planetf1.com

Someone please explain how a breaking car returns energy (electricity) back to the KERS unit. Where are the armatures and coils located ?

Each car would be different I suspect. Also Williams (and maybe others) are using a flywheel, unless that changed and I didn't notice or they haven't publicized it. Have you tried the obvious places?
http://scarbsf1.com/blog1/category/kers/
http://en.wikipedia.org/wiki/Regenerative_brake
http://en.wikipedia.org/wiki/KERS
http://www.formula1.com/inside_f1/under ... /8763.html

I think Williams abandoned their flywheel system before it ever raced.

You're correct, I think I confused their F1 and non-F1 activities.

http://www.williamshybridpower.com/technology/
"The rigours of Formula One offer a stringent proving ground for automotive technology and whilst the flywheel KERS was never raced due to regulation changes, WHP has developed industry-leading capabilities that now transcend the world of motorsport."

Thanks for the initial response. I keep reading how the F1 cars under braking are charging the KERS unit, how ? A flywheel does not fit into the braking question.

I have read all the hyperlinked articles but no one has explained how a decelerating wheel/tire can produce excess electricity to spin a flywheel or charge a battery/capacitor. Does the engine/transaxle spin the KERS unit on deceleration ?

Did you ride a bicycle with a 'dynamo' fitted that 'rubbed' against the wheel to run the lights?
(not the dyno built into the hub as you can not feel the retardation the same)

If you did not have the lights on, there are roads it would freewheel along, but not when you had the lights on, you had to peddle.

You've confused me, it sounds here like you're just asking how is electricity produced. Most power plants create heat, to heat water into steam which then turns a turbine. "Steam turbine plants use the dynamic pressure generated by expanding steam to turn the blades of a turbine. Almost all large non-hydro plants use this system. About 90% of all electric power produced in the world is by use of steam turbines." wiki
Turbine axle or a wheel axle, doesn't matter, still an opportunity to generate power.
Maybe these two can help? -
http://en.wikipedia.org/wiki/Dynamo#Dis ... principles
http://www.youtube.com/watch?v=jKFTAobM ... ct=1#t=169
Or are you asking specifically why only a decelerating wheel?

Look at this

http://www.instructables.com/id/Make-a-tiny-Dynamo-flashlight-from-junk-in-2-steps/

same, except the wheel (actually the crank, over running from the wheel) turns it

If you look at gas fired power plants, gas is fired in a turbine which directly turns a generator. Heat is formed as a "byproduct" and this heat is recovered in the form of HP steam which in turn, also drives a steam turbine, driving a generator. The sole purpose is creating motion which drives the generator - this is driving coils through a magnetic field which creates a current.

Put simply for the KERS units, on the drive shaft there will be a coil surrounded by a magnetic field. Under acceleration the coil is uncoupled from the shaft so is not turning. When a driver brakes the coil is coupled to the shaft so it can create electricity and will have a braking effect. This is a massive simpilication but is the basic physics behind it

In a Formula One car there is a motor/generator unit connected usually to the front of the engine crankshaft. It does not have to be there, but does have to be located sometwhere in the drivetrain.

This motor/generator for KERS is named MGU-K, for motor generator unit kinetic. The thing about an electric motor is that it can be designed to either turn electricity into rotational force, or vice versa. And that is what the MGU-K does, under braking it harvests energy by taking rotational energy off the drivetrain and converting it into electricy. That electricity is usually stored in batteries or supercapicators. Then when the driver desires, he pushes a button and the batteries power the MGU-K to provide additional power to the drivetrain.

Thanks Blinky. If the energy is harvested from the crankshaft, that makes sense. If the energy is harvested from the brake/wheel, I find it hard to believe.

I think they cause a lot of undue confusion by saying things like "storing braking energy" when it is really coming off the engine while braking.

As Blinky said it's attached to the crank of the engine (at least in this application) instead of the brakes or the wheel but it does effect braking in that when the driver is off throttle and on the brakes the MGU goes into generator/harvest mode causing drag on the engine and adding more engine braking. So when a drivers KERS malfuntions and the pitwall tells them to shut it off the brake bias needs to be adjusted by adding more mechanical braking power to the rear wheels.

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There is more to this equipment, a method of dumping excess electrical energy.

The regulations state:


So there is a fixed rate of power transfer, and a fixed maximum capacity of the energy storage device. But what happens if a car is in braking and KERS phase, and the storage capacity reaches the maximum of 300kJ? If you just shut off the harvesting process, suddenly there is less braking force at the rear wheels, and this could unbalance the car enough to become a problem. But what happens is that the MGU-K keeps retarding the drivetrain, and the electrical energy is dumped into a device that offload it from the car in the form of heat. That would be resistors, think of the elements of a toaster.