Can someone explain why a plane has a 24 volt electrical system?

Answer 1

Actually smaller airplanes typically uses 24V DC system, but airliners like the B747 are equipped with generators that provides 115 V AC, which they could step down to 26 VAC and also convert to DC .

Now let me just limit my answer to your question.

Small aircraft typically use lead acid batteries rated at either 12 VDC or 24 VDC. A 12 VDC battery is consist of 6 lead acid cells and a 24 VDC consists of 12 lead acid cells. Each lead acid cells has an open circuit voltage of
2.1 VDC.

So why 12 or 24 and why not 36 or 48. 36 or 48 would mean adding more cells to each batteries thus adding more weight. If the work of starting an engine, can be done by a 24 VDC system hence it is not wise and practical to use a 48 VDC system since weight is a critical factor in the design of an airplane. Hence, the 24 VDC system became the standard.

Answer 2

Main reason is that with a higher voltage you get more power for the same current.

e.g a resistive load such as a pitot heater might take 8 amps at 14 volts but only 4 amps at 28 volts. Thus thinner and lighter wires are required for a 28 volt system compared to a 14 volt system (and weight saving is important in aircraft)

Answer 3

A automobile battery is somewhat six lead-acid batteries related in series. because of this complicated shape, the burden is greater effective than if a similar quantity of lead and acid have been used to make a single-cellular battery of two volts. the income of greater cells is that each time you double the voltage this is driving any electric gadget, then for the comparable ability output, you are able to cut back the quantity of cutting-edge flowing in the path of the gadget to one / 4 of what it replace into till now. Fifty volts d.c is the utmost voltage that would not choose particular insulation or precautions to stay away from electric ask your self yet even twelve volts is sufficient to cut back the present by using a automobile's starter motor to a practicable quantity of purely some hundred amperes. This makes a huge selection of huge-unfold battery length this is neither too heavy or demands too many cells.

Answer 4

Planes have a 28 Volt ac/dc system e.g. for the avionics units in the cockpit and a 115 Volt/400 Hertz system e.g. for
the cabin lighting or the galley.

Answer 5

As mentioned earlier, the 24V system is used as a result of Ohm's Law...P(watts) = I (current) x E (voltage)
Now in an aircraft weight is a primary design consideration and on modern aircraft....wiring makes up a very significant portion of the aircraft's empty weight.....so it's imperative to make the wiring sufficiently capable of carrying the loads but also to keep it as light as possible.
As Ohm's law dictates....for any given power (watts) if more voltage is used....less current is required. Now, the thickness of wire determines the amount of current a wire can carry....
So if we double the voltage....we can half the current and still get the same power....therefore we can use much lighter wire!

Answer 6

Mostly because it needs more power, probably just for the starter circiut. I know the Big Rigs on the highway have a 48 volt system because the starter needs that power to start that big motor.

Answer 7

So aircraft mechanics won't keep stealing the landing/taxi lights to use on their cars/motorcycles.