LEM LA 55-P Closed-Loop Hall Effect Current Sensor

LA 55-P Product Overview

The LA 55-P is a high-precision current sensor based on closed-loop Hall effect technology, from LEM (Switzerland), the global leader in electrical measurement. Featuring closed-loop (compensated) Hall effect principle, it is designed for electronic measurement of DC, AC, and pulsed currents.

The sensor operates on a ±12V to ±15V bipolar supply, with a rated current of 50A, a measuring range of up to ±100A (2x overload capability), and a 25mA current output. It features a 12.7×7mm rectangular aperture for easy busbar or conductor passage on PCB. With a wide operating temperature range of -40℃ to +85℃, its insulating plastic case complies with UL 94-V0 flame retardant rating.

As one of the core models in the LA series, the LA 55-P delivers ±0.65% high accuracy, <1µs response time, and 200kHz high bandwidth — making it a classic choice for 50A-class current monitoring in AC variable frequency drives, servo drives, and UPS systems.

LA 55-P Key Technical Specifications

LA 55-P Key Advantages

Closed-Loop Hall Technology: Active compensation design eliminates core saturation effects — accuracy ±0.65%, linearity <0.15%

<1µs Fast Response + 200kHz High Bandwidth: Response time <1µs, delay time <500ns, bandwidth up to 200kHz — perfectly matched for high-frequency IGBT/PWM switching applications

±100A Wide Range: 2x overload capability — handles current surges during motor starting and load changes

Superior Noise Immunity: Closed-loop architecture provides high external magnetic field rejection — stable operation in complex industrial EMI environments such as VFDs and high-power drives

2.5kV High-Voltage Isolation + UL 94-V0 Flame Retardant Case: Reinforced insulation between primary and secondary — ensures control system safety — compliant with EN 50178 industrial safety standards

Compact PCB Mount Design: 12.7×7mm rectangular aperture, 3 secondary pins (recommended PCB hole φ1.2mm) — easy integration, weight only 18g

-40℃~+85℃ Ultra-Wide Temperature Range + 5-Year Warranty: Covers applications from cold outdoor to high-temperature industrial environments — LEM quality commitment with 5-year warranty

Why Choose the LA 55-P?

±0.65% High Accuracy + <0.15% Linearity: Closed-loop compensation technology ensures accurate measurement across the full range — meets industrial precision control requirements

<1µs Fast Response + <500ns Delay: Accurately captures IGBT switching transients and current spikes during load changes — provides timely and reliable triggering signals for overcurrent protection

200kHz High Bandwidth: Accurately measures current waveforms up to 200kHz — perfectly matches the output characteristics of modern high-frequency switching power supplies and VFDs

2.5kV High-Voltage Isolation: Reinforced insulation between primary and secondary — EN 50178 compliant — ensures control system safety

-40℃~+85℃ Wide Temperature Operation + Low Drift: Extremely low temperature drift — suitable for outdoor enclosures, industrial field environments, and other harsh temperature scenarios

12.7×7mm Rectangular Aperture + Compact PCB Design: Easy busbar passage — PCB mounting saves cabinet space — compact structure

LA 55-P Target Applications

AC variable frequency drives and servo motor drives, DC motor static converters, uninterruptible power supplies (UPS), switch-mode power supplies (SMPS), battery-powered equipment, welding power supplies