Aircraft electrical system operating method

Abstract

A method of controlling an aircraft electrical system (40). The electrical system (40) comprises an alternating current electrical machine (56, 58) comprising a plurality of phases, each phase having a power rating, the electrical machine (56, 58) being configured to operate on failure of one or more phases. The method comprises: determining a power requirement; sensing a fault of one or more phases of the electrical machine (56, 58), and controlling the electrical machine (56, 58) to operate in a fault condition, in which the remaining phases of the electrical machine (56, 58) provide the electrical power requirement; and providing an overrating signal to a flight computer (66) of the aircraft (2) where the power provided by each phase exceeds the power rating of the respective phase.

Description

FIELD OF THE INVENTION[0001]The present invention relates to an aircraft electrical system, and to a method of controlling an aircraft electrical system to provide fault tolerant operation.BACKGROUND TO THE INVENTION[0002]Aircraft such as passenger aircraft comprise a number of powered systems, such as control surface actuators, passenger air systems and avionics. In traditional aircraft, some of these systems are electrically powered, while others are pneumatically or hydraulically powered. Aircraft engines, such as gas turbine engines, also comprise a number of powered accessory systems, such as fuel and oil pumps, which are powered by the engine itself. In recent years, there has been a move to provide electrically powered systems for aircraft and aircraft engine accessory systems to replace some or all of the pneumatic or hydraulic systems in order to save weight or reduce fuel burn, or a combination of the two. Aircraft having more electrical systems compared to traditional air...

AI Technical Summary

Benefits of technology

The patent describes a method for controlling an aircraft's electrical system that allows the machine to operate at a higher power level for a limited period of time in case of a fault. This prevents loss of thrust control and allows for the use of a lighter, more efficient electrical machine. The method also includes detecting and isolating the location of the fault, and maintaining the machine's normal operation while the fault is diagnosed. Additionally, the method includes sensing and controlling the oil and fuel pressures to prevent fuel leakage into the oil system.

Problems solved by technology

In the case of an MEE, where the engine accessory is required for continued operation of the engine, such as where the engine accessory comprises the fuel or oil pump, a fault within the electrical system may result in an undemanded drop in power and consequently a loss of thrust control, or possibly an engine shutdown.

Consequently, where essential engine accessory systems are electrically powered, such accessory systems may require redundancy, i.e. multiple independent systems, in order to prevent a fault with a single system from resulting in loss of thrust control.

Such redundancy however increases weight and costs to the extent that the advantages of an MEE may not be realised.

Consequently, conventional fault tolerant electrical machines must be relatively large, and therefore heavy and expensive.

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