How much power is removed from an aircraft engine through the use of an alternator?

Question

I would like to know this in regards to commercial aircraft. Any information regarding powering on-board electrical systems would be greatly appreciated.

Answer 1

Jason, sorry friend, but you are wrong.

Even when IDG is not producing electrical power, there is a certain amount of power drawn from the engine, in a 777 120KVA IDG that´s being loaded to a 100% rated capacity, THERE WILL BE power drawn!!!

So, even when it does not mens much to the engine, there is power drawn.

cheers.

Answer 2

Commercial aircraft use fairly large generators, but they still aren't big enough to make much of a difference. While I can't post any specific numbers, I can say that the power lost generating electricity is negligible. Commercial aircraft generate thousands upon thousands of pounds of thrust, yet the electrical systems on board can be powered by a generator with output measured in horsepower.

Answer 3

An alternator will be rated in Watts.

There are about 750 Watt.s per horsepower.

The alternator is about 75% efficient.

You can figure it out.

Answer 4

Answer: 0

Nearly all jet engines currently flying have something known as an integrated drive generator (IDG) or something of a similar name.  This means that the generator is actually integrated as part of the engine.  It is impossible to turn the engine without turning the IDG.  If you measure power as the output of an engine either at the shaft or at the exhaust section, that number already takes into account what it takes to turn the IDG and generate power.

And since its not something that can be un-integrated, the power output of the engine does not change based on whether or not the generator switches are "ON" or "OFF" which does not actually turn the generator on, but simply completes a circuit allowing electrical power to flow to the rest of the electrical components of the airplane.

Answer 5

If I get you right you're talking about power loss, actually electrical system isn't generating much power loss. The shaft rotational speed is even lessen by having a series of gearing's which is called accessory gearbox where through a series of gears makes a constant rpm of around 20,000rpm to drive the IDG or generator, to make a 115VAC 400Hz elect. power.  This acc. gearbox also drives the fuel pump and  engine driven hydraulic pump.

The one that really takes power loss to the engine is its bleed air wherein during flight if the wings anti-ice valve is open to give engine bleed air to heat the wings, the Electronic Control Unit adjust fuel, to compensate for the bleed loss for de-icing.