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.
Current Transformer Coil and 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.
The current transformer coil, or secondary winding, is wound around the magnetic core and contains many more turns than the primary winding. The current produced by the CT transformer is proportional to the primary current but reduced according to the transformer’s turns ratio.
Load (Burden):
- The secondary winding is connected to measuring instruments or protective relays. These devices form the “burden” of the CT.
How a CT Transformer Works
- 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.