Low-cost 50 A current transducers improve on shunt measurement techniques

Today, at the SPS/IPC/Drives Exhibition (Nuremberg, Germany) LEM introduces its new HLSR series of current transducers, that provide a cost-effective and technically superior alternative to resistive shunt/optocoupler configurations for insulated current measurements up to 50 Amps. The five new HLSR transducers will satisfy application requirements in, for example, industrial inverters and motor drives; switch-mode and uninterruptible power supplies; specialist power supplies such as welding units; air conditioning; home appliances; but also in renewable-energy systems, for example, in solar combiner boxes and in solar inverters to track the maximum-power-point (MPPT).

LEM’s HLSR series uses open-loop Hall-effect current sensing technology, to measure AC, DC or pulsed currents with nominal values of 10, 20, 32, 40 or 50 ARMS. LEM’s proven expertise in open-loop Hall-effect technology allows these new devices to achieve a response time of only2.5 µsec, with very low gain and offset drift over their operating temperature range of -40 to +105 °C.

HLSR transducers deliver their output as an analogue voltage proportional to the primary measured current. In most applications, this voltage will be converted to a digital value by an analogue-to-digital converter: LEM has equipped the HLSR with an internal voltage reference of 1.65 or 2.5 V made available on a dedicated pin for use by an external device such as A/D converter, for example, or designers can choose to use an external reference from 0.5 to 2.65 V. The voltage reference is just one feature of the new ASIC (Application-Specific Integrated Circuit) that LEM’s designers created for this development, which enables the HLSR series to deliver typical accuracy of  ±1% at +25 °C, and ±3.4% at +105 °C, with a bandwidth of 100 kHz (-3 dB). LEM offers versions that operate from either + 3.3 or + 5 V single supplies.

LEM packaged the five models of the HLSR series in an unique, compact and innovative outline that occupies only 387 mm2 of PCB area representing less surface than many solutions based on resistive shunts.

Variants of the package cater for either surface-mount or through-hole connection of both primary conductor path and signal/power connections. The low-profile package weighs just 5.5 g, and is less than 12 mm high.

Safe measurements are assured with a high level of insulation between primary and measurement circuitry thanks to long creepage and clearance distances (8 mm as standard and 14 mm on request), and a comparative tracking index (CTI) of 600. HLSR transducers are CE marked,  conform to the EN 50178 standard for industrial applications, and are granted of a five-year warranty.