Current Transducers

LEM is a leading supplier of current transducers (also called current sensors), offering a wide range of galvanically isolated transducers that have become industry standards. The broad range of sizes, measuring range from tiny currents to 24kA and ease of use make them ideal solutions for a broad range of applications. LEM offers a variety of current sensor technologies: Hall Effect Fluxgate Air-Core (Coreless)

Hall Effect Current Transducers

LEM Hall Effect current sensors are available in open-loop, closed-loop and Eta configurations. Open-loop Hall Effect sensors are highly cost effective, as well as being small and consuming minimal power. Closed-loop sensors offer higher accuracy and enhanced speed to enable currents with a wider range of frequencies to be measured.     

Hall Effect Eta transducers are similar in construction to closed loop transducers , with the same magnetic circuit geometry, a Hall generator and secondary winding. A Hall Effect Eta transducer is a mix of open loop and current transformer technologies operating as an open loop transducer at low frequencies (up to 2…10 kHz depending on the specific transducer design), and as a current transformer at higher frequencies. Both the Hall Effect and transformer signals are electronically added to form a common output signal.

Hall Effect Current Transducers
 

Fluxgate Current Transducers

A “standard” closed-loop Fluxgate sensor uses a secondary winding to counteract the field generated in a magnetic circuit by the primary conductor. Although similar in operation to a closed-loop Hall Effect sensor, the Fluxgate uses a saturable inductor using a small thin magnetic core to sense the airgap field, rather than a Hall Effect transducer.

Fluxgate Current Transducers

Other Fluxgate transducers built on the technology to deliver specific benefits. They are:

  • Low-Frequency, where the field sensing element is wrapped around the toroidal core, rather than using a gap to make more cost-effective sensors
  • C-Type, built like the low-frequency Fluxgate sensor, but with a separate core to improve high frequency performance
  • IT-type that uses two toroidal cores with opposing excitation coils.
     

Air-Core Current Transducers

The material used to create the core can limit the performance of the transducer due to characteristics such as remanence, hysteresis, non-linearity, losses and saturation. So the design of an air-core or coreless transducer is often considered.

Examples of air-core current sensors include Rogowski coil transducers.

More information:

For more information about different current transducer technologies, download Isolated Current and Voltage Transducers: Characteristics, Applications, Calculations.
To find a current transducer for your application, visit the LEM Current Transducer Selector Tool.