UAV Generator
Generator PMU
The Millswood Engineering Generator Power Management Unit provides up to 500 Watts of on-board electrical power generation for small to medium-sized UAVs. The generator PMU includes active rectification technology for cooler, more efficient operation, as well as several other innovative features not found on competing products.
The PMU connects to a suitable brushless DC electric motor, which is in turn driven by the aircraft's primary power plant, usually an internal combustion engine.
Features:
- Active rectification avoids the diode losses with traditional passive rectifiers, resulting in superior low voltage performance and higher efficiency.
- Buck-boost converter keeps the output voltage on target and the battery being charged even when the input voltage is less than the output voltage.
- Programmable main output voltage can be set to any voltage from 10 to 30VDC in 0.1V steps. Rated at 15A continuous.
- Auxiliary power output provides 6V at 5A continuous.
- Built-in universal (CCCV) battery charger with charging current programmable up to 5A in 0.1A steps.
- Programmable input current and input power limits prevent overloading the internal combustion engine and BLDC motor.
- RS232 or CAN control and monitoring interface.
- Main 3-phase input voltage range of 10 to 70Vpp.
- External DC input voltage range of 12 to 70VDC.
- Inputs and ouputs protected from reverse polarity, over-voltage, ESD and short-circuits.
- Extensive monitoring and reporting of voltages, currents, battery charge status, temperature.
Benefits of on-board electrical power generation
Typical generator system
Minimising the mass that must be carried by an airframe is central to maximising performance and range. Batteries can constitute a significant part of the overall mass of small to medium-sized UAVs, and so storing the necessary electrical energy in an alternative form is one way of reducing the battery mass.
The gravimetric energy density of liquid hydrocarbon fuels remain more than an order of magnitude better than the best battery technology (12 kWh/kg for aviation fuel versus 0.35 kWh/kg for Li-S). Even allowing for the relatively poor efficiency of internal combustion engines, onboard electric power generation remains a highly effective way of reducing the battery mass.
Existing solutions typically use a brushless DC electric motor configured as a generator as shown opposite. The Millswood Engineering PMU also uses this arrangement.
Benefits of active rectification
Power loss of a typical 3-phase Silicon diode bridge, a high-performance
3-phase Schottky diode bridge, and our 3-phase active rectifier.
The first step in turning high-voltage AC into regulated DC is rectification. This process is traditionally performed using a diode bridge, which is an inefficient device that wastes some potentially useful power as heat. Active rectification replaces the diodes with FETs, which have lower loss than either Silicon or Schottky diodes.
As can be seen from the graph on the right, there is up to 90% reduction in the power lost in the rectification process when an active rectifier is used. This translates into improved overall efficiency, particularly at low rpm where the diode drop is a significant fraction of the rectifier's total voltage.
For the UAS, active rectification means:
- Higher efficiency and therefore reduced fuel consumption and greater aircraft endurance;
- Reduced heating and heatsinking requirements and therefore smaller enclosed volume; and
- Operation to lower rpm.
Further information
- Generator PMU product brief
- Generator PMU product manual
- Generator PMU CAN protocol (custom CAN protocols available on request)
Please contact us for price, availability or further technical information.
