Current Transformers (CT)
High-Precision Current Transformers for Global Power Systems
A Current Transformer (CT) is an essential instrument transformer engineered so that its secondary current is proportional to its primary current under normal operating conditions, maintaining an accurate phase relationship that approaches zero degrees with appropriate connection orientation.
Beyond high transformation fidelity, a critical engineering function of the CT is galvanic isolation. Regardless of system primary operating voltage levels (up to 3.3kV), the secondary measuring circuits, connected protective relays, and personnel remain safely isolated and operate at standardized low-voltage levels.
Operating on the fundamental principle of variable magnetic flux, real-world transformers require a controlled magnetizing current. Prima Transformers minimizes ratio error and phase displacement error by utilizing top-tier, low-loss Cold-Rolled Grain-Oriented (CRGO) magnetic steel laminations and precision computer-controlled winding techniques.
Features & Technical Capabilities
Engineered to satisfy demanding international procurement standards including IS 2705 and IEC 61869 specifications.
Key Design Features
- Robust Execution Types: Manufactured in Tape Wound, Flame-Retardant ABS Enclosure, or Epoxy Cast Resin Potted configurations.
- Premium Magnetic Cores: Assembled exclusively with high-permeability, ultra-low-loss CRGO silicon steel.
- Superior Dielectric Strength: Reinforced using high-grade multi-layer insulating papers and specialized casting compounds.
- Guaranteed Accuracy: Exceptional precision limits matching metrology and protection standards, down to Class 0.1.
- Custom Engineering: Fully customizable primary current ratings, inner core diameters, mounting dimensions, and multicore builds.
Electrical & Protection Parameters
- Dual Purpose: Steps down heavy transmission/distribution line currents to standard 5A or 1A instrument inputs while feeding protective relay logic.
- Continuous Thermal Rating (Ith): Rated at 1.2 times continuous primary current without thermal degradation.
- Short-Time Withstand: Withstands minimum 30 times rated primary current, and up to 40kA for 1 second.
- Low Instrument Safety Factor (ISF): Metering cores feature ISF < 5 to prevent downstream instrument burnouts under network faults.
- Controlled Thermal Rise: Engineered temperature rise remains below 30°C above ambient, preserving lifetime insulation integrity.
Typical Industrial Deployments
- 3-CT blocks for trivector meters, multi-function energy meters, and digital power analyzers.
- Precision power metering including active (WATT), reactive (VAR), and apparent energy monitoring.
- Current sensing, logging, fault isolation, and automation feedback loops in industrial switchgear.
- Motor Control Centers (MCC), Power Control Centers (PCC), and variable frequency drive panels.
- Laboratory standard reference CTs for calibration benches and testing laboratories.
- Winding Temperature Indicators (WTI) and protective interlocks for large power transformers.
Information Required with Your Inquiry
To ensure rapid quotations and optimum design accuracy, please specify:
- Current transformation ratio (e.g., 200/5A, 1000/1A, dual ratio).
- Rated burden capacity in VA (e.g., 5VA, 15VA, 30VA).
- Required accuracy class (Class 0.2, 0.5, 1.0, 5P10, 10P10, or PS).
- Execution format: Ring type, Busbar window dimensions (ID), or Wound type.
- Short-time thermal current withstand rating (kA/second), if critical.
- Knee-point voltage (Vk) and excitation current limits for PS class protection CTs.
- Mechanical mounting requirements and terminal type preferences.
Engineering & Manufacturing Notes
Every current transformer is built to customer project specifications and undergoes comprehensive routine testing in our computerized testing facility prior to dispatch. Data presented here outlines typical engineering baselines; custom secondary outputs (e.g., 0.577A, 2A), specialized primary bar geometries, high-burden custom casings, and multi-core configurations can be manufactured upon request.