Horsepower: Where do we measure it?

[Randy Stahl]

Thats the answer I was looking for...good job!!
Randy

[ericsp]

QUOTE: Originally posted by ericsp

QUOTE: Originally posted by Randy Stahl

Thats the answer I was looking for...good job!!
Randy

Using 1 HP = 745.7 W, 3000 HP = 2237100 W
Assume the voltage is 1250 V
Use W=(V^2)/R to get R=W/(V^2)
R=2237100/(1250^2)=0.6984 Ohms
To make sure that the current does not exceed the current for 3000HP and 1250V the resistance cannot drop below the above value.
Therefore 2 grids are used.

QUOTE: Originally posted by Randy Stahl

Thats the answer I was looking for...good job!!
Randy

It seems like Sierra Railroad has done that up at Oakdale, CA.

[oltmannd]

Back to the original question, the "Traction HP" for a locomotive is the shaft horsepower going into the main generator (or alternator) that will be converted to electrical HP for traction. It is to be measured at AAR std conditions, 28.86" Hg (1000 ft elevation) 60 deg F ambient air and fuel temp, 7.043 #/gal fuel density and 19350 BTU/# HHV.

It is engine brake HP less external auxillaries (such as TM blower, cooling fans, air compressor). The brake HP does not include internal auxillaries such as water pumps and lube oil pumps.

In practice, you measure the electrical output from the main generator and adjust for generator efficiency (that is why Randy divides by 700 instead of 743), calculate the auxillaries, add them up, then adjust results back to standard conditions.

[Anonymous]

Ok Randy. Since i'm a machinist and not a " sparky ", when I would put a SD40-2 in self-load test, I was only using 2 of the 6 availible DB grids???[%-)]

[Randy Stahl]

You use all six grids.
Randy

[Anonymous]

Thats why i'll stick to pulling wrenches and not wire. Me no savvy. Besides that stuff bites hard!!!!!!!!!!!!!!!![bow]

[ericsp]

QUOTE: Originally posted by drailed1999

Ok Randy. Since i'm a machinist and not a " sparky ", when I would put a SD40-2 in self-load test, I was only using 2 of the 6 availible DB grids???[%-)]

If you use all 6, it just lowers the current.

[Randy Stahl]

ericsp had the right idea i commend him for the thought on the matter. Each grid section is .43 ohms each grig has two .43 sections for a total of .86 ohms each locomotive (SD40-2) has 2 grids in series for a total of 1.72 ohms , in self load the grids are arranged in series parellell in pairs. That means voltage will be set at 1204 and current will be 700 amps per grid or 4200 amps plenty of capacity to test a 5057 horse power locomotive. On an SD45 the voltage limit settings are 900 volts and 4000 amps total 3600 horsepower.
Randy

[ericsp]

QUOTE: Originally posted by Randy Stahl

ericsp had the right idea i commend him for the thought on the matter. Each grid section is .43 ohms each grig has two .43 sections for a total of .86 ohms each locomotive (SD40-2) has 2 grids in series for a total of 1.72 ohms , in self load the grids are arranged in series parellell in pairs. That means voltage will be set at 1204 and current will be 700 amps per grid or 4200 amps plenty of capacity to test a 5057 horse power locomotive. On an SD45 the voltage limit settings are 900 volts and 4000 amps total 3600 horsepower.
Randy

Do you know the about what temperature the grids usually reach when doing the self-load test?

[Randy Stahl]

really really hot!!!!!!! Calculate the watts and compare to a household appliance.
Randy

[Anonymous]

Thats one heck of a toaster!!!!!!!!!!!!!!!!!!!!!!!!!