Regenerative AC drives have the capacity to recover the braking
energy of a load moving faster than the designated motor speed (an overhauling load) and return it to the power system.
Cycloconverter, Scherbius, matrix, CSI and LCI drives inherently
allow return of energy from the load to the line, while voltage-source
inverters require an additional converter to return energy to the
Regeneration is only useful in variable-frequency drives where the
value of the recovered energy is large compared to the extra cost of a
regenerative system, and if the system requires frequent braking and starting. An example
would be conveyor belt drives for manufacturing, which stop every few
minutes. While stopped, parts are assembled correctly; once that is
done, the belt moves on. Another example is a crane, where the hoist
motor stops and reverses frequently, and braking is required to slow the
load during lowering. Regenerative variable-frequency drives are widely
used where speed control of overhauling loads is required.