DC Immune Current Transformer
DC Immune Current Transformer

DC immune current transformers (CTs) are used in electrical devices, such as electricity meters to measure the current in the AC circuit where DC offset exists. Each piece of Xianyu’s DC immune current transformer consists of the amorphous & nancrystalline dual core manufacured by ourselves. As we used high-grade DC immune CT core inside, the final CT have the ability to handle the DC offsets in the circuit. We make the round winding coil by high-grade enamel wire and turns ratio can range from 1:1000 to 1:25000.

The winding coil of CT should be protected by wrapped insulation tape or plastic case fixed by harden epoxy resin. Plastic case current transformers usually have the advantage of cost, as the coil fix (resin pouring) can be handled by automatic machines. Insulation tape wrapped CT are suitable for flexible demands, as no plastic mold is required, but the price may not so cheap as the insulation tape is wrapped manually.

For some circumstances, we’ll assemble the coils by metal shieldings outside for further protection and magnetic shielding. We have another type anti-magnetic current transformers with metal case inside, which are key components for anti-tamper or anti-theft energy meters. The metal shield or metal case provides good protection for the coil of a current transformer, which may be affected by the outside magnetic field. We can make toroidal current transformers, as well as busbar built-in type. Due to our design of sophisicated structure, we can also provide busbar removable CT, which can be easliy assembled inside the case of energy meters or other electrical devices.

The most common structure of DC immune CT is toroidal or ring type, and the through-hole is used to assemble busbar or primary wires, maybe together with shunt resistors. But we can also make bus type or busbar built-in current transformers, which can be easily fixed or installed in the meter cases by screwing. In some circumstances, the busbar may be replaced by primary wire manganin shunt.

While the busbar or neutral bar carrying the primary current, the coil will carry the secondary current, and its two ends will connected with the lead wires, whose length and gauge are usually specified by end users. For PCB mount type DC immune CT, the lead wires are replaced by 2 pins or 4 pins.

Our precision current transformers have high linearity, very low phase shift (or phase error), and low amplitude error (or current error). And we can provide different accuracy class CT, range from 0.05 to 0.2 class stipulated by the Chinese National Standard, for different grades of residential or commercial meters.

As a professional manufacturer of more than 15 years experience, we can provide customzied DC immune current transformer with a wide-range of dimensions for single phase or three phase watt-hour meters. We can make very small CT, or big ones with max. current as high as 600A for industry meters. Due to our quick prototype technology (3-D printing or resin casting), we can provide samples within a couple of days.

DC Immune Current Transformer


  • A variety of encapsulations, busbar or through-hole type
  • Amorphous & nanocrystalline dual core inside
  • High linearity over the whole primary current range
  • Accuracy up to 0.05 or 0.1 class, low phase shift & amplitude error
  • Safe galvanic seperation and high dynamic range
  • Quick prototype development and sampling
  • Automatic coil winding for large-scale production
  • Meet the standard JB/T10665
  • Customized current transformer available


  • Energy meters, smart meters
  • Electromechanical meter
  • Electrical measuring instruments
  • Electrical protective devices
  • Current sensing modules
  • Adjustable speed drives
  • Variable-frequency drives
  • Wind power converter
  • Power supply

Current error and phase error limits

Current error ±(%) in the following currents

Accuracy Class 0.01In≥0.05In

Phase error(′) In the following currents. Note: When current is 0.2In~Imax, phase error(δe ) is the average of δmax and δmin; When current is i, the phase error of i is the difference of betweenδi and δe. (△δi=δi-δe)

Accuracy Class0.01In0.05In0.2In1In2In3InImax

Basic Parameters

DescriptionDC Immune Type Current Transformer
Structure Of WindingToroidal
PhaseSingle, Three
Input / Output10~600A/1~40mA
Max. Current10~600 A
Turns Ratio1:1000~25000
Burden (Rb)5~100 Ω
Accuracy Class0.05/0.1/0.2 Class
Core InsideDC Immune Dual Core
EncapsulationPlastic Case, Metal Shield, Double Insulation
Busbar TypeNone / Built-in / Removable Busbar
Mounting MethodScrew Fixing, Metal Clamp, Through Hole
ApplicationMeters, Instruments
Accept CustomizedYes

Technological requirements

  1. Insulation level: while put the secondary winding to ground and input 3kV voltage (RMS value) between primary and secondary winding for 1 minute, the leakage current is 1mA, no breakdown, no arcing or spark.
  2. Insulation resistance: under test voltage of 500VDC, the resistance value between primary and secondary winding of current transformer is ≥1000MΩ.
  3. Impact voltage test between primary winding and secondary winding: put 6kV current between primary winding and secondary winding for 10 times, there’s no breakdown, no arcing or spark.
  4. Overload requirements: put 30 times Imax current impact of half a cycle under rated load, the current transformer has no breakdown, no arcing or spark.
  5. Temperature increase: work continuously for 30 min, while ambient temperature is 40°C , primary current is 100% Imax, the temperature increase of current transformer’s case is less than 25°C .
  6. DC immune requirements: assemble the current transformer to the energy meter and input current of Imax/1.414, the tolerance of energy meter is less than 80% of what specified in the State Standard GB/T17215, i.e, 2.4%.
  7. Anti-magnetic Performance (optional): up to 300mT, special structure is required.
  8. Winding coil: the secondary winding coil is connected by black/red lead wires.
  9. Outward appearance: the trade mark is clear and exact, no dirty material in the surface of current transformer.
  10. The gauge, length and position of lead wires should be follow the drawings.

Packing and shipment

  • Packing: suitable paper boxes and cartons, plywood case is optional, strong enough for anticollision, antiseismic, antimoist, make sure the current transformers are protected well during shipment.
  • Inner and outer packaging marks: the product model, company name or trademark, date of manufacture or batch number and quantity are clearly indicated on the product.
  • Shipment: vibration, damping, impact, and rain or snow should be avoided during transportation.
  • Storage: under the condition of good packaging, store the current transformers on the shelves of the warehouse and avoid direct sunlight.
  • The storage place should be clean, the ambient temperature is 0~40°C, the relative humidity is not more than 80%, and the air should not contain harmful materials enough to cause corrosion of the current transformer.


Model (Part Number)Input/OutputCurrent Rating(A)Turns RatioID(Hole) (mm)OD(Dist.) (mm)HT (mm)
DMB60-25A5(60)A/2mA601:25002-Φ5.2Φ33 (15)31
DPB120-25B10(120)A/4mA1201:25002-Φ6.532 (18)30
DSB120-25A10(120)A/4mA1201:25002-Φ6.2Φ34 (20)20.5

The above data are selected from some popular models we produce. Please contact us for detail datasheet. We can also design some special current transformers to meet customers’ requirements.

DC Immune Current Transformer