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China Current Transformer Suppliers - SF Series Factory for Power System Monitoring and Safety Solutions

A current transformer (CT) is a vital component of electrical equipment that regulates, monitors, and protects power systems. In China, suppliers and factories focus on producing high-quality CTs that accurately reduce large alternating currents (AC) to small, measurable levels. This essential technology connects high-current power circuits to safety relays or sensitive measurement devices, making it indispensable in power generation, transmission, distribution, and various industrial applications. When sourcing your current transformers, choose reputable suppliers in China for reliable performance and compliance with industry standards
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    Product Details

    Product Overview

    Electromagnetic induction powers a CT, which has two windings: a primary winding with a few turns linked in series with the high-current circuit and a secondary winding with numerous turns connected to safety or measurement devices. The primary winding receives a high current while the secondary winding, which is usually tuned to 5A or 1A for most industrial applications, receives a low current. This proportionality—also referred to as the transformation ratio—allows for accurate current monitoring while shielding workers and equipment from potentially dangerous voltages.

    CTs require sufficient insulation to maintain high voltage between windings, sufficient linearity to minimize measurement error, and high precision for energy metering. When using a CT, the secondary winding should never be open circuit. This is because an open circuit might result in extremely high voltages that could harm electrical equipment. In conclusion, since they enable more precise current monitoring and improved problem avoidance, current transformers are crucial to ensuring the reliability, efficiency, and safety of modern electrical systems.

    ⚡
    Electromagnetic Induction Dual-winding design with primary (high-current) and secondary (low-current) windings for safe current step-down.
    🎯
    High Precision Measurement Secondary output tuned to 5A or 1A for accurate energy metering with minimal measurement error.
    🛡️
    Safety & Reliability High-grade insulation between windings protects personnel and equipment from dangerous voltages.
    Technical Parameters
    Type Rated Current (A) Rated Burden (VA) Class Rated Voltage (V) Rated Frequency (Hz)
    SF45/14 30/5A ~ 100/5A 1.5 ~ 2.5 1.0 ~ 0.5 720 50/60
    SF62/20 30/5A ~ 200/5A 1.5 ~ 2.5 3.0 ~ 0.5 720 50/60
    SF62/30 100/5A ~ 400/5A 1.5 ~ 5 1.0 ~ 0.5 720 50/60
    SF62/40 200/5A ~ 600/5A 5 ~ 10 1.0 ~ 0.5 720 50/60
    SF74/40 150/5A ~ 600/5A 2.5 ~ 20 1.0 ~ 0.5 720 50/60
    SF74/50 250/5A ~ 1000/5A 5 ~ 20 1.0 ~ 0.5 720 50/60
    SF86/60 250/5A ~ 1200/5A 5 ~ 30 1.0 ~ 0.5 720 50/60
    SF104/80 600/5A ~ 2000/5A 5 ~ 45 1.0 ~ 0.5 720 50/60
    SF140/100 1000/5A ~ 3200/5A 5 ~ 50 1.0 ~ 0.5 720 50/60

    📐 Outline Drawing (unit: mm)

    Type A B C D E F G H I J K L M N O
    SF45/14 65 30 — 30 53 68 15 — — — — — 45 — —
    SF62/20 78 36 6.6 36 55 71 30.1 30.1 11 23 44 21 62 21 26
    SF62/30 78 47 6.6 35 55 71 31 31 16 31 44 31 62 21 26
    SF62/40 78 47 6.6 35 55 71 33 33 11 31 47 41 74 21 31
    SF74/40 98 61 6.6 45 67 81 41 41 31 41 47 41 74 21 31
    SF74/50 98 61 6.6 45 67 81 51 51 21 51 68 51 86 31 44
    SF86/60 110 56 6.6 40 62 76 65 65 31 61 86 61 104 31 56
    SF104/80 126 56 6.6 40 62 76 — — — — — 81 — — —
    Frequently Asked Questions
    Q What is a current transformer (CT) and how does it work?
    A current transformer (CT) operates on the principle of electromagnetic induction. It consists of a primary winding connected in series with the high-current circuit and a secondary winding connected to measuring or protection devices. The high current in the primary is proportionally reduced to a safe, measurable level (typically 5A or 1A) in the secondary winding, allowing accurate monitoring without direct exposure to dangerous voltages.
    Q What is the rated voltage for the SF-series current transformers?
    All SF-series current transformers listed in the technical parameters table have a rated voltage of 720V, making them suitable for a wide range of low-voltage industrial and commercial electrical systems.
    Q Why should the secondary winding of a CT never be left open circuit?
    If the secondary winding is left open circuit while the primary carries current, the transformer will attempt to drive all the magnetomotive force through the core with no opposing secondary current. This results in an extremely high voltage across the secondary terminals, which can be dangerous to personnel and can cause severe damage to the transformer and connected equipment.
    Q What accuracy classes are available for the SF-series CTs?
    The SF-series current transformers are available in accuracy classes ranging from 0.5 to 3.0, depending on the model. For example, the SF62/20 supports classes from 0.5 to 3.0, while most other models support 0.5 to 1.0 class. Higher accuracy classes (e.g., 0.5) are preferred for precision energy metering applications.
    Q Which SF-series model supports the highest rated current?
    The SF140/100 model supports the highest rated current range in this series, from 1000/5A up to 3200/5A, with a rated burden of 5 to 50 VA. It is designed for large-scale industrial applications requiring measurement of very high currents.
    Q Are these current transformers compatible with both 50Hz and 60Hz systems?
    Yes, all SF-series current transformers support a rated frequency of both 50Hz and 60Hz, making them suitable for global deployment across different regional power grid standards without requiring separate model variants.