A power generation system for a drilling tool includes a turbine, an alternator, a converter and a first active rectifier control (ARC). The turbine is adapted to be driven by a fluid flow in a well. The alternator is coupled to the turbine and generates an alternative current (AC). The converter converts the AC to direct current (DC) and carries out active rectification. The first active rectifier control (ARC) controls the active rectification of the converter.

As a configuration of carrying out a turning operation of a brushless synchronous power generation apparatus, there are provided a synchronous generator, an AC exciter, a rotary rectifier attached to an armature of the AC exciter, and short-circuiting means which three-phase short-circuits armature windings of the AC exciter, wherein the armature windings of the AC exciter are short-circuited, causing the AC exciter to operate as an induction motor, thus rotating the rotor shaft of the synchronous generator.

A system may include a first bus transfer switch configured to open and close connections between a generator control unit, a pilot permanent magnet generator stage of an independent speed variable frequency (ISVF) generator, and an external power source. The system may further include an inverter configured to set a main field winding of the ISVF generator into a motor state. The system may also include a second bus transfer switch configured to open and close a connection between a main armature winding of the ISVF generator, a power distribution bus, and a motor start driver configured to send a current through the main armature winding to generate a magnetic field pattern that causes the rotor to turn, enabling startup of an engine.

An alternator includes an exciter field device generating an exciter magnetic field in a first air gap, an exciter armature device configured to rotate with respect to the exciter magnetic field and impart a first voltage in a first set of coils at the first air gap, a main stator device including a second set of coils, and a rotor field device configured to be energized by the first current in the first set of coils and generate a main magnetic field that imparts a second voltage on the main stator device at a second air gap. The main stator device and the exciter field device lie in on a common plane normal to an axis of rotation, and the exciter armature device is inwardly spaced from the exciter field device, main stator device, and the rotor field device.

In one embodiment, a generator includes a rotor configured to rotate in cooperation with a stator to generate electrical power. An exciter of the generator includes at least one circuit board, a stationary exciter stator, and a control circuit. The circuit board is mechanically coupled to a rotor of the generator and includes at least one coil of an electrical conductor. The stationary exciter stator is configured to induce a current in the at least one coil of the at least one circuit board. The control circuit is configured to modify the current from the at least one coil and provide the modified current to a field of the generator.

An aircraft main power generation system includes a rotor shaft, a main power generator a permanent magnet, an exciter, an aircraft power bus, and a generator control unit. The generator control unit is configured to provide a control current to the exciter in response to a speed of the main power generator reaching a threshold speed and electrically couple the main power generator to the aircraft power bus in response to the speed of the main power generator reaching a minimum operating speed, the threshold speed being lower than the minimum operating speed; or provide a control current to the exciter in response to the speed of the main power generator reaching a predetermined speed and electrically coupling the main power generator to the aircraft power bus in response to a time period elapsing after the speed of the main power generator has reached the predetermined speed.

A regulating device for a brushless excitation system for supplying at least one excitation coil of a rotor of a synchronous machine with excitation current, having a detection device to detect a strength of a magnetic flux; a regulating unit to generate an auxiliary excitation DC current supplied to the main excitation machine by rectifying an auxiliary excitation three-phase current, and to regulate the current strength of the auxiliary excitation DC current such that a magnetic flux generated between the rotor and the stator of the main excitation machine is kept constant independently of the current strength of the excitation current; and an adjusting unit rotationally fixed to a rotor shaft of the synchronous machine to generate the excitation current by rectifying an excitation three-phase voltage generated by the main excitation machine and to regulate the current strength of the excitation current supplied to the rotor of the synchronous machine.

A hybrid permanent magnet machine has a stator including armature windings. A rotor includes permanent magnets, a main field winding, and a rechargeable energy source. An output voltage control circuit, including an H bridge circuit configured to provide control current magnitude and direction in the main field winding to control the current passing across the main field windings.

An aircraft starting and generating system includes a starter/generator and an inverter/converter/controller (200) that is connected to the starter/generator and that generates AC power to drive the starter/generator in a start mode for starting a prime mover of the aircraft, and that converts AC power, obtained from the starter/generator after the prime mover have been started, to DC power in a generate mode of the starter/generator. A four leg inverter is coupled with a DC power output (452) of the starter/generator and has an inverter/converter/controller (ICC) (580) with a four leg MOSFET-based bridge configuration that drives the starter/generator in a start mode for starting a prime mover of the aircraft, and converts DC power to AC power in a generate mode of the starter/generator. A four leg bridge gate driver (560) is configured to drive the four leg MOSFET-based bridge (580) during start and generate mode using bi-polar pulse width modulation (PWM).

A stator defines multiple stator poles with associated stator windings. A rotor defines multiple rotor poles with associated rotor windings configured to be energized substantially by the stator. The rotor defines a rotor field energizable by magnetic fields produced by the stator windings to produce relative force between the rotor and the stator. An active rectifier is conductively coupled to one or more first rotor windings. The active rectifier is configured to control a direction of current flow through the one or more first rotor windings responsive to a signal received wirelessly from the stator by one or more second rotor windings.