Coreless high-current sensors
Capable of measuring high DC currents from 2kA up to 42kA without surge current limitations, the Open Loop Coreless Integral (OLCI) sensors feature a large aperture for accurate measuring of high currents on large busbars, with up to 1MHz bandwidth for high frequency applications. They are also significantly lighter (80%) and more cost-effective than open-loop or closed-loop current transducers operating within the same current measuring range.
Two versions of the new OLCI high current sensors are available from LEM – the FRS model supporting primary busbar apertures of 104mm x 22mm and the FL for apertures up to 300mm x 100mm. Because it is a split transducer, the FL can be opened and attached directly anywhere on the busbar without the need to open the busbar, making it easy to install and maintain.
The new sensors’ sustainability credentials stem from them consuming 85% less energy than similar closed-loop sensors, saving up to 150 kilowatt hours (kWh) over a year. With no magnetic core, no secondary copper winding, an integrated Rogowski coil and an array of Hall elements, the FRS sensor slashes raw material costs and reduces power losses. While the simple busbar design and assembly cut the number of fixtures required, both sensors are made from material that is 100% recyclable at end-of-life. At the same time, with LEM operating short, local supply chains within Europe and using 100% recyclable packaging, the sensors’ overall carbon footprint is minimised in terms of product transportation and delivery.
Equally suited to trackside and onboard traction applications in the railway industry as they are for high-power wind turbines and hydrogen electrolysers, the new sensors can also be used on industrial low-voltage and medium-voltage variable frequency drives, in induction welding applications, and for DC grid monitoring.
Among the major benefits offered by the two new sensors from LEM is a combination of excellent accuracy and high signal integrity, with 4mA to 20mA current output. The Hall elements ensure lower drift over temperature, lower electric offset and lower noise compared to open loop alternatives. Other benefits include rapid response time due to the elimination of any low pass filter effect from Eddy currents in the magnetic core. The new sensors are rugged against high dI/dt and high-frequency content and their coreless measurement design enables them to maintain accuracy and functionality despite any overcurrents. Also, their unipolar power supply ensures lower power consumption and system costs compared to traditional bi-polar power supplies.
