calculate the equivilent horsepower of an electric locomotive take the continuous rated power in Kilowatts and multiply by 1.34. So a typical Siemens Eurosprinter like the ÖBB 1116 Taurus is rated at 6400 kW which converts to 8583 hp. To convert US horsepower ratings to kilowatts multiply the horsepower by .746

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Posted by CSSHEGEWISCH on Friday, July 28, 2017 6:44 AM

I'm going to throw a large wrench into the works.  Since electrics draw their power from an outside source, their horsepower ratings can vary.  The continuous rating is the most horsepower that the onboard electrical equipment can handle without being damaged or destroyed.  There are also higher short-term ratings which are limited by the time that the equipment can handle the overload before being damaged.  I'm sure that others can explain this much better than I just did.

The daily commute is part of everyday life but I get two rides a day out of it. Paul
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Posted by VOLKER LANDWEHR on Friday, July 28, 2017 11:18 AM

beaulieu
To calculate the equivilent horsepower of an electric locomotive take the continuous rated power in Kilowatts and multiply by 1.34. So a typical Siemens Eurosprinter like the ÖBB 1116 Taurus is rated at 6400 kW which converts to 8583 hp. To convert US horsepower ratings to kilowatts multiply the horsepower by .746

I'm not sure if you can compare horsepower of diesel-electrics and electrics directly.

AFAIR horsepower of a Diesel-electric of an American locomotive is the input into the alternator, in an electric locomotive it is horsepower at the traction motors.
Regards, Volker

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Posted by VOLKER LANDWEHR on Friday, July 28, 2017 11:32 AM

CSSHEGEWISCH
The continuous rating is the most horsepower that the onboard electrical equipment can handle without being damaged or destroyed. There are also higher short-term ratings which are limited by the time that the equipment can handle the overload before being damaged.

That is not different between Diesel-electrics and straight elelectrics. In both locomotives the electrical equipment is the limiting factor in most cases the traction motors.

Both types have short time limits.

Than there is the difference between DC and AC motor. DC is much more prone to overheating which determines the short term rating. AC motors are much more robust that short term rating doesn't matter anymore.
Regards, Volker

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Posted by timz on Friday, July 28, 2017 1:28 PM

VOLKER LANDWEHR
in an electric locomotive it is horsepower at the traction motors.

That's probably true in most of the world, but when Amtrak got the 5100-continuous-rail-hp E60 they called it a 6000 hp engine, and they called the 5800-continuous-rail-hp AEM7 a 7000 hp.

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Posted by VOLKER LANDWEHR on Friday, July 28, 2017 3:55 PM

timz
That's probably true in most of the world, but when Amtrak got the 5100-continuous-rail-hp E60 they called it a 6000 hp engine, and they called the 5800-continuous-rail-hp AEM7 a 7000 hp.

I think that doesn't change that the horsepower is given at the traction motor. I don't that the catenary or the power electronics would limit the power.

All I found in my literature is 5,200 kW (7,000 hp) for AEM 7 and 4,500 kW (6,000 hp) for the E60. I haven't found your smaller numbers.

Perhaps your smaller numbers is the continous power rating while Amtrak choose to give the maximum (short term) rating. The hourly rating is sometimes given in Germany. Short term (3 to 10 min) can be much higher.
Regards, Volker

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Posted by blue streak 1 on Friday, July 28, 2017 6:10 PM

You can check Wiki for information.  One advantage of the ACS-64 is the dual HEP does not reduce the HP available for traction.  It can pull 18 Amfleets.  Its HP ratings are 6700 continous and 8600 short time the length is not listed. What seems to be is that the tractive effort for the ACS-64s is higher at various speeds especially 125 MPH. If You check the E-60s only 6000HP listed.,

AEM-7 ACs, & HHP-8s on Wiki it does not list the HP loss for HEP if any.  The EP capacity is listed for the others uch less than ACS-64s  . 

https://en.wikipedia.org/wiki/Siemens_ACS-64

 

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Posted by VOLKER LANDWEHR on Saturday, July 29, 2017 9:58 AM

blue streak 1
Its HP ratings are 6700 continous and 8600 short time the length is not listed.

Here in Europe the maximum power is usually the hourly rating. Short term ratings of 3 to 10 minutes would lead to temperatures that need stops for cooling after its use.

Amtrak has named the ACS-64 for its maximum (hourly) rating of 6,400 kW (8,600 hp), the same presumably as E-60 (6,000 hp) and AEM-7 (7,000 hp)
Regards, Volker


Regards, Volker

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Posted by nfotis on Saturday, July 29, 2017 10:43 AM

As far as I know, European electrics are rated at the rails and for one-hour horsepower.

