Hybrid electric vehicles (HEV) use two or more energy conversion technologies. This is usually a combination of a conventional engine with extra batteries driving electric motors.
There are three hybrid vehicle systems which combine an internal combustion engine with an electric motor. They are: series; parallel; and series-parallel.
The series-parallel hybrid system uses an electric motor to drive the vehicle at low loads and speeds and a gasoline engine when loads and speeds increase. A control unit determines the best balance of power to achieve the most efficient vehicle operation.
A permanent magnet brushless motor/generator is mounted adjacent to the engine. A smaller motor/generator replaces the engine flywheel. The motor control unit controls the delivery of electric current to and from the battery and the electric motors.
When the vehicle is moving off from a stationary position, and when travelling at low to moderate speeds, the main electric motor drives the vehicle. During normal driving, the combustion engine starts and drives the generator & the power divider.
