Simply put, regenerative braking converts kinetic energy − usually lost during deceleration − into electrical energy that can be stored and reused. The system works by using the electric traction motor as a generator during braking. Typically, an electric motor converts electrical energy into mechanical energy to drive the wheels. During regenerative braking, this process is reversed: the kinetic energy of the moving vehicle causes the motor’s rotor to spin within its magnetic field, making it act as a generator. When braking starts, the inverter – a power electronics component – produces alternating current (AC) from the rotational energy of the wheels. The AC is then converted to direct current (DC) by the inverter and sent to the vehicle’s battery for storage. The amount of current flowing back into the battery corresponds to the braking torque during regeneration. If the battery nears full capacity or the braking demand exceeds what regenerative braking alone can handle, traditional friction braking provides the necessary deceleration.

Some regenerative braking systems utilize permanent magnet synchronous motors, which are efficient at both motor and generation functions, while others may employ induction motors or switched reluctance motors, depending on the design goals. The system’s effectiveness is highest at higher speeds and when the battery can accept more charge.

As detailed in the “Train technology driver” article in this issue of ABB Review, ABB offers a broad range of regenerative braking solutions for the rail industry, aimed at improving energy efficiency, sustainability and system reliability. Key products include items from the ABB EnvilineTM lineup, such as the Enviline Energy Recuperation System and the Enviline Traction Controlled Rectifier, along with the ACS880-11 and ACS880-17 drives, ABB traction converters (which handle AC/DC conversion) and the ABB Traction Battery Pro series.

ABB’s ACS880-11 and ACS880-17 regenerative drives support both motor and generator functions, offering smooth transitions between braking and acceleration. They are energy-efficient, grid-compatible and designed for demanding applications like trains.

Future trends in regenerative braking include wayside storage and smart grid integration. Also, ABB is investing in AI-powered control systems for energy management that could show promise for application in predictive braking.

Overall, regenerative braking not only enhances the energy efficiency of electric and hybrid vehicles by capturing otherwise lost energy, but also decreases wear on traditional braking parts, resulting in lower maintenance costs.