Definition
An electrical transformer used to measure large amounts of alternating current. The wire carrying the current to be measured passes through (or acts as) the primary winding, and a secondary winding wound around a shared iron core produces a much smaller, proportional current that can be safely read by an ammeter or sensed by a protective circuit.
Plain English
A device that lets you measure a large electrical current safely by producing a small, scaled-down copy of it for the meter to read.
Context Anchor
Seen in aircraft electrical systems when measuring generator or alternator output, battery charging current, or overall electrical load.
Derivation
Transformer comes from the Latin trans- (across) and formare (to shape or form) -- it 'transforms' electrical energy from one circuit to another. 'Current' transformer simply specifies that this type is built to scale current rather than voltage.
Why Pilots Care
The cockpit ammeter or load meter that shows how much current the generator or alternator is producing is fed by a current transformer. If a pilot understands what it does, the load reading makes sense as a real measurement of electrical demand, not just an arbitrary needle.
Intuition Check
Current does not mean “present time” here; it means the flow of electricity. A current transformer does not power the aircraft by itself; it creates a smaller measured copy of the electrical flow.
Example Sentence 1
The load meter reads generator output through a current transformer mounted around the main feeder cable.
Example Sentence 2
During preflight, the technician verified that the current transformers were producing the correct secondary output for the overcurrent relays.