GLENAIR
question—including test methods to meet the unique environmental challenges associated with these high-cycle, dynamic air taxi missions—from basic considerations of galvanic corrosion and dissimilar metal design principles, to a wide range of other environmental constraints. In this regard, the UAM environment may ultimately be considered as basically a modification to the DO- 160 Category A4, which states: Equipment intended for installation in a controlled temperature and pressurized location on an aircraft within which pressures are normally no lower than the altitude equivalent of 15,000 ft Mean Sea Level. The category may also be applicable to equipment installed in temperature controlled but unpressurized locations on an aircraft that operate at altitudes no higher than 15,000 ft MSL.
Why is understanding the power system voltage so important? Higher voltages in aircraft operating environments characterized by broad temperature ranges, altitude, and pressure define wire insulation thickness and electrical connector geometry creepage and clearance dimensions. Per AS50881, paragraph 6.6, “For DC, electrical cables can be used without ionization to a maximum voltage of 340 volts independent of the usual practical range of wire covering thicknesses. Under certain conditions (notably at high ambient temperatures and/or high altitude) some wire types may not be free from corona at rated voltage.” In certain applications of this type, Power Feeders (as opposed to mateable interconnects) combined with highly engineered power cabling, offer a viable solution which mitigates certain challenges associated with the use of conventional mil-spec insulated cables and connectors in high-power applications. Glenair Duralectric Power Feeders are in development for UAM applications with variable dielectric wall thicknesses IAW insulated conductor size and material and addressing the overall voltage / weight / flexibility requirements of the emerging UAM market. Glenair has several methods of terminating our aircraft-grade TurboFlex / Duralectric cables for use in applications of this type. For applications that do require the ability to mate and un-mate—such as for electric motors— purpose-designed interconnects with proven performance in rigorous commercial airplane environments are preferred for compliance to FAA part regulations. Interconnects of this type typically incorporate design features that enable connectorization of high voltage, high current, as well as high-frequency power distribution systems providing safe and reliable protection of power lines from arcing or other safety hazards.
Environment Constraints: • Operating Low Temperature: • Operating High Temperature: • Ground Survival Low Temperature: • Ground Survival High Temperature:
-15° C +70°C -55°C +85°C
• Altitude:
4572 m (15,000 ft)
• Absolute Pressure (at 15kft):
57.18kPa (751.8mbars, 16.89 inHg, 429 mmHg)
Electrical Power Distribution System Voltage Requirements The core technology for the electrical power distribution system in autonomous air taxis is based on the lithium-ion battery series/parallel design used in electric automobiles which, depending on the vehicle performance factors, produces a voltage of between 375Vdc to 800Vdc. An important benchmark in evaluating power distribution interconnect requirements can also be drawn from past successful NASA-instituted programs in which nominal voltage of 461Vdc (416Vdc – 525Vdc) with a maximum operating altitude of 15,000 ft. was achieved. Both of these power distribution models rely on lithium battery technology and are useful as a basis for selection of EWIS interconnect components suitable for the current generation of UAM lithium-ion HVDC power distribution systems.
QwikConnect • July 2021
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