Hybrid Electric Vehicles Regenerative...

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HybridElectric Vehicles & Regenerative Braking Cool technology? Or marketing tool? Ken Stanton, PhD Engineering Education Dept. of Mechanical Engineering

Transcript of Hybrid Electric Vehicles Regenerative...

Page 1: Hybrid Electric Vehicles Regenerative Brakingprojects-web.engr.colostate.edu/VEEP/pdf_presentations/Hybrid... · Hybrid‐Electric Vehicles & Regenerative Braking Cool technology?

Hybrid‐Electric Vehicles &  Regenerative Braking

Cool technology?  Or marketing tool?

Ken Stanton, PhD

Engineering Education

Dept. of Mechanical Engineering

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How does hybridization improve MPG?

Downsize engine & run in more efficient zones

Electric motor torque & efficiency

Aerodynamics (not unique to hybrids, though)

Plug‐in for electric power recharge

Regenerative braking

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So what is “regenerative braking?”

Is it a special technology added to HEVs?

Or is it just a marketing tool?

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How electric motors work

Force in opposite directions, around a rotational object,  creates torque

Force is from 2 magnetic fields interacting

Can be 2 magnets, 1 magnet & 1 coil, or 2 coils

Permanent magnets can’t be “controlled”

But we need to control an electric motors’

torque & speed

Coils can act like magnets AND are controllable

Direction and magnitude of electricity determines magnetic field

direction and magnitude

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How electric motors work

Electrical energy ‐> Mechanical energy (rotational)

Also…

Mechanical energy ‐> Electrical energy

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Flux Linkage

Flux linkage λ

= ∫B dS = BA 

λ

= NBA for multiple turns

ϕ = BA for uniform field  λ

= Nϕ

λ

= NBA cos θ

most complete equation

Also, λ

= Li

for coil flowing current

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Back EMF

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Bring it all together…

Vehicle is in motion ‐> kinetic energy

Wheels rotate with vehicle ‐> rotational energy

Wheels rotate electric motor

Motor rotation induces current in coils ‐> electrical energy

Induction creates opposing torque ‐> braking

Current is rectified (to DC) and sent to batteries ‐> stored  electrical energy (in chemical form)

= Regenerative Braking

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Controlling regenerative braking force

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In conclusion…

Regenerative braking is just a property of electric  motors

Benefits:

Reduces use of mechanical brakes (waste heat, materials)

Doesn’t require extra equipment

Recovers kinetic energy 

Recharges batteries

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Ken Stanton, PhD Research Scientist Mechanical Engineering Colorado State University [email protected]

Questions?