The present invention provides a modulation controller for use with a three phase converter. In one embodiment, the modulation controller includes a three phase modulator configured to provide vector control signals for the three phase converter that generate a common mode voltage. Additionally, the modulation controller also includes a transition modifier coupled to the three phase modulator and configured to provide a shaping function for the vector control signals that extends a transition period of the common mode voltage.

The invention relates to a method of ensuring the stability of a synchronous machine in controlling the synchronous machine on the basis of direct control of flux and torque, in which the torque generated by the synchronous machine is increased/decreased by increasing/decreasing the instantaneous angular velocity of the stator flux. In accordance with the invention, the method comprises the steps of determining the direction of the stator flux vector (.psi.s) in rotor coordinates (dq), and forcing the stator flux vector (.psi.s) to remain in quadrants I and IV (Q1, Q4) of the rotor coordinates by rotating the stator flux in the rotor coordinates to a necessary degree.

A device for driving a multi-phase d.c. motor (8) includes a multi-phase inverter (11) for supplying drive signals to the windings (2, 4, 6) of the motor. The multi-phase inverter (11) supplies a first and a second drive signal at a time to at least one winding (2) of the motor. The first and the second drive signal flow in opposite directions in the at least one winding (2). The device further has pulse-width modulators means (40.1-40.6) for applying a first pulse-width modulation to the first drive signal and a second pulse-width modulation to the second drive signal. The pulse-width modulation means (40.1-40.6) are adapted to vary the pulse-width of the pulse-width modulation in order to accelerate, actively decelerate or maintain the speed of the motor 8 and to select a direction of rotation of the motor.

An apparatus and method for treating sleep apnea includes a bilevel flow generator having an alternating current (AC) synchronous motor coupled to a low inertia centrifugal rotor/impeller. The process of acceleration and deceleration of the rotor involves moving from frequency A, amplitude A to frequency B, amplitude B in an optimal linear fashion using the so-called Bresenham algorithm. This is coupled with a tuned increase of the amplitude during the acceleration process which will produce the acceleration using minimum current allowing the use of smaller power supplies. During deceleration the process is accomplished in reverse fashion using a tuned decrease of the amplitude coupled with a special shunt circuit to prevent power supply voltage changes. These changes in amplitude overlay a current feedback mechanism used to prevent loss of synchronization of the motor by changing amplitude. Speed changes can also be timed so as to prevent desynchronization.

Three phase sinusoidal waveforms generated from a DC bus voltage using Space Vector PWM method are used to obtain multi-speeds from a 3 Phase AC Induction motor. A novel algorithm generates the switching signals from a micro controller to drive the power devices of the Inverter Bridge, the output of which is applied to the motor. At different speeds, below the rated voltage of the motor, the output voltage V and the frequency f are maintained to keep V/f constant so that the motor torque is kept constant. At above the rated voltage of the motor, only the frequency is increased to obtain constant output from the motor at increased speeds.