Combined instrument transformers typically consist of an iron core, primary and secondary windings, and insulating materials. The current transformer component utilizes electromagnetic induction to proportionally step down high primary currents to lower secondary currents (such as 5A or 1A) for use by measuring instruments or protective devices, while the voltage transformer component steps down high primary voltages to standard low voltages (such as 100V or 100/√3V). Configurations range from integrated "current + voltage" units to modular "multi-current + multi-voltage" designs; the latter employs independent windings to enable multi-circuit measurement, making it suitable for complex power distribution systems.