UAVs (unmanned aerial vehicles) and drones are typically powered either by an engine – which may be a two- or four-stroke internal combustion engine, a rotary engine, or a gas turbine engine – or by batteries. They will also contain a variety of subsystems, such as imaging and sensor payloads, flight and engine control, and communications and navigation systems, that will require either an AC or DC electrical power source.
Engine-powered drones, particularly larger ones, may include an electrical generator powered by the engine. This generator will typically produce a three-phase AC (alternating current) power output at 115V. This three-phase power supply can be converted into a single-phase power supply by means of an AC-AC power converter. UAV subsystems that require AC power may include radars and transmitters. AC power can be fed into an AC-DC power converter in order to supply the large amount of components onboard that require DC power.
Battery-powered drones have a DC power source – the battery itself. This DC power can be used to provide AC power, if required, by using a device called an inverter. Inverters may provide multiple AC voltages, such as 26V AC and 115V AC. The DC voltage from the battery can also be fed into a DC-DC power converter in order to supply other DC voltages that may be needed for different equipment and subsystems. Engine-powered drones will typically have a battery on board as well that can be used for starting the engine and to provide vital systems with backup power in the event of engine failure.
UAVs that contain multiple sources for electrical power may utilise a power management system that can control each individual source to generate power as needed, depending on the power supply and demand, the requirements at any particular stage of the mission, and the environmental conditions.
Power supplies may be designed specifically for the embedded systems utilised in UAVs and drones, and may thus be designed in various form factors such as PCI-104 and VPX 3U. Power supplies and power converter cards for embedded systems may take in a larger DC voltage such as 270V DC or 28V DC and output a much lower voltage such as 5V DC or 3.3V DC.
Power supplies for UAVs and unmanned systems may have to be engineered to withstand especially harsh environments, including extremes of temperature, shock, vibration and EMI (electromagnetic interference). These rugged power supplies may be engineered to particular military specifications and standards, such as MIL-STD-810F for shock and vibration, and MIL-STD-461E for EMI.