Primary Winding:
- The primary winding of the CT is connected to the conductor carrying the current to be measured.
- This winding usually has a single turn, as it may simply be the conductor itself passing through the CT.
Core:
- The CT contains a magnetic core, typically made of laminated silicon steel, which guides the magnetic flux generated by the primary current.
Secondary Winding:
- The secondary winding is wound around the core and contains many more turns than the primary winding.
- The current induced in the secondary winding is proportional to the current in the primary but scaled down by the turns ratio of the transformer.
Load (Burden):
- The secondary winding is connected to measuring instruments or protective relays. These devices form the "burden" of the CT.
Operating Principle:
- When current flows through the primary winding, it creates a magnetic field in the core.
- This magnetic field induces a proportional current in the secondary winding, allowing the measurement of the high primary current through the low secondary current.
Applications:
Current transformers are widely used in:
- Measuring instruments (e.g., ammeters)
- Protective relays in power systems
- Monitoring equipment
Important Points:
The secondary winding of a CT should never be left open-circuited while the primary current is flowing, as this can cause dangerously high voltages.