1 Answer
A **Current Transformer (CT)** is a type of transformer used to measure alternating current (AC) in a circuit. It works on the same principle as any other transformer but is designed specifically for current measurement rather than voltage.
### Principle of a CT Transformer:
1. **Electromagnetic Induction**:
The basic working principle of a CT is **electromagnetic induction**. When an alternating current (AC) flows through the primary winding of the CT, it generates a magnetic field around it. This magnetic field induces a current in the secondary winding of the transformer.
2. **Current Proportionality**:
The current induced in the secondary winding is **proportional** to the current flowing in the primary winding. The ratio of the primary current to the secondary current is defined by the **turns ratio** of the transformer, which is typically a high ratio (e.g., 1000:1). This allows large currents to be scaled down to measurable levels for easy monitoring or protection.
* If the primary current is 1000 A and the CT's turns ratio is 1000:1, the secondary current will be 1 A.
3. **Magnetic Flux Linkage**:
The primary current creates a magnetic flux that links with the secondary winding. Since the transformer is designed to operate with high accuracy, this flux is designed to be proportional to the current in the primary conductor.
4. **No Direct Electrical Connection**:
A current transformer works **without a direct electrical connection** between the primary and secondary windings. This means the secondary side can be used for measurement and protection purposes without disturbing the primary circuit.
5. **Burden and Accuracy**:
The CT provides accurate measurements within its specified **burden** (the load on the secondary side). The burden is typically a small resistance or instrument like an ammeter or protective relay that is connected to the secondary winding.
### Key Points:
* **Primary winding**: The conductor (or wire) carrying the current to be measured.
* **Secondary winding**: The winding that provides a reduced current proportional to the primary current.
* **Core**: Usually made of iron or ferrite, the core supports the magnetic field produced by the primary current.
The CT's main use is in **measuring and monitoring high currents**, such as in power distribution and electrical protection systems.
### Principle of a CT Transformer:
1. **Electromagnetic Induction**:
The basic working principle of a CT is **electromagnetic induction**. When an alternating current (AC) flows through the primary winding of the CT, it generates a magnetic field around it. This magnetic field induces a current in the secondary winding of the transformer.
2. **Current Proportionality**:
The current induced in the secondary winding is **proportional** to the current flowing in the primary winding. The ratio of the primary current to the secondary current is defined by the **turns ratio** of the transformer, which is typically a high ratio (e.g., 1000:1). This allows large currents to be scaled down to measurable levels for easy monitoring or protection.
* If the primary current is 1000 A and the CT's turns ratio is 1000:1, the secondary current will be 1 A.
3. **Magnetic Flux Linkage**:
The primary current creates a magnetic flux that links with the secondary winding. Since the transformer is designed to operate with high accuracy, this flux is designed to be proportional to the current in the primary conductor.
4. **No Direct Electrical Connection**:
A current transformer works **without a direct electrical connection** between the primary and secondary windings. This means the secondary side can be used for measurement and protection purposes without disturbing the primary circuit.
5. **Burden and Accuracy**:
The CT provides accurate measurements within its specified **burden** (the load on the secondary side). The burden is typically a small resistance or instrument like an ammeter or protective relay that is connected to the secondary winding.
### Key Points:
* **Primary winding**: The conductor (or wire) carrying the current to be measured.
* **Secondary winding**: The winding that provides a reduced current proportional to the primary current.
* **Core**: Usually made of iron or ferrite, the core supports the magnetic field produced by the primary current.
The CT's main use is in **measuring and monitoring high currents**, such as in power distribution and electrical protection systems.