Originally Posted by
ST Dog
But the power for the trim motor is fed through a relay (R64 in the attachment on this post
737MAX Stab Trim architecture) and that relay is only engaged (passing power) when the stab trim breaker is closed and the cutout switched are in the NORM position.
Also the control signals (up, down, etc) are 28V DC while the motor power is 3 phase 115V AC.
My understanding is that the wire isolation concern is with the potential for 28 VDC hot shorts to either the up or down control signal wires and the arm circuit wire (the circuit that closes the R64 motor power contactor relay). Those control and arm wires are routed together over much of their runs and are co-routed with numerous 28 VDC power wires. Hot shorts to the motor power wires themselves are not the issue.