What is Electric Motor ?

The most common form of regenerative brake involves an electric motor as an electric generator. In electric railways the electricity generated is fed back into the supply

system. In battery electric and hybrid electric vehicles, the energy is stored chemically in a battery, electrically in a bank of capacitors, or mechanically in a rotating

flywheel. Hydraulic hybrid vehicles use hydraulic motors to store energy in the form of compressed air. In a fuel cell powered vehicle, the electric energy generated by

the motor is used to break waste water down into oxygen, and hydrogen which goes back into the fuel cell for later reuse.

Practical regenerative braking

Regenerative braking is not by itself sufficient as the sole means of safely bringing a vehicle to a standstill, or slowing it as required, so it must be used in conjunction

with another braking system such as friction-based braking.

The regenerative braking effect drops off at lower speeds, and cannot bring a vehicle to a complete halt reasonably quickly with current technology, although some

referred to as One Pedal Driving.

cars like the Chevrolet Bolt can bring the vehicle to a complete stop on even surfaces when the driver knows the vehicle's regenerative braking distance. This is

referred to as One Pedal Driving

Current regenerative brakes do not immobilize a stationary vehicle; physical locking is required, for example to prevent vehicles from rolling down hills.

Many road vehicles with regenerative braking do not have drive motors on all wheels (as in a two-wheel drive car); regenerative braking is normally only applicable

to wheels with motors. For safety, the ability to brake all wheels is required.

The regenerative braking effect available is limited, and mechanical braking is still necessary for substantial speed reductions, to bring a vehicle to a stop, or to hold

a vehicle at a standstill.

Regenerative and friction braking must both be used, creating the need to control them to produce the required total braking. The GM EV-1 was the first commercial car

to do this. In 1997 and 1998 engineers Abraham Farag and Loren Majersik were issued two patents for this brake-by-wire technology.[2][3]

Early applications commonly suffered from a serious safety hazard: in many early electric vehicles with regenerative braking, the same controller positions were used to

apply power and to apply the regenerative brake, with the functions being swapped by a separate manual switch. This led to a number of serious accidents when

drivers accidentally accelerated when intending to brake, such as the runaway train accident in Wädenswil, Switzerland in 1948, which killed twenty-one people.

Conversion to electric energy: the motor as a generator

Electric motors, when used in reverse function as generators, convert mechanical energy into electrical energy. Vehicles

propelled by electric motors use them as generators when using regenerative braking, braking by transferring mechanical

energy from the wheels to an electrical load.