An aircraft propulsion system (10) comprises at least first and second electrical generators (15a, 15b), each being configured to provide electrical power to a respective first and second AC electrical network (16a, 16b). The system (10) further comprises at least first and second AC electrical motors (19a, 19b) directly electrically coupled to a respective AC network (16a, 16b) and coupled to a respective propulsor (4), and a DC electrical network electrically coupled to the first and second AC networks (16a, 16b) via respective first and second AC to DC converters (17a, 17b), and to a further electrical motor 19c), the further electrical motor (19c) being coupled to a propulsor (4).

A propulsion system for an unmanned underwater vehicle includes a turbine engine, a generator mechanically coupled to an output shaft of the turbine engine, an electrical motor mechanically decoupled from the turbine engine and electrically coupled to the generator via a power bus architecture, and a propulsor mechanically coupled to a rotational output of the electrical motor. The power bus architecture includes a pair of AC buses and a DC bus.

A propulsion system for an unmanned underwater vehicle includes a turbine engine, a generator mechanically coupled to an output shaft of the turbine engine, an electrical motor mechanically decoupled from the turbine engine and electrically coupled to the generator via a power bus architecture, and a propulsor mechanically coupled to a rotational output of the electrical motor. The power bus architecture includes a pair of AC buses and a DC bus.

An electric motor system includes a drive shaft that rotationally drives a load, a bearingless motor, a power source unit, and a control unit. The bearingless motor includes a rotor and a stator having armature and support windings. The bearingless motor rotationally drives the drive shaft and supports a radial load of the drive shaft in a contactless manner. The power source unit applies a voltage to the armature and support windings. The control unit controls the power source unit so that a radial support force that is a sum of a radial support force caused by a support current and a radial support force caused by both the support current and an armature current is output, and so that one of an armature voltage across the armature winding and the support current is increased and the other of the armature voltage and the support current is decreased.

An electric motor system includes a drive shaft that rotationally drives a load, a bearingless motor, a power source unit, and a control unit. The bearingless motor includes a rotor and a stator having armature and support windings. The bearingless motor rotationally drives the drive shaft and supports a radial load of the drive shaft in a contactless manner. The power source unit applies a voltage to the armature and support windings. The control unit controls the power source unit so that a radial support force that is a sum of a radial support force caused by a support current and a radial support force caused by both the support current and an armature current is output, and so that one of an armature voltage across the armature winding and the support current is increased and the other of the armature voltage and the support current is decreased.

An aircraft having a differential rotor speed resonance avoidance system. The aircraft includes an airframe having structural elements subject to resonant vibration at critical frequencies. A thrust array is coupled to the airframe. The thrust array includes at least four rotor systems distributed about the airframe, each rotor system operable over a range of rotor speeds. A flight control system is operably associated with the thrust array and is configured to independently control the rotor speed of each rotor system. While preserving flight dynamics during flight operations, the flight control system selectively increases the rotor speed of some of the rotor systems by a speed delta and decreases the rotor speed of others of the rotor systems by the speed delta to avoid generating excitation frequencies by the rotor systems at the critical frequencies.

An aircraft having a differential rotor speed resonance avoidance system. The aircraft includes an airframe having structural elements subject to resonant vibration at critical frequencies. A thrust array is coupled to the airframe. The thrust array includes at least four rotor systems distributed about the airframe, each rotor system operable over a range of rotor speeds. A flight control system is operably associated with the thrust array and is configured to independently control the rotor speed of each rotor system. While preserving flight dynamics during flight operations, the flight control system selectively increases the rotor speed of some of the rotor systems by a speed delta and decreases the rotor speed of others of the rotor systems by the speed delta to avoid generating excitation frequencies by the rotor systems at the critical frequencies.

A device for estimating a rotation speed and/or a direction of rotation of an induction machine is presented. The device controls stator voltages (uu, uv, uw) of the induction machine so that a voltage space-vector constituted by the stator voltages has a fixed direction and a current space-vector constituted by stator currents (iu, iv, iw) of the induction machine has a pre-determined length or a predetermined d-component. The rotation speed and/or the direction of rotation is/are estimated based on a waveform of a q-component of the current space-vector, where the d-component of the current space-vector is parallel with the voltage space-vector and the q-component of the current space-vector is perpendicular to the voltage space-vector. The device is usable when the induction machine does not have enough magnetic flux for flux-based determination of the rotation speed and/or the direction of rotation.

A device for estimating a rotation speed and/or a direction of rotation of an induction machine is presented. The device controls stator voltages (uu, uv, uw) of the induction machine so that a voltage space-vector constituted by the stator voltages has a fixed direction and a current space-vector constituted by stator currents (iu, iv, iw) of the induction machine has a pre-determined length or a predetermined d-component. The rotation speed and/or the direction of rotation is/are estimated based on a waveform of a q-component of the current space-vector, where the d-component of the current space-vector is parallel with the voltage space-vector and the q-component of the current space-vector is perpendicular to the voltage space-vector. The device is usable when the induction machine does not have enough magnetic flux for flux-based determination of the rotation speed and/or the direction of rotation.

A propulsion system for an unmanned underwater vehicle includes a turbine engine, a generator mechanically coupled to an output shaft of the turbine engine, an electrical motor mechanically decoupled from the turbine engine and electrically coupled to the generator via a power bus architecture, and a propulsor mechanically coupled to a rotational output of the electrical motor. The power bus architecture includes a pair of AC buses and a DC bus.