Whether you know the specifications of the current transformer you need or not, Competitive Magnetics can help you. We can design the current transformer that best applies to your needs, or we can build the custom current transformer that you need. We can provide you with a free sample, contact us for details.

A Current Transformer measures alternating current flowing through a conductor. Since it is used to measure current, a current transformer is often classified as a type of instrument transformer. One could measure the voltage drop across a known resistor. This is okay for low current applications but is often impractical for high current applications. The resistor consumes a lot of power (lowering efficiency) unless the resistor is very low in value, in which case there may be very little voltage to measure. The resistor could be excessively large. The resistor’s heat may affect the resistor value, thereby reducing the accuracy of the measurement. A current transformer can accurately measure the alternating current and put out a reasonable voltage, which is proportional to the current, but without as much heat and size that an appropriate resistor would require. The current transformer can perform its function with very little insertion loss into the conductor current being measured. The current transformer also provides voltage isolation between the conductor and the measuring circuitry. Proper function of a current transformer requires use of a load resistor. The load resistor is often referred to as a “burden resistor”.

The best core to use for a current transformer in terms of electrical performance is a toroidal core. Many toroidal current transformers have only one winding. This winding is usually a “high turns” winding which functions as the secondary winding. In application, the toroidal current transformer is slipped over an end of a high current wire or buss bar, which conducts the primary current. The wire or buss bar represents a one turn primary winding. Split core current transformers are designed so that they can be assembled around a buss bar without disconnecting the buss bar. "C"- cores and "U" core structures are commonly used for split-core current transformers because they are relatively easy to take apart and put back together around the buss bar. Historically, this has not been practical for toroidal coils, but there are now some flexible toroids, which permit the “split-core” feature of installing it around a buss bar. They have limited application. Some printed circuit board applications will utilize bobbin wound current transformers with two or more windings. One winding is an integral part of the circuitry, while the other winding acts the secondary.

Competitive Magnetics manufactures electronic transformers and Current Transformers in a wide variety of shapes and sizes. This includes; various standard types of “core with bobbin” structures (E, EP, EFD, PQ, POT, U and others), toroids, and some custom designs. Our maximum weight and power limitations are 40 pounds of weight and 2 kilowatts of power. We have experience with foil windings, litz wire windings, and perfect layering. For toroids, special winding techniques such as sector winding, progressive winding, bank winding, and progressive bank winding can be accomplished to satisfy your dielectric, creepage distance, capacitance, and leakage inductance requirements