1 Answer
The **CT ratio** in a transformer refers to the ratio of the number of turns in the primary coil (input side) to the number of turns in the secondary coil (output side) of a **current transformer** (CT).
A **current transformer** is a special type of transformer used for measuring electrical currents. It reduces the current flowing in the power circuit to a much lower, manageable level so that it can be safely measured by standard instruments like ammeters or connected to protection relays.
### Formula for CT Ratio:
\[
\text{CT Ratio} = \frac{\text{Primary Current (High Voltage Side)}}{\text{Secondary Current (Low Voltage Side)}}
\]
For example, if a CT has a **ratio of 1000:5**, it means that for every 1000 amps flowing through the primary side, only 5 amps will flow through the secondary side. This allows accurate measurement of large currents using standard measuring devices designed for much smaller currents.
### Purpose of CT Ratio:
1. **Current Measurement**: It allows measuring high currents indirectly by stepping down the current to a lower value.
2. **Protection**: It helps in protecting electrical systems by providing accurate current values for protection relays.
The ratio of the CT is essential because it helps in calibrating the measurement instruments and ensuring that they show the correct value.
A **current transformer** is a special type of transformer used for measuring electrical currents. It reduces the current flowing in the power circuit to a much lower, manageable level so that it can be safely measured by standard instruments like ammeters or connected to protection relays.
### Formula for CT Ratio:
\[
\text{CT Ratio} = \frac{\text{Primary Current (High Voltage Side)}}{\text{Secondary Current (Low Voltage Side)}}
\]
For example, if a CT has a **ratio of 1000:5**, it means that for every 1000 amps flowing through the primary side, only 5 amps will flow through the secondary side. This allows accurate measurement of large currents using standard measuring devices designed for much smaller currents.
### Purpose of CT Ratio:
1. **Current Measurement**: It allows measuring high currents indirectly by stepping down the current to a lower value.
2. **Protection**: It helps in protecting electrical systems by providing accurate current values for protection relays.
The ratio of the CT is essential because it helps in calibrating the measurement instruments and ensuring that they show the correct value.