Simple strategy to recovery energy during stopping period in large high-inertia line-fed induction motor driven systems

The three-phase, squirrel-cage, induction motor (IM) is the most used type of electrical motor in industry. Nowadays, energy recovering during deceleration or breaking periods is a well-explored technique in IMs fed by converters, incorporating special rectifier/inverter input stages, allowing energy to be injected back into the power grid. However, for line-fed IMs, during stopping or deceleration period, after disconnecting the power supply, the energy stored in the system inertia is, in general, not recovered. In this paper, a novel principle to recovery energy during stopping period in line-fed, multi-speed IMs, based on the stator connection change from a lower pole-number mode(s) to a higher pole-number mode(s), is proposed. The principle is described and a connection mode management strategy is proposed, on the basis of preliminary simulations. Considerations on the stator windings are made and the final prototype of an electronic device for the stator winding connection mode management is also briefly described.