Hi HBA,
Those who know electric powered (self-launch or sustainer) gliders could probably answer this question definitively, but please chime in with your aircraft electrics understanding in any case:
If I add a ~72V battery, motor controller, and motor to my homebuilt all-metal glider, should that high voltage / high amperage system be electrically isolated from the glider's metal frame (to which the glider's existing 12V avionics system is grounded)? Or should it be grounded to the airframe as well?
My inclination is to isolate because the electric propulsion system's thick, dedicated wires provide the DC "source" and "return" paths between the components, which negates the need for an airframe common ground to serve as a return pathway.
Any low-voltage signals (e.g., for throttle, voltage and temperature monitoring) would be grounded to the propulsion system via a connection to the motor battery's negative terminal. So there's no electrical interface between the propulsion and the avionics systems.
Also, the thought of touching a metal airplane that's electrically isolated from a high-voltage system is more appealing than the opposite case.
Am I on the right track? Or am I missing out on why the two systems should/must share a common ground? I believe DC circuits of different voltages can share the same common ground, so that's probably not the issue. Can the 72V and 12V system grounds be joined by a ~5A fused bridge that effects a common ground while minimizing high-voltage shock and avionics-interference risks?
What's the standard practice on gliders with electric motors, if there's a standard practice?
Those who know electric powered (self-launch or sustainer) gliders could probably answer this question definitively, but please chime in with your aircraft electrics understanding in any case:
If I add a ~72V battery, motor controller, and motor to my homebuilt all-metal glider, should that high voltage / high amperage system be electrically isolated from the glider's metal frame (to which the glider's existing 12V avionics system is grounded)? Or should it be grounded to the airframe as well?
My inclination is to isolate because the electric propulsion system's thick, dedicated wires provide the DC "source" and "return" paths between the components, which negates the need for an airframe common ground to serve as a return pathway.
Any low-voltage signals (e.g., for throttle, voltage and temperature monitoring) would be grounded to the propulsion system via a connection to the motor battery's negative terminal. So there's no electrical interface between the propulsion and the avionics systems.
Also, the thought of touching a metal airplane that's electrically isolated from a high-voltage system is more appealing than the opposite case.
Am I on the right track? Or am I missing out on why the two systems should/must share a common ground? I believe DC circuits of different voltages can share the same common ground, so that's probably not the issue. Can the 72V and 12V system grounds be joined by a ~5A fused bridge that effects a common ground while minimizing high-voltage shock and avionics-interference risks?
What's the standard practice on gliders with electric motors, if there's a standard practice?
