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transformer(FK)
Current Transformer

transformer(FK)

Expanded Technical Specification: FK Series Current Transformer (CT)

The FK series current transformer (CT) is a high-precision, isolation-type electrical device engineered to step down high alternating current (AC) values in power systems to standardized, low-current secondary outputs. Serving as a critical interface between high-current primary power circuits and low-voltage measuring instruments, protective relays, and control systems, the FK series CT ensures safe, accurate, and reliable current monitoring across power generation, transmission, distribution, and industrial applications.

    Product Overview

    Unlike direct current measurement methods, which risk damaging sensitive devices or endangering personnel when exposed to high primary currents, the FK series CT provides galvanic isolation between primary and secondary circuits. This isolation eliminates direct electrical connectivity, mitigating overload risks and ensuring compliance with electrical safety standards for both equipment and operators.

    Core Working Principle
    The FK series CT operates on the mutual induction principle, leveraging a closed magnetic core (typically constructed from silicon steel or amorphous alloy for low magnetic loss) with two concentric winding sets:
    1. Primary Winding: Consists of a small number of turns (or a single pass-through conductor for bar-type CTs) connected in series with the high-current primary circuit. The primary current (Iₚ) flowing through this winding generates a magnetic flux in the core.

    2. Secondary Winding: Features a large number of precisely wound turns, connected to measuring instruments or protective relays. The magnetic flux induced by the primary winding generates a proportional secondary current (Iₛ) in this winding.
    The CT adheres to the ampere-turn balance relationship:
    Iₚ × Nₚ = Iₛ × NₛWhere:
    ● Nₚ = Number of primary winding turns
    ● Nₛ = Number of secondary winding turns
    This relationship ensures the secondary current is a fixed, scaled fraction of the primary current. The FK series CT is standardized to common secondary output ratings of 1 A or 5 A AC—values compatible with virtually all industrial ammeters, power meters, and protective relays.

    Key Application Scenarios
    The FK series CT is indispensable in the following electrical system applications:
    ● Power System Monitoring: Paired with digital ammeters, power meters, and energy meters to measure primary currents ranging from tens to thousands of amps (e.g., generator output current, distribution feeder current, industrial motor load current).
    ● Protective Relaying: Integrated with overcurrent, short-circuit, and earth-fault relays to trigger fast, selective tripping of circuit breakers during fault conditions, preventing equipment damage and system downtime.
    ● Industrial Process Control: Used in motor control centers, switchgear, and automation systems to provide current feedback for load regulation, overload protection, and process optimization.
    ● Revenue Metering: Deployed in utility-grade metering systems to ensure accurate, traceable current measurement for energy billing purposes.

    Critical Performance Characteristics
    1.High Measurement Accuracy: Classified by accuracy grade (e.g., Class 0.2, Class 0.5, Class 1.0) to meet diverse application requirements—from precision revenue metering to general-purpose monitoring.

    2.Low Magnetic Saturation: The core material is selected to resist magnetic saturation under normal and moderate overload conditions, ensuring linear current transformation and preventing secondary current distortion.

    3.Robust Isolation Rating: Designed to withstand high dielectric voltage between primary and secondary windings, complying with international safety standards (e.g., IEC 61869) for reliable operation in high-voltage environments.

    4.Versatile Installation Design: Available in multiple configurations (e.g., wound-type, bar-type, bushing-type) to suit different cabinet layouts, busbar sizes, and installation space constraints.

    Technical Parameters

    Type

    Main Loop Current

    (mm) Outline Size

    A

      B

       C

       D

       E

    F

       M

    FK-1025

           ﹤100A

    162

     

    28

    155

    100

    25

      c5*7

    FK-1435

    < 250A

    202

     

    28

    195

    140

    35

      c5*7

    FK-1835

    <400A

    242

    82

    28

    235

    180

    35

      c5*7

    FK-2245

    <630A

    282

    92

    28

    275

    220

    45

    c5*7

    FK-3045

    < 1 250 A

    363

    92

    28

    355

    300

    45

    c5*7

    Rated Primary Current: IA

    Rated Second Current: O. 5mA