LEM LF Series Current Transducers

Technical Dossier

Product Details And Specifications

LEM LF Series: Comprehensive Module Range and Technical Overview

The LEM LF Series represents one of the most widely deployed families of closed-loop Hall-effect current transducers in global heavy industry. Designed for high-accuracy, galvanically isolated current measurement, LF Series transducers are installed across chemical processing plants, nuclear power stations, petroleum refineries, steel mills, and large-scale drive systems. Their combination of ±0.5% accuracy class, wide operating temperature range (−40°C to +85°C), and robust PCB-mount or panel-mount form factors has made them a default specification in IEC 61800-compliant variable speed drive systems and DCS analog input loops worldwide. The series covers nominal measuring ranges from 100 A to 2000 A, with supply voltage options of ±15 V and ±24 V, making them interoperable with the majority of legacy and modern PLC/DCS analog I/O infrastructure.

The Evolution of LF Series Architecture

The LEM LF Series was introduced as a successor to the earlier LA and LT closed-loop transducer families, addressing the demand for higher nominal currents and improved immunity to external magnetic fields in industrial bus-bar installations. Early LF variants used a single-aperture toroidal core with a fixed secondary winding ratio, requiring external burden resistors to define the output voltage range. As industrial standards evolved toward ±10 V and 4–20 mA signal conditioning, LEM introduced the /SP variants — integrated signal processing versions — which embed the burden resistor and output conditioning circuitry directly within the transducer housing. The /SP16 designation specifically indicates a 16-pin DIN-rail-compatible footprint with integrated ±15 V regulated output. Subsequent generations added the /SP5 (5 V logic-compatible output) and /SP6 (±24 V supply) sub-variants to address the proliferation of 24 V DC control architectures in modern PLC cabinets. Compatibility between generations is maintained at the mechanical mounting level, but electrical substitution requires verification of supply voltage, output range, and aperture diameter. Many LF Series models have entered the mature/end-of-life phase; LEM has transitioned new designs toward the CKSR and HLSR Series for lower-current applications and the ITN Series for high-current bus-bar measurement. However, installed base volumes in legacy DCS and drive systems ensure continued demand for LF Series spares through at least 2035.

LF Series Full Catalog & Functionalities (SKU List)

The following SKUs represent the core LF Series product range, classified by nominal current and output variant. All models are closed-loop (compensated) Hall-effect transducers with galvanic isolation.

LF 205-S: 200 A nominal, ±15 V supply, current output, PCB mount, standard aperture 28 mm.
LF 205-S/SP5: 200 A nominal, ±15 V supply, ±5 V voltage output with integrated SP conditioning.
LF 205-S/SP6: 200 A nominal, ±24 V supply, ±10 V voltage output, enhanced noise immunity.
LF 305-S: 300 A nominal, ±15 V supply, current output, 28 mm aperture, DIN-rail compatible.
LF 305-S/SP5: 300 A nominal, integrated ±5 V output, suitable for 5 V ADC interfaces.
LF 510-S: 500 A nominal, ±15 V supply, current output, 51 mm aperture, heavy bus-bar use.
LF 510-S/SP6: 500 A nominal, ±24 V supply, ±10 V output, refinery and drive panel standard.
LF 1005-S: 1000 A nominal, ±15 V supply, current output, 51 mm aperture, steel mill drives.
LF 1005-S/SP16: 1000 A nominal, ±15 V supply, integrated 16-pin SP output conditioning, DCS loop compatible — this listing.
LF 1005-S/SP5: 1000 A nominal, ±5 V integrated output, logic-level compatible analog interface.
LF 1005-S/SP6: 1000 A nominal, ±24 V supply, ±10 V output, modern 24 V DC panel standard.
LF 1010-S: 1000 A nominal, dual-range variant, selectable 500 A / 1000 A via external pin.
LF 2005-S: 2000 A nominal, ±15 V supply, current output, 80 mm aperture, large bus-bar.
LF 2005-S/SP6: 2000 A nominal, ±24 V supply, ±10 V output, nuclear and petrochemical standard.
LF 2010-S: 2000 A nominal, dual-range, 80 mm aperture, used in high-current rectifier monitoring.
LF 3010-S: 3000 A nominal, ±15 V supply, current output, 80 mm aperture, smelter and EAF applications.
LF 3010-S/SP6: 3000 A nominal, ±24 V supply, ±10 V output, large drive and transformer monitoring.

Sourcing Hard-to-Find & Obsolete LF Series Parts

A significant portion of the LF Series catalog has been discontinued by LEM as production has shifted to newer HLSR, CKSR, and ITN platform transducers. However, the installed base of LF Series units in legacy DCS systems — particularly in Yokogawa CENTUM, Honeywell TDC 3000, and ABB Advant OCS environments — means that replacement demand remains active. DriveKNMS maintains a dedicated inventory of LF Series transducers sourced through authorized distribution channels and verified surplus stock. For end-of-life models such as the LF 3010-S and early LF 205-S variants, DriveKNMS provides lifecycle extension support including cross-reference analysis, functional equivalence verification, and long-term supply agreements. All surplus stock is subject to full incoming inspection before dispatch. Customers operating under IEC 61511 functional safety requirements can request traceability documentation upon order.

Quality Control for the LF Series Range

LF Series transducers incorporate a precision toroidal magnetic core and a secondary winding assembly that are sensitive to mechanical shock and electrostatic discharge during handling. DriveKNMS applies a dedicated test protocol for all LF Series units prior to shipment. Each unit undergoes: (1) supply voltage verification at ±15 V and ±24 V as applicable; (2) zero-current offset measurement against LEM factory specification (typically <±0.1% of IPN); (3) linearity check at 25%, 50%, 75%, and 100% of nominal current using a calibrated primary conductor; (4) output signal integrity verification under simulated bus-bar load; (5) insulation resistance test at 500 V DC between primary aperture and secondary circuit. Units exhibiting drift beyond ±0.5% of nominal output at any test point are quarantined and not dispatched. Test records are retained for a minimum of five years and are available to customers on request.

For sourcing inquiries, cross-reference requests, or long-term supply agreements for LEM LF Series transducers: