Losseless Starting Method For The Wound Rotor Induction Motor

In heavy duty drives in the range of hundreds kW, like cement and minerals industries, wound rotor induction motors are used. Important users make use of hundred of such drives, summing hundreds of MW. This type of motors have technical capabilities to easily operate at variable speed. Despite this simple capability, the large amount of losses which occur at low speeds determine the users to use the facility given by the wound rotor only for starting. Even so, the losses specific to the additional rotor resistors are quite important, given the range of power. The paper describes the existing technologies involved in the variable speed drives based on wound rotor induction machines. Finally, it proposes a technique for starting which avoids the use of additional rotor resistors and consequently it eliminates the corresponding losses. The simulations confirm the viability of the technique.