Why does a diesel locomotive require so much horsepower?
I’m a 37 year old train fanatic and have been my entire life but one thing I’ve never understood fully is the horsepower behind a diesel locomotive. I understand how they work, they’re basically enormous generators on wheels; the engine, prime mover, spins the electric generator which then powers the traction motors that turn the wheels. I know the faster the generator turns, the more power is generated, but why does the actual engine have to be so big, and produce so much horsepower, to spin the generator? Is the actual electric generator THAT HEAVY that it requires a 4,000 horsepower, 16 cylinder diesel engine, to spin it? Is there resistance back from the traction motors that require the engine to work harder? Thank you
In: Physics
The generator pushes against the engine. This force comes from electricity running through it. The more electricity it makes, the more it resists turning. For a train that’s a lot of energy, and so a lot of force slowing it down from the electricity. Energy is always conserved, so any energy that goes into moving the train comes originally from the engine, and that energy is measured in horsepower.
If you took a generator and spun it by hand with nothing hooked up, it would move pretty easily. If you shorted the output, so that it was generating as much electricity as possible, you’d find it suddenly gets very hard to turn, and the faster you turn it the harder still it gets. A train’s drivetrain is way more controlled than this, so waste is minimized, but the energy spent moving the train still comes from the engine.
Latest Answers