LF505-S/SP22 Closed-Loop Hall Effect Current Sensor | LEM 500A High-Precision Current Measurement Expert

LF505-S/SP22 Product Overview

The LF505-S/SP22 is a high-accuracy current sensor based on closed-loop Hall effect technology, developed by LEM (Switzerland). Designed for electronic measurement of DC, AC, and pulsed currents, it operates from a bipolar external supply of ±15 V to ±24 V. The sensor accurately measures rated currents up to 500 ARMS and offers a wide measurement range covering ±1200 A of overload current, accommodating instantaneous high-current surges. The output is a proportional 143 mA current signal via M4 screw terminals.

In modern high-power electronic systems, current measurement accuracy directly determines protection performance and control quality. With its closed-loop compensation architecture and advanced Hall sensing technology, the LF505-S/SP22 provides reliable, stable current monitoring for variable frequency drives, traction systems, and renewable energy equipment. It is widely used in single-phase/three-phase inverters, traction choppers, traction converters, auxiliary converters, high-power drives, and substations across industrial and commercial applications.

LF505-S/SP22 Key Features & Performance Advantages

Closed-Loop Hall Effect Technology – Precision Meets Stability

Utilizing a closed-loop (compensated) Hall effect architecture, the sensor’s secondary winding generates a magnetic force that continuously compensates the magnetic field produced by the primary current. This fundamentally eliminates the systematic errors caused by core hysteresis, temperature drift, and gain nonlinearity inherent in openloop sensors. This technology delivers the following hardcore performance:

Linearity error below ±0.1% FS ensures nearly perfect linear output across the full range. The total accuracy of ±0.6% over temperature delivers clear advantages in demanding applications such as motor drives, UPS systems, and servo drives.

Excellent Immunity to Interference & Overload Capability

High common-mode rejection: With wide bandwidth (DC–100 kHz) and the inherent advantages of closed-loop technology, the sensor provides high immunity to external electromagnetic interference, suitable for electrically noisy industrial environments.

Strong overload capability: A dynamic range of ±1200 A handles inrush currents from motor starting or load transients, ensuring stable operation under severe conditions.

No insertion loss: Non-contact measurement via the Hall principle introduces no additional energy loss to the primary circuit, preserving system efficiency.

Wide Temperature Range – Designed for All Environments

Operating temperature: –40°C to +70°C, covering applications from cold outdoor settings to hot industrial interiors.

Storage temperature: –40°C to +85°C, ensuring long-term reliability during storage.

Secondary winding resistance @ 70°C: 56 Ω, stable output over the full temperature range.

Low temperature drift: The offset current temperature variation is kept within ±0.5 mA over the entire operating temperature range, making output characteristics highly insensitive to temperature changes.

Flexible Mounting & Robust Mechanical Construction

Integrated aperture: 30.2 mm diameter for easy busbar or conductor passage.

Multiple panel mounting options: Space-saving compact design suits various industrial cabinet layouts.

Highgrade flameretardant housing: UL94-V0 rated insulating plastic meets electrical safety standards.

Turns ratio: 1:3500 for fine secondary output granularity.

LF505-S/SP22 Target Applications

The LF505-S/SP22 design incorporates more than 25 years of LEM experience in industrial, traction, and transportation applications, targeting the following demanding scenarios:

Railway Traction Systems

Designed for traction and auxiliary converters in high-speed trains, metros, trams, and other urban transit systems. LEM sensors directly participate in drive control and protection. EN 50155 certification guarantees reliability under severe vibration, wide temperature variation, and complex electrical environments.

Industrial Motor Drives & Frequency Converters

AC variable frequency drives and servo drives demand high real-time closed-loop current accuracy. The <1 µs response time and 100 kHz bandwidth of the LF505-S/SP22 perfectly track high-frequency current variations, enabling precise torque control.

Uninterruptible Power Supplies (UPS) & Switch-Mode Power Supplies (SMPS)

UPS and SMPS applications require real-time input/output current monitoring for overload protection and output voltage regulation. The closed-loop Hall architecture ensures stable output accuracy over a wide temperature range, avoiding the interference susceptibility of open-loop sensors.

Renewable Energy Systems

In wind turbines, photovoltaic inverters, and energy storage systems, the sensor accurately detects DC/AC currents on the converter side, providing reliable data for MPPT control and grid-side protection.

DC Motor Drives & Welding Power Supplies

DC drives and large welding equipment experience significant inrush currents and sustained high temperatures. The ±1200 A wide range and –40 to +70°C wide temperature design of the LF505-S/SP22 are tailor-made for such rugged applications.

Why Choose LF505-S/SP22?