Definition
A power supply that holds its output voltage steady at a set value while the current it delivers varies with the load. As the equipment connected to it draws more or less current, the supply automatically adjusts to keep the voltage from changing.
Plain English
A power source that keeps its voltage at a fixed level no matter how much electrical load is placed on it. The current can go up or down with demand, but the voltage stays the same.
Context Anchor
Seen in aircraft electrical-system discussions, battery charging, and ground testing of radios, instruments, and other electrical equipment.
Derivation
From Latin constans, 'standing firm,' and volta, named after Alessandro Volta who developed the first electric battery. The term simply describes a supply where the voltage stands firm.
Why Pilots Care
Prevents erratic behavior in instruments and navigation equipment that could compromise flight safety.
Analogy
Like a water tap that automatically adjusts to keep pressure steady whether you're filling a cup or a bucket. The amount of water flowing changes with demand, but the pressure stays the same.
Grounding Statement
If more equipment is switched on, a constant-voltage power supply should still hold the selected voltage unless it is overloaded.
Intuition Check
Constant-voltage does not mean the supply can provide unlimited power. It means the voltage stays steady while the current changes to match what the connected equipment needs, up to the supply’s limit.
Example Sentence 1
The aircraft's alternator acts as a constant-voltage power supply, holding the bus at 28 volts while the current draw rises and falls with each system that switches on.
Example Sentence 2
During preflight, the mechanic verified that the constant-voltage power supply was delivering steady power to the radios.