Formula E testing Donnington
Discussion
Hehe, I'm struggling to read that graph after a quick look.
I'm not quite sure what I should be taking from it in reference to my thoughts above.
All I can see is that if I want peak bhp and running up into a peak power rpm, my efficiency is around half of peak at peak power, and the only way to run efficiently is to generate less power and rev the e-motor harder from that point.
But that doesn't seem to be the shape of the power curves on offer in Formula E, from what I can tell.
Again maybe the specs are not clear on the websites available... for some odd reason given it's a generic series engine. But it suggests a fairly moderate and flat torque output which is completely contrary to what you'd expect from an e-motor.
In your example it's the classic high torque at low rpm, with lower power and high efficiency at higher rpm. So they literally use a gearbox to run high rpm more of the time?
It must feel really odd to be constantly driving away from peak power to get the best efficiency performance.
I suppose the only reason they don't use the torquey low end of the e-motor then, is that it's simply inefficient. Even more inefficient than just running 1 long gear and removing the gearbox weight and friction from the equation...?
Dave
I'm not quite sure what I should be taking from it in reference to my thoughts above.
All I can see is that if I want peak bhp and running up into a peak power rpm, my efficiency is around half of peak at peak power, and the only way to run efficiently is to generate less power and rev the e-motor harder from that point.
But that doesn't seem to be the shape of the power curves on offer in Formula E, from what I can tell.
Again maybe the specs are not clear on the websites available... for some odd reason given it's a generic series engine. But it suggests a fairly moderate and flat torque output which is completely contrary to what you'd expect from an e-motor.
In your example it's the classic high torque at low rpm, with lower power and high efficiency at higher rpm. So they literally use a gearbox to run high rpm more of the time?
It must feel really odd to be constantly driving away from peak power to get the best efficiency performance.
I suppose the only reason they don't use the torquey low end of the e-motor then, is that it's simply inefficient. Even more inefficient than just running 1 long gear and removing the gearbox weight and friction from the equation...?
Dave
Mr Whippy said:
...lower power and high efficiency at higher rpm. So they literally use a gearbox to run high rpm more of the time?
Pretty much, I'd guess. At least that's how I'd design it...Mr Whippy said:
I suppose the only reason they don't use the torquey low end of the e-motor then, is that it's simply inefficient. Even more inefficient than just running 1 long gear and removing the gearbox weight and friction from the equation...?
I would say so, because heating your electric motor up by running it inefficiently is also bad for it in terms of resistance losses increasing with winding temperature and over-temping of it the permanent magnets leading to permanent loss of magnetism. While the graph says it can produce x kW at whatever rpm, it's definitely going to be time/temperature limited at that power level.Gassing Station | General Motorsport | Top of Page | What's New | My Stuff