May 6, 2010

Regenerative braking of electrical machines

   Regenerative braking is one type of electrical braking procedure. Normally energy is
dissipated in any braking procedure and in most cases, energy is lost as heat.Regenerative braking has been designed to utilize this energy,so the amount of energy lost as heat in other braking processes will be used for some productive purpose in this process.For example, in some areas with lot of mountains, a train is allowed to come down from top of mountain only when another is going up, so that one train can transfer its energy to another.Its charming, na!!

Fig:Regenerative braking

Look at the schematic. when we apply braking, stator is of course disconnected from main supply using switch set-4. But the rotor is rotating due to its inertia. In case of DC, synchronous and permanent magnet motor, rotor has distinct flux source. And in case of induction motor, rotor has residual magnetism. Therefore, virtually all machine has some sort of flux source on its rotor. When rotating due to inertia, this flux cuts