Current Transformers (CT’s) are instrument transformers that are used to supply a reduced proportionate value of current to meters, protective relays, and other instruments. CT’s provide isolation from the high voltage primary, permit grounding of the secondary for safety, and step-down the magnitude of the measured current to a value that can be safely handled by the instruments. We are manufacturing Current transformers for electrical Panel Industry as well as for electronics industry.
Current transformer is an instrument transformer used to measure alternating current. Current transformer comes with protective and measuring devices. In Current transformer secondary current is proportional to the primary current. Current transformers are used to determine the current in the circuit, for the protection of sensitive measuring equipments, and to protect the main lines of the grid.
Depending on the functions performed by the current transformer, they are classified as follows :
- Measuring current transformer.
- Protective current transformer.
Depending on the construction of the current transformer, they are classified as follows :
- Bar type current transformer.
- Wound current transformer.
- Window current transformer.
AB Engineering manufactures following types of Current Transformer :
- Metering and protection Current Transformer
- Resin Cast and Tape wound Current Transformer as per IS.
- Special application Current Transformer for MV range.
Specifications of measurement current transformers :
- Ratio
- Burden
- Class of accuracy
- Voltage Class
- Instrument security factor
Limits of error for Standard Measurement current transformer :
| Accuracy Class | ± Percentage current (Ratio) error at Percentage of Rated Current | ± Phase Displacement in Minutes at Percentage of Rated Current | ||||||
| 5 | 20 | 100 | 120 | 5 | 20 | 100 | 120 | |
| 0.2 | 0.8 | 0.4 | 0.2 | 0.2 | 30 | 15 | 10 | 10 |
| 0.5 | 1.5 | 0.8 | 0.5 | 0.5 | 90 | 45 | 30 | 30 |
| 1.0 | 3.0 | 1.5 | 1.0 | 1.0 | 180 | 90 | 60 | 60 |
Specifications for Protective current transformers :
- Ratio
- Burden
- Accuracy limit factor-( standard accuracy limit factors shall be 5, 10, 15, 20 and 30)
- Accuracy class (Standard accuracy classes for protective current transformers shall be 5P, 10P and 15P)
- Voltage class
Specifications :
| Type | Current Transformer |
| Range | LT |
| Secondary Current | 5 or 1 Amp |
| System Voltage | 0.66/3.0 kV |
| Frequency | 50 Hz |
| Duty of operation | Continuous |
| Winding material | Electrolytic copper |
| Insulation class | Resin Cast or Tape Insulated |
| Cooling | Air Natural |
| Reference Standard | IS 2705 |