3 ms·
>>put a big resistor in the circuit and waste 50+% of the energy That Is Insane!! Rail needs a complete rethink of design from the ground up. There are certa
by toss1 4y ago
>>put a big resistor in the circuit and waste 50+% of the energy
That Is Insane!!
Rail needs a complete rethink of design from the ground up. There are certainly vast efficiencies from rolling steel wheels on steel rails. But I've seen little evidence of light-weighting and indeed active resistance to steps like making cars using composites, which would save enormous amounts of energy and cost over the lifetime, as well as reduce maintenance costs. Yet their approach to everything seems to be sticking with an approach of 'brute force and ignorance'. Sure that works in the 19th century when you're just starting to put some carbon in iron and make it stronger than pig iron, but materials are sooo far past that now, yet it's still the same old approach. (&yes, I strongly support the Chesterton's Fence checking but this seems way beyond that)
- alar44 4y agoYeah, it's insane because it's 100% not true.
- londons_explore 4y agoSurprising then that a company sells resistors just for rail speed control applications: https://www.cressall.com/applications/rail-traction-dynamic-braking/ https://www.cressall.com/applications/rail-traction-dynamic-... (scroll down to "MOTOR STARTING AND SPEED CONTROL RESISTORS")
- s0rce 4y agoThats not to "go slower" but to slow down: Whenever possible regenerative braking is used. In this case the drive motors convert the kinetic energy of the train into electricity, which is fed back into the power supply and used elsewhere on the network. If it cannot be absorbed by the system the energy may have to be dissipated with braking resistors. These braking resistors can be either mounted on the rail vehicle or as a fixed (trackside) installation connected to the third rail or overhead catenary via Automatic Assured Receptivity Unit (AARU) systems.
- fredoralive 4y agoThat section starts with "This was the traditional approach...". I guess the Bakerloo and Picadilly line trains from the 1970s might still use them on London Underground? Wikipedia mentions stuff like GTO thyristers and IGBTs on descriptions of stuff like the 1992 (Central line) and 1995 (Northern) stock trains, so the next oldest trains from the 1990s seem to have modern(ish) power control. And new trains are coming to the Picadilly line, and presumably must come to the Bakerloo at some point before the old ones fall apart.
- alar44 4y agoThat doesn't mean that's all that's used. It would also imply that it only has 2 speeds or something. Use your head. Or learn some basic electronics.
- Symbiote 4y agoI don't think it's anywhere near 50% that is wasted, since if I understand correctly the resistors are used only during initial acceleration. But anyway, the affected trains are the oldest in use in Britain, from 1972 (Bakerloo Line, 36 trains) and 1973 (Piccadilly Line, 87 trains), out of 620 passenger trains across the whole system. New trains have been ordered and should be introduced in 2025. There's been a 10 year delay, due in part to the 1990s attempt to privatize chunks of the system.