Gas turbine engines

Abstract

The generator uses a permanent magnet electrical machine providing three phase, unregulated DC voltage, from three windings feeding a rectifier circuit. A capacitor across the DC voltage acts as a buffer between the DC supply and the load. Regulation of the DC supply seen by the load is achieved by a switch in parallel with the DC voltage and with the load. The switch allows current to be drawn by the capacitor or load from the windings, or shorts the windings. The inductance of the windings makes it safe to short them. A blocking diode prevents current returning from the capacitor when the switch is closed. The result is a regulated DC output of adequate quality for e.g. aerospace applications and with low component count and complexity.

1 . A gas turbine engine comprising:
 an electrical generator having inductive windings;   the generator being driven, in use, by a moving component of the engine, to generate electrical power from the windings;   and the engine further comprising:   a switch arrangement in parallel with the output of the windings and operable to control the output voltage from the generator by selectively shorting the inductance of the windings.   
     
     
         2 . An engine according to  claim 1 , further comprising a capacitor in parallel with the switch. 
     
     
         3 . An engine according to  claim 2 , further comprising a diode, the capacitor and diode being in series with each other and together in parallel with the switch, the diode being oriented to isolate the capacitor from supplying current to the switch, when the switch is closed. 
     
     
         4 . An engine according to  claim 2 , wherein the generator is an AC generator, the engine further comprising a rectifier circuit between the generator output and the switch. 
     
     
         5 . An engine according to  claim 4 , wherein the rectifier circuit is passive. 
     
     
         6 . An engine according to  claim 4 , wherein the rectifier circuit is a diode bridge. 
     
     
         7 . An engine according to  claim 1 , wherein the generator is a three-phase generator. 
     
     
         8 . An engine according to  claim 1 , wherein the generator is a permanent magnet machine. 
     
     
         9 . An engine according to  claim 1 , wherein the generator is a brushless DC machine. 
     
     
         10 . An engine according to  claim 1 , wherein the generator is driven, in use, from a shaft of the engine. 
     
     
         11 . An electrical generator for a gas turbine engine, the generator having inductive windings and being driven, in use, by a moving component of the engine, to generate electrical power from the windings, and the generator further comprising a switch arrangement in parallel with the output of the windings and operable to control the output voltage from the generator by selectively shorting the inductance of the windings. 
     
     
         12 . A gas turbine engine comprising:
 an electrical generator, a moving component, a rectifier circuit and a switch arrangement,   the electrical generator having inductive windings and the electrical generator being a permanent magnet machine,   the electrical generator being driven, in use, by the moving component of the gas turbine engine, to generate electrical power from the inductive windings,   the switch arrangement being arranged in parallel with the output of the inductive windings and operable to control the output voltage from the electrical generator by selectively shorting the inductance of the inductive windings, and   the rectifier circuit being arranged between the generator output and the switch arrangement and the rectifier circuit comprising a diode bridge.