An auxiliary power unit (APU) control system for an aircraft is disclosed, and includes an APU drivingly coupled to one or more generators, one or more processors, and a memory coupled to the one or more processors. The memory stores data comprising a database and program code that, when executed by the one or more processors, causes the APU control system to receive one or more ambient signals indicative of an air density value and one or more power signals indicative of a specific amount of power generated by the APU. The system is further caused to determine a first variable rotational speed of the APU based on the air density value. The APU continues to generate the specific amount of power when operating at the first variable rotational speed. After instructing the APU to operate at the first variable rotational speed, the system receives an electrical load signal.

A control for a multi-shaft turbine engine system using electrical machines seeks optimal system performance while accommodating hard and soft component limits. To accommodate the component limits, the control may generate a number of possible operating point options reflecting potential trade-offs in performance, lifing, efficiency, or other objectives.

One example aspect of the present disclosure is directed to a method for operating a gas turbine engine. One example aspect of the present disclosure is directed to a method for operating a gas turbine engine, the gas turbine engine including at least a high pressure spool and a low pressure spool. The method includes causing, by one or more control devices, electrical power to be drawn from the high pressure spool and the low pressure spool into a power distribution system. The method includes determining, by the one or more control devices, a power adjustment event associated with the high pressure spool. The method includes initiating, by the one or more control devices, a power assist operation to redirect electrical power to the high pressure spool based at least in part on the power adjustment event.

A hybrid electric propulsion system includes a gas turbine engine having a low speed spool and a high speed spool. The low speed spool includes a low pressure compressor and a low pressure turbine, and the high speed spool includes a high pressure compressor and a high pressure turbine. The hybrid electric propulsion system also includes an energy storage system, an electric motor configured to augment rotational power of the high speed spool, and a controller. The controller is operable to detect a start condition of the gas turbine engine, control power delivery from the energy storage system to the electric motor based on detecting the start condition, and provide a compressor stall margin using a power-assist provided by the electric motor to the high speed spool over a targeted speed range during starting of the gas turbine engine.

A voltage generator circuit can be structured to provide an output voltage having a substantially flat temperature coefficient by use of a circuit loop having transistors and a resistor arranged such that, in operation, current through the resistor has a signed temperature coefficient. The current behavior can be controlled by an output transistor coupled to another transistor, which is coupled to the circuit loop, with this other transistor sized such that, in operation, a voltage of this other transistor has a signed temperature coefficient that is opposite in sign to the signed temperature coefficient of the current through the resistor. Embodiments of voltage generator circuits can also include additional components to trim output voltage, to provide unconditional stability, or other features for the respective voltage generator circuit. In various embodiments, a voltage generator circuit can be implemented as a low drop-out (LDO) voltage regulator.

Systems and methods for dual voltage power generation are provided. Aspects include a generator having an input connected to an engine to receive rotational energy proportional to a rotation speed of a fan and having an output through which electrical energy is output, a rectifier circuit having an input coupled to the output of the generator and a rectifier output that outputs rectified power, a bypass switch connected to the output of rectifier and operates in a plurality of states including a normal operation state where the rectified power is provided a power converter and a bypass state where the rectified power is provided directly to a load, and a controller configured to determine an occurrence of an event associated with the engine, and operate the bypass switch in the bypass state based on the occurrence of the event associated with the engine.

A variable speed, constant frequency (VSCF) generator system is provided and includes a generator portion, a first cooling circuit and a second cooling circuit. The generator portion includes a generator, electronics configured to control operations of the generator and a housing to house the generator and the electronics. The first cooling circuit is provided such that first fluid exiting the generator passes through a first cooling element prior to returning to the generator. The second cooling circuit is provided such that second fluid exiting the electronics passes through a second cooling element prior to being pumped back toward the electronics.

The disclosure relates to an electric machine and in particular to the monitoring of the electric machine for the presence of a fault, (e.g., in the stator windings). A monitoring unit is provided, wherein the monitoring unit measures the multiphase electrical time signals transmitted from or to the machine and with the aid of a Hilbert filter determines substantially in real time the envelopes and the phase positions of the individual phases of the time signal. The envelopes corresponding to the different phases or the corresponding phase positions are compared with one another by way of forming differences and, in the event that one or more of the differences deviate(s) from a specified expectation value, the presence of a fault is inferred. The approach allows significantly increased operational reliability of the electric machine to be achieved in particular.

A system including a variable frequency generator (VFG) including a generator configured to conduct alternating current to a first rectifier configured to convert alternating current from the VFG to direct current and drive it to an HVDC Bus Network, a variable frequency second generator including a second generator configured to conduct alternating current to a second rectifier configured to convert alternating current from the second generator to direct current and conduct it to the HVDC Bus Network, a speed correcting gearbox operatively connected to the VFG configured to align generator frequency to the second generator frequency, and a VFG control unit operatively connected to the generator configured to control the VFG, and a second generator control unit operatively connected to the second generator and the HVDC Bus Network configured to control the second generator.

An aircraft includes an engine and a first variable frequency generator having a first rotor that is rotatable at a rate that is based on a rotational rate of the engine to cause the first variable frequency generator to generate a first multiphase signal. The aircraft further includes a second variable frequency generator having a second rotor that is rotatable at the rate to cause the second variable frequency generator to generate a second multiphase signal. The first multiphase signal is phase aligned with the second multiphase signal. The aircraft further includes one or more switches coupled to a first electrical system and configured to selectively provide power to the first electrical system based on either the first multiphase signal or the second multiphase signal.