Definition
An electrical control device used in aircraft DC charging systems that connects the generator to the battery bus when the generator's voltage exceeds the battery voltage by a preset amount, and disconnects them when current begins to flow from the battery back into the generator. It prevents the battery from discharging through the generator when the generator output drops below battery voltage.
Plain English
A switch that automatically links the generator to the battery only when the generator is producing enough voltage to charge it, and breaks that link the moment electricity tries to flow the wrong way -- from the battery back into the generator.
Context Anchor
Seen in aircraft electrical system descriptions, especially older DC generator systems and maintenance troubleshooting of generator control circuits.
Derivation
Differential-voltage' means it acts on the difference between two voltages (generator vs. battery). 'Reverse-current cutout' means it cuts the circuit off when current reverses direction. The name describes exactly what the device watches for and what it does.
Why Pilots Care
Prevents generator damage and uncontrolled battery discharge, maintaining reliable electrical power for flight instruments and systems.
Analogy
It works like an automatic one-way gate for electrical power: it opens when power should move from the generator into the airplane, and closes the path off when power tries to move the wrong way.
Grounding Statement
When the generator is producing enough voltage, the cutout closes; when the generator falls behind the battery, it opens.
Intuition Check
Do not read “reverse current” as simply “less current.” It means current flowing in the opposite direction from the intended generator-to-aircraft direction.
Example Sentence 1
When the generator output dropped below battery voltage during taxi, the differential-voltage reverse-current cutout opened and isolated the generator from the bus.
Example Sentence 2
If the generator voltage drops below bus voltage in flight, the differential-voltage reverse-current cutout disconnects the generator to protect it from reverse current.