LEM low-cost 50-A current transducers improve on shunt-measurement techniques

LEM has introduced 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 A. 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, and home appliances and in renewable-energy systems such as solar combiner boxes and solar inverters. 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 A RMS. LEM's proven expertise in open-loop Hall-effect technology allows these new devices to achieve a response time of only 2.5 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, an ADC will convert this voltage to a digital value. LEM has equipped the HLSR with an internal voltage reference of 1.65 or 2.5 V available on a dedicated pin for use by an external device such as an ADC, 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 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 ?3 dB bandwidth of 100 kHz. LEM offers versions that operate from either + 3.3- or + 5-V single supplies. LEM packaged the five models of the HLSR series in a unique, compact, and innovative outline that occupies only 387 mm² of PCB area representing less surface than many alternative designs based on resistive shunts. Variants of the package accommodate either surface-mount or through-hole connection of the primary-conductor path, signal, and 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 CTI (comparative tracking index) of 600. HLSR transducers are CE marked, conform to the EN 50178 standard for industrial applications, and carry a five-year warranty. LEM