If you want to compare with diesels, subtract approximately 16% for the various parasitic loads in order to get the power to the rails.

So, a 5.6 MW Bombardier IORE module at 180 tonnes is essentially two 4.400 diesels in power when you subtract the parasitic loads.

N.F.

 

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Posted by erikem on Saturday, July 29, 2017 11:23 AM

timz

 

VOLKER LANDWEHR
in an electric locomotive it is horsepower at the traction motors.

That's probably true in most of the world, but when Amtrak got the 5100-continuous-rail-hp E60 they called it a 6000 hp engine, and they called the 5800-continuous-rail-hp AEM7 a 7000 hp.

 

Yes in the sense that the E60 had the same continuous power at the rails as a 6,000HP diesel. The difference is that electrics have a short term power rating that can be significantly higher than the continuous rating, which can be as high as 2X the continuous rating for a brief time. This is particularly improtant for passenger service as the full acceleration periods typically last less than a minute.

The ratings for DC electric locomotives are a bit more complicated as drawbar horsepower drops off above the speed that maximum continuous traction is acheived without field weakening (shunting or separately excited).

 - Erik

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Posted by nfotis on Saturday, July 29, 2017 2:53 PM

We have data for a typical DC locomotive, the German railways BR103, which was built in the seventies:

7.440 kW was the continuous power

7.780 kW was their peak power

So, the difference is not as great as you imply.

 

Cheers,

N.F.

 

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Posted by erikem on Saturday, July 29, 2017 3:47 PM

Continuous rating for GG1 was ~4,600 horsepower and they were capable of over 8,000hp for short periods. The Milwaukee "Little Joes" at maximum continuous power would draw 1,500 amps but could briefly draw 3,000 amps, though 1 hour rating was only about 10% higher than the continuous rating. The Milwaukee also had 30 minute and 90 minute ratings for their electrics.

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Posted by nfotis on Saturday, July 29, 2017 5:02 PM

It seems that European locomotives were ran at nearer the maximum performance in one hour trips

(usually, running at full throttle for a hour meant lots of mileage - the BR103 was a 125 mph 6-axle locomotive, so at one hour they could cover quite a distance).

Even freight trains were quite fast, in order to keep up with average passenger train speeds. Watch the following video from the Rhine double-tracked route of a fast empty (I think) freight going for loading at 6.000 tonnes, to get an idea:

https://www.youtube.com/watch?v=XfVxkiYxcgw

N.F.

 

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Posted by VOLKER LANDWEHR on Saturday, July 29, 2017 5:25 PM

Regarding the E03/103: The continous rating is 7,440 kW and the hourly rating is 7,780 kW. For the ACS-64 the difference is higher: 5,000 kW hourly and 6,400 kW continous.

If you take the short term rating, e.g. 3 minutes, the rating would be much higher.
Regards, Volker

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Posted by timz on Saturday, July 29, 2017 7:40 PM

VOLKER LANDWEHR
All I found in my literature is 5,200 kW (7,000 hp) for AEM 7 and 4,500 kW (6,000 hp) for the E60.

Apparently your literature is quoting Amtrak. No one actually claimed the AEM7 could do 7000 continuous rail horsepower-- Amtrak called it 7000 "diesel equivalent" horsepower.

(Might have been GE's idea-- the BM&LP E60Cs were probably 5100 continuous rail horsepower too?)

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Posted by VOLKER LANDWEHR on Sunday, July 30, 2017 9:06 AM

timz
Apparently your literature is quoting Amtrak. No one actually claimed the AEM7 could do 7000 continuous rail horsepower-- Amtrak called it 7000 "diesel equivalent" horsepower.

I just tried to that only found the higher ratings not that continous ratings were wrong.

My literature were The Contemporary Diesel Spotter's Guide, Brian Solomon's Electric Locomotives and a number of websites. Nowhere I found the continous rating only what you call the diesel-equivalent horsepower. I hear this term for the first time. The Diesel rating is the input to the generator/alternator.

To get from continous horsepower to diesel-equivalent horsepower they included the efficiency of generator and traction motor, in this case about 83%

5,800 hp continous/0,83 = 7,000hp diesel-equivalent.

The Contemporary Diesel Spotter's Guide had it right then. They named it 7,000 CHP. Now I understand that the supposedly meant Crank horsepower.

When you do the same mathe for the E60,
6,000 CHP becomes 6,000 x 0.83 = 4,980 hp cont.

I calculated the efficiency of 83% backward to get the wanted results. Literature often says 81%.

I assume it was done to compare the electric directly with diesel-electrics to show its advantages.
Regards, Volker

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