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China CT3 Series Current Transformer - High-Quality Suppliers & Factory Solutions for Power Monitoring & Protection

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A current transformer (CT) is a crucial component in electrical systems, utilized for the control, monitoring, and protection of power networks. By converting massive alternating currents (AC) into small, measurable levels, it plays a vital role in various applications such as power generation, transmission, distribution, and industrial use. In China, leading suppliers and factories manufacture high-quality current transformers that ensure reliable connections with safety relays and sensitive measuring devices for high-current power circuits. Trust in our products to enhance the efficiency and safety of your power systems.

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    Product Details

    Product Overview

    A CT operates on electromagnetic induction and has two windings: a primary winding with a few turns linked in series to the high-current circuit, and a secondary winding with many turns connected to safety or measurement devices. The primary winding receives a significant current, whereas the secondary winding, which is normally tuned to 5A or 1A for most industrial applications, receives very little current.

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    This proportionality, also known as the transformation ratio, allows for accurate current measurement while safeguarding workers and equipment from potentially hazardous voltages.

    CTs require enough insulation to maintain a high voltage between windings, linearity to minimize measurement error, and high precision for energy metering.

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    Important: When using a CT, never leave the secondary winding open circuit. An open circuit may produce extremely high voltages, which can harm electrical equipment.

    Since they enable more precise current monitoring and improved issue detection, current transformers are crucial to ensuring the reliability, efficiency, and safety of modern electrical systems.

    Technical Parameters

    Type Specification (mm) Outline Size
    A B C D E F M
    CT3-100 100A / 100mA 118 60 30 108 18 20 c4*7
    CT3-250 250A / 100mA 136 64 35 123.5 22 25 c4*7
    CT3-400 400A / 100mA 180 93 40 165.5 32 35 c4*7
    CT3-630 630A / 100mA 212 102 40 198 43 41 c4*7
    Accuracy Grade: 0.5  |  Lead Length: 1 m Overload Current: ≥ 1.2% ln

    Frequently Asked Questions

    Q What is a current transformer (CT) and how does it work?
    A current transformer (CT) works on the principle of electromagnetic induction. It has a primary winding connected in series with the high-current circuit and a secondary winding connected to measuring or protection devices. The CT steps down the large primary current to a smaller, proportional secondary current — typically 5A or 1A — making it safe and practical for measurement and monitoring equipment.
    Q Why should the secondary winding of a CT never be left open circuit?
    Leaving the secondary winding open circuit is extremely dangerous. Without a connected load, all the primary magnetomotive force is used to drive the core, generating an extremely high and potentially lethal voltage across the secondary terminals. This can also cause overheating and permanent damage to the transformer core and insulation.
    Q What accuracy grade do the CT3 series current transformers offer?
    The CT3 series current transformers are rated at Accuracy Grade 0.5, which makes them suitable for precise energy metering and measurement applications. This grade ensures minimal ratio and phase errors, meeting international standards for billing-grade metering.
    Q What current ratings are available in the CT3 series?
    The CT3 series is available in four current ratings to suit different industrial applications: CT3-100 (100A/100mA), CT3-250 (250A/100mA), CT3-400 (400A/100mA), and CT3-630 (630A/100mA). Each model has different outline dimensions to accommodate the respective busbar or conductor sizes.
    Q What is the overload current capability of the CT3 series?
    The CT3 series current transformers are designed to handle an overload current of ≥ 1.2% of the rated current (ln). This overload capacity ensures the transformers can withstand temporary current surges without compromising measurement accuracy or damaging the unit.
    Q What are the key requirements for a current transformer to perform accurately?
    For accurate and safe performance, a current transformer must meet three key requirements: (1) Sufficient insulation — to maintain high voltage isolation between primary and secondary windings; (2) Linearity — to minimize measurement errors across the operating range; and (3) High precision — especially critical for energy metering and billing applications.