Field oriented control drives for naval mechanisms

In this paper, the authors propose the embracing of a solution regarding the implementation of the direct vector control in torque and flux on the induction motor with squirrel cage rotor for the electrical drive systems of the naval mechanisms. Through this is desired the replacement of the actual technical solution, at which for the drive of the loading equipments are used induction motors with squirrel cage rotor with three speed steps obtained with the help of three separate stator windings in star connection. The main disadvantages of the actual solution are: large size, complicated construction of the driving machine, the modification of the speed can be made only in steps. In order to eliminate these disadvantages a technical solution is proposed which keeps the induction machine as the executive element, but at which the control of the movement, that assumes the control of the speed and/or the control of the position respectively the control of the torque is made through direct vector control in torque and flux. The main advantages that are obtained are: - a fast answer in torque and functioning in a wide range of speed, a robust control and relatively simple to implement, does not need current regulators and coordinate transformers, does not need a decoupling circuit of the stator voltage equation and neither a separate vector modulator for the command of the PWM frequency converter, an efficient rejection of the disturbances is assured and it folds well on the numerical control, a normal induction motor with squirrel cage rotor can be used, with only one winding on the stator, the modification of the speed being made through vector control, the command panel is eliminated, on which the direction, acceleration, breaking contacts and time relays can be found